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Maternal Antibody and Viral Factors in the Pathogenesis of Dengue Virus in Infants
... DF involves primary and secondary infections most frequently encountered in adults and older children. The onset of symptoms is marked by a biphasic, high-grade fever lasting from three days to one week [25]. It is also associated with severe headaches (mostly retro bulbar), muscle cramps, joint pain, diarrhea, vomiting, and cutaneous rash. ...
... DHF may occur during a primary infection due to maternally attained dengue antibodies in infants but is frequently followed by a secondary infection in the case of adults [26]. Hemorrhagic episodes presenting at least one of the following: petechiae, purpura, ecchymosis, nose/gum bleeding and mucosal bleeding, hematemesis, and/or melena form the diagnostic criteria of DHF [25]. ...
... Hypovolemic shock, multi-organ damage, and consumption coagulopathy contribute to a high mortality rate in DSS. Usually, the shock persists for a short span, and the patient promptly recovers with supportive therapy [25]. ...
The recent emergence and re-emergence of viral infections transmitted by vectors, Zika, chikungunya, dengue, and others, is a cause for international concern. Here, we provide a summary of the current understanding of the transmission, clinical features, diagnosis, global burden, and the likelihood of future epidemics by these viruses. Arboviruses transmitted by mosquitoes are challenging to diagnose and can have surprising clinical complications. Dengue, chikungunya, and Zika are the most important diseases caused by arboviruses worldwide, especially in tropical and subtropical regions. These are transmitted to humans by day-biting Aedes aegypti and Aedes albopictus mosquitoes. In India, the increase in the incidence of dengue and chikungunya cases is primarily linked to the dissemination of Aedes aegypti. A rapid and accurate diagnosis is paramount for effectively controlling dengue outbreaks. As there is no vaccination or specific treatment available for these viruses, vector control is the only comprehensive solution available.
... The phenomenon of antibody dependent enhancement (ADE) of viral infectivity of cultured cells by sera from severe dengue patients lent support to the epidemiological finding of enhanced risk for DHF/DSS in patients after a secondary dengue infection (5)(6)(7). However, multiple studies exist that reported both negative and positive correlations between dengue severity and dengue viral load, duration of viremia or NS1 antigen levels (8)(9)(10)(11)(12)(13)(14)(15)(16)(17), suggesting that enhanced viral titers achieved by ADE alone cannot fully account for dengue severity. In addition to direct enhancement of uptake of antibody-bound virus leading to increased viral titers, excessive activation of innate immune cells by binding of dengue-specific antibodies to Fc receptors that are expressed generously on multiple innate cell subsets was also implicated in the 'cytokine storm' of vasoactive and pro-inflammatory cytokines. ...
... Despite the demonstration of enhancement of viral infectivity in dengue by pre-existing immunity and the strong association of severity with high viral loads in multiple studies (9,11,15,16,45), other studies reporting no association between viral load and severity (8,10,13,14) precluded its use as a biomarker to predict severity. While studies on cohorts from Thailand and Cuba have both demonstrated the highest proportion of severe cases in secondary dengue patients infected with serotype 2 following serotype 1 (46,47), determining the serotype of both current and previous infection(s) requires technically skilled serology investigations that are not routinely used in diagnostic laboratories. ...
... Significantly higher innate activation associating with high serum NS1 levels used as a surrogate of viral load also suggested that high viral antigen levels early in infection contributed to vigorous stimulation of all innate cell subsets. As mentioned above, the relationship between dengue viral load and disease severity is rather tenuous with reports showing both positive and negative correlations (8,10,13,14,49,50). In our large cohort however, the direct correlation between high NS1 antigenemia and good prognosis regardless of day post symptom onset was strong and convincing. ...
... The phenomenon of antibody dependent enhancement (ADE) of viral infectivity of cultured cells by sera from severe dengue patients lent support to the epidemiological finding of enhanced risk for DHF/DSS in patients after a secondary dengue infection (5)(6)(7). However, multiple studies exist that reported both negative and positive correlations between dengue severity and dengue viral load, duration of viremia or NS1 antigen levels (8)(9)(10)(11)(12)(13)(14)(15)(16)(17), suggesting that enhanced viral titers achieved by ADE alone cannot fully account for dengue severity. In addition to direct enhancement of uptake of antibody-bound virus leading to increased viral titers, excessive activation of innate immune cells by binding of dengue-specific antibodies to Fc receptors that are expressed generously on multiple innate cell subsets was also implicated in the 'cytokine storm' of vasoactive and pro-inflammatory cytokines. ...
... Despite the demonstration of enhancement of viral infectivity in dengue by pre-existing immunity and the strong association of severity with high viral loads in multiple studies (9,11,15,16,45), other studies reporting no association between viral load and severity (8,10,13,14) precluded its use as a biomarker to predict severity. While studies on cohorts from Thailand and Cuba have both demonstrated the highest proportion of severe cases in secondary dengue patients infected with serotype 2 following serotype 1 (46,47), determining the serotype of both current and previous infection(s) requires technically skilled serology investigations that are not routinely used in diagnostic laboratories. ...
... Significantly higher innate activation associating with high serum NS1 levels used as a surrogate of viral load also suggested that high viral antigen levels early in infection contributed to vigorous stimulation of all innate cell subsets. As mentioned above, the relationship between dengue viral load and disease severity is rather tenuous with reports showing both positive and negative correlations (8,10,13,14,49,50). In our large cohort however, the direct correlation between high NS1 antigenemia and good prognosis regardless of day post symptom onset was strong and convincing. ...
Background
Early biomarkers of progression to severe dengue are urgently required to enable effective patient management and control treatment costs. Innate immune cells, which comprise the earliest responders to infection and along with the cytokines and chemokines they secrete, play a vital role in orchestrating the subsequent adaptive immune response and have been implicated in the enhancement of infection and “cytokine storm” associated with dengue severity. We investigated the early innate immune cytokine profile of dengue patients during acute phase of disease in a prospective blinded study that included subjects with acute dengue and febrile controls from four major hospitals in Bengaluru, India along with healthy controls. We used intracellular cytokine staining and flow cytometry to identify innate immune biomarkers that can predict progression to severe dengue.
Results
Dengue infection resulted in enhanced secretion of multiple cytokines by all queried innate immune cell subsets, dominated by TNF-α from CD56⁺CD3⁺ NKT cells, monocyte subsets, and granulocytes along with IFN-γ from CD56⁺CD3⁺ NKT cells. Of note, significantly higher proportions of TNF-α secreting granulocytes and monocyte subsets at admission were associated with mild dengue and minimal symptoms. Dengue NS1 antigenemia used as a surrogate of viral load directly correlated with proportion of cytokine-secreting innate immune cells and was significantly higher in those who went on to recover with minimal symptoms. In patients with secondary dengue or those with bleeding or elevated liver enzymes who revealed predisposition to severe outcomes, early activation as well as efficient downregulation of innate responses were compromised.
Conclusion
Our findings suggested that faulty/delayed kinetics of innate immune activation and downregulation was a driver of disease severity. We identified IFN-γ ⁺CD56⁺CD3⁺ NKT cells and IL-6⁺ granulocytes at admission as novel early biomarkers that can predict the risk of progression to severity (composite AUC = 0.85–0.9). Strong correlations among multiple cytokine-secreting innate cell subsets revealed that coordinated early activation of the entire innate immune system in response to dengue virus infection contributed to resolution of infection and speedy recovery.
... Seropositivity rate was found to be 35.8% in Malaysia and as high as 94.7% in Thailand [18,19]. Maternally derived, neutralizing anti-DENV antibodies are postulated to confer immunity to dengue during the first months of life [20]. The prime cause of fetal and neonatal morbidity and mortality in DENV infection during pregnancy is insufficient maternally derived IgG neutralizing antibodies. ...
... The prime cause of fetal and neonatal morbidity and mortality in DENV infection during pregnancy is insufficient maternally derived IgG neutralizing antibodies. The incremental decay of the IgG antibody generates a window period that possesses sub-neutralizing levels of antibody, which effectively enhances DENV infection in Fc receptor-bearing host cells and uncontrollable viremia, implying the corollary of antibody-dependent enhancement of DENV infectivity [19,20]. However, it is still mysterious whether sub-neutralizing levels of maternally derived anti-DENV IgG increases fetal DENV infection risk. ...
... In earlier reports, viral hematodepressive disease without serological identity has been diagnosed in Thai children [55]. Infants with primary dengue had significantly lower platelet nadirs and greater hemoconcentration [20]. This raises the distinct possibility that certain aspects of hematopoietic response to virus infection remain obscure. ...
Background
Recent studies have shown that dengue virus (DENV) can efficiently infect bone marrow hematopoietic stem cells (HSCs) as well as the placenta of pregnant women. Although mother-to-infant vertical transmission of DENV through the placenta has been well documented, the evidence of cell-associated vertical transmission is still unknown. Whether DENV can infect umbilical cord blood (UCB) cells before reaching the fetus remains to be explored. Here, we proposed that human UCB cells were permissive to the DENV infection and DENV infected CD133+ and CD34+ HSCs are reservoir of the virus that could be reactivated upon re-culturing in suitable cells.
Methods
Human UCB cells were freshly obtained and subjected to DENV infection. Multicolor flow cytometry (MFCM) was used to demonstrate the phenotypes of the infected HSC populations. Immunofluorescence analysis (IFA) and T-distributed Stochastic Neighbor Embedding (t-SNE) were used to show the association of the DENV antigen, non-structural protein1 (NS1) with HSCs.
Key findings
UCB cells were highly permissive to DENV infection. DENV altered the phenotype of the infected HSC population, increased the expression of HSCs, and affected the balance of transcription factors (TFs, GATA1/2/3). IFA revealed the association of the DENV antigen, non-structural protein1 (NS1), with CD34⁺ and CD133⁺ cells. T-distributed Stochastic Neighbor Embedding (t-SNE) analysis revealed heterogeneity in the distribution of CD133⁺NS1⁺, and CD34⁺ NS1⁺ cells. DENV particles were recovered from CD133⁺ and CD34⁺ cells even when virus production in the supernatant was negligible.
Significance
We predict that infection of CD133+ and CD34+ cells in the UCB serve as reservoirs for the amplification of DENV in UCB prior to the virus reaching the fetus and facilitate vertical transmission.
... As antibody levels decay further, the ability to enhance the severity of heterologous infections is thought to be lost, though infants remain at risk of DENV infection. Peaks in reported dengue hospitalizations among infants less than 1 y of age are consistently observed in DENV-endemic countries and are widely attributed to maternal antibody-facilitated ADE (8,12,14). However, the specific concentrations of maternally derived DENV antibodies that may place infants at increased risk of severe disease have not been well characterized. ...
... Accounting for these measurement processes, we infer the underlying dynamics of maternally derived mean DENV antibody titers in Thai infants and find that constant exponential decay models are best able to capture the observed infant antibody dynamics in this setting (Fig. 2 A-C and SI Appendix, Table S1 and Fig. S13). Our estimates of infant DENV antibody half-lives, ranging from a median of 28 to 47 d across cohorts and assays, are consistent with previous estimates of 41 d estimated in Thai infants (21), serotype-specific antibody half-lives ranging from 33 to 53 d in Thai infants (22), and in Vietnamese infants with an estimated half-life of 42 d (14). ...
Infants less than 1 y of age experience high rates of dengue disease in dengue virus (DENV) endemic countries. This burden is commonly attributed to antibody-dependent enhancement (ADE), whereby concentrations of maternally derived DENV antibodies become subneutralizing, and infection-enhancing. Understanding antibody-related mechanisms of enhanced infant dengue disease risk represents a significant challenge due to the dynamic nature of antibodies and their imperfect measurement processes. Further, key uncertainties exist regarding the impact of long-term shifts in birth rates, population-level infection risks, and maternal ages on the DENV immune landscape of newborns and their subsequent risks of severe dengue disease in infancy. Here, we analyze DENV antibody data from two infant cohorts (N = 142 infants with 605 blood draws) and 40 y of infant dengue hospitalization data from Thailand. We use mathematical models to reconstruct maternally derived antibody dynamics, accounting for discretized measurement processes and limits of assay detection. We then explore possible antibody-related mechanisms of enhanced infant dengue disease risk and their ability to reconstruct the observed age distribution of hospitalized infant dengue cases. We find that ADE mechanisms are best able to reconstruct the observed data. Finally, we describe how the shifting epidemiology of dengue in Thailand, combined with declining birth rates, have decreased the absolute risk of infant dengue disease by 88% over a 40-y period while having minimal impact on the mean age of infant hospitalized dengue disease.
