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A role for IFN-alpha beta in virus infection-induced sensitization to endotoxin
Abstract
Underlying viral infections can heighten sensitivity and worsen cytokine-mediated disease following secondary inflammatory challenges, Mechanisms for this are poorly understood. The impact of the innate response to lymphocytic choriomeningitis virus (LCMV) infection on sensitivity to endotoxin (LPS) was investigated, Compared with uninfected mice, infection with LCMV for 2-days-sensitized mice to LPS by similar to2-fold for lethality and by 2- to 6-fold for serum TNF-alpha levels. Priming for LPS-induced TNF-alpha was also seen with splenic and peritoneal leukocytes isolated from infected mice and challenged with LPS ex vivo, The effect on TNF-alpha production was present in the absence of IFN-gamma, its major producers NK and T cells, and the major pathways for its induction through IL-12 and the signal transducer and activator of transcription 4 (STAT4), and therefore was IFN-gamma independent. ;Early LCMV infection induces high concentrations of the type 1 IFNs, IFN-alpha beta. Administration of recombinant IFN-alpha alone heightened the TNF-alpha response to LPS, Innate IFN-alpha beta and IFN-gamma responses to LCMV exist in a delicate balance. To reduce priming for LPS-induced TNF-alpha during LCMV, deficiencies in both the IFN-alpha beta and IFN-gamma receptors or STATI, a transcription factor downstream to bath IFNs, were required. These data demonstrate that early viral infection can enhance sensitivity to bacterial products, and that this sensitization can occur in part as a result of endogenously expressed IFN-alpha beta. This work also raises issues about potential complications associated with IFN-alpha beta therapies.
... Similarly, varicella has been reported to predispose human to severe streptococcal and staphylococcal infection (Barnes et al., 1996;Zerr et al., 1999). Consistent with the human studies, infection of mice with multiple viruses increases the sensitivity and lethality to bacterial products including lipopolysaccharide (LPS) (Doughty et al., 2001;Fejer et al., 2005;Nansen and Randrup Thomsen, 2001). The mechanism whereby viral infections enhance and aggravate bacterial superinfection is poorly understood, but it is likely to involve multiple factors including local destruction of antibacterial barriers at epithelial surfaces, suppression of anti-bacterial immunity, induction of apoptosis in immune cells and sensitization to LPS (Doughty et al., 2001;Fejer et al., 2005;Herold et al., 2008;Jamieson et al., 2010;Nansen and Randrup Thomsen, 2001;Navarini et al., 2006). ...
... Consistent with the human studies, infection of mice with multiple viruses increases the sensitivity and lethality to bacterial products including lipopolysaccharide (LPS) (Doughty et al., 2001;Fejer et al., 2005;Nansen and Randrup Thomsen, 2001). The mechanism whereby viral infections enhance and aggravate bacterial superinfection is poorly understood, but it is likely to involve multiple factors including local destruction of antibacterial barriers at epithelial surfaces, suppression of anti-bacterial immunity, induction of apoptosis in immune cells and sensitization to LPS (Doughty et al., 2001;Fejer et al., 2005;Herold et al., 2008;Jamieson et al., 2010;Nansen and Randrup Thomsen, 2001;Navarini et al., 2006). ...
... Although pro-inflammatory cytokines are critical for bacterial killing and activation of adaptive immunity, excessive amounts of certain cytokines such as TNF-α produced in response to infection are harmful to the host and can lead to septic shock and multi-organ failure (Cook et al., 2004;Danner et al., 1991). During infection with viruses, TLR and RIG-I-like receptor activation induce production of type I IFNs which can potentiate the inflammatory response to TLR ligands including LPS (Doughty et al., 2001;Nansen and Randrup Thomsen, 2001). In addition, viral infection can augment or repress the immune response to bacteria (Navarini et al., 2006). ...
Secondary bacterial infection is a common sequela to viral infection and is associated with increased lethality and morbidity. However, the underlying mechanisms remain poorly understood. We show that the TLR3/MDA5 agonist poly I:C or viral infection dramatically augments signaling via the NLRs Nod1 and Nod2 and enhances the production of proinflammatory cytokines. Enhanced Nod1 and Nod2 signaling by poly I:C required the TLR3/MDA5 adaptors TRIF and IPS-1 and was mediated by type I IFNs. Mechanistically, poly I:C or IFN-β induced the expression of Nod1, Nod2, and the Nod-signaling adaptor Rip2. Systemic administration of poly I:C or IFN-β or infection with murine norovirus-1 promoted inflammation and lethality in mice superinfected with E. coli, which was independent of bacterial burden but attenuated in the absence of Nod1/Nod2 or Rip2. Thus, crosstalk between type I IFNs and Nod1/Nod2 signaling promotes bacterial recognition, but induces harmful effects in the virally infected host.
... Both inflammatory mediators substantially reduced the HSV-driven increase in pLN cellularity, FRC expansion, as well as B cell responses ( Figure 6B). Systemic LCMV infection induces the production of pro-inflammatory cytokines, including IFN-I (Doughty et al., 2001). LCMV induced a substantial lymphopenia in mice that was dependent on IFN-I receptor (IFNAR) signaling as it did not occur in Ifnar2 À/À mice ( Figure S5A). ...
... *p < 0.05, **p < 0.01, ****p < 0.0001, ns, nonsignificant, by unpaired two-tailed t test. (Doughty et al., 2001;Nansen and Randrup Thomsen, 2001), which can lead to NK cell-mediated impairment of the CD8 + T cell responses (Straub et al., 2018). Coinfection of mice with two systemic viral pathogens, LCMV and Ectromelia virus (McAfee et al., 2015) or LCMV and Pichinde virus, was also found to impair CD8 + T cell responses to LCMV (Kenney et al., 2015). ...
Concurrent infection with multiple pathogens occurs frequently in individuals and can result in exacerbated infections and altered immunity. However, the impact of such coinfections on immune responses remains poorly understood. Here, we reveal that systemic infection results in an inflammation-induced suppression of local immunity. During localized infection or vaccination in barrier tissues including the skin or respiratory tract, concurrent systemic infection induces a type I interferon-dependent lymphopenia that impairs lymphocyte recruitment to the draining lymph node (dLN) and induces sequestration of lymphocytes in non-draining LN. This contributes to suppressed fibroblastic reticular cell and endothelial cell expansion and dLN remodeling and impairs induction of B cell responses and antibody production. Our data suggest that contemporaneous systemic inflammation constrains the induction of regional immunity.
... During bacterial infections, the influence of type I IFNs on neutrophil functions appears to be controversial. In certain studies, the protective role of IFNs for the host was shown (19)(20)(21)(22)(23)(24), while others revealed increased tissue damage and bacteria colonization in the presence of IFNs (25)(26)(27)(28)(29). At the same time, little is known about the influence of IFNs on neutrophil antibacterial functions during infection with P. aeruginosa. ...
... Interestingly, the effect of type I IFNs varies between different models of bacterial, fungal and parasite infections. In certain studies the protective role of IFNs for the host was proven during the microbial infections (19)(20)(21)(22)(23)(24), while others revealed increased tissue damage and bacteria colonization in the presence of IFNs (25-29). These differences might be partly explained by the involvement of the distinct cell subsets in antibacterial immune responses, which is due to the diverse, extra-or intracellular, localization of pathogens. ...
Pseudomonas aeruginosa is an opportunistic multidrug-resistant pathogen, able to grow in biofilms. It causes life-threatening complications in diseases characterized by the up-regulation of type I interferon (IFN) signaling, such as cancer or viral infections. Since type I IFNs regulate multiple functions of neutrophils, which constitute the first line of anti-bacterial host defense, in this work we aimed to study how interferon-activated neutrophils influence the course of P. aeruginosa infection of the lung. In lungs of infected IFN-sufficient WT mice, significantly elevated bacteria load was observed, accompanied by the prominent lung tissue damage. At the same time IFN-deficient animals seem to be partly resistant to the infection. Lung neutrophils from such IFN-deficient animals release significantly lower amounts of neutrophil extracellular traps (NETs) and reactive oxygen species (ROS), as compared to WT neutrophils. Of note, such IFN-deficient neutrophils show significantly decreased capacity to stimulate biofilm formation by P. aeruginosa. Reduced biofilm production impairs in turn the survival of bacteria in a lung tissue. In line with that, treatment of neutrophils with recombinant IFN-β enhances their NETosis and stimulates biofilm formation by Pseudomonas after co-incubation with such neutrophils. Possibly, bacteria utilizes neutrophil-derived NETs as a scaffold for released biofilms. In agreement with this, in vivo treatment with ROS-scavengers, NETs disruption or usage of the bacterial strains unable to bind DNA, suppress neutrophil-mediated biofilm formation in the lungs. Together, our findings indicate that the excessive activation of neutrophils by type I IFNs leads to their boosted NETosis that in turn triggers biofilm formation by P. aeruginosa and supports its persistence in the infected lung. Targeting these mechanisms could offer a new therapeutic approach to prevent persistent bacterial infections in patients with diseases associated with the up-regulation of type I IFNs.
... This has not been examined for the PRRSV-LPS combination. (Doughty et al., 2001;Nansen and Thomsen, 2001). ...
... By use of knockout mice, it was demonstrated that virus-induced interferon was responsible for the increased sensitivity to LPS (Doughty et al., 2001;Nansen and Thomsen, 2001). Both interferon-/ and -were able to sensitize mice to systemic LPS exposure. ...
Pathogenesis of the clinical synergy between respiratory viruses and bacterial endotoxin in the lungs of pigs
... In this respect, lipopolysaccharide (LPS), an immunogenic cell wall component of Gram negative bacteria, signals through TLR-4 via both MyD88-dependent MyD88-independent pathways resulting in expression of type-I IFNs and other proinflammatory cytokines. Intraperitoneal, as well as intravenous (IV), administration of LPS is associated with a fatal, sepsis-like syndrome in both mice and humans [15][16][17][18][19][20] and would therefore, not be used clinically. However, with its known activities as a TLR-4-activating agent, we tested its activity in a proof-of-principle capacity to investigate whether combination with VSV would enhance immune-mediated viro-immunotherapy through the simultaneous activation of different innate immune-stimulating pathways. ...
... However, detrimental synergy between concurrent viral and bacterial infections in both animal models and humans, have been amply demonstrated. 15,17,18,[35][36][37][38] Therefore, with an increasing repertoire of combination therapies between oncolytic viruses and chemotherapeutics, biologics, radiotherapy or immunotherapies, [39][40][41] our results show that careful combination dose escalation phase I trials will be needed to optimize such combination therapies. ...