... For preconception vaccination, the literature was taken from various populations. From SEA, a Malaysian study [106], a Singaporean study [107], and a Vietnamese study [108] were used. Articles [109][110][111] did not consider or stratify by country of origin. ...
... This occurs in secondary infections when antibody-antigen complexes do not neutralize viruses, but facilitate further adsorption into host leukocytes, precipitating higher viral loads [111]. Further research on Vietnamese infants showed that declining maternal IgG to critical levels can lead to ADE and that DHF was likely only to be present in infants if the mothers are seropositive [108]. Further preconception studies are needed to confirm the fetal impact. ...
Dengue cases have been rising in recent years. In 2019 alone, over 658,301 of the 5.6 million reported cases originated from Southeast Asia (SEA). Research has also shown detrimental outcomes for pregnant infected women. Despite this, existing literature describing dengue's effects on pregnancy in SEA is insufficient. Through this narrative review, we sought to describe dengue's effects on pregnancy systemically and emphasize the existing gaps in the literature. We extensively searched various journals cited in PubMed and Ovid Medline, national clinical practice guidelines, and governmental reports. Dengue in pregnancy increases the risk of pre-eclampsia, Dengue Hem-orrhagic Fever (DHF), fetal distress, preterm delivery, Caesarean delivery, and maternal mortality. Vertical transmission, intrauterine growth restriction, and stillbirth are possible sequelae of dengue in fetuses. We found that trimester-specific physiological impacts of dengue in pregnancy (to both mother and child) and investigations and management methods demanded further research, especially in the SEA region.
... As antibody levels decay further, the ability to enhance the severity of heterologous infections is thought to be lost, though infants remain at risk of DENV infection. Peaks in reported dengue hospitalisations among infants less than 1 year of age are consistently observed in DENV-endemic countries and are widely attributed to ADE (7,11,12). However, the specific concentrations of maternally-derived DENV antibodies that may place infants at increased risk of severe disease have not been well characterised. ...
... We find that constant exponential decay models are able to capture the dynamics of maternally-derived dengue antibodies ( Figure 2A-C and Figure S11) and our estimates of antibody half-life, ranging from a median of 29-47 days across cohorts and assays, are consistent with previous estimates. Previous studies investigating the persistence of maternally-derived dengue antibodies in Thai infants estimated a DENV antibody half-life of 41 days (22) serotype-specific antibody half-lives ranging from 33-53 days (23) while another study in Vietnamese infants estimated a half-life of 42 days (12). The use of parametric models that characterise antibody titer dynamics are especially useful in the context of assay limits of detection. ...
Dengue virus (DENV) immunity is complex. Maternally-derived DENV antibodies initially provide protection against infection, however, as antibodies decay they can enhance disease severity upon infection. Quantifying antibody titers that are associated with disease risk is complicated by their dynamic nature and imperfect measurement processes. It also remains unknown whether long-term trends in birth rates, population-level infection risks, and maternal ages have altered immune profiles in child-bearing women, leading to shifts in age-specific infant disease risks. Here, we analyse DENV antibody data from two infant cohorts (N=165 infants with 665 blood draws) and 40 years of infant dengue hospitalisation data from Thailand. We use mathematical models to reconstruct maternally-derived antibody dynamics and estimate hospitalisation risk by titer. We find the relative risk of dengue hospitalisation ranges from 0.13 (0.00-0.89) in 1 month olds to 3.52 (3.25-3.79) in 8 month olds, compared to the risk in 12 month olds. We estimate the highest risk of infant dengue hospitalisation occurs at PRNT50 titers of 6.0 (5.7-6.6). Our inferred titer-related risk estimates are consistent with previously identified titer-based correlates of severe disease among older individuals experiencing secondary DENV infections, suggesting a common mechanism of risk enhancement from pre-existing antibodies. Finally, we describe how the shifting epidemiology of dengue in Thailand, combined with declining birth rates, have decreased the absolute risk of infant dengue disease by 64% over a 40 year period while having minimal impact on the mean age of infant hospital-attended dengue disease.
... IgG antibodies against the specific DENV serotype could cross the placenta and enter into the blood to fetuses, resulting in a detrimental immune response against other serotypes after the birth. In fact, children with passive immunity from immunized mothers tend to present DHF during their first DENV infection (10,11). Similar to natural infection and passive-acquired immunity, vaccines against one specific serotype produce cross-reactive non-neutralizing antibodies against other serotypes, predisposing the enhanced illness in secondary heterotypic infection (12). ...
... The phenomenon, in which preexisting non-neutralizing antibodies lead to enhanced infection, is termed ADE. Beyond studies with patients suggesting this phenomenon in DENV infection, highlighting those described above with newborn infants and children (10,11,15), studies in vitro and with animal model also suggest ADE upon secondary DENV infections. Growth curves of DENV in vitro with peripheral blood leukocytes from non-immunized and immunized animals indicated that preexisting antibodies play a role in ADE (16). ...
SARS-CoV-2 pandemic and recurrent dengue epidemics in tropical countries have turned into a global health threat. While both virus-caused infections may only reveal light symptoms, they can also cause severe diseases. Here, we review the possible antibody-dependent enhancement (ADE) occurrence, known for dengue infections, when there is a second infection with a different virus strain. Consequently, preexisting antibodies do not neutralize infection, but enhance it, possibly by triggering Fcγ receptor-mediated virus uptake. No clinical data exist indicating such mechanism for SARS-CoV-2, but previous coronavirus infections or infection of SARS-CoV-2 convalescent with different SARS-CoV-2 strains could promote ADE, as experimentally shown for antibodies against the MERS-CoV or SARS-CoV spike S protein. © 2020 International Society for Advancement of Cytometry.
... Dengue virus infections are unusual in that non-neutralizing anti-dengue virus IgGs can play a central role in triggering progression to the severe forms of disease through antibodydependent enhancement (ADE) mechanisms (Anderson et al., 2014;Burke et al., 1988;Chau et al., 2009;Guzmá n et al., 1990;Halstead et al., 1970;Katzelnick et al., 2017;Libraty et al., 2009;Sangkawibha et al., 1984;Wang et al., 2017). ADE can occur in the presence of reactive, non-neutralizing IgGs, as are found in secondary heterologous dengue infections or in primary infections in infants of dengue-immune mothers due to acquisition of anti-dengue virus IgGs during gestation (Halstead et al., 1970;Kliks et al., 1988;Simmons et al., 2007). These antibodies are thought to promote disease by forming immune complexes with the virus that modulate infection in FcgRbearing cells, primarily monocytes and macrophages, leading to higher viral titers and altered cytokine production during infection (Aye et al., 2014;Durbin et al., 2008;Kou et al., 2008;Thein et al., 1997). ...
... Susceptibility to Clinically Significant Disease during Infant Dengue Infections Maternal IgG levels in the serum of newborns generally match or exceed those in maternal serum (1,012 mg/mL IgG), and the halflife of maternal IgGs in infants is >40 days (Watanaveeradej et al., 2003). Thus, when a mother is seropositive for dengue viruses, maternal anti-dengue IgGs have the potential to modulate infant dengue infections for over 1 year after birth (Alkan Ozdemir et al., 2016;Nicoara et al., 1999;Simmons et al., 2007;Thompson et al., 2016). ...
Infant mortality from dengue disease is a devastating global health burden that could be minimized with the ability to identify susceptibility for severe disease prior to infection. Although most primary infant dengue infections are asymptomatic, maternally derived anti-dengue immunoglobulin G (IgGs) present during infection can trigger progression to severe disease through antibody-dependent enhancement mechanisms. Importantly, specific characteristics of maternal IgGs that herald progression to severe infant dengue are unknown. Here, we define ≥10% afucosylation of maternal anti-dengue IgGs as a risk factor for susceptibility of infants to symptomatic dengue infections. Mechanistic experiments show that afucosylation of anti-dengue IgGs promotes FcγRIIIa signaling during infection, in turn enhancing dengue virus replication in FcγRIIIa⁺ monocytes. These studies identify a post-translational modification of anti-dengue IgGs that correlates with risk for symptomatic infant dengue infections and define a mechanism by which afucosylated antibodies and FcγRIIIa enhance dengue infections.
... This indicates exposure to mosquito-borne arboviruses early in life, reflecting maternal antibodies, exposure at very young age, or likely a combination of both. [37][38][39] Our study has several limitations that need to be addressed in the future. The study cohort was small, and larger enrollment numbers could have changed the seroprevalence data. ...
Diagnostics for febrile illnesses other than malaria are not readily available in rural sub-Saharan Africa. This study assessed exposure to three mosquito-borne arboviruses—dengue virus (DENV), Zika virus (ZIKV), and chikungunya virus (CHIKV)—in southern Mali. Seroprevalence for DENV, CHIKV, and ZIKV was analyzed by detection of IgG antibodies and determined to be 77.2%, 31.2%, and 25.8%, respectively. Among study participants, 11.3% were IgG-positive for all three arboviruses. DENV had the highest seroprevalence rate at all sites; the highest seroprevalence of CHIKV and ZIKV was observed in Bamba. The seroprevalence for all three arboviruses increased with age, and the highest seroprevalence was observed among adults older than 50 years. The prevalence of Plasmodium spp. in the cohort was analyzed by microscopy and determined to be 44.5% ( N = 600) with Plasmodium falciparum representing 95.1% of all infections. This study demonstrates the co-circulation of arboviruses in a region hyperendemic for malaria and highlights the needs for arbovirus diagnostics in rural sub-Saharan Africa.
... When performed in conventional cell types, such assays measure antibody blockade of virus attachment, or fusion, or both [9]. In the case of dengue, conventional assays provide an imperfect correlation between neutralizing antibody titre and protection [3,4,10]. This might not be surprising as DENVs preferentially replicate in cells of monocyte or macrophage lineage in vivo [11], and neutralization might be governed by different mechanisms in cells that display antibody Fc-γ receptors (FcγRs) than in those that do not. ...
Dengue fever is a major tropical infectious disease that affects 50–100 million people each year. Its complications, namely dengue haemorrhagic fever and dengue shock syndrome, disproportionately afflict children and young adults. The primary goal of several vaccines now in development is to elicit protective neutralizing antibody responses; however, the exact definition of such responses remain unclear. Here, we review briefly the historical aspects of dengue vaccine development and current candidate dengue vaccines, and discuss various laboratory assays for gauging the neutralizing antibody responses to infection or vaccination, or both. We conclude that modification of current neutralization assays is required to improve the correlation between neutralization end point determinations and protection against secondary heterotypic dengue infections.
... Further work is needed to determine whether the relative sensitivity of the Ifnar1 −/− model to low viral load is dependent on mouse genetics or ADE. However, this supports the notion that viral load is not the only determinant of disease severity (50,70). Rather, the virus-dependent immune response is key in causing gut damage. ...
Severe dengue virus (DENV) infection can cause hemorrhage and shock, with onset at a time when viremia is decreasing and fever has abated. The factors contributing to the sudden deterioration of patient condition are debated. Gastrointestinal symptoms including vomiting, diarrhea, and abdominal pain are prevalent in severe diseases. The reported correlation of serum lipopolysaccharide levels with disease severity suggests that the gut barrier is compromised. We examined gastrointestinal tract (GIT) pathology in dengue infection, employing AG129 and Ifnar1 −/− mice, as models of primary or antibody-dependent enhancement of infection, respectively. DENV replication peaked early in the spleen, with infected cells appearing later in the GIT, followed by kidney and liver. On day 4 of infection, histological examination showed that DENV-mediated inflammation and tissue damage were severe in the GIT, with non-GIT tissues showing only limited pathology. The inflammatory pathology was found in focal areas, first in the small intestine and later in the proximal and distal colon. The main features included infiltration by neutrophils and monocytes, edema, villus blunting, exfoliation of enterocytes, crypt abscesses, lymphocyte depletion within Peyer’s patches, and mucus discharge from goblet cells. Loss and thinning of the mucus layer resulted in aberrant contact of luminal bacteria with the gut epithelial cells. We hypothesize that DENV-induced gut inflammation compromises the integrity of the gut barrier, subsequently promoting severe dengue disease.