Injection of oncolytic vesicular stomatitis virus (VSV) into established B16ova melanomas results in tumor regression, in large part by inducing innate immune reactivity against the viral infection, mediated by MyD88- and type III interferon (IFN)-, but not TLR-4-, signaling. We show here that intratumoral (IT) treatment with lipopolysaccharide (LPS), a TLR-4 agonist, significantly enhanced the local therapy induced by VSV by combining activation of different innate immune pathways. Therapy was further enhanced by co-recruiting a potent antitumor, adaptive T-cell response by using a VSV engineered to express the ovalbumin tumor-associated antigen ova, in combination with LPS. However, the combination of IT LPS with systemically delivered VSV resulted in rapid morbidity and mortality in the majority of mice. Decreasing the intravenous (IV) dose of VSV to levels at which toxicity was ameliorated did not enhance therapy compared with IT LPS alone. Toxicity of the systemic VSV + IT LPS regimen was associated with rapidly elevated levels of serum tumor necrosis factor-α (TNF-α) and interleukin (IL)-6, which neither systemic VSV, nor IT LPS, alone induced. These data show that therapy associated with direct IT injections of oncolytic viruses can be significantly enhanced by combination with agonists of innate immune activation pathways, which are not themselves activated by the virus alone. Importantly, they also highlight possible, unforeseen dangers of combination therapies in which an immunotherapy, even delivered locally at the tumor site, may systemically sensitize the patient to a cytokine shock-like response triggered by IV delivery of oncolytic virus.Molecular Therapy (2012); doi:10.1038/mt.2012.204.
... However, it has become clear that priming, such as occurs during a viral infection, also results in hyper-responsiveness on subsequent exposure to microbes or environmental antigens. This hyper-responsiveness can have deleterious consequences in terms of increased tissue damage and even increased lethality secondary to excessive cytokine production (6)(7)(8). We and others (4,(9)(10)(11)(12) have considered the possibility that priming may also occur during the course of autoimmune and inflammatory diseases, in which case enhanced inflammatory responses to cytokines and other activating factors could contribute to pathogenesis. ...
... Elevated STAT1 expression, measured both at the mRNA and protein levels, and implying priming in vivo, has been observed in other inflammatory processes, such as T-cell-mediated hepatitis, RA, and dermatomyositis (9,11,25,26). In SLE patients who have not undergone treatment, isolated monocytes displayed an enhanced response to TLR activators, such as LPS and IL-1β (107), and it is thought that such a hyperresponsiveness of TLRs in vivo can be secondary to the effects of IFN priming (6)(7)(8)(108)(109)(110). Moreover, as a consequence of this hyper-responsiveness, patients with rheumatic diseases have been observed to mount exaggerated immune responses to infections (104). ...
Activated macrophages and their inflammatory products play a key role in innate immunity and in pathogenesis of autoimmune/inflammatory diseases. Macrophage activation needs to be tightly regulated to rapidly mount responses to infectious challenges but to avoid toxicity associated with excessive activation. Rapid and potent macrophage activation is driven by cytokine-mediated feedforward loops, while excessive activation is prevented by feedback inhibition. Here we discuss feedforward mechanisms that augment macrophage responses to Toll-like receptor (TLR) ligands and cytokines that are mediated by signal transducer and activator of transcription 1 (STAT1) and induced by interferon-gamma (IFN-gamma). IFN-gamma also drives full macrophage activation by inactivating feedback inhibitory mechanisms, such as those mediated by interleukin-10 (IL-10), and STAT3. Priming of macrophages with IFN-gamma reprograms cellular responses to other cytokines, such as type I IFNs and IL-10, with a shift toward pro-inflammatory STAT1-dominated responses. Similar but partially distinct priming effects are induced by other cytokines that activate STAT1, including type I IFNs and IL-27. We propose a model whereby opposing feedforward and feedback inhibition loops crossregulate each other to fine tune macrophage activation. In addition, we discuss how dysregulation of the balance between feedforward and feedback inhibitory mechanisms can contribute to the pathogenesis of autoimmune and inflammatory diseases, such as rheumatoid arthritis and systemic lupus erythematosus.
... Mice. The 129 IFN-␥R Ϫ/Ϫ , IFN-␣/R Ϫ/Ϫ , or IFN-␣/␥R Ϫ/Ϫ mice were obtained from B&K Universal Limited (North Humberside, United Kingdom) or Joan Durbin, Ohio State University, Columbus (10). STAT1 Ϫ/Ϫ C57BL/6 mice were from Joan Durbin (16). ...
... Mice were anesthetized and bled before sacrifice for organ harvesting. Sera, spleen homogenates, and peritoneal cells were prepared as previously described (8,10,16). Viral titers in spleen homogenates were determined by plaque assays on Vero cells (18,19) and expressed as PFU per gram. ...
Viruses and viral components can be potent inducers of alpha/beta interferons (IFN-alpha/beta). In culture, IFN-alpha/beta prime for their own expression, in response to viruses, through interferon regulatory factor 7 (IRF-7) induction. The studies presented here evaluated the requirements for functional IFN receptors and the IFN signaling molecule STAT1 in IFN-alpha/beta induction during infections of mice with lymphocytic choriomeningitis virus (LCMV). At 24 h after infection, levels of induced IFN-alpha/beta in serum were reduced 90 to 95% in IFN-alpha/beta receptor-deficient (IFN-alpha/betaR(-/-)) and STAT1(-/-) mice compared to those in wild-type mice. However, at 48 h, these mice showed elevated expression in the serum whereas IFN-alpha/beta levels were still reduced >75% in IFN-alpha/betagammaR(-/-) mice even though the viral burden was heavy. Levels of IFN-beta, IFN-alpha4, and non-IFN-alpha4 subtype mRNA expression correlated with IFN-alpha/beta bioactivity, and all IFN-alpha/beta subtypes were coincidentally detectable. IRF-7 mRNA was induced under conditions of IFN-alpha/beta production, including late production in IFN-alpha/betaR(-/-) mice. These data demonstrate that the presence of the virus alone is not sufficient to induce IFN-alpha/beta during LCMV infection in vivo. Instead, autocrine amplification through the IFN-alpha/betaR is necessary for optimal induction. In the absence of a functional IFN-alpha/betaR, however, alternative mechanisms, independent of STAT1 but requiring a functional IFN-gammaR, take over.
... LPS exacerbates DV infection. Concurrent bacterial infection during the course of a viral infection usually aggravates disease progression (4,12,44). Here we showed that production of infectious DV was enhanced and prolonged in the presence of bacterial LPS, suggesting a potential role for bacterial infection in increasing viral load during DV infection. ...
... Given the multiple roles of IFN-␣ in shaping both innate and adaptive immunity, enhanced IFN-␣ production by DV-infected MO/M treated with LPS provided a potential pathogenic mechanism whereby bacterial coinfection may modulate immunity and/or immunopathology during DV infection. (12,44). ...
Dengue virus (DV) primarily infects blood monocytes (MO) and tissue macrophages (M phi). We have shown in the present study that DV can productively infect primary human MO/M phi regardless of the stage of cell differentiation. After DV infection, the in vitro-differentiated MO/M phi secreted multiple innate cytokines and chemokines, including tumor necrosis factor alpha, alpha interferon (IFN-alpha), interleukin-1 beta (IL-1 beta), IL-8, IL-12, MIP-1 alpha, and RANTES but not IL-6, IL-15, or nitric oxide. Secretion of these mediators was highlighted by distinct magnitude, onset, kinetics, duration, and induction potential. A chemokine-to-cytokine hierarchy was noted in the magnitude and induction potential of secretion, and a chemokine-to-cytokine-to-chemokine/Th1 cytokine cascade could be seen in the production kinetics. Furthermore, we found that terminally differentiated MO/M phi cultured for more than 45 days could support productive DV infection and produce innate cytokines and chemokines, indicating that these mature cells were functionally competent in the context of a viral infection. In addition, DV replication in primary differentiated human MO/M phi was enhanced and prolonged in the presence of lipopolysaccharide (LPS), and LPS-mediated synergistic production of IFN-alpha could be seen in DV-infected MO/M phi. The secretion of innate cytokines and chemokines by differentiated MO/M phi suggests that regional accumulation of these mediators may occur in various tissues to which DV has disseminated and may thus result in local inflammation. The LPS-mediated enhancement of virus replication and synergistic IFN-alpha production suggests that concurrent bacterial infection may modulate cytokine-mediated disease progression during DV infection.
... Furthermore, the production of IL-12, IFNγ and TNF-α are also reduced in these patients [85]. These data are in keeping with the observation that STAT-1 increases the levels of both IL-12 and TNF-α in mice [86,87]. ...
The signal transducer and activator of transcription (STAT) 1 protein plays a key role in the immune response against viruses and other pathogens by transducing, in the nucleus, the signal from type I, type II and type III IFNs. STAT1 activates the transcription of hundreds of genes, some of which have been well characterized for their antiviral properties. STAT1 gene deletion in mice and complete STAT1 deficiency in humans both cause rapid death from severe infections. STAT1 plays a key role in the immunoglobulin class-switch recombination through the upregulation of T-bet; it also plays a key role in the production of T-bet+ memory B cells that contribute to tissue-resident humoral memory by mounting an IgG response during re-infection. Considering the key role of STAT1 in the antiviral immune response, many viruses, including dangerous viruses such as Ebola and SARS-CoV-2, have developed different mechanisms to inhibit this transcription factor. The search for drugs capable of targeting the viral proteins implicated in both viral replication and IFN/STAT1 inhibition is important for the treatment of the most dangerous viral infections and for future viral pandemics, as shown by the clinical results obtained with Paxlovid in patients infected with SARS-CoV-2.
... L'anifrolumab est un anticorps monoclonal inhibant de façon efficace la sous-unité IFNAR1 du récepteur des interférons de type I. L'anifrolumab a été développé dans le cadre de la recherche clinique sur le lupus érythémateux systémique (Morand, et al. 2020), Figure 28). Par ailleurs, l'implication de STAT1 dans la réponse à la stimulation endotoxinique a bien été montrée (Doughty, et al. 2001;Durbin, et al. 2003). ...
Le sepsis résulte d’une dysfonction de la réponse immunitaire de l’hôte en réponse à une infection, menant à une dysfonction endothéliale, qui peut aboutir à une coagulation intravasculaire disséminée (CIVD). Les mécanismes demeurant mal compris, nous avons étudié le rôle des interférons (IFNs) de type I et de leur voie de signalisation (STAT1) sur la dysfonction endothéliale au cours du sepsis. Nous avons montré que les souris présentant un déficit global en récepteur de l’IFN-α (Ifnar1-/-), ou en Stat1 ciblé sur l’endothélium, étaient protégées face au choc septique induit par ligature et perforation cӕcale (CLP), en lien avec une réduction des marqueurs d’inflammation, de dysfonction endothéliale, et de coagulopathie. Nous avons conforté ces résultats, chez l’Homme, en montrant une corrélation entre le taux plasmatique d’IFN-α d’une part, et la présence d’une CIVD et le niveau de microparticules endothéliales circulantes CD105+ d’autre part. Ainsi, notre travail confirme que l’inhibition de STAT1, ciblée sur l’endothélium, réduit la dysfonction endothéliale au cours du sepsis, ouvrant des perspectives thérapeutiques centrées sur l’endothélium.