IMPORTANCE
Dengue virus, an arbovirus, causes an estimated 100 million symptomatic infections annually and is an increasing threat as the mosquito range expands with climate change. Dengue epidemics are a substantial strain on local economies and health infrastructure, and an understanding of what drives severe disease may enable treatments to help reduce hospitalizations. Factors exacerbating dengue disease are debated, but gut-related symptoms are much more frequent in severe than mild cases. Using mouse models of dengue infection, we have shown that inflammation and damage are earlier and more severe in the gut than in other tissues. Additionally, we observed impairment of the gut mucus layer and propose that breakdown of the barrier function exacerbates inflammation and promotes severe dengue disease. This idea is supported by recent data from human patients showing elevated bacteria-derived molecules in dengue patient serum. Therapies aiming to maintain gut integrity may help to abrogate severe dengue disease.
... In the case of dengue, it has also been reported that maternal antibodies can enhance disease severity in infants [3][4][5][6]. Consistent with this observation, transfer of dengue antibodies to dengue-infected monkeys can greatly increase viral load [7,8]. ...
Antibodies and humoral memory are key components of the adaptive immune system. We consider and computationally model mechanisms by which humoral memory present at baseline might increase rather than decrease infection load; we refer to this effect as EI-HM (enhancement of infection by humoral memory). We first consider antibody dependent enhancement (ADE) in which antibody enhances the growth of the pathogen, typically a virus, and typically at intermediate 'Goldilocks' levels of antibody. Our ADE model reproduces ADE in vitro and enhancement of infection in vivo from passive antibody transfer. But notably the simplest implementation of our ADE model never results in EI-HM. Adding complexity, by making the cross-reactive antibody much less neutralizing than the de novo generated antibody or by including a sufficiently strong non-antibody immune response, allows for ADE-mediated EI-HM. We next consider the possibility that cross-reactive memory causes EI-HM by crowding out a possibly superior de novo immune response. We show that, even without ADE, EI-HM can occur when the cross-reactive response is both less potent and 'directly' (i.e. independently of infection load) suppressive with regard to the de novo response. In this case adding a non-antibody immune response to our computational model greatly reduces or completely eliminates EI-HM, which suggests that 'crowding out' is unlikely to cause substantial EI-HM. Hence, our results provide examples in which simple models give qualitatively opposite results compared to models with plausible complexity. Our results may be helpful in interpreting and reconciling disparate experimental findings, especially from dengue, and for vaccination.
... In this regard, anti-DENV IgG can bind to the virus and enhance infection of monocytes/macrophages through its Fc receptor (opsonization) [107][108][109][110]. ADE can result in infection of a large number of cells, increasing the viral load [107]. It has also been reported that entry of the virus via the Fc receptor in the ADE mechanism can suppress antiviral genes and increase the production of anti-inflammatory cytokines such as IL-10 and IL-6 and suppress the production of IL-12, IFN-γ, TNF-β, and nitric oxide, promoting viral replication [111][112][113]. ...
Dengue is a disease caused by a flavivirus that is transmitted principally by the bite of an Aedes aegypti mosquito and represents a major public-health problem. Many studies have been carried out to identify soluble factors that are involved in the pathogenesis of this infection. Cytokines, soluble factors, and oxidative stress have been reported to be involved in the development of severe disease. Angiotensin II (Ang II) is a hormone with the ability to induce the production of cytokines and soluble factors related to the inflammatory processes and coagulation disorders observed in dengue. However, a direct involvement of Ang II in this disease has not been demonstrated. This review primarily summarizes the pathophysiology of dengue, the role of Ang II in various diseases, and reports that are highly suggestive of the involvement of this hormone in dengue.
... Antibodies against a certain dengue virus serotype might pass the placenta and enter the bloodstream of fetuses, causing a harmful immune response against other serotypes after birth [55]. Children with passive immunity from their mothers are more likely to develop dengue hemorrhagic fever during their initial dengue infection [58,59]. In addition, many participants failed to correctly identify the breeding locations for Aedes mosquitoes, resulting in an increased risk of severe DF, as reported by a previous study [6,60]. ...
Objectives: This study intends to evaluate Dhaka city slum dwellers’ responses to Dengue fever (DF).
Methods: 745 individuals participated in a KAP survey that was pre-tested. Face-to-face interviews were performed to obtain data. Python with RStudio was used for data management and analysis. The multiple regression models were applied when applicable.
Results: 50% of respondents were aware of the deadly effects of DF, its common symptoms, and its infectious nature. However, many were unaware that DF could be asymptomatic, a previously infected person could have DF again, and the virus could be passed to a fetus. Individuals agreed that their families, communities, and authorities should monitor and maintain their environment to prevent Aedes mosquito breeding. However, overall 60% of the study group had inadequate preventative measures. Many participants lacked necessary practices such as taking additional measures (cleaning and covering the water storage) and monitoring potential breeding places. Education and types of media for DF information were shown to promote DF prevention practices.
Conclusion: Slum dwellers lack awareness and preventative activities that put them at risk for DF. Authorities must improve dengue surveillance. The findings suggest efficient knowledge distribution, community stimulation, and ongoing monitoring of preventative efforts to reduce DF. A multidisciplinary approach is needed to alter dwellers’ behavior since DF control can be done by raising the population’s level of life. People and communities must perform competently to eliminate vector breeding sites.
... Additionally, decreased neutralising antibody concentrations due to waning immunity may also predispose to ADE. Decay in maternal anti-DENV antibody titres, estimated at <1:20 (determined by serial dilution of plasma via ELISA technique), was associated with increased likelihood of severe dengue during an infant's primary DENV infection [10]. In another paediatric cohort, high anti-DENV antibody levels, >1:320 titres, protected against symptomatic dengue, whereas individuals with anti-DENV antibody titres between 1:21 and 1:80 were more susceptible to severe dengue [2,3]. ...
... However, the potential effect of ZIKV immunity passively acquired by babies from their mothers in utero on subsequent flavivirus exposure is not known. It has been described that a DENV infection occurring in the latter half of the first year of life can be exacerbated by low levels of residual DENV-reactive maternal antibodies (Ab) in young children that no longer confer protection [20,21]. ...
Objective: To understand the dynamics of Zika virus (ZIKV)-specific antibody immunity in children born to mothers in a flavivirus-endemic region during and after the emergence of ZIKV in the Americas. Methods: We performed serologic testing for ZIKV cross-reactive and type-specific IgG in two longitudinal cohorts, which enrolled pregnant women and their children (PW1 and PW2) after the beginning of the ZIKV epidemic in Nicaragua. Quarterly samples from children over their first two years of life and maternal blood samples at birth and at the end of the two-year follow-up period were studied. Results: Most mothers in this dengue-endemic area were flavivirus-immune at enrollment. ZIKV-specific IgG (anti-ZIKV EDIII IgG) was detected in 82 of 102 (80.4%) mothers in cohort PW1 and 89 of 134 (66.4%) mothers in cohort PW2, consistent with extensive transmission observed in Nicaragua during 2016. ZIKV-reactive IgG decayed to undetectable levels by 6–9 months in infants, whereas these antibodies were maintained in mothers at the year two time point. Interestingly, a greater contribution to ZIKV immunity by IgG3 was observed in babies born soon after ZIKV transmission. Finally, 43 of 343 (13%) children exhibited persistent or increasing ZIKV-reactive IgG at ≥9 months, with 10 of 30 (33%) tested demonstrating serologic evidence of incident dengue infection. Conclusions: These data inform our understanding of protective and pathogenic immunity to potential flavivirus infections in early life in areas where multiple flaviviruses co-circulate, particularly considering the immune interactions between ZIKV and dengue and the future possibility of ZIKV vaccination in women of childbearing potential. This study also shows the benefits of cord blood sampling for serologic surveillance of infectious diseases in resource-limited settings.
... Breastfeeding is also a potential mode of DENV transmission [65]. Infants born with maternal anti-DENV antibodies who are subsequently infected with a different DENV serotype may experience a severe disease course, akin to secondary dengue in adult populations [66][67][68]. ...
Flaviviruses are a diverse group of enveloped RNA viruses that cause significant clinical manifestations in the pregnancy and postpartum periods. This review highlights the epidemiology, pathophysiology, clinical features, diagnosis, and prevention of the key arthropod-borne flaviviruses of concern in pregnancy and the neonatal period—Zika, Dengue, Japanese encephalitis, West Nile, and Yellow fever viruses. Increased disease severity during pregnancy, risk of congenital malformations, and manifestations of postnatal infection vary widely amongst this virus family and may be quite marked. Laboratory confirmation of infection is complex, especially due to the reliance on serology for which flavivirus cross-reactivity challenges diagnostic specificity. As such, a thorough clinical history including relevant geographic exposures and prior vaccinations is paramount for accurate diagnosis. Novel vaccines are eagerly anticipated to ameliorate the impact of these flaviviruses, particularly neuroinvasive disease manifestations and congenital infection, with consideration of vaccine safety in pregnant women and children pivotal. Moving forward, the geographical spread of flaviviruses, as for other zoonoses, will be heavily influenced by climate change due to the potential expansion of vector and reservoir host habitats. Ongoing ‘One Health’ engagement across the human-animal-environment interface is critical to detect and responding to emergent flavivirus epidemics.
... [129][130][131] Long-term cohort analysis and clinical evidence support that babies born to DENV-infected mothers were more likely to face DHF complications upon primary infections when maternally transferred antibody titres reached sub-neutralising levels. 132 unique set of HLA alleles that play an essential role in cellular response. ...
Dengue illness can range from mild illness to life‐threatening haemorrhage. It is an Aedes‐borne infectious disease caused by the dengue virus, which has four serotypes. Each serotype acts as an independent infectious agent. The antibodies against one serotype confer homotypic immunity but temporary protection against heterotypic infection. Dengue has become a growing health concern for up to one third of the world's population. Currently, there is no potent anti‐dengue medicine, and treatment for severe dengue relies on intravenous fluid management and pain medications. The burden of dengue dramatically increases despite advances in vector control measures. These factors underscore the need for a vaccine. Various dengue vaccine strategies have been demonstrated, that is, live attenuated vaccine, inactivated vaccine, DNA vaccine, subunit vaccine, and viral‐vector vaccines, some of which are at the stage of clinical testing. Unfortunately, the forefront candidate vaccine is less than satisfactory, and its performance depends on serostatus and age factors. The lessons from clinical studies depicted ambiguity concerning the efficacy of dengue vaccine. Our study highlighted that viral structural heterogeneity, epitope accessibility, autoimmune complications, genetic variants, genetic diversities, antigen competition, virulence variation, host‐pathogen specific interaction, antibody‐dependent enhancement, cross‐reactive immunity among Flaviviruses, and host‐susceptibility determinants not only influence infection outcomes but also hampered successful vaccine development. This review integrates dengue determinants allocated necessities and challenges, which would provide insight for universal dengue vaccine development.
... This response is due to a hyper-reactive immune reaction that destabilizes all organ systems [26]. Various studies indicate that children can acquire crossreactive antibodies through maternal passive immunity and thus develop complications from the first contact with DENV [27]. In this case, however, the patient and her mother did not report past dengue infections. ...
Mexico is an endemic region for dengue virus (DENV). The increase in this disease coincides with outbreaks of COVID-19, both of which are single-stranded positive RNA viruses. These characteristics make it difficult to distinguish each disease because they share clinical and laboratory features, which can consequently result in misdiagnoses. This is why the use of precision confirmatory tests (qRT-PCR) are crucial for early diagnosis. We herein report a pediatric patient who presented a coinfection for DENV and COVID-19, “SARS-CoV-2/Dengue”. This patient initially presented a fever, cough, and headache and, three days later, developed generalized pain and epistaxis. Blood studies revealed thrombocytopenia and leukopenia, and the patient was admitted to the hospital for a probable DENV infection. Within 48 h, qRT-PCR tests specific for SARS-CoV-2 and DENV were performed and resulted as positive. The patient immediately received pharmacological treatment with azithromycin, oseltamivir, and metamizole. During hospitalization (9 days), the patient had no signs of respiratory distress and maintained normal body temperature and normal blood oxygen saturation. This case warns of the need for early diagnosis and adequate clinical and pharmacological management in the face of a “SARS-CoV-2/Dengue” coinfection. Early molecular detection of both viruses and timely treatment helped the patient to achieve a favorable recovery.
... Although the pathogenesis of DENV infection in infants is poorly understood, the presence of maternally derived sub neutralizing levels of anti-DENV antibodies were postulated to be a critical risk factor for severe DENV disease outcomes in infants (91). A study conducted with 75 Vietnamese infants with primary DENV infection indicated that infants experienced dengue hemorrhagic fever when maternally derived neutralizing antibody titers have declined (92). Additionally, Ribeiro et al. reported DENV in fetal tissues of pregnant women diagnosed with DENV, when a spectrum of clinical presentations ranging from asymptomatic to dengue hemorrhagic fever and dengue shock syndrome was observed in the newborn. ...
Pregnancy significantly elevates the risk of developing severe viral diseases, which can have a detrimental effect on fetal development and increases maternal mortality. In addition, certain viruses can be transmitted vertically from mother to babies, either in utero, during delivery, or postnatally during breastfeeding, resulting in congenital or neonatal diseases and associated sequelae. While neonates are highly susceptible to viral infections and severe disease outcomes, due to the immaturity of their developing immune system, virus-specific maternal antibodies transferred either trans-placentally or via breast milk provide protection to infants against intestinal, respiratory, or systemic infections, during the first months of life. Thus, maternal prenatal immunization is important not only to protect pregnant women from viral diseases, but also to prevent infection and/or improve disease outcomes for the fetuses and neonates via passively transferred antibodies. In this review, we discuss the protective role of maternal antibodies against three categories of viruses: (i) viruses that cause severe maternal disease outcomes with mainly indirect consequences to the fetus (e.g. SARS-CoV-2, influenza, DENV, filovirus), (ii) those that are vertically transmitted from mother to their infants and cause congenital diseases (e.g. HIV, ZIKV and CMV), and (iii) those that cause elevated disease severity among neonates and infants postnatally (e.g. RSV, Rotavirus, Norovirus, HSV and HBV). Furthermore, we review relevant pre-clinical animal models that can be employed to develop novel immunization strategies against these viruses to enhance protection of pregnant women and their babies.
... The level of NS1 circulating in the bloodstream of DENV-1-infected patients is estimated to range from 0.01 to 50 µg/mL [25]. Detection of soluble NS1 by immunochromatographic assays has become standard for dengue diagnosis because it allows early diagnosis and more effective patient management due to their convenience [26][27][28][29][30][31]. ...
Four serotypes of dengue virus (DENV), type 1 to 4 (DENV-1 to DENV-4), exhibit approximately 25–40% of the difference in the encoded amino acid residues of viral proteins. Reverse transcription of RNA extracted from specimens followed by PCR amplification is the current standard method of DENV serotype determination. However, since this method is time-consuming, rapid detection systems are desirable. We established several mouse monoclonal antibodies directed against DENV non-structural protein 1 and integrated them into rapid DENV detection systems. We successfully developed serotype-specific immunochromatography systems for all four DENV serotypes. Each system can detect 104 copies/mL in 15 min using laboratory and clinical isolates of DENV. No cross-reaction between DENV serotypes was observed in these DENV isolates. We also confirmed that there was no cross-reaction with chikungunya, Japanese encephalitis, Sindbis, and Zika viruses. Evaluation of these systems using serum from DENV-infected individuals indicated a serotype specificity of almost 100%. These assay systems could accelerate both DENV infection diagnosis and epidemiologic studies in DENV-endemic areas.
... Recently reported findings that neonatal transferred antibodies may be short-lived 46 raise further concern not only for poor initial transfer efficacy, but also for shorter durability of vertically transmitted immunity. Given data that demonstrate increased neonatal risk in the setting of reduced transplacental transfer secondary to native dengue virus infection,[47][48][49] and maternal HIV (ie, reduced transfer of antibodies against tetanus, varicella-zoster virus, Epstein-Barr virus, measles, polio, and pertussis), 50-52 it is certainly possible that reduced transplacental transfer of anti-SARS-CoV-2 antibodies increases risk of SARS-CoV-2 infection for neonates and infants. Recent data from the CDC indicate that infants aged 0 to 2 months comprise nearly 20% of all hospitalizations for SARS-CoV-2 infection among children aged 0 to 18 years. ...
Importance
Biological data are lacking with respect to risk of vertical transmission and mechanisms of fetoplacental protection in maternal severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection.
Objective
To quantify SARS-CoV-2 viral load in maternal and neonatal biofluids, transplacental passage of anti–SARS-CoV-2 antibody, and incidence of fetoplacental infection.
Design, Setting, and Participants
This cohort study was conducted among pregnant women presenting for care at 3 tertiary care centers in Boston, Massachusetts. Women with reverse transcription–polymerase chain reaction (RT-PCR) results positive for SARS-CoV-2 were recruited from April 2 to June 13, 2020, and follow-up occurred through July 10, 2020. Contemporaneous participants without SARS-CoV-2 infection were enrolled as a convenience sample from pregnant women with RT-PCR results negative for SARS-CoV-2.
Exposures
SARS-CoV-2 infection in pregnancy, defined by nasopharyngeal swab RT-PCR.
Main Outcomes and Measures
The main outcomes were SARS-CoV-2 viral load in maternal plasma or respiratory fluids and umbilical cord plasma, quantification of anti–SARS-CoV-2 antibodies in maternal and cord plasma, and presence of SARS-CoV-2 RNA in the placenta.
Results
Among 127 pregnant women enrolled, 64 with RT-PCR results positive for SARS-CoV-2 (mean [SD] age, 31.6 [5.6] years) and 63 with RT-PCR results negative for SARS-CoV-2 (mean [SD] age, 33.9 [5.4] years) provided samples for analysis. Of women with SARS-CoV-2 infection, 23 (36%) were asymptomatic, 22 (34%) had mild disease, 7 (11%) had moderate disease, 10 (16%) had severe disease, and 2 (3%) had critical disease. In viral load analyses among 107 women, there was no detectable viremia in maternal or cord blood and no evidence of vertical transmission. Among 77 neonates tested in whom SARS-CoV-2 antibodies were quantified in cord blood, 1 had detectable immunoglobuilin M to nucleocapsid. Among 88 placentas tested, SARS-CoV-2 RNA was not detected in any. In antibody analyses among 37 women with SARS-CoV-2 infection, anti–receptor binding domain immunoglobin G was detected in 24 women (65%) and anti-nucleocapsid was detected in 26 women (70%). Mother-to-neonate transfer of anti–SARS-CoV-2 antibodies was significantly lower than transfer of anti-influenza hemagglutinin A antibodies (mean [SD] cord-to-maternal ratio: anti–receptor binding domain immunoglobin G, 0.72 [0.57]; anti-nucleocapsid, 0.74 [0.44]; anti-influenza, 1.44 [0.80]; P < .001). Nonoverlapping placental expression of SARS-CoV-2 receptors angiotensin-converting enzyme 2 and transmembrane serine protease 2 was noted.
Conclusions and Relevance
In this cohort study, there was no evidence of placental infection or definitive vertical transmission of SARS-CoV-2. Transplacental transfer of anti-SARS-CoV-2 antibodies was inefficient. Lack of viremia and reduced coexpression and colocalization of placental angiotensin-converting enzyme 2 and transmembrane serine protease 2 may serve as protective mechanisms against vertical transmission.
... may pose greater risk. 6,7 So far, the pathogenic and immune mechanisms of DHF/DSS have not been fully elucidated, although the antibody-dependent enhancement (ADE) of DENV has been identified as a crucial factor. [8][9][10] The difficulties in balancing immunity to the four serotypes and the risk of ADE are major hurdles in the development of an effective vaccine against DENV infection. ...
Introduction
The antibody‐dependent enhancement (ADE) of Dengue virus (DENV) has critically restricted vaccine development. Prior research suggested pr4 as the probable ADE epitope of DENV.
Methods
Chimeric dengue virus was constructed by replacing the DENV pr4 gene with Japanese encephalitis virus (JEV) corresponding gene to verify whether it can reduce ADE activities. Alanine scanning method and bioinformatics analysis were utilized to identify the amino acid of pr4 that was crucial as an ADE epitope.
Results
chimeric virus had reduced ADE and virulence, the amino acids at the following locations on the mutant peptides showed significantly reduced binding ability to prM antibody: pr4.5 (position 5 – leucine), pr4.6 (position 6 – leucine), pr4.7 (position 7 – phenyalanine) and pr4.16 (position 16 – cysteine), the 4 amino acids had formed a pocket‐like structure, which could increase the possibility to bind to antibody.
Conclusion
The ADE activities could be reduced by replacing the DENV pr4 gene with JEV corresponding gene. Leucine at the fifth position, leucine at the sixth position, phenyalanine at the seventh position, and cysteine at the sixteenth position were the key amino acid sites in the ADE response of DENV. The occurrence of ADE can potentially be reduced by the replacements of key amino acids, hence highlighting its possible contribution to dengue vaccine design, therefore paving a way for other vaccine research.
... Sekonder enfeksiyon geliştiğinde primer enfeksiyona göre daha ağır klinik tablo gözlenmektedir (110) . Bununla birlikte, küçük bebeklerde primer enfeksiyon da ciddi hastalık sonuçlarıyla ilişkili olabilir (111) . ...
... In vivo, iADE requires an initial immunological event, termed "sensitization." In dengue, this occurs in three settings: 1) first infections, [14] 2) multitypic dengue antibodies passively transferred to infants (high antibody levels protect, low levels enhance), [15] and 3) vaccination resulting in incomplete protective immunity. [16,17] Crucial to the occurrence of iADE is the circulation of four antigenically related DENVs. ...
Might COVID 19 vaccines sensitize humans to antibody dependent enhanced (ADE) breakthrough infections? This outcome is unlikely because coronavirus diseases in humans lack the clinical, epidemiological, biological or pathological attributes of ADE disease exemplified by the dengue viruses (DENV). In contrast to DENV, SARS and MERS CoVs predominantly infect respiratory epithelium, not macrophages. Severe disease centers on older persons with pre-existing conditions and not young infants or individuals with previous coronavirus infections. Live virus challenge of animals given SARS or MERS vaccines has resulted in vaccine hypersensitivity reactions (VAH), similar to those in humans given inactivated measles or respiratory syncytial virus vaccines. Safe and effective COVID 19 vaccines must avoid VAH.
... Warning signs appear late in DENV disease, usually around day 5 post-fever onset, making it extremely difficult to predict DHF/DSS or Severe dengue in the early acute/febrile phase of disease. Other factors, such as high viremia and high levels of viral secretory protein NS1 have been suggested to be associated with DHF/DSS, but with conflicting reports [23][24][25][26][27][28][29][30][31][32] . ...
Dengue induces a spectrum of severity in humans from the milder dengue fever to severe disease, or dengue hemorrhagic fever (DHF). Chymase is a candidate biomarker that may aid dengue prognosis. This prospective study aimed to identify whether warning signs of severe dengue, including hypovolemia and fluid accumulation, were associated with elevated chymase. Serum chymase levels were quantified prospectively and longitudinally in hospitalized pediatric dengue patients in Sri Lanka. Warning signs were determined based on daily clinical assessments, laboratory tests and ultrasound findings. Chymase was significantly elevated during the acute phase of disease in DHF or Severe dengue, defined by either the 1997 or 2009 WHO diagnosis guidelines, and persisted longer in the most severe patients. Chymase levels were higher in patients with narrow pulse pressure and clinical warning signs such as severe leakage, fluid accumulation, pleural effusion, gall-bladder wall thickening and rapid haematocrit rise concurrent with thrombocytopenia. No association between chymase and liver enlargement was observed. This study confirms that serum chymase levels are associated with DHF/Severe dengue disease in hospitalized pediatric patients. Chymase levels correlate with warning signs of vascular dysfunction highlighting the possible functional role of chymase in vascular leakage during dengue.