... With this question in mind, we secondly showed an increased resistance and improved hemodynamics in Ifnar1 -/mice following CLP, in agreement with previous studies demonstrating a protective effect of type I IFN blockade during murine sepsis (13,25,26,42). ...
Septic shock and disseminated intravascular coagulation (DIC) are known to be characterized by an endothelial cell dysfunction. The molecular mechanisms underlying this relationship are, however, poorly understood. In this work, we aimed to investigate human circulating IFN-α in patients with septic shock-induced DIC and tested the potential role of endothelial Stat1 (signal transducer and activator of transcription 1) as a therapeutic target in a mouse model of sepsis. For this, circulating type I, type II, and type III IFNs and procoagulant microvesicles were quantified in a prospective cohort of patients with septic shock. Next, we used a septic shock model induced by cecal ligation and puncture in wild-type mice, in Ifnar1 (type I IFN receptor subunit 1)-knockout mice, and in Stat1 conditional knockout mice. In human samples, we observed higher concentrations of circulating IFN-α and IFN-α1 in patients with DIC compared with patients without DIC, whereas concentrations of IFN-β, IFN-γ, IFN-λ1, IFN-λ2, and IFN-λ3 were not different. IFN-α concentration was positively correlated with CD105 microvesicle concentrations, reflecting endothelial injury. In Ifnar1-/- mice, cecal ligation and puncture did not induce septic shock and was characterized by lesser endothelial cell injury, with lower aortic inflammatory cytokine expression, endothelial inflammatory-related gene expression, and fibrinolysis. In mice in which Stat1 was specifically ablated in endothelial cells, a marked protection against sepsis was also observed, suggesting the relevance of an endothelium-targeted strategy. Our work highlights the key roles of type I IFNs as pathogenic players in septic shock-induced DIC and the potential pertinence of endothelial STAT1 as a therapeutic target.
... They may also interfere, to a certain extent, with bacterial multiplication since IFN can also be induced by Intracellular Bacterial Pathogens (IBPs) or some extracellular bacteria [107,112]. Nevertheless, in some situations type 1 IFNs can also increase the host susceptibility to subsequent bacterial infection [113] through impaired macrophage recruitment with a reduced CXCL1 and CXCL2 transcription [114] and a reduced IL17 [115] production. Then, there is also the non-interferon-mediated viral interference (or intrinsic interference) which is a cellular state of resistance induced by the virus to new viral infection by closely related or unrelated viruses [116]. ...
Understudied, coinfections are more frequent in pig farms than single infections. In pigs, the term "Porcine Respiratory Disease Complex" (PRDC) is often used to describe coinfections involving viruses such as swine Influenza A Virus (swIAV), Porcine Reproductive and Respiratory Syndrome Virus (PRRSV), and Porcine CircoVirus type 2 (PCV2) as well as bacteria like Actinobacillus pleuropneumoniae, Mycoplasma hyopneumoniae and Bordetella bronchiseptica. The clinical outcome of the various coinfection or superinfection situations is usually assessed in the studies while in most of cases there is no clear elucidation of the fine mechanisms shaping the complex interactions occurring between microorganisms. In this comprehensive review, we aimed at identifying the studies dealing with coinfections or superinfections in the pig respiratory tract and at presenting the interactions between pathogens and, when possible, the mechanisms controlling them. Coinfections and superinfections involving viruses and bacteria were considered while research articles including protozoan and fungi were excluded. We discuss the main limitations complicating the interpretation of coinfection/superinfection studies, and the high potential perspectives in this fascinating research field, which is expecting to gain more and more interest in the next years for the obvious benefit of animal health.
... In spite of their important role as a bactericidal, proinflammatory cytokines such as TNF-α synthesized in response to illness could be harmful to the host cells (Cook et al., 2004). During a viral illness, TLR and RIG-I-like receptor activation prompts the synthesis of type I IFNs, which can boost the inflammatory response to TLR ligands including lipopolysaccharide (LPS) ( Nansen et al.,2001;Doughty et al., 2001). In addition, some bacteria such as S. aureus incorporate into the A549 respiratory epithelial cells (adeno-carcinomic human-alveolar basal-epithelial cells) during a respiratory viral illness by boosting the expression of ICAM-1 ( Passariello et al.,2006) . ...
Viral respiratory infections are very common and they are frequently eliminated from the body without any detrimental consequences. Secondary serious bacterial infection has been an apprehension expressed by health care providers, and this fear has been exacerbated in the era of Covid-19. Several published studies have shown an association between Covid-19 illness and secondary bacterial infection. However, the proposed mechanism by which a virus can develop a secondary bacterial infection is not well delineated. The aim of this commentary is to update the current evidence of the risk of bacterial infection in patients with Covid-19. We present several clinical studies related to the topic as well as a brief review of the potential pathophysiology of secondary infections that could present with Covid-19.
... 44 Hendaus Dovepress Throughout a viral episode, TLR and RIG-I-like receptor activation prompts fabrication of type I IFNs, which can then boost the inflammatory response to TLR ligands including lipopolysaccharide (LPS). 45,46 Interface between type I IFNs and Nod1/Nod2 signalling results in bacterial recognition, and causes damaging effects in the virally infected host. 47 Conclusions And Recommendations ...
Mohamed A Hendaus1,2 1Department of Pediatrics, Section of Academic General Pediatrics, Sidra Medicine, Doha, Qatar; 2Department of Clinical Pediatrics, Weill- Cornell Medicine, Doha, QatarCorrespondence: Mohamed A HendausDepartment of Pediatrics, Sidra Medicine, Doha 26999, QatarTel +974-4003-6559Email mhendaus@yahoo.comAbstract: Viral respiratory infections are frequently eliminated from human bodies without any sequelae. Secondary serious bacterial infection (SBI) in children with acute bronchiolitis has been an apprehension expressed by health care providers. Several published studies have shown an association between acute bronchiolitis and secondary bacterial infection, including urinary tract infections (UTI). However, the proposed mechanism by which a virus can induce UTIs is not yet known. The aim of this commentary is to update the current evidence of risk of UTI in children with bronchiolitis. We present several clinical studies related to the topic as well as a brief review of the potential pathophysiology of secondary infections that could present with viral respiratory illness.Keywords: bronchiolitis, infection, urine
... These data show that the LCMV infection can aggravate secondary infections with certain bacteria but may also protect against Gram-positive pathogens [2][3][4] . Enhanced susceptibility of LCMV-infected mice to LPS treatment has also been reported [5][6][7] . However, the reverse scenario, i.e., the effect of a bacterial coinfection on LCMVspecific T-cell immunity, has so far only been analyzed in a polymicrobial sepsis model 8 . ...
Infection of specific pathogen-free mice with lymphocytic choriomeningitis virus (LCMV) is a widely used model to study antiviral T-cell immunity. Infections in the real world, however, are often accompanied by coinfections with unrelated pathogens. Here we show that in mice, systemic coinfection with E. coli suppresses the LCMV-specific cytotoxic T-lymphocyte (CTL) response and virus elimination in a NK cell- and TLR2/4-dependent manner. Soluble TLR4 ligand LPS also induces NK cell-mediated negative CTL regulation during LCMV infection. NK cells in LPS-treated mice suppress clonal expansion of LCMV-specific CTLs by a NKG2D- or NCR1-independent but perforin-dependent mechanism. These results suggest a TLR4-mediated immunoregulatory role of NK cells during viral-bacterial coinfections.
... As demonstrated in chicken lung macrophages and in a cell line, IFNa strongly induced ISGs but a negligible pro-inflammatory gene expression profile. Indeed, IFNa has been used in priming strategies to assess the impact of type I IFNs in cellular responses to cytokines, pathogen-associated molecular patterns (PAMPs) or pathogens in chickens and mammalian species (Doughty et al., 2001;Jiang et al., 2011;Pei et al., 2001;Sharif et al., 2004). We therefore asked . ...
... The ability of immune cells to respond to TLR ligands is critical to clearance of infections and can affect the outcome of antigen presentation to CD8+ T cells after infection [42,43]. Moreover, virus infection may influence the ability of immune cells to respond to a secondary infections as it has been shown that infection with LCMV sensitizes mice to secondary stimulation with LPS resulting in increased serum TNFα levels resulting in higher lethality [44]. In addition, LCMV infection inhibits type I IFN production by pDCs in vivo, leading to increased susceptibility to secondary opportunistic infections [45]. ...
Dendritic cells produce IL-12 and IL-23 in response to viral and bacterial infection and these cytokines are responsible for successful pathogen clearance. How sequential viral and bacterial infections affect the production of IL-12 and IL-23 is currently not known. Our study demonstrates that in dendritic cells infected with Lymphocytic choriomeningitis virus (LCMV), TLR activation with bacterial PAMPs resulted in reduced IL-12 and IL-23 expression compared to non-infected cells. Furthermore, expression of other proinflammatory cytokines, TNF-α and IL-6, were not inhibited under these conditions. We discovered that TLR-induced phosphorylation of p38 was significantly inhibited in LCMV-infected cells. We detected enhanced expression of suppressor of cytokine signalling (SOCS)-3 and IL-10. Yet, neutralizing IL-10 did not restore IL-12/IL-23 expression. Taken together, these results show that virus infection interferes with the magnitude of TLR-mediated inflammatory responses by repressing specific cytokine expression.
... During infection with viruses, TLR activation induces the production of type I IFN, which plays an important role in antiviral defense [136,137]. TLR-recognizing viral motifs include TLR3 for viral double stranded RNA [138], TLR7 and TLR8 for viral single stranded RNA [139], TLR9 for DNA containing unmethylated CpG motifs present in numerous viral pathogens, and TLR13 for bacterial ribosomal RNA. The regulatory role of Nod2 in viral infections is related to its capacity to sense microbiota-derived MDP and to modulate the TLR pathways activated by RNA and DNA viruses, including respiratory syncytial virus (RSV), influenza A virus (IAV), human immunodeficiency virus type-1 (HIV-1), norovirus (NV), and human enterovirus species B (HEV-B) ( Table 2). ...
Nucleotide-binding oligomerization domain 2 (NOD2) is an intracellular pattern recognition receptor that senses bacterial peptidoglycan (PGN)-conserved motifs in cytosol and stimulates host immune response. The association of NOD2 mutations with a number of inflammatory pathologies, including Crohn disease (CD), Graft-versus-host disease (GVHD), and Blau syndrome, highlights its pivotal role in host–pathogen interactions and inflammatory response. Stimulation of NOD2 by its ligand (muramyl dipeptide) activates pro-inflammatory pathways such as nuclear factor-κB (NF-κB), mitogen-activated protein kinases (MAPKs), and Caspase-1. A loss of NOD2 function may result in a failure in the control of microbial infection, thereby initiating systemic responses and aberrant inflammation. Because the ligand of Nod2 is conserved in both gram-positive and gram-negative bacteria, NOD2 detects a wide variety of microorganisms. Furthermore, current literature evidences that NOD2 is also able to control viruses’ and parasites’ infections. In this review, we present and discuss recent developments about the role of NOD2 in shaping the gut commensal microbiota and pathogens, including bacteria, viruses, and parasites, and the mechanisms by which Nod2 mutations participate in disease occurrence.
... Therefore, it is necessary to develop new strategies against JEV. Type I interferons (IFNs, including IFN-α) mediate a wide range of biological activities, including antiviral activity, cell growth, differentiation, apoptosis, and immune response [5]. Type I IFNs bind a ...
Mx proteins are interferon (IFN)-induced dynamin-like GTPases that are present in all vertebrates and inhibit the replication of myriad viruses. However, the role Mx proteins play in IFN-mediated suppression of Japanese encephalitis virus (JEV) infection is unknown. In this study, we set out to investigate the effects of Mx1 and Mx2 expression on the interferon-α (IFNα) restriction of JEV replication. To evaluate whether the inhibitory activity of IFNα on JEV is dependent on Mx1 or Mx2, we knocked down Mx1 or Mx2 with siRNA in IFNα-treated PK-15 cells and BHK-21 cells, then challenged them with JEV; the production of progeny virus was assessed by plaque assay, RT-qPCR, and Western blotting. Our results demonstrated that depletion of Mx1 or Mx2 did not affect JEV restriction imposed by IFNα, although these two proteins were knocked down 66% and 79%, respectively. Accordingly, expression of exogenous Mx1 or Mx2 did not change the inhibitory activity of IFNα to JEV. In addition, even though virus-induced membranes were damaged by Brefeldin A (BFA), overexpressing porcine Mx1 or Mx2 did not inhibit JEV proliferation. We found that BFA inhibited JEV replication, not maturation, suggesting that BFA could be developed into a novel antiviral reagent. Collectively, our findings demonstrate that IFNα inhibits JEV infection by Mx-independent pathways.
... 51 During a viral infection, TLR and RIG-I-like receptor activation induces production of type I IFNs, which can augment the inflammatory response to TLR ligands including lipopolysaccharide (LPS). 52,53 In addition, certain bacteria such as S. aureus integrate into the A549 respiratory epithelial cells (adeno-carcinomic α β ...
Respiratory diseases are a very common source of morbidity and mortality among children. Health care providers often face a dilemma when encountering a febrile infant or child with respiratory tract infection. The reason expressed by many clinicians is the trouble to confirm whether the fever is caused by a virus or a bacterium. The aim of this review is to update the current evidence on the virus-induced bacterial infection. We present several clinical as well in vitro studies that support the correlation between virus and secondary bacterial infections. In addition, we discuss the pathophysiology and prevention modes of the virus-bacterium coexistence. A search of the PubMed and MEDLINE databases was carried out for published articles covering bacterial infections associated with respiratory viruses. This review should provide clinicians with a comprehensive idea of the range of bacterial and viral coinfections or secondary infections that could present with viral respiratory illness.
... IFNAR1-deficient mice appear more resistant to secondary pulmonary bacterial infections, showing that IFN-I responsiveness contributes to disease (130). Similarly, after lymphochoriomeningitis virus (LCMV) infection, wild-type but not IFNAR1-deficient mice are more susceptible to LPSinduced septic shock (131). Several mechanisms may contribute to the detrimental role of IFN-I in secondary bacterial infections ( Figure 5). ...
Type I interferons (IFN-I) were identified over 50 years ago as cytokines critical for host defense against viral infections. IFN-I promote anti-viral defense through two main mechanisms. First, IFN-I directly reinforce or induce de novo in potentially all cells the expression of effector molecules of intrinsic anti-viral immunity. Second, IFN-I orchestrate innate and adaptive anti-viral immunity. However, IFN-I responses can be deleterious for the host in a number of circumstances, including secondary bacterial or fungal infections, several autoimmune diseases, and, paradoxically, certain chronic viral infections. We will review the proposed nature of protective versus deleterious IFN-I responses in selected diseases. Emphasis will be put on the potentially deleterious functions of IFN-I in human immunodeficiency virus type 1 (HIV-1) infection, and on the respective roles of IFN-I and IFN-III in promoting resolution of hepatitis C virus (HCV) infection. We will then discuss how the balance between beneficial versus deleterious IFN-I responses is modulated by several key parameters including (i) the subtypes and dose of IFN-I produced, (ii) the cell types affected by IFN-I, and (iii) the source and timing of IFN-I production. Finally, we will speculate how integration of this knowledge combined with advanced biochemical manipulation of the activity of the cytokines should allow designing innovative immunotherapeutic treatments in patients. Specifically, we will discuss how induction or blockade of specific IFN-I responses in targeted cell types could promote the beneficial functions of IFN-I and/or dampen their deleterious effects, in a manner adapted to each disease.
... Also, IFN-␣ alone given intranasally drove a rapid and transient induction of proinflammatory cytokines in the lung. It has been shown that bone marrow-derived macrophages can produce CCL2 after stimulation with IFN- (38) and that recombinant IFN-␣ (rIFN-␣) potentiates serum TNF-␣ response to LPS administration (39). Furthermore, the dependence on IFNAR signaling for cytokine production has previously been suggested in studies where BMDCs from IFNAR1 Ϫ/Ϫ mice were found to produce less IL-12p70 after RSV exposure (37) or after treatment with select combinations of TLR agonists (36). ...
Unlabelled:
Type I interferons (IFNs) are produced early upon virus infection and signal through the alpha/beta interferon (IFN-α/β) receptor (IFNAR) to induce genes that encode proteins important for limiting viral replication and directing immune responses. To investigate the extent to which type I IFNs play a role in the local regulation of inflammation in the airways, we examined their importance in early lung responses to infection with respiratory syncytial virus (RSV). IFNAR1-deficient (IFNAR1(-/-)) mice displayed increased lung viral load and weight loss during RSV infection. As expected, expression of IFN-inducible genes was markedly reduced in the lungs of IFNAR1(-/-) mice. Surprisingly, we found that the levels of proinflammatory cytokines and chemokines in the lungs of RSV-infected mice were also greatly reduced in the absence of IFNAR signaling. Furthermore, low levels of proinflammatory cytokines were also detected in the lungs of IFNAR1(-/-) mice challenged with noninfectious innate immune stimuli such as selected Toll-like receptor (TLR) agonists. Finally, recombinant IFN-α was sufficient to potentiate the production of inflammatory mediators in the lungs of wild-type mice challenged with innate immune stimuli. Thus, in addition to its well-known role in antiviral resistance, type I IFN receptor signaling acts as a central driver of early proinflammatory responses in the lung. Inhibiting the effects of type I IFNs may therefore be useful in dampening inflammation in lung diseases characterized by enhanced inflammatory cytokine production.
Importance:
The initial response to viral infection is characterized by the production of interferons (IFNs). One group of IFNs, the type I IFNs, are produced early upon virus infection and signal through the IFN-α/β receptor (IFNAR) to induce proteins important for limiting viral replication and directing immune responses. Here we examined the importance of type I IFNs in early responses to respiratory syncytial virus (RSV). Our data suggest that type I IFN production and IFNAR receptor signaling not only induce an antiviral state but also serve to amplify proinflammatory responses in the respiratory tract. We also confirm this conclusion in another model of acute inflammation induced by noninfectious stimuli. Our findings are of relevance to human disease, as RSV is a major cause of infant bronchiolitis and polymorphisms in the IFN system are known to impact disease severity.
... Other viruses such as Lymphocytic Choriomeningitis Virus (LCMV) have also been shown to induce LPS hypersensitivity. In these cases, early production of IFN-αβ 2-3 days after infection mediates a relatively weak (2-4-fold) hypersensitivity (or even downregulation of TNF production ) [92], while later (after 7 days) IFN-production mediates a strong hypersensitivity to LPS, characterized by the overproduction of TNF [89][90][91][92][93]. In contrast, Ad-induced early-type I IFN production mediates a very strong LPS hypersensitivity characterized by the dramatic overproduction of TNF (50-100-fold) and IL-6 (5-10-fold) [88]. ...
Adenoviruses are important infectious agents and also emerging vectors in different biomedical applications. These viruses elicit a strong innate and adaptive immune response, which influences both the course of disease and the success of the applied vectors. Several Toll-like Receptor (TLR)-dependent and -independent mechanisms contribute to these responses. Understanding of the involved viral and cellular factors is crucial for the treatment of various adenovirus diseases and the optimal design of adenovirus vector applications. Here we summarize our current understanding of the complex nature of adenovirus-induced innate immune mechanisms.
... It was purified and had no detectable endotoxin, i.e., LPS, using standard assays. However, because previous work from our laboratory has demonstrated that sensitivity to endotoxin can be increased 10-to 100-fold during viral infections (37,38), and because treatment of both mutated and functional sIL-15R␣ had stimulatory effects on NK cells in C57BL/6 mice, experiments with this reagent were performed in the endotoxin-resistant C3H/ HeJ mice. Under these conditions, this very specific blocker of IL-15 functions inhibited the accumulation of NK cells. ...
... However, TNF levels were only slightly diminished (Fig. 4E). This strongly suggests that IL-12 and IL-10 secretion evoked by bacterial infections is MyD88-dependent, whereas TNF production is also regulated in a MyD88-independent fashion, possibly triggered via TRIF or cytosolic PRR-induced IFN-I [27]. ...
IRAK4, a serine/threonine kinase is a central adaptor protein in TLR signaling. To better understand the clinical significance of IRAK4 deficiency we examined the impact of IRAK4 on bacterial recognition in human monocytes. We show that IRAK4 knockdown modulates monocyte-derived cytokine secretion in response to S. aureus and S. pneumoniae, resulting in decreased IL-12 and elevated IL-10 production, a finding also reproducible with ligands for TLR2 and TLR4. In contrast, silencing of MyD88 leads to a complete loss of cytokine secretion, indicating that IRAK4 acts as a differential regulator of bacteria/TLR-induced cytokine secretion downstream of MyD88. Further analysis revealed that this modulatory function results from IRAK4 suppression of protein kinase B (PKB/Akt). Release of suppression upon IRAK4 silencing (but not MyD88 knockdown) increases phosphorylation of PKB/Akt, counteracts NF-κB activation and finally results in a monocyte phenotype with tolerogenic features, thus unleashing Akt- and mTOR-dependent release of IL-10, along with concomitant phosphorylation of FOXO transcription factors. In line with these observations IRAK4-deficient monocytes failed to induce allogeneic CD8(+) and CD4(+) T-cell responses, an effect reverted by neutralization of IL-10. Taken together, our data highlight an unexpected role of IRAK4, Akt and mTOR in the regulation of tolerance in human monocytes.
... ELISAs were preformed as per manufacture's instructions. For detection of mouse IFN-α an ELISA was developed as previously described using a rat anti-mouse IFNα capture antibody (PBL, Piscataway, NJ) and a rabbit anti-IFN-α detection antibody (US Biological, Swampscott, MA) [28,29]. ELISAs were developed with tetramethylbenzidine substrate (Sigma Chemical Co, St Louis, MO) and absorbance measured at 450 nm with an optical plate reader (Thermo Labsystems, Waltham, MA). ...