... Although haemorrhagic manifestations occur (for example, epistaxis, gastrointestinal tract bleeding and menorrhagia), fluid loss into tissue spaces and the resulting hypotension carries the greatest risk of mortality 141 . Whereas severe dengue occurs principally after secondary infection in children and adults 142 , in infants under the age of one born to dengue-immune mothers, a primary DENV infection can cause substantial morbidity and mortality 143 . Maternal anti-dengue antibody titers and the age of the infant correlated with disease. ...
Flaviviruses are vector-borne RNA viruses that can emerge unexpectedly in human populations and cause a spectrum of potentially severe diseases including hepatitis, vascular shock syndrome, encephalitis, acute flaccid paralysis, congenital abnormalities and fetal death. This epidemiological pattern has occurred numerous times during the last 70 years, including epidemics of dengue virus and West Nile virus, and the most recent explosive epidemic of Zika virus in the Americas. Flaviviruses are now globally distributed and infect up to 400 million people annually. Of significant concern, outbreaks of other less well-characterized flaviviruses have been reported in humans and animals in different regions of the world. The potential for these viruses to sustain epidemic transmission among humans is poorly understood. In this Review, we discuss the basic biology of flaviviruses, their infectious cycles, the diseases they cause and underlying host immune responses to infection. We describe flaviviruses that represent an established ongoing threat to global health and those that have recently emerged in new populations to cause significant disease. We also provide examples of lesser-known flaviviruses that circulate in restricted areas of the world but have the potential to emerge more broadly in human populations. Finally, we discuss how an understanding of the epidemiology, biology, structure and immunity of flaviviruses can inform the rapid development of countermeasures to treat or prevent human infections as they emerge.
Background
Viremia is a critical factor in understanding the pathogenesis of dengue infection, but limited data exist on viremia kinetics. This study aimed to investigate the kinetics of viremia and its effects on subsequent platelet count, severe dengue, and plasma leakage.
Methods
We pooled data from three studies conducted in Vietnam between 2000 and 2016, involving 2340 dengue patients with daily viremia measurements and platelet counts after symptom onset. Viremia kinetics were assessed using a random effects model that accounted for left-censored data. The effects of viremia on subsequent platelet count and clinical outcomes were examined using a landmark approach with a random effects model and logistic regression model with generalized estimating equations, respectively. The rate of viremia decline was derived from the model of viremia kinetics. Its effect on the clinical outcomes was assessed by logistic regression models.
Results
Viremia levels rapidly decreased following symptom onset, with variations observed depending on the infecting serotype. DENV-1 exhibited the highest mean viremia levels during the first 5–6 days, while DENV-4 demonstrated the shortest clearance time. Higher viremia levels were associated with decreased subsequent platelet counts from day 6 onwards. Elevated viremia levels on each illness day increased the risk of developing severe dengue and plasma leakage. However, the effect size decreased with later illness days. A more rapid decline in viremia is associated with a reduced risk of the clinical outcomes.
Conclusions
This study provides comprehensive insights into viremia kinetics and its effect on subsequent platelet count and clinical outcomes in dengue patients. Our findings underscore the importance of measuring viremia levels during the early febrile phase for dengue studies and support the use of viremia kinetics as outcome for phase-2 dengue therapeutic trials.
Funding
Wellcome Trust and European Union Seventh Framework Programme.
Background
Viremia is a critical factor in understanding the pathogenesis of dengue infection, but limited data exist on viremia kinetics. This study aimed to investigate the kinetics of viremia and its effects on subsequent platelet count, severe dengue, and plasma leakage.
Methods
We pooled data from three studies conducted in Vietnam between 2000 and 2016, involving 2340 dengue patients with daily viremia measurements and platelet counts after symptom onset. Viremia kinetics were assessed using a random effects model that accounted for left-censored data. The effects of viremia on subsequent platelet count and clinical outcomes were examined using a landmark approach with a random effects model and logistic regression model with generalized estimating equations, respectively. The rate of viremia decline was derived from the model of viremia kinetics. Its effect on the clinical outcomes was assessed by logistic regression models.
Results
Viremia levels rapidly decreased following symptom onset, with variations observed depending on the infecting serotype. DENV-1 exhibited the highest mean viremia levels during the first 5–6 days, while DENV-4 demonstrated the shortest clearance time. Higher viremia levels were associated with decreased subsequent platelet counts from day 6 onwards. Elevated viremia levels on each illness day increased the risk of developing severe dengue and plasma leakage. However, the effect size decreased with later illness days. A more rapid decline in viremia is associated with a reduced risk of the clinical outcomes.
Conclusions
This study provides comprehensive insights into viremia kinetics and its effect on subsequent platelet count and clinical outcomes in dengue patients. Our findings underscore the importance of measuring viremia levels during the early febrile phase for dengue studies and support the use of viremia kinetics as outcome for phase-2 dengue therapeutic trials.
Funding
Wellcome Trust and European Union Seventh Framework Programme.
Vertical transmission of the dengue virus is rare and infrequently reported in the literature. We report the case of a term newborn presented with high-grade fever, generalised petechial rash and hepatomegaly at the age of 5 days, with a history of dengue fever in the mother at 3 days before delivery. The diagnosis was nearly missed because the infant’s dengue NS1 antigen test was initially negative and subsequently positive. After the convalescent phase, the infant developed a new-onset fever with lethargy and drowsiness. Dengue encephalitis was diagnosed with support from a positive dengue reverse-transcriptase PCR in the cerebrospinal fluid. This report has shown the importance of clinical awareness. Early recognition of congenital dengue and vigilant monitoring will contribute to appropriate early management and decrease neonatal morbidity and mortality.
Dengue is an infectious disease caused by dengue virus (DENV) and is a serious global burden. Antibody-dependent enhancement and the ability of DENV to infect immune cells, along with other factors, lead to fatal Dengue Haemorrhagic Fever and Dengue Shock Syndrome. This necessitates the development of a robust and efficient vaccine but vaccine development faces a number of hurdles. In this review, we look at the epidemiology, genome structure and cellular targets of DENV and elaborate upon the immune responses generated by human immune system against DENV infection. The review further sheds light on various challenges in development of a potent vaccine against DENV which is followed by presenting a current account of different vaccines which are being developed or have been licensed.
Dengue virus (DENV) is responsible for approximately 100 million cases of dengue fever annually, including severe forms such as hemorrhagic dengue and dengue shock syndrome. Despite intensive vaccine research and development spanning several decades, a universally accepted and approved vaccine against dengue fever has not yet been developed. The major challenge associated with the development of such a vaccine is that it should induce simultaneous and equal protection against the four DENV serotypes, because past infection with one serotype may greatly increase the severity of secondary infection with a distinct serotype, a phenomenon known as antibody-dependent enhancement (ADE). Using a lentiviral vector platform that is particularly suitable for the induction of cellular immune responses, we designed a tetravalent T-cell vaccine candidate against DENV (“LV-DEN”). This vaccine candidate has a strong CD8⁺ T-cell immunogenicity against the targeted non-structural DENV proteins, without inducing antibody response against surface antigens. Evaluation of its protective potential in the preclinical flavivirus infection model, i.e., mice knockout for the receptor to the type I IFN, demonstrated its significant protective effect against four distinct DENV serotypes, based on reduced weight loss, viremia, and viral loads in peripheral organs of the challenged mice. These results provide proof of concept for the use of lentiviral vectors for the development of efficient polyvalent T-cell vaccine candidates against all DENV serotypes.
The quest for an effective dengue vaccine has culminated in two approved vaccines and another that has completed phase 3 clinical trials. However, shortcomings exist in each, suggesting that the knowledge on dengue immunity used to develop these vaccines was incomplete. Vaccine trial findings could refine our understanding of dengue immunity, because these are experimentally derived, placebo-controlled data. Results from these trials suggest that neutralizing antibody titers alone are insufficient to inform protection against symptomatic infection, implicating a role for cellular immunity in protection. These findings have relevance for both future dengue vaccine development and application of current vaccines for maximal public health benefit.
El dengue es una enfermedad viral, que se transmite a través de la picadura de un mosquito perteneciente al género Aedes, principalmente el Aedes aegypti, vector de la enfermedad. Este mosquito es de transmisión predominantemente doméstica. El virus del dengue pertenece a la familia Flaviviridae y existen cuatro variantes, los serotipos 1, 2, 3 y 4. La inmunidad es serotipo-específica por lo que la infección con un serotipo determinado confiere inmunidad permanente contra el mismo (inmunidad homóloga), y sólo por unos meses contra el resto de los serotipos (inmunidad heteróloga). En teoría, una persona podría padecer dengue hasta cuatro veces a lo largo de su vida (una por cada serotipo), hasta el momento solo se han comprobado hasta tres infecciones en un mismo individuo. Cualquier serotipo puede producir formas graves de la enfermedad, aunque los serotipos 2 y 3 han sido asociados a la mayor cantidad de casos graves y fallecidos.
El dengue es un problema creciente para la Salud Pública Mundial, debido a varios factores: cambio climático, aumento de la población mundial en áreas urbanas y de forma desorganizada, insuficiente provisión de agua potable que obliga a su almacenamiento en recipientes caseros habitualmente descubiertos, la inadecuada recolección de residuos y la gran producción de recipientes descartables que sirven como criaderos de mosquitos al igual que los neumáticos desechados. A esto se suman el aumento de viajes y migraciones, fallas en el control de los vectores y la falta de una vacuna eficaz para prevenir la enfermedad.
Background:
Antibody dependent enhancement (ADE) is a unique immunopathological phenomenon in which pre-existing immunity to a viral agent accentuate disease severity upon secondary exposure. Multiple viruses have been shown to demsotrate ADE with no clear understanding of the underlying mechansims. Recently, with the emeregence of Sever acute respiratory syndrome-2 (SARS-CoV2) and the need for rapid vaccine prodcution, ADE have emerged as an important issue that need to be assessed.
Objective:
The aim of this study was to review ADE, proposed mechanisms and impact of ADE in the era of rapid SARS-CoV2 vaccine production.
Methods:
Review of existing published literature on ADE and SARS-CoV2 and identify facts that support or otherwise contradict the impact of ADE on SARS-CoV2 vaccination.
Results:
SARS-CoV2 demonstrate high genetic homology to other members of the Coronaviridae viral family and animal studies and studies on SARS-CoV, another member of the Coronaviridae have been shown to induce ADE. In addition sever SARS-CoV2 infection have been associated with high antibody titer. Yet vaccine efficacy studies and studies on breakthrough infection showed reduced severity in individual with preexisting immunity.
Conclusion:
Although evidence exist to support ADE in SARS-CoV2, multiple studies do not support its occurrence, indicating the need for more case control studies to understand the role of high antibody titer and disease severity and compare disease severity in patient with preexisting immunity vs naïve individuals.
Dengue is a mosquito-borne arboviral infection of increasing public health importance. Globally, children account for a significant proportion of infections. No pathogen-specific treatment currently exists, and the current approach to reducing disease burden is focused on preventative strategies such as vector control, epidemiological interventions, and vaccination in selected populations. Once infected, the mainstay of treatment is supportive, of which appropriate fluid management is a cornerstone. The timely provision of fluid boluses has historically been central to the management of septic shock. However, in patients with dengue shock, particular emphasis is placed on judicious fluid administration. Certain colloids such as hydroxyethyl starches and dextran, despite no longer being used routinely in intensive care units due to concerns of acute kidney injury and impairment of coagulation, are still commonly used in dengue shock syndrome. Current guidelines recommend initial crystalloid therapy, with consideration of colloids for severe or recalcitrant shock in patients with dengue. In this review, we discuss the pathophysiology of septic shock, and consider whether any differences in dengue exist that may warrant a separate approach to fluid therapy. We critically review the available evidence for fluid management in dengue, including the role of colloids. In dengue, there is increasing recognition of the importance of tailoring fluid therapy to phases of disease, with attention to the need for fluid "deresuscitation" once the critical phase of vascular leak passes.