Tumor-associated macrophages (TAM) are very abundant in tumors and are thought to play a major role in promoting tumor growth.
The generation of TAM is positively regulated by several cytokines, including colony stimulating factor-1 (CSF-1) and monocyte
chemoattractant protein-1 (CCL2). However, endogenous factors that suppress the generation of TAM within tumors have not been
previously identified. An earlier study showed that endogenously produced type I interferons (IFN) suppressed tumor growth
via their effects on hematopoietic cells rather than through direct effects on tumor cells. Therefore, we used mouse tumor
models to investigate the effects of endogenously produced type I IFNs on the generation of TAM. We found using immunohistochemistry
and flow cytometry that TAM density was significantly increased in tumors of mice lacking the type I IFN receptor (IFN-α/βR−/− mice) compared to wild type mice. Moreover, the increase in TAM density was associated with a significant increase in tumor
growth rate and angiogenesis. The phenotype of TAM was similar in IFN-α/βR−/− mice and wild type mice and tumors in both mice produced similar amounts of CSF-1 and CCL2. However, in vitro assays indicated
that low concentrations of type I IFNs significantly inhibited the generation of bone marrow macrophages in response to CSF-1.
These findings indicate that endogenously produced type I IFNs suppress the generation of TAM, which may in turn account for
inhibition of tumor growth and angiogenesis.
... Some viral infections strongly exacerbate mouse sensitivity to endotoxin and the severity of septic shock (Nansen et al., 1997;Doughty et al., 2001). This is the case for lactate dehydrogenase-elevating virus (LDV), a common mouse nidovirus that triggers a strong, but transient activation of innate immune cells (Le-Thi-Phuong et al., 2007a). ...
Lactate dehydrogenase-elevating virus (LDV) exacerbates mouse susceptibility to endotoxin shock through enhanced tumour necrosis factor (TNF) production by macrophages exposed to lipopolysaccharide (LPS). However, the in vivo enhancement of TNF production in response to LPS induced by the virus largely exceeds that found in vitro with cells derived from infected animals. Infection was followed by a moderate increase of Toll-like receptor (TLR)-4/MD2, but not of membrane CD14 expression on peritoneal macrophages. Peritoneal macrophages from LDV-infected mice unresponsive to type I interferons (IFNs) did not show enhanced expression of TLR-4/MD2 nor of CD14, and did not produce more TNF in response to LPS than cells from infected normal counterparts, although the in vivo response of these animals to LPS was strongly enhanced. In contrast, the virus triggered a sharp increase of soluble CD14 and of LPS-binding protein serum levels in normal mice. However, production of these LPS soluble receptors was similar in LDV-infected type I IFN-receptor deficient mice and in their normal counterparts. Moreover, serum of LDV-infected mice that contained these soluble receptors had little effect if any on cell response to LPS. These results suggest that enhanced response of LDV-infected mice to LPS results mostly from mechanisms independent of LPS receptor expression.
... In mouse models of lupus, administration of LPS greatly accelerates disease (71). Although these studies do not directly implicate type I IFN in pathogenesis, it is noteworthy that many of the toxic effects of LPS in vivo require type I IFN induction (72), and type I IFN induces sensitization to subsequent LPS challenge (73,74). Endogenous TLR4 ligands could act similarly. ...
Exacerbation of disease in systemic lupus erythematosus (SLE) is associated with bacterial infection. In conventional dendritic cells (cDCs), the TLR4 ligand bacterial LPS induces IFN-beta gene expression but does not induce IFN-alpha. We hypothesized that when cDCs are primed by cytokines, as may frequently be the case in SLE, LPS would then induce the production of IFN-alpha, a cytokine believed to be important in lupus pathogenesis. In this study we show that mouse cDCs and human monocytes produce abundant IFN-alpha following TLR4 engagement whether the cells have been pretreated either with IFN-beta or with a supernatant from DCs activated by RNA-containing immune complexes from lupus patients. This TLR4-induced IFN-alpha induction is mediated by both an initial TRIF-dependent pathway and a subsequent MyD88-dependent pathway, in contrast to TLR3-induced IFN-alpha production, which is entirely TRIF-dependent. There is also a distinct requirement for IFN regulatory factors (IRFs), with LPS-induced IFN-alpha induction being entirely IRF7- and partially IRF5-dependent, in contrast to LPS-induced IFN-beta gene induction which is known to be IRF3-dependent but largely IRF7-independent. This data demonstrates a novel pathway for IFN-alpha production by cDCs and provides one possible explanation for how bacterial infection might precipitate disease flares in SLE.
... These observations demonstrate that an ongoing natural viral infection can differentially modulate the ability of the innate immune system to produce IFN-I upon in vivo TLR stimulation, specifically suppressing selective pathways while re-enforcing others. This differential deregulation may be applicable to other viral infections that, as LCMV (Doughty et al., 2001; Durbin et al., 2003; Nguyen and Biron, 1999 ), induce an enhanced response to LPS and/or susceptibility to endotoxic shock (Baqui et al., 2000; Bender et al., 1993; Fejer et al., 2005; Nansen and Randrup Thomsen, 2001). ...
Emerging studies indicate an association between virus-induced impairment in type I interferon (IFN-I) production and enhanced susceptibility to opportunistic infections, which represent a major health problem. Here, we provide in vivo evidence that lymphocytic choriomeningitis virus (LCMV) infection of its natural murine host dramatically diminishes the unique capacity of plasmacytoid dendritic cells (pDCs) to secrete high levels of systemic IFN-I. While both acute and persistent LCMV infections suppress pDC IFN-I response, only the persistent virus induces a long-lasting diversion of this innate immune pathway. The consequent reduction in IFN-I production serves to impair natural killer cell responses in LCMV-infected mice challenged subsequently with murine cytomegalovirus (MCMV) as an opportunistic pathogen. This innate defect also compromises the host's ability to counteract early MCMV spread. These findings provide a mechanistic explanation for the occurrence of opportunistic infections following viral insults and have important implications for treating such medical complications.
... It was purified and had no detectable endotoxin, i.e., LPS, using standard assays. However, because previous work from our laboratory has demonstrated that sensitivity to endotoxin can be increased 10-to 100-fold during viral infections (37,38), and because treatment of both mutated and functional sIL-15R␣ had stimulatory effects on NK cells in C57BL/6 mice, experiments with this reagent were performed in the endotoxin-resistant C3H/ HeJ mice. Under these conditions, this very specific blocker of IL-15 functions inhibited the accumulation of NK cells. ...
NK cell cytotoxicity, IFN-gamma expression, proliferation, and accumulation are rapidly induced after murine CMV infections. Under these conditions, the responses were shown to be elicited in overlapping populations. Nevertheless, there were distinct signaling molecule requirements for induction of functions within the subsets. IL-12/STAT4 was critical for NK cell IFN-gamma expression, whereas IFN-alphabeta/STAT1 were required for induction of cytotoxicity. The accumulation/survival of proliferating NK cells was STAT4-independent but required IFN-alphabeta/STAT1 induction of IL-15. Taken together, the results define the coordinated interactions between the cytokines IFN-alphabeta, IL-12, and IL-15 for activation of protective NK cell responses during viral infections, and emphasize these factors' nonredundant functions under in vivo physiological conditions.
Sepsis is a common disease in sub-Saharan Africa and Asia, where malaria is also prevalent. To determine whether Plasmodium infection might enhance susceptibility to endotoxin shock, we used a mouse model of lipopolysaccharide (LPS) administration. Our results indicated that Plasmodium yoelii infection in mice strongly enhanced the susceptibility of the host to develop endotoxin shock. This increased susceptibility to endotoxin shock was correlated with a synergistic effect of Plasmodium and LPS on the secretion of Tumor Necrosis Factor (TNF). TNF contributed mostly to lethality after the dual challenge since neutralization with an anti-TNF antibody provided protection from death. Plasmodium infection also induced an enhancement of the serum levels of LPS soluble ligands, sCD14 and Lipopolysaccharide Binding Protein. In this regard, our data confirm that Plasmodium infection can profoundly modify responses to secondary bacteria challenges, resulting in dysregulated cytokine expression and pathological effects. If confirmed in humans, LPS soluble receptors might serve as markers of susceptibility to septic shock.
Cellular communication mediated by cytokines is an important mechanism dictating immune responses, their cross talk and final immune output. Cytokines play a major role in dictating the immune outcome to cancer by regulating the events of development, differentiation and activation of innate immune cells. Cytokines are pleiotropic in nature, hence understanding their role individually or as member of network cytokines is critical to delineate their role in tumour immunity. Tumour systemically manipulates the immune system to evade and escape immune recognition for their uncontrollable growth and metastasis. The developing tumour comprise a large and diverse set of myeloid cells which are vulnerable to manipulation by the tumour-microenvironment. The innate immune cells of the monocytic lineage skew the fate of the adaptive immune cells and thus dictating cancer elimination or progression. Targeting cells at tumour cite is preposterous owing to their tight network, poor reach and abundance of immunosuppressive mechanisms. Monocytic lineage-derived cytokines (monokines) play crucial role in tumour regression or progression by either directly killing the tumour cells with TNFα or promoting its growth by TGFβ. In addition, the monokines like IL-12, IL-1β, IL-6, IL-10 and TGFβ direct the adaptive immune cells to secrete anti-tumour cytokines, TNFα, IFNγ, perforin and granzyme or pro-tumour cytokines, IL-10 and TGFβ. In this review, we elucidate the roles of monokines in dictating the fate of tumour by regulating responses at various stages of generation, differentiation and activation of immune cells along with the extensive cross talk. We have attempted to delineate the synergy and antagonism of major monokines among themselves or with tumour-derived or adaptive immune cytokines. The review provides an update on the possibilities of placing monokines to potential practical use as cytokine therapy against cancer.
Secondary bacterial infections manifest during or after a viral infection(s) and can lead to negative outcomes and sometimes fatal clinical complications. Research and development of clinical interventions is largely focused on the primary pathogen, with research on any secondary infection(s) being neglected. Here we highlight the impact of secondary bacterial infections and in particular those caused by antibiotic-resistant strains, on disease outcomes. We describe possible non-antibiotic treatment options, when small molecule drugs have no effect on the bacterial pathogen and explore the potential of phage therapy and phage-derived therapeutic proteins and strategies in treating secondary bacterial infections, including their application in combination with chemical antibiotics.
That macrophages adapt to environmental cues is well-established. This adaptation has had several reiterations, first with innate imprinting and then with various combinations of trained, tolerant, paralyzed, or primed. Whatever the nomenclature, it represents a macrophage that is required to perform very different functions. First, alveolar macrophages are one of the sentinel cells that flag up damage and release mediators that attract other immune cells. Next, they mature to support T cell priming and survival. Finally they are critical in clearing inflammatory immune cells by phagocytosis and extracellular matrix turnover components by efferocytosis. At each functional stage they alter intrinsic components to guide their activity. Training therefore is akin to changing function. In this mini-review we focus on the lung and the specific role of type I interferons in altering macrophage activity. The proposed mechanisms of type I IFNs on lung-resident alveolar macrophages and their effect on host susceptibility to bacterial infection following influenza virus infection.