As the causative agent of coronavirus disease 2019 (COVID-19), severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is one of the seven coronaviruses pathogenic to human and one of the four human coronaviruses that cause acute respiratory disease syndrome. Although it affects people of all age groups, the risk of mortality is age-dependent. As in many other diseases, elderly patients have a higher risk of infection, mortality, and morbidity [1]. While it is a common belief that children fare better than adult and elderly, recent evidence merged that neonates and infants are associated with a higher risk of mortality and morbidity, compared to children and adolescents [2, 3]. For instance, a cross-country study found that the infection–fatality ratio of those aged < 5 years was found to be 0.003, higher than those aged between 5 and 14 years of 0.001 despite lower than those aged between 20 and 59 that vary between 0.006 and 0.323 [4]. However, whether this holds true in the risk of infection is not yet verified. Against this background, the present work aimed to verify whether neonates are more susceptible to COVID-19 using publicly available data of all polymerase chain reaction (PCR) tests performed in the state of São Paulo of Brazil.
Introduction:
Dengue virus (DENV) is the causative agent of the most prevalent human disease transmitted by mosquitoes in tropical and subtropical regions worldwide. At present, no antiviral drug is available and the difficulties to develop highly protective vaccines against the four DENV serotypes maintain the requirement of effective options for dengue chemotherapy.
Areas covered:
The availability of animal models that reproduce human disease is a very valuable tool for the preclinical evaluation of potential antivirals. Here, the main murine models of dengue infection are described, including immunocompetent wild-type mice, immunocompromised mice deficient in diverse components of the interferon (IFN) pathway and humanized mice. The main findings in antiviral testing of DENV inhibitory compounds in murine models are also presented.
Expert opinion:
At present, there is no murine model that fully recapitulates human disease. However, immunocompromised mice deficient in IFN-α/β and -γ receptors, with their limitations, have shown to be the most suitable system for antiviral preclinical testing. In fact, the AG129 mouse model allowed the identification of celgosivir, an inhibitor of cellular glucosidases, as a promising option for DENV therapy. However, clinical trials still were not successful, emphasizing the difficulties in the transition from preclinical testing to human treatment.
Background: Dengue is the most prevalent and rapidly spreading mosquito-borne viral disease. We present the global, regional, and national burden of dengue from 1990 to 2019 based on the findings from the Global Burden of Diseases, Injures, and Risk Factors Study 2019 (GBD 2019).
Methods: Based upon GBD 2019 dengue data on age-standardized incidence rate (ASIR), age-standardized death rate (ASDR) and age-standardized disability-adjusted life years (DALYs) rate, this study estimates and presents annual percentage change (EAPC) to quantify trends over time to assess potential correlates of increased dengue activity such as global travel, and warming.
Results: Globally from 1990 to 2019, dengue incident cases, deaths and DALYs gradually increased. Those under 5, once accounting for the largest portion of deaths and DALYs in 1990, were eclipsed by those 15–49 years old in 2019. Age standardized incidence (ASIR: EAPC 3.16, 95%CI: 2.90–3.43), death (ASDR: EAPC 5.42, 95%CI: 2.64–8.28), and DALY rates (EAPC 2.31, 95%CI: 2.00–2.62) accelerated most among high-middle and high socio-demographic index (SDI) regions. Southeast Asia and South Asia had most of the dengue incident cases, deaths and DALYs, but East Asia had the fastest rise in ASIR (EAPC 4.57, 95%CI: 4.31, 4.82), while Tropical Latin America led in ASDR (EAPC 11.32, 95%CI: 9.11, 13.58) and age-standardized DALYs rate (EAPC 4.13, 95%CI: 2.98, 5.29). SDI showed consistent bell shape relationship with ASIR, ASDR and age-standardized DALYs rate. Global Land-Ocean Temperature Index and air passenger travel metrics were found to be remarkably positively correlated with dengue burden.
Conclusions: The burden of dengue has become heavier from 1990 to 2019, amidst the three decades of urbanization, warming climates and increased human mobility in much of the world. Southeast Asia and South Asia remain regions of concern, especially in conjunction with the Americas swift rise in dengue burden.
There is still knowledge gap about the antibody response in COVID-19 patients. Factors affecting the kinetics/titers of the elicited neutralizing antibodies (NAbs), the mean persistence time of NAbs after infection, risk of reinfection, and enhanced respiratory disease via antibody-dependent enhancement (ADE) are the main issues needing to be clarified. Recently published studies have suggested an association between increased antibody titers and COVID-19 infection severity. Although there exist insufficient data, the titers of antibodies have been reported to be decreasing rapidly, suggesting a risk of reinfection. If reinfection occurs, another concern is whether it will be more severe due to the preexisting low level antibodies. To combat the continuing pandemic, antibody-based treatments, such as monoclonal antibodies (mAbs), convalescent plasma (CP) therapies, and vaccine studies, have been investigated. Although it may not be as troublesome as in the Dengue fever, clinicians should be alert about the possible risk of ADE. Non-neutralizing antibodies or sub-protective levels of NAbs may trigger immunopathogenic events via immune complex-mediated or Fc receptor-dependent endocytosis, resulting in enhanced viral infection. In this chapter, literature findings revealing the factors with an impact on eliciting NAbs, possible mechanisms and risks of ADE, and safety concerns for SARS-CoV-2 treatment interventions are outlined.
Dengue remains a major problem in the tropics. Several Asian countries have reported an increasing trend in the proportion of infants with dengue fever. However, most studies are limited to case reports or small case series from isolated outbreaks. We planned this study to look at clinico-laboratory profile, outcome, and predictors of severity in a large cohort of infants over a decade. Electronic medical records of infants admitted at a tertiary center of South India, with laboratory confirmed dengue infection between 2009 and 2019 were reviewed. Diagnosis was based on detection of NS-1 antigen and/or immunoglobulin M antibody against DENV(dengue virus) or positive DENV RNA polymerase chain reaction in infants presenting with acute febrile illness and clinical features consistent with dengue. Of 395 children with dengue admitted during study period, 99 (25%) were infants. A cyclical incidence pattern was noted, with higher cases in alternate years. Fever (99%) was most common, followed by gastrointestinal symptoms (vomiting, diarrhea—28%) and upper respiratory symptoms (cough, coryza—22%). Fifty-three infants had severe dengue, and 39 had shock. Fourteen children had multiorgan dysfunction syndrome, and 13 died. Infants with severe dengue were older than those with nonsevere disease, had lower serum albumin and greater frequency of severe thrombocytopenia, and had coagulopathy. On multivariable analysis, low serum albumin predicted development of severe dengue [ P = 0.003, odds ratio 12.4 (95% confidence interval: 2.42–63.7)]. Dengue in infants may be challenging to recognize because of its undifferentiated presentation, with gastrointestinal and upper respiratory symptoms that are similar to other viral illness. Severe dengue is common in this sample, and lower serum albumin at presentation was predictive of severe disease.
Sequential infections with different dengue serotypes (DENV-1, 4) significantly increase the risk of a severe disease outcome (fever, shock, and hemorrhagic disorders). Two hypotheses have been proposed to explain the severity of the disease: (1) antibody-dependent enhancement (ADE) and (2) original T cell antigenic sin. In this work, we explored the first hypothesis through mathematical modeling. The proposed model reproduces the dynamic of susceptible and infected target cells and dengue virus in scenarios of infection-neutralizing and infection-enhancing antibody competition induced by two distinct serotypes of the dengue virus during secondary infection. The enhancement and neutralization functions are derived from basic concepts of chemical reactions and used to mimic binding to the virus by two distinct populations of antibodies. The analytic study of the model showed the existence of two equilibriums: a disease-free equilibrium and an endemic one. Using the concept of the basic reproduction number \({\mathcal {R}}_0\), we performed the asymptotic stability analysis for the two equilibriums. To measure the severity of the disease, we considered the maximum value of infected cells as well as the time when this maximum is reached. We observed that it corresponds to the time when the maximum enhancing activity for the infection occurs. This critical time was calculated from the model to be a few days after the occurrence of the infection, which corresponds to what is observed in the literature. Finally, using as output \({\mathcal {R}}_0\), we were able to rank the contribution of each parameter of the model. In particular, we highlighted that the cross-reactive antibody responses may be responsible for the disease enhancement during secondary heterologous dengue infection.
Flaviviruses are a group of positive-sense RNA viruses that are primarily transmitted through arthropod vectors and are capable of causing a broad spectrum of diseases. Many of the flaviviruses that are pathogenic in humans are transmitted specifically through mosquito vectors. Over the past century, many mosquito-borne flavivirus infections have emerged and re-emerged, and are of global importance with hundreds of millions of infections occurring yearly. There is a need for novel, effective, and accessible vaccines and antivirals capable of inhibiting flavivirus infection and ameliorating disease. The development of therapeutics targeting viral entry has long been a goal of antiviral research, but most efforts are hindered by the lack of broad-spectrum potency or toxicities associated with on-target effects, since many host proteins necessary for viral entry are also essential for host cell biology. Mosquito-borne flaviviruses generally enter cells by clathrin-mediated endocytosis (CME), and recent studies suggest that a subset of these viruses can be internalized through a specialized form of CME that has additional dependencies distinct from canonical CME pathways, and antivirals targeting this pathway have been discovered. In this review, we discuss the role and contribution of endocytosis to mosquito-borne flavivirus entry as well as consider past and future efforts to target endocytosis for therapeutic interventions.
Background
One of the generally accepted constructs of dengue pathogenesis is that clinical disease severity is at least partially dependent upon plasma viremia, yet data on plasma viremia in primary versus secondary infections and in relation to clinically relevant endpoints remain limited and contradictory.
Methods
Using a large database comprising detailed clinical and laboratory characterization of Vietnamese participants enrolled in a series of research studies executed over a 15-year period, we explored relationships between plasma viremia measured by RT-PCR and three clinically relevant endpoints – severe dengue, plasma leakage, and hospitalization – in the dengue-confirmed cases. All four dengue serotypes and both primary and secondary infections were well represented. In our logistic regression models we allowed for a non-linear effect of viremia, and for associations between viremia and outcome to differ by age, serotype, host immune status, and illness day at study enrolment.
Results
Among 5642 dengue-confirmed cases we identified 259 (4.6%) severe dengue cases, 701 (12.4%) patients with plasma leakage, and 1441/4008 (40.0%) patients recruited in outpatient settings who were subsequently hospitalized. From the early febrile phase onwards, higher viremia increased the risk of developing all three endpoints but effect sizes were modest (ORs ranging from 1.12-1.27 per 1-log increase) compared to the effects of a secondary immune response (ORs 1.67-7.76). The associations were consistent across age, serotype and immune status groups, and in the various sensitivity and subgroup analyses we undertook.
Conclusions
Higher plasma viremia is associated with increased dengue severity, regardless of serotype or immune status.
Severe disease is associated with serial infection with DENV of different
serotypes. Thus, primary DENV infections normally cause asymptomatic infections,
and secondary heterotypic infections with a new DENV serotype potentially
increase the risks of developing severe disease. Despite many proposed hypotheses
trying to explain it, the exact immunological mechanism leading to severe dengue
disease is unknown. In turn, severe manifestations are believed to be a consequence
of the combinations of many immunopathogenic mechanisms involving viral
and host factors leading to increased pathogenesis and disease. Of these mechanisms,
the adaptive immune response has been proposed to play a critical role
in the development of severe dengue manifestations. This includes the effect of
non-neutralizing but enhancing antibodies produced during primary infections,
which results in enhanced-DENV infection of Fc-γ-receptor-expressing cells (e.g.
monocytes and macrophages) during DENV heterotypic exposure in a phenomenon
called antibody-dependent enhancement (ADE); the increased activation of memory
T cells during secondary infections, which has low affinity for the current infecting
serotype and high affinity for a past infection with a different serotype known as
the original antigenic sin; the unbalanced production of pro-inflammatory cytokines
that have a direct effect on vascular endothelial cells resulting in plasma leak in a
phenomenon known as cytokine storm; and the excessive activation of the complement
system that causes exacerbated inflammatory responses, increasing disease
severity. In addition to the adaptive immune responses, a secreted viral factor known
as the nonstructural protein 1 (NS1) has been recently proposed as the missing corner
piece of the DENV pathogenesis influencing disease. This Part II of the chapter
will discuss the interplay between the distinct host adaptive immune responses and
viral factors that together contribute to the development of DENV pathogenesis and
severe disease.