Concurrent infection with multiple pathogens occurs frequently in individuals and can result in exacerbated infections and altered immunity. However, the impact of such coinfections on immune responses remains poorly understood. Here we reveal that systemic infection results in an inflammation-induced suppression of local immunity. During localized infection or vaccination in barrier tissues including the skin or respiratory tract, concurrent systemic infection induces a type I interferon-dependent lymphopenia that impairs lymphocyte recruitment to the draining lymph node (dLN). This leads to suppressed lymphoid stromal cell expansion and dLN remodelling and impaired induction of B cell responses and antibody production. Our data suggest that contemporaneous systemic inflammation constrains the induction of regional immunity.
Risk factors (RFs) and mortality data of community acquire respiratory virus (CARVs) lower respiratory tract disease (LRTD) with concurrent pulmonary co‐infections in the setting of allogeneic hematopoietic stem cell transplantation (allo‐HSCT) is scarce. From January 2011 to December 2017, we retrospectively compared the outcome of allo‐HSCT recipients diagnosed of CARVs LRTD mono‐infection (n= 52, group 1), to those with viral, bacterial or fungal pulmonary CARVs LRTD co‐infections (n=15, group 2; n= 20, group 3, and n=11, group 4, respectively), and with those having bacterial pneumonia mono‐infection (n= 19, group 5). Overall survival (OS) at day 60 after BAL was significantly higher in group 1, 2 and 4 compared to group 3 (77%, 67% and 73% vs 35%, respectively, p= 0.012). Recipients of group 5 showed a trend to better OS compared to those of group 3 (62% vs 35%, p= 0.1). Multivariate analyses showed bacterial co‐infection as a RF for mortality (HR 2.65, 95% C.I. 1.2‐6.9, P = 0.017). We identified other 3 RFs for mortality: lymphocyte count < 0.5 × 109/L (HR 2.6, 95% 1.1‐6.2, P= 0.026), the occurrence of and CMV DNAemia requiring anti‐viral therapy (CMV‐DNAemia‐RAT) at the time of BAL (HR 2.32, 95% C.I. 1.1‐4.9, P = 0.03) and the need of oxygen support (HR 8.3, 95% C.I. 2.9‐35.3, P = 0.004). CARV LRTD co‐infections are frequent and may have a negative effect in the outcome, in particular in the context of bacterial co‐infections.
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STAT1 phosphorylation in response to exogenous interferon (IFN) administration can be inhibited by rotaviral replication both in vitro and in vivo. In addition many rotavirus strains are resistant to the actions of different IFN types. The regulation by rotaviruses (RVs) of antiviral pathways mediated by multiple IFN types is not well understood. In this study, we find that during infection in vitro and in vivo, RVs significantly deplete IFN type I, II, and III receptors (IFNRs). Regulation of IFNRs occurred exclusively within RV-infected cells and could be abrogated by inhibiting the lysosomal-endosomal degradation pathway. In vitro, IFNR degradation was conserved across multiple RV strains that differ in their modes of regulating IFN induction. In suckling mice, exogenously administered type I, II, or III IFN induced phosphorylation of STAT1-Y701 within intestinal epithelial cells (IECs) of suckling mice. Murine EW strain RV infection transiently activated intestinal STAT1 at 1 day postinfection (dpi) but not subsequently at 2 to 3 dpi. In response to injection of purified IFN-α/β or -λ, IECs in EW-infected mice exhibited impaired STAT1-Y701 phosphorylation, correlating with depletion of different intestinal IFNRs and impaired IFN-mediated transcription. The ability of EW murine RV to inhibit multiple IFN types led us to test protection of suckling mice from endotoxin-mediated shock, an outcome that is dependent on the host IFN response. Compared to mortality in controls, mice infected with EW murine RV were substantially protected against mortality following parenteral endotoxin administration. These studies identify a novel mechanism of IFN subversion by RV and reveal an unexpected protective effect of RV infection on endotoxin-mediated shock in suckling mice.
IMPORTANCE
Antiviral functions of types I, II, and III IFNs are mediated by receptor-dependent activation of STAT1. Here, we find that RV degrades the types I, II, and III IFN receptors (IFNRs) in vitro. In a suckling mouse model, RV effectively blocked STAT1 activation and transcription following injection of different purified IFNs. This correlated with significantly decreased protein expression of intestinal types I and II IFNRs. Recent studies demonstrate that in mice lipopolysaccharide (LPS)-induced lethality is prevented by genetic ablation of IFN signaling genes such as IFNAR1 and STAT1. When suckling mice were infected with RV, they were substantially protected from lethal exposure to endotoxin. These findings provide novel insights into the mechanisms underlying rotavirus regulation of different interferons and are likely to stimulate new research into both rotavirus pathogenesis and endotoxemia.
The Jak-STAT signaling pathway is activated by multiple immune cytokines and plays a key role in mediating inflammatory responses. The functional outcomes of Jak-STAT signaling are modulated by signaling crosstalk with heterologous signaling pathways. Conversely, Jak-STAT signaling regulates cell responses to multiple cytokines and inflammatory factors. Emerging evidence suggests that on balance Jak-STAT signaling is pathogenic in chronic inflammatory disorders, as Jak inhibitors have demonstrated efficacy in preclinical disease models and early clinical trials in rheumatoid arthritis (RA). This review describes Jak-STAT signaling crosstalk with pathways activated by inflammatory cytokines such as TNF-α, pattern recognition receptors such as Toll-like receptors, and ITAM-associated receptors, including crosstalk at the level of chromatin modification and gene expression. The Jak-STAT pathway is placed within the context of a signaling network that determines functional responses and outcomes during inflammation and in chronic inflammatory diseases such as RA.
Dendritic cell (DC)-dependent activation of liver NKT cells triggered by a single i.v. injection of a low dose (10-100 ng/mouse) of alpha-galactosyl ceramide (alphaGalCer) into mice induces liver injury. This response is particularly evident in HBs-tg B6 mice that express a transgene-encoded hepatitis B surface Ag in the liver. Liver injury following aGalCer injection is suppressed in mice depleted of NK cells, indicating that NK cells play a role in NK T cell-initiated liver injury. In vitro, liver NKT cells provide a CD80/86-dependent signal to alphaGalCer-pulsed liver DC to release IL-12 p70 that stimulates the IFN-gamma response of NKT and NK cells. Adoptive transfer of NKT cell-activated liver DC into the liver of nontreated, normal (immunocompetent), or immunodeficient (RAG(-/-) or HBs-tg/RAG(-/-)) hosts via the portal vein elicited IFN-gamma responses of liver NK cells in situ. IFN-beta down-regulates the pathogenic IL-12/IFN-gamma cytokine cascade triggered by NKT cell/DC/NK cell interactions in the liver. Pretreating liver DC in vitro with IFN-beta suppressed their IL-12 (but not IL-10) release in response to CD40 ligation or specific (alphaGalCer-dependent) interaction with liver NKT cells and down-regulated the IFN-gamma response of the specifically activated liver NKT cells. In vivo, IFN-beta attenuated the NKT cell-triggered induction of liver immunopathology. This study identifies interacting subsets of the hepatic innate immune system (and cytokines that up- and down-regulate these interactions) activated early in immune-mediated liver pathology.
The systemic inflammatory response is elicited in a multitude of clinical scenarios including infection, tissue injury (surgical
or traumatic), ischemia-reperfusion, post-cardiopulmonary bypass, as well as autoimmune phenomena. There are many factors
capable of modulating the magnitude and quality of the immune response during critical illness/injury. Some factors precede
critical illness/injury such as chronic poor nutrition, chronic stress (physiologic and/or psychologic), and underlying infectious
disease (chronic and acute). Other factors become important modulators during a critical illness/injury including acute stress,
infection, tissue injury, poor nutrition, and pharmacologic agents not usually associated with immunomodulation.
Secondary bacterial infections that follow infection with influenza virus result in considerable morbidity and mortality in young children, the elderly, and immunocompromised individuals and may also significantly increase mortality in normal healthy adults during influenza pandemics. We herein describe a mouse model for investigating the interaction between influenza virus and the bacterium Haemophilus influenzae. Sequential infection with sublethal doses of influenza and H. influenzae resulted in synergy between the two pathogens and caused mortality in immunocompetent adult wild-type mice. Lethality was dependent on the interval between administration of the bacteria and virus, and bacterial growth was prolonged in the lungs of dual-infected mice, although influenza virus titers were unaffected. Dual infection induced severe damage to the airway epithelium and confluent pneumonia, similar to that observed in victims of the 1918 global influenza pandemic. Increased bronchial epithelial cell death was observed as early as 1 day after bacterial inoculation in the dual-infected mice. Studies using knockout mice indicated that lethality occurs via a mechanism that is not dependent on Fas, CCR2, CXCR3, interleukin-6, tumor necrosis factor, or Toll-like receptor-4 and does not require T or B cells. This model suggests that infection with virulent strains of influenza may predispose even immunocompetent individuals to severe illness on secondary infection with H. influenzae by a mechanism that involves innate immunity, but does not require tumor necrosis factor, interleukin-6, or signaling via Toll-like receptor-4.
We have previously shown that administration of a low-dose of melphalan (L-phenylalanine mustard; L-PAM) to mice bearing a large s.c. MOPC-315 tumor leads to up-regulation of TNF-alpha expression, which is first evident at the mRNA level at 24 h after the chemotherapy. In this study, we show accumulation of IFN-beta mRNA in the spleen and tumor nodule of such mice as early as 1 h after the chemotherapy followed by elevated production of IFN-beta protein. IFN-beta protein in turn was found to be important for the L-PAM-induced up-regulation of TNF-alpha expression, as neutralization of IFN-beta inhibited the L-PAM-induced up-regulation of TNF-alpha mRNA expression in MOPC-315 tumor cells. In addition, L-PAM failed to up-regulate TNF-alpha expression in spleen cells from mice in which signaling by IFN-beta is deficient. Studies into the mechanism through which L-PAM leads to rapid accumulation of IFN-beta mRNA revealed that it requires de novo RNA synthesis, indicating that the regulation is at the transcriptional level. However, it did not require de novo protein synthesis, indicating that activation of pre-existing transcription factors is sufficient for IFN-beta gene expression. The L-PAM-induced accumulation of IFN-beta mRNA was mimicked with H(2)O(2) and was prevented with the antioxidant N-acetyl-L-cysteine, indicating that reactive oxygen species are involved in the transcriptional regulation of L-PAM-induced IFN-beta gene expression. Thus, the IFN-beta gene is an early response gene that is activated in response to L-PAM via a pathway that involves reactive oxygen species, and IFN-beta in turn plays an important role in L-PAM-induced TNF-alpha up-regulation.