Pre-existing immunity to dengue virus (DENV) can either protect against or exacerbate, a phenomenon known as antibody dependent enhancement (ADE), a secondary DENV infection. DENV, as an escalating health problem worldwide, has increased the urgency to understand the precise parameters shaping the anti-DENV antibody (Ab) and T cell responses, thereby tipping the balance towards protection versus pathogenesis. Herein, we present the current state of knowledge of about the interplay between the Ab and T cell responses that dictate the outcome of DENV infection and discuss how this newfound knowledge is reshaping strategies for developing safe and effective DENV vaccines.
Background
Dengue is an arboviral disease caused by dengue virus. Symptomatic dengue infection causes a wide range of clinical manifestations, from mild dengue fever(DF) to potentially fatal disease, such as dengue hemorrhagic fever(DHF) or dengue shock syndrome(DSS). We conducted a literature review to analyze the risks of DHF and current perspectives for DHF prevention and control.
Methods
According to the PRISMA guidelines, the references were selected from PubMed, Web of Science and Google Scholar database using search strings containing a combination of terms that included dengue hemorrhagic fever, pathogenesis, prevention and control. Quality of references were evaluated by independent reviewers.
Results
DHF was first reported in the Philippines in 1953 and further transmitted to the countries in the region of South-East Asia and Western Pacific. Plasma leakages is the main pathophysiological hallmark that distinguishes DHF from DF. Severe plasma leakage can result in hypovolemic shock. Various factors are thought to impact disease presentation and severity. Virus virulence, preexisting dengue antibodies, immune dysregulation, lipid change and host genetic susceptibility are factors reported to be correlated with the development of DHF. However, the exact reasons and mechanisms that triggers DHF remains controversial. Currently, no specific drugs and licensed vaccines are available to treat dengue disease in any of its clinical presentations.
Conclusion
This study concludes that antibody-dependent enhancement, cytokine dysregulation and variation of lipid profiles are correlated with DHF occurrence. Prompt diagnosis, appropriate treatment, active and continuous surveillance of cases and vectors are the essential determinants for dengue prevention and control.
We describe the development of a capture enzyme-linked immunosorbent assay for the detection of the dengue virus nonstructural protein NS1. The assay employs rabbit polyclonal and monoclonal antibodies as the capture and detection antibodies, respectively. Immunoaffinity-purified NS1 derived from dengue 2 virus-infected cells was used as a standard to establish a detection sensitivity of approximately 4 ng/ml for an assay employing monoclonal antibodies recognizing a dengue 2 serotype-specific epitope. A number of serotype cross-reactive monoclonal antibodies were also shown to be suitable probes for the detection of NS1 expressed by the remaining three dengue virus serotypes. Examination of clinical samples demonstrated that the assay was able to detect NS1 with minimal interference from serum components at the test dilutions routinely used, suggesting that it could form the basis of a useful additional diagnostic test for dengue virus infection. Furthermore, quantitation of NS1 levels in patient sera may prove to be a valuable surrogate marker for viremia. Surprisingly high levels of NS1, as much as 15 microg/ml, were found in acute-phase sera taken from some of the patients experiencing serologically confirmed dengue 2 virus secondary infections but was not detected in the convalescent sera of these patients. In contrast, NS1 could not be detected in either acute-phase or convalescent serum samples taken from patients with serologically confirmed primary infection. The presence of high levels of secreted NS1 in the sera of patients experiencing secondary dengue virus infections, and in the context of an anamnestic antibody response, suggests that NS1 may contribute significantly to the formation of the circulating immune complexes that are suspected to play an important role in the pathogenesis of severe dengue disease.
In Southeast Asia, dengue viruses often co-circulate with other flaviviruses such as Japanese encephalitis virus, and due to the presence of shared antigenic epitopes it is often difficult to use serological methods to distinguish between previous infections by these flaviviruses.
Convalescent sera from 69 individuals who were known to have had dengue or Japanese encephalitis virus infection were tested by western blotting against dengue, Japanese encephalitis and West Nile virus antigens. We determined that individuals who had been infected with dengue viruses had IgG responses against the premembrane protein of dengue viruses but not Japanese encephalitis, whereas individuals who had been infected with Japanese encephalitis had IgG specific for the premembrane protein of Japanese encephalitis virus but not the dengue viruses. None reacted with the premembrane protein of West Nile virus. Using the Pearson Chi Square test, it was determined that the difference between the two groups was highly significant with a p value of <0.001.
The use of flavivirus premembrane protein in seroepidemiological studies will be useful in determining what flaviviruses have circulated in a community.
Antibodies of all four dengue virus serotypes were detected by hemagglutination inhibition (HI) in 97% of 2,000 infants' cord sera at the time of delivery. In comparison with 250 mother-infant's paired sera, we found that 53% of the infants' serum HI titers were higher than those of the mother's. The mother/infant IgG subclasses 1, 2, 3, and 4 titers were 53.1/87.0, 8.4/11.7, 0.14/0.11, and 1.1/1.0 mg/dL, respectively. In 18 months of follow-up of 100 infants studied, we observed that antibody to dengue virus disappeared in 3% by two months of age, in 19% by four months of age, in 72% by six months of age, in 99% by nine months of age, and in 100% by 12 months of age, with a half-life of 41 days. We conclude that the antibodies to dengue virus disappeared in the first year of life. We suggest that the most appropriate age for vaccination with a live-attenuated dengue vaccine in an endemic area is one year of age.
A prospective study of clinical and cytokine profiles of 107 infants with dengue hemorrhagic fever (DHF)/dengue shock syndrome
(DSS) was conducted. Fever, petechiae on the skin, and hepatomegaly were the most common clinical findings associated with
DHF/DSS in infants. DSS occurred in 20.5% of the patients. Hemoconcentration and thrombocytopenia were observed in 91.5% and
92.5% of the patients, respectively. Serologic testing revealed that almost all of the patients (95.3%) had primary dengue
virus infections. These data demonstrate that clinical and laboratory findings of DHF/DSS in infants are compatible with the
World Health Organization’s clinical diagnostic criteria for pediatric DHF. The present study is the first to report evidence
of production of cytokines in infants with DHF/DSS and to describe the difference between the cytokine profile of infants
with primary dengue virus infections and children with secondary infections. Overproduction of both proinflammatory cytokines
(interferon-γ and tumor necrosis factor–α) and anti-inflammatory cytokines (interleukin-10 and -6) may play a role in the
pathogenesis of DHF/DSS in infants
The association between sex, nutritional status, and the severity of dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS), and immune status was investigated in 245 Vietnamese infants with predominantly primary infections with dengue virus. Male and female infants were at equal risk of developing DHF/DSS. However, infants of low height and weight for age were under-represented among DHF/DSS cases compared with 533 healthy baby clinic infant controls. Acute illness phase blood levels of selected cytokines (interferon-gamma and tumor necrosis factor-alpha) and serum levels of antibodies to dengue virus were elevated in the same range in male and female infants with DHF/DSS, as well as in infants with and without malnutrition.
Dengue hemorrhagic fever, the most severe form of dengue illness, is associated with secondary dengue virus (DV) infection. Preexisting nonneutralizing antibodies to DV that enhance the infection of Fc gamma receptor-bearing cells have been implicated in DV pathogenesis.
We conducted a prospective cohort study in Thai schoolchildren. Enhancing activity (EA) was measured as the percentage of DV-infected K562 cells, and viral titer (infected K562 cell supernatants) was measured in preillness plasma samples from children who subsequently had secondary DV2 or DV3 infection.
Plaque-reduction neutralizing titers to the child's own DV2 or DV3 isolate were detected in 23 of 32 and 8 of 27 of the preillness plasma samples, and EA was detected to a low-passage Thai DV2 or DV3 in 31 of 32 and 26 of 27, respectively, of the samples. EA in undiluted preillness plasma did not correlate with subsequent disease severity or peak viremia levels in either secondary DV2 or DV3 infections.
Preillness plasma enhances DV infection of K562 cells even in the presence of detectable neutralizing antibodies in LLC-MK2 cells. However, levels of preillness plasma EA of DV infection in K562 cells did not correlate with the clinical severity or viral burden of secondary DV infection.
Volume replacement was studied prospectively in 208 infants with dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS). The mean volume of intravenous fluid used was 110.4 mL/kg administered over a mean period of 25.8 hours. The mean volumes of intravenous fluid replacement in infants with DSS was significantly higher than in those with non-shock DHF (129.8 mL/kg versus 102.1 mL/kg; P = 0.001). Patients with DSS had significantly higher proportional requirements for dextran and blood transfusions than non-shock infants. Recurrent shock, prolonged shock, and acute respiratory failure were recorded in 8, 6, and 13 patients, respectively. Four patients with DSS died of severe complications. Intravenous fluid replacement with special care to avoid fluid overload requires careful attention to established indications for use of colloidal solutions and blood transfusions. To improve case fatality rates, special efforts need to be directed to infants with DHF/DSS accompanied by severe complications.
Understanding dengue virus infection in children and the kinetics of maternal dengue neutralizing antibodies is essential for effective dengue immunization of children in endemic areas.
Serum samples from 219 mother-child pairs and 140 children at 3, 6, 9, 12, 18, and 24 months of age from Bangkok, Thailand, were tested for serotype-specific dengue antibodies. Febrile episodes in the children were recorded.
Antibodies were found in 97% of cord serum samples and disappeared in 27%, 80%, and 95% of the children by the age of 6, 9, and 12 months, respectively. Geometric mean titers (GMTs) of the antibodies to 4 dengue serotypes decreased to 5.4-15.5 in 6-month-old infants. Eleven of 12 children acquired dengue virus infection at 6 months of age and beyond; 1 had the infection at 3 months of age. Two exhibited undifferentiated febrile illnesses, and 10 had subclinical infections.
Evidence of dengue virus infection and very low GMTs against all dengue serotypes in children at 6 months of age and beyond was demonstrated. There was no evidence that maternal antibodies were harmful to infants. Dengue virus infection rates increase from 12 months of age onward. These data provide information for supporting the optimal age at vaccination.
The age distribution of cases of dengue hemorrhagic fever and dengue shock syndrome (DHF/DSS) in infants under the age of 1 year are reported from Bangkok, Thailand, and for the first time for Ho Chi Minh City, Vietnam; Yangon, Myanmar; and Surabaya, Indonesia. The four dengue viruses were isolated from Thai infants, all of whom were having a primary dengue infection. Progress studying the immunologically distinct infant DHF/DSS has been limited; most contemporary research has centered on DHF/DSS accompanying secondary dengue infections. In designing research results obtained in studies on a congruent animal model, feline infectious peritonitis virus (FIPV) infections of kittens born to FIPV-immune queens should be considered. Research challenges presented by infant DHF/DSS are discussed.
Infection with any 1 of the 4 dengue viruses (DVs) can produce several illnesses, ranging from a mild febrile illness to classic dengue fever (DF) to dengue hemorrhagic fever (DHF), a potentially life-threatening disease. Most DHF cases occur after sequential heterotypic DV infections. The role of preexisting humoral immunity in modifying severity of dengue disease is not well understood.
We conducted a prospective cohort study of children in a region where dengue disease is hyperendemic and examined the role of preexisting neutralizing anti-DV antibodies (Abs) in modifying secondary dengue-3 virus (D3V), dengue-2 virus (D2V), and dengue-1 virus (D1V) infections.