CD1d-deficient mice have normal numbers of T lymphocytes and natural killer cells but lack Vα14+ natural killer T cells. Respiratory syncytial virus (RSV) immunopathogenesis was evaluated in 129×C57BL/6, C57BL/6, and BALB/c
CD1d−/− mice. CD8+ T lymphocytes were reduced in CD1d−/− mice of all strains, as shown by cell surface staining and major histocompatibility complex class I tetramer analysis, and
resulted in strain-specific alterations in illness, viral clearance, and gamma interferon (IFN-γ) production. Transient activation
of NK T cells in CD1d+/+ mice by α-GalCer resulted in reduced illness and delayed viral clearance. These data suggest that early IFN-γ production
and efficient induction of CD8+-T-cell responses during primary RSV infection require CD1d-dependent events. We also tested the ability of α-GalCer as an
adjuvant to modulate the type 2 immune responses induced by RSV glycoprotein G or formalin-inactivated RSV immunization. However,
immunized CD1-deficient or α-GalCer-treated wild-type mice did not exhibit diminished disease following RSV challenge. Rather,
some disease parameters, including cytokine production, eosinophilia, and viral clearance, were increased. These findings
indicate that CD1d-dependent NK T cells play a role in expansion of CD8+ T cells and amplification of antiviral responses to RSV.
Dendritic cell (DC)-dependent activation of liver NKT cells triggered by a single i.v. injection of a low dose (10-100 ng/mouse) of alpha-galactosyl ceramide (alphaGalCer) into mice induces liver injury. This response is particularly evident in HBs-tg B6 mice that express a transgene-encoded hepatitis B surface Ag in the liver. Liver injury following alphaGalCer injection is suppressed in mice depleted of NK cells, indicating that NK cells play a role in NK T cell-initiated liver injury. In vitro, liver NKT cells provide a CD80/86-dependent signal to alphaGalCer-pulsed liver DC to release IL-12 p70 that stimulates the IFN-gamma response of NKT and NK cells. Adoptive transfer of NKT cell-activated liver DC into the liver of nontreated, normal (immunocompetent), or immunodeficient (RAG(-/-) or HBs-tg/RAG(-/-)) hosts via the portal vein elicited IFN-gamma responses of liver NK cells in situ. IFN-beta down-regulates the pathogenic IL-12/IFN-gamma cytokine cascade triggered by NKT cell/DC/NK cell interactions in the liver. Pretreating liver DC in vitro with IFN-beta suppressed their IL-12 (but not IL-10) release in response to CD40 ligation or specific (alphaGalCer-dependent) interaction with liver NKT cells and down-regulated the IFN-gamma response of the specifically activated liver NKT cells. In vivo, IFN-beta attenuated the NKT cell-triggered induction of liver immunopathology. This study identifies interacting subsets of the hepatic innate immune system (and cytokines that up- and down-regulate these interactions) activated early in immune-mediated liver pathology.
Although much remains to be learned, the study of early responses to LCMV infections of mice has contributed to the basic understanding of the regulation of a variety of important innate immune responses. Major discoveries have included the appreciation of the levels of type 1 IFNs induced during endogenous responses to viral infections, the importance of IFN-alpha/beta for induction of NK cell cytotoxicity, and the roles for IFN-alpha/beta in regulating the expression of other innate cytokines, i.e., IL-12 and IFN-gamma produced by NK cells (Fig. 11). Taken together with the characterization of adaptive responses to LCMV, a paradigm is emerging for a possible initial to innate to adaptive response cascade during infections with viruses eliciting endogenous expression of high levels of IFN-alpha/beta. The results not only advance the understanding of endogenous responses to viral infections and how they are balanced to achieve the best possible outcome for the host, but also give insights into possible consequences of therapeutic intervention with type 1 IFNs.
Priming with heat-killed Propionibacterium acnes enhances the sensitivity of mice to lipopolysaccharide (LPS) and other biologically active bacterial components. We show
that P. acnes priming has protective and deleterious effects on a subsequent serovar Typhimurium infection. It may result in a complete
protection or prolonged survival, or it may accelerate mortality of the infected mice, depending on the number of serovar
Typhimurium bacteria administered and on the degree of LPS hypersensitivity at the time of infection. Both effects of P. acnes-induced hypersensitivity are mediated by gamma interferon (IFN-γ) and are based on a differential activation of the innate
immune mechanisms which recognize and react against the LPS present in infecting bacteria. In P. acnes-primed mice null for LPS-binding protein (LBP−/− mice), the impaired LPS recognition, due to the absence of LBP, resulted in a higher resistance to serovar Typhimurium infection.
A similar P. acnes priming of mice had a protective, but no deleterious effect on a subsequent L. monocytogenes infection. This effect was IFN-γ dependent but independent of LBP.
Porcine reproductive-respiratory syndrome virus (PRRSV) is a key agent in multifactorial respiratory disease of swine. Intratracheal administration of bacterial lipopolysaccharides (LPSs) to PRRSV-infected pigs results in markedly enhanced respiratory disease, whereas the inoculation of each component alone results in largely subclinical disease. This study examines whether PRRSV-LPS-induced respiratory disease is associated with the excessive production of proinflammatory cytokines in the lungs. Gnotobiotic pigs were inoculated intratracheally with PRRSV and then with LPS at 3, 5, 7, 10, or 14 days of infection and euthanatized 6 h after LPS inoculation. Controls were inoculated with PRRSV or LPS only or with phosphate-buffered saline. Virus titers, (histo)pathological changes in the lungs, numbers of inflammatory cells, and bioactive tumor necrosis factor alpha (TNF-alpha), interleukin-1 (IL-1), and IL-6 levels in bronchoalveolar lavage fluids were examined. All pigs inoculated with PRRSV-LPS developed severe respiratory disease, whereas the controls that were inoculated with PRRSV or LPS alone did not. PRRSV infection significantly enhanced cytokine production in response to LPS. Peak TNF-alpha, IL-1, and IL-6 titers were 10 to 100 times higher in the PRRSV-LPS-inoculated pigs than in the pigs inoculated with PRRSV or LPS alone; and the titers correlated with the respiratory signs. The levels of neutrophil infiltration and the pathological changes detected in the lungs of PRRSV-LPS-inoculated pigs resembled those detected when the effects of PRRSV and LPS inoculated alone are combined, but with no synergistic effects between PRRSV and LPS. These data demonstrate a synergism between PRRSV and LPS in the induction of proinflammatory cytokines and an association between induction of these cytokines and disease.
Tumor necrosis factor (TNF) is a macrophage product under active study as an anticancer drug. However, this agent can be very toxic and has been implicated in the pathogenesis of endotoxic shock. After intravenous injection of human recombinant TNF (4 micrograms/g), growing rats showed an unusual constellation of physiological responses, and all died within 2-4 hr. In 1 hr, TNF caused a sharp fall (2.5 degrees C) in body temperature and a large increase in plasma prostaglandin E2 levels. Blood glucose initially increased, but then a profound hypoglycemia developed by 2 hr. The TNF-treated animals also showed diarrhea, cyanosis, and a severe metabolic acidosis. A single injection of the cyclooxygenase inhibitors indomethacin or ibuprofen before the TNF treatment completely prevented the rapid killing and reduced eventual lethality by 70%. These agents blocked prostaglandin E2 production and prevented the hypothermia, changes in blood glucose, acidosis, and other symptoms. Since similar physiological changes have been reported after endotoxin injection, our data support the suggestion that TNF production is a critical factor in the development of septic shock. These findings also indicate that increased production of prostaglandins or thromboxanes is important in endotoxic shock and argue that cyclooxygenase inhibitors should be useful in its therapy. Indomethacin did not block the cytotoxic effects of TNF in vitro on several transformed cell lines (HeLa, Me 180, or L929). Therefore, combined use of TNF with a cyclooxygenase inhibitor may allow safer administration of high doses of this polypeptide to cancer patients.
Tumor necrosis factor (cachectin), a protein produced by monocytes and macrophages, has been implicated as an important mediator of the lethal effects of endotoxic shock and the cachexia of chronic infection. Recombinant human tumor necrosis factor alpha (rTNF) was given intravenously to patients as part of an antineoplastic trial. Fever, tachycardia, and at higher doses, hypotension occurred after a single injection of rTNF. Metabolic effects after rTNF administration were dose related and included enhanced energy expenditure with elevated CO2 production, increased whole body protein metabolism and peripheral amino acid efflux from the forearm, and decreased total arterial amino acid levels associated with a significant increase in plasma cortisol. Elevated serum triglycerides, as well as increased glycerol and free fatty acid turnover were seen, suggesting increased whole body lipolysis and fat utilization after rTNF. These findings indicate that administration of TNF in man reproduces many of the acute physiologic and metabolic responses to tissue injury, including energy substrate mobilization.
The toxic properties of human recombinant tumor necrosis factor (TNF) were investigated in mice made hypersensitive to endotoxin by treatment with D-galactosamine. C3H/TifF mice treated with D-galactosamine were rendered sensitive to the lethal effects of submicrogram amounts of TNF. In the absence of D-galactosamine, TNF caused approximately 80% lethality with 500 micrograms. The duration of sensitization to TNF lasted up to 8 h after D-galactosamine administration, that towards LPS, up to 4 h. As with LPS, with TNF sensitization could be inhibited by uridine administered up to 2 h after D-galactosamine/TNF, showing that the early biochemical alterations in the liver known to be necessary for sensitization to LPS are also necessary for sensitization to TNF. In contrast to LPS, the toxicity of TNF was expressed also in D-galactosamine-treated endotoxin-resistant C3H/HeJ mice. The susceptibility of these mice to TNF was identical to that of endotoxin sensitive mice. In the absence of D-galactosamine the toxicity of TNF in C3H/HeJ mice was comparable to that obtained in C3H/TifF mice, being lethal with amounts of the order of 500 micrograms. The present results support the hypothesis that TNF is a mediator of lethal toxicity of endotoxin.