In secondary D3V infection, higher levels of preexisting neutralizing Ab directed against D3V (reference virus strain and patient's virus isolate) were associated with lower viremia levels and milder disease. Preexisting neutralizing Ab levels against D2V were not associated with severity of secondary D2V infection. The levels of preexisting neutralizing Ab against the infecting virus isolates were not associated with viremia levels in secondary D2V or D1V infections.
Cross-reactive memory humoral immune responses appear to be beneficial in symptomatic secondary D3V infection, but not in secondary D2V or D1V infection. These results may have important implications for the development of live attenuated tetravalent dengue vaccines.
Viremia titers in serial plasma samples from 168 children with acute dengue virus infection who were enrolled in a prospective
study at 2 hospitals in Thailand were examined to determine the role of virus load in the pathogenesis of dengue hemorrhagic
fever (DHF). The infecting virus serotype was identified for 165 patients (DEN-1, 46 patients; DEN-2, 47 patients; DEN-3,
47 patients, DEN-4, 25 patients). Patients with DEN-2 infections experienced more severe disease than those infected with
other serotypes. Eighty-one percent of patients experienced a secondary dengue virus infection that was associated with more
severe disease. Viremia titers were determined for 41 DEN-1 and 46 DEN-2 patients. Higher peak titers were associated with
increased disease severity for the 31 patients with a peak titer identified (mean titer of 107.6 for those with dengue fever vs. 108.5 for patients with DHF, P = .01). Increased dengue disease severity correlated with high viremia titer, secondary dengue virus infection, and DEN-2
virus type.
Dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS) in children is reliably associated with the presence of dengue antibody
- actively or passively acquired - before the onset of illness. Limited observations by electron microscopy and fluorescent
antibody testing and the recovery of virus from tissues obtained at autopsy show that dengue viruses are consistently associated
with cells of mononuclear phagocyte lineage. In particular, virus is associated with Kupffer cells, pulmonary macrophages,
and mononuclear cells in skin and blood. Endothelial cells fail to demonstrate necrosis or inflammatory changes. Since acute
vascular permeability, shock, and hemorrhage occur late in illness, a plausible hypothesis is that phlogistic factors, resulting
from interactions with elements of the immune response, are released from virus-infected mononuclear phagocytes. Such phenomena
as generalized depression of mitotic activity of bone marrow cells, destruction of mature polymorphonuclear leukocytes, complement
activation, and abnormal hemostasis may serve as markers of these phlogistic factors. It will be of interest to establish
whether other viral hemorrhagic fevers involve the same target cells as in DHF/DSS and are mediated by similar effector mechanisms.
Dengue infections were prospectively studied among 4- to 16-year-old students at a Bangkok school. Blood samples were obtained from 1,757 students in June 1980, before the dengue season, and in January 1981, after the season, and tested for dengue antibodies by the hemagglutination inhibition method. Classrooms were monitored daily for school absences. Fifty percent of the children had antibodies to, and were presumably immune to, at least 1 dengue serotype by the age of 7 years. Most (90/103, 87%) students who became infected by dengue viruses during the study period were either asymptomatic or minimally symptomatic (absent only 1 day). Most (7/13, 53%) of the symptomatic dengue infections (absent with fever for greater than or equal to 2 days) were clinically recognized as cases of dengue hemorrhagic fever which required hospitalization. None of 47 primary dengue infections required hospitalization, whereas 7 of 56 secondary infections did (P = 0.012). Preexistent dengue immunity, as detected by conventional serologic techniques, was a significant (odds ratio greater than or equal to 6.5) risk factor for development of dengue hemorrhagic fever.
To establish the role of maternal dengue-specific antibodies in the development of dengue hemorrhagic fever and dengue shock syndrome caused by dengue 2 virus in infants, we examined sera from mothers of infants and toddlers with dengue hemorrhagic fever or dengue shock syndrome and mothers of infants with pyrexia of unknown origin. The mean titers of hemagglutination inhibition, neutralization, and infection-enhancing activities against dengue 2 virus were not statistically different among the three groups. However, among infants who developed dengue hemorrhagic fever/dengue shock syndrome there was a strong correlation between the mothers' dengue 2 neutralizing titers and infant age at the time of onset of severe illness, where no such correlation was found among the other two groups. Furthermore, the actual age at which dengue hemorrhagic fever/dengue shock syndrome occurred in each infant correlated with the age at which maximum enhancing activity for dengue 2 infection in mononuclear phagocytes was predicted. This critical time for the occurrence of dengue hemorrhagic fever/dengue shock syndrome was observed to be approximately 2 months after the time calculated for maternal dengue 2 neutralizing antibodies to degrade below a protective level. In addition, sera of mothers of infants with dengue hemorrhagic fever/dengue shock syndrome enhanced dengue 2 virus infection to a slightly greater degree than did sera from mothers of infants with pyrexia of unknown origin and toddlers with dengue hemorrhagic fever/dengue shock syndrome. These data are consistent with the hypothesis that maternal dengue antibodies play a dual role by first protecting and later increasing the risk of development of dengue hemorrhagic fever/dengue shock syndrome in infants who become infected by dengue 2 virus.
In January 1980, the municipal area of Rayong, Thailand, and contiguous suburban villages were chosen for a long-term study on dengue epidemiology. From 3,185 children randomly sampled in schools and households, the population prevalence of neutralizing antibody to the four dengue serotypes was estimated. To estimate the incidence of infection with each dengue virus serotype (dengue seroconversions), first grade children were re-bled in January 1981 (cohort study). Children admitted to hospital were studied for dengue virus isolation and antibody responses in paired sera. An epidemic of dengue occurred in 1980. Plaque reduction neutralization tests of 1,009 pre-epidemic sera from children aged less than 1-10 years of age determined that 3.3% were immune to dengue 1, 13.2% to dengue 2, 6.4% to dengue 3, and 5.8% to dengue 4. Examination of pre- and post-epidemic cohort blood samples revealed that the incidence of dengue infection in 251 seronegative children was 39.4% (15.1% dengue 1, 11.1% dengue 2, 2.0% dengue 3, 4.8% dengue 4, and 6.4% two or more dengue viruses). Among the 52,935 residents of the study area, there were 22 cases of virologically and clinically confirmed dengue shock syndrome, in children 15 years or younger. All 22 shock syndrome cases had secondary type antibody responses. Eight of 22 had been included in the random serologic sample prior to onset of shock; five had been immune to dengue 1, two to dengue 3, one to dengue 4, and none to dengue 2. Despite the high rate of dengue 1 infections in 1980, only dengue 2 viruses were recovered from dengue shock syndrome cases, including two dengue 1 immune children with pre-illness serum specimens. Although the pre-epidemic prevalence of antibodies to dengue 1 was the lowest to any type, children with this immunologic background contributed disproportionately to shock cases. In descending order of magnitude, risk factors for dengue shock syndrome in Rayong were secondary infections with dengue 2 which followed primary infections with dengue 1, dengue 3, or dengue 4.
Dengue viruses are members of the Flaviviridae, transmitted principally in a cycle involving humans and mosquito vectors. In the last 20 years the incidence of dengue fever epidemics has increased and hyperendemic transmission has been established over a geographically expanding area. A severe form, dengue hemorrhagic fever (DHF), is an immunopathologic disease occurring in persons who experience sequential dengue infections. The risk of sequential infections, and consequently the incidence of DHF, has risen dramatically, first in Asia and now in the Americas. At the root of the emergence of dengue as a major health problem are changes in human demography and behavior, leading to unchecked populations of and increased exposure to the principal domestic mosquito vector, Aedes aegypti. Virus-specified factors also influence the epidemiology of dengue. Speculations on future events in the epidemiology, evolution, and biological expression of dengue are presented.
Despite a growing body of evidence predominantly, but not exclusively, from Thailand suggesting that the risk of developing dengue shock syndrome (DSS) is greatest following an anamnestic dengue infection, particularly if the most recent infection was with dengue 2 virus, there continues to be debate about the justification for these claims. This report describes a five-year, prospective study in two townships (suburbs) in Yangon (Rangoon) Myanmar (Burma) in which attempts were made to confirm the data from an earlier prospective study in Thailand and to address some of the criticism of earlier studies. This investigation found the incidence of anamnestic dengue infections in DSS patients to be significantly higher than in the community from which they were drawn and a significantly higher risk of developing DSS following an anamnestic infection (particularly with dengue 2 virus) than following a primary infection with any serotype.
A prospective study on dengue (DEN) viruses was initiated in October 1995 in Gondokusuman kecamatan, Yogyakarta, Indonesia. This report presents data from the first year of the study. The studied cohort included all children 4-9 years of age living in the kecamatan. Blood samples for serology were collected from 1,837 children in October 1995 and again in October 1996. Blood samples for virus isolation and serology were collected from cohort children who were seen in municipal health clinics with febrile syndromes or admitted to hospitals with a provisional diagnosis of dengue hemorrhagic fever. Dengue serotype antibody prevalence and 1995-1996 infection rates were calculated using a single dilution (1:60) 70% plaque reduction endpoint neutralization test. Prevalence of dengue antibody at the beginning of the study was DEN 1 = 12%, DEN 2 = 16%, DEN 3 = 2%, DEN 4 = 4%, and two or more dengue infections = 22%. Total dengue antibody prevalence increased from 38% in 4-year-old children to 69% in 9-year-old children. During the observation period, primary dengue infection rates were DEN 1 = 4.8%, DEN 2 = 7.7%, DEN 3 = 4.2%, and DEN 4 = 3.4%, while two or more dengue infections occurred in 6.7% of the study population. The secondary dengue infection rate was 19.0%. From febrile cases, all four dengue viruses were isolated with DEN 3 predominating. Seven children were hospitalized, including one fatal case with a hospital diagnosis of dengue shock syndrome. Based upon presence of antibody in the initial cohort bleeding and the serologic response both weeks and several months following illness, all had secondary dengue infections. Neutralizing antibody patterns in the initial cohort bleeding and in late convalescent serum samples permitted recognition of dengue infection sequence in five patients: DEN 2-DEN 1 (3), DEN 2-DEN 4 (1), DEN 1-DEN 3 (1), and none in the sequence DEN 1-DEN 2. In the total cohort 6.5% of the observed secondary infections were of the sequence DEN 2-DEN 1, while 4.9% were DEN 1-DEN 2, a highly pathogenic sequence in previous studies. Reduced pathogenic expression of secondary DEN 2 with enhanced pathogenic expression of secondary DEN 1 infections was an unexpected finding. Further studies will be required to understand the respective contributions to pathogenicity of antibody from initial dengue infections versus the biological attributes of the second infecting dengue viruses.
This review is an update of dengue and dengue haemorrhagic fever (DHF) based on international and Cuban experience. We describe the virus characteristics and risk factors for dengue and DHF, and compare incidence and the case fatality rates in endemic regions (southeast Asia, western Pacific, and the Americas). The clinical picture and the pathogenesis of the severe disease are explained. We also discuss the viral, individual, and environmental factors that determine severe disease. Much more research is necessary to clarify these mechanisms. Also reviewed are methods for viral isolation and the serological, immunohistochemical, and molecular methods applied in the diagnosis of the disease. We describe the status of vaccine development and emphasise that the only alternative that we have today to control the disease is through control of its vector Aedes aegypti.
Infection with any 1 of 4 dengue viruses produces a spectrum of clinical illness ranging from a mild undifferentiated febrile
illness to dengue fever (DF) to dengue hemorrhagic fever (DHF), a potentially life-threatening disease. The morbidity and
mortality of DHF can be reduced by early hospitalization and careful supportive care. To determine its usefulness as a predictor
of DHF, plasma levels of the secreted dengue virus nonstructural protein NS1 (sNS1) were measured daily in 32 children with
dengue-2 virus infections participating in a prospective, hospital-based study. Free sNS1 levels in plasma correlated with
viremia levels and were higher in patients with DHF than in those with DF. An elevated free sNS1 level (⩾600 ng/mL) within
72 h of illness onset identified patients at risk for developing DHF
World Health Organization (WHO) Dengue haemorrhagic fever: diagnosis , treatment, prevention and control
World Health Organization (WHO). Dengue haemorrhagic fever: diagnosis, treatment, prevention and control. Geneva: WHO, 1997.