The presence of natural killer (NK) cells contributes to early defense against murine cytomegalovirus (MCMV) infection. Although NK cells can mediate in vivo protection against MCMV, the mechanism by which they do so has not been defined. The studies presented here evaluate cytokine production by NK cells activated during MCMV infection and the role of NK cell-produced cytokines in early in vivo antiviral defenses. Experiments with normal C57BL/6, T cell-deficient C57BL/6 nude, and severe combined immunodeficient mice lacking T and B cells demonstrated that both interferon gamma (IFN-gamma) and tumor necrosis factor (TNF) production were induced at early times after infection with MCMV. Conditioned media samples prepared with cells from these mice, on day 2 after infection, produced 11-43 pg/million cells of IFN-gamma and 12-19 pg/million cells of TNF as evaluated by specific protein enzyme-linked immunosorbent assays. Studies in the NK- and T cell-deficient mouse line, E26, in mice that had been depleted in vivo of NK cells by treatment with antibodies eliminating NK cells, anti-asialo ganglio-N-tetraosylceramide or anti-NK1.1, and with populations of cells that had been depleted of NK cells by complement treatment with the anti-NK cell antibody, SW3A4, demonstrated that NK cells were solely responsible for the IFN-gamma but were not required for TNF production. The in vivo absence of NK cells was accompanied by increased viral hepatitis and viral replication in both immunocompetent and immunodeficient mice, as well as decreased survival time of immunodeficient mice. In vivo treatments with antibodies neutralizing IFN-gamma demonstrated that this factor contributed to the NK cell-mediated antiviral defense and reduced the measured parameters of viral defense to levels indistinguishable from those observed in NK cell-deficient mice. These effects appeared to be independent of cytolytic activity, as NK cells isolated from anti-IFN-gamma-treated mice mediated killing at levels comparable to those observed in control-treated mice. The consequences of interleukin 12 (IL-12) administration, a known potent inducer of IFN-gamma production by NK cells, were evaluated in MCMV-infected mice. Low IL-12 doses, i.e., 1 ng/d, increased NK cell cytotoxicity and IFN-gamma production up to twofold and resulted in improved antiviral status; virus-induced hepatitis was decreased as much as fivefold, and viral burdens were decreased to levels below detection.(ABSTRACT TRUNCATED AT 400 WORDS)
Interleukin 12 (IL-12) doses in excess of 100 ng/d have been shown to induce profound immunotoxicities in mice infected with lymphocytic choriomeningitis virus (LCMV). These immunotoxicities are characterized by almost complete inhibition of virus-induced CD8+ T cell expansion and CTL activation, and up to 2 log increases in viral replication. They are accompanied by induction of serum tumor necrosis factor (TNF). The studies presented here were undertaken to characterize mechanisms for the IL-12-induced toxicities and to examine expression and function of TNF in this context. Several physiological changes were induced in IL-12-treated uninfected and dramatically elevated in IL-12-treated virus-infected mice. IL-12 induced (a) decreases in body weights, > 10% in uninfected and > 20% in LCMV-infected mice; (b) elevation of circulating glucocorticoid levels to > 10 micrograms/dl in uninfected and > 20 micrograms/dl in infected mice; and (c) decreases in thymic mass, > 30% in uninfected and up to 95% in infected mice. These changes are known to be associated with circulating TNF. Northern blot and in situ hybridization analyses demonstrated that IL-12 induced TNF-alpha expression and that LCMV infection synergized with IL-12 for induction of this factor. Antibodies neutralizing TNF reversed all of the IL-12-induced toxicities in LCMV-infected mice including the immunotoxicities against CD8+ T cells and anti-viral defenses. The TNF-mediated immunotoxicities appeared to result from an induced cellular sensitivity to the factor, as splenic leukocytes and CD8+ T cell subsets isolated from LCMV-infected mice were more sensitive to TNF-mediated cytotoxicity in culture than were equivalent populations prepared from uninfected mice. Experiments with the glucocorticoid type II receptor antagonist, RU486, demonstrated that endogenous glucocorticoids were secondary intermediaries in IL-12-induced thymic atrophy. Studies in IL-2-deficient mice showed that the synergism was dependent upon endogenous IL-2. The results delineate a unique mechanism of TNF-mediated toxicity. In addition, they have significant implications concerning potential detrimental consequences of in vivo TNF induction and of IL-12 administration for protective anti-viral responses.
The Shwartzman reaction is elicited by two injections of lipopolysaccharide (LPS) in mice. The priming LPS injection is given in the footpad, whereas the lethal LPS challenge is given intravenously 24 h later. The injection of interferon gamma (IFN-gamma) or interleukin 12 (IL-12) instead of the LPS priming injection induced the lethal reaction in mice further challenged with LPS. Antibodies against IFN-gamma when given together with the priming agent, prevented the lethal reaction in mice primed with either LPS, IL-12, or IFN-gamma. Antibodies against IL-12, when given together with the priming agent, prevented the lethal reaction in mice primed with either LPS or IL-12 but not with IFN-gamma. These results strongly suggest that LPS induces the release of IL-12, that IL-12 induces the production of IFN-gamma, and that IFN-gamma is the cytokine that primes macrophages and other cell types. Upon LPS challenge, the lethal Shwartzman reaction is induced by a massive production of inflammatory cytokines that act on the target sites already sensitized by IFN-gamma. If mixtures of TNF and IL-1 or mixtures of TNF and IFN-gamma are used to challenge mice previously primed with IFN-gamma or IL-12, mortality is induced. In the same conditions, the individual cytokines or a mixture of IL-1 and IFN-gamma do not replace the LPS challenge. When the mice are primed with LPS, the combination of TNF, IL-1, and IFN-gamma induced only a partial mortality incidence suggesting that the involvement of other LPS-induced factors.
The interplay between viral infection and lipopolysaccharide (LPS) was studied. Infection with a noncytopathogenic virus,
lymphocytic choriomeningitis virus (LCMV), was found to sensitize mice to low doses of LPS. In vivo, this hypersensitivity
correlated with hyperproduction of tumor necrosis factor-α (TNF-α), and in vitro, LPS-stimulated splenic adherent cells produced
increased amounts of TNF-α. Hyperproduction of TNF-α was temporally correlated with virus-induced production of interferon-γ
(IFN-γ); only marginally increased IFN-γ and TNF-α production was observed in LCMV-infected, T cell-deficient mice and in
mice infected with vesicular stomatitis virus, a virus that induces much less T cell activation than does LCMV. Finally, LCMV
infection was much less efficient in priming IFN-γ knockout mice for hyperproduction of TNF-α. These findings indicate that
clinically silent viral infections may induce hypersensitivity to LPS through T cell activation and subsequent production
of IFN-γ; this sensitizes monocytes/macrophages for hyperproduction of TNF-α.
The involvement of cytokines in the pathogenesis of a generalized, Shwartzman-like lethal inflammatory response to bacterial lipopolysaccharides (LPS) was studied by testing the ability of cytokines or neutralizing anticytokine antibodies to modify the course of the syndrome. The reaction was elicitable in non-SPF NMRI mice by two consecutive injections of S. marcescens LPS: a first injection in the footpad, followed after 24 h by an intravenous dose; the size and route of the preparatory LPS dose were found to be critical. Treatment with mAbs against IFN-gamma was found to completely prevent the reaction. Treatment with IFN-gamma on the other hand, rendered the mice more sensitive to elicitation of the reaction. In contrast, systemic administration of IFN-alpha/beta exerted a desensitizing effect. The role of endogenous cytokines in the pathogenesis of this generalized Shwartzman reaction was also documented by a study of the cytokine levels in the serum of the mice. In comparisons between mice given lethal and nonlethal induction schedules, a good correlation was found between mortality rates and height of IFN or TNF levels, but no correlation was seen with IL-6 levels. Also, in mice that were protected by anti-IFN-gamma antibody, serum IFN and TNF were undetectable, whereas IL-6 levels were as high as in unprotected mice. These data provide evidence that among the cytokines that govern the inflammatory response to LPS, endogenous IFN-gamma occupies a key position. These findings therefore also open perspectives for clinical application of IFN-gamma antagonists.
Endotoxins, the lipopolysaccharide (LPS) moieties on the bacterial cell wall, cause many of the pathological features of Gram-negative septicemia. Tumor necrosis factor (TNF), primarily a product of monocyte/macrophages, has been shown to mediate many of the pathophysiological effects of endotoxin. Kupffer cells, the largest macrophage population in the body, release TNF when stimulated by LPS in vitro. A recombinant human hybrid interferon-alpha A/D (rIFN-alpha) markedly inhibited this LPS-elicited TNF production by Kupffer cells. The effects of rIFN-alpha were further tested in C57BL/6 mice receiving a lethal dose (400 micrograms/mouse) of LPS. All LPS-treated mice died within 2 days. Pretreatment with rIFN-alpha 1 h before LPS challenge improved the survival at 3 days to 22% (5/23, p < 0.04). In contrast, rIFN-alpha was more effective when administered 20 min after LPS injection, increasing the survival rate to 81% (13/16, p < 0.0001). TNF mRNA expression in the liver and spleen 50 min after LPS challenge, and plasma TNF 1.5 h after LPS were also reduced by either pretreatment or post-treatment with rIFN-alpha. Subsequently, experiments were carried out to test the efficacy of delayed rIFN-alpha treatment. A significant protective effect was still apparent when rIFN-alpha was administered 6, 10 and even 14 h (81%, 62% and 28% survival, respectively) after LPS challenge when serum TNF levels had already returned to near baseline. These experimental results suggest that rIFN-alpha might have a therapeutic potential for the prevention and treatment of the deleterious effects associated with endotoxemia besides mechanisms initially blocking TNF production.
The V(D)J recombination activation gene RAG-1 was isolated on the basis of its ability to activate V(D)J recombination on an artificial substrate in fibroblasts. This property and the expression pattern in tissues and cell lines indicate that RAG-1 either activates or catalyzes the V(D)J recombination reaction of immunoglobulin and T cell receptor genes. We here describe the introduction of a mutation in RAG-1 into the germline of mice via gene targeting in embryonic stem cells. RAG-1-deficient mice have small lymphoid organs that do not contain mature B and T lymphocytes. The arrest of B and T cell differentiation occurs at an early stage and correlates with the inability to perform V(D)J recombination. The immune system of the RAG-1 mutant mice can be described as that of nonleaky scid mice. Although RAG-1 expression has been reported in the central nervous system of the mouse, no obvious neuroanatomical or behavioral abnormalities have been found in the RAG-1-deficient mice.
Tumour necrosis factors, TNF-alpha and TNF-beta (previously called lymphotoxin), are the products of activated monocytes and lymphocytes, respectively, and both have recently been purified, sequenced and cloned by recombinant DNA methods, revealing 35% identity and 50% homology in the amino-acid sequence. Both proteins have been found to be specifically toxic to many tumour cells. Furthermore, it has been reported that various interferons are synergistic with TNF for anti-tumour effects in vitro, while activities attributed to the two proteins have also been shown to necrotize various tumours in vivo. We have now prepared 125I-labelled highly purified recombinant human TNF-alpha to study in detail its binding to the human cervical carcinoma cell line ME-180. Our results indicate that there is a single class of specific high-affinity receptors for TNF on this cell line which has a Kd of about 0.2 nM and an average of 2,000 receptor sites per cell. The binding of labelled TNF-alpha to these cells can be inhibited by both TNF-alpha and TNF-beta but not by gamma-interferon (IFN-gamma). However, preincubation of cells with IFN-gamma increases the total number of TNF receptors two to threefold without any significant change in the affinity constant. This is the first report that TNF-alpha and -beta share a common receptor and that the receptors can be up-regulated by interferon. Our results may explain previous observations regarding similar biological activities observed for these two cytotoxic proteins and also their synergistic action with interferons.
A highly specific polyclonal rabbit antiserum directed against murine cachectin/tumor necrosis factor (TNF) was prepared. When BALB/c mice were passively immunized with the antiserum or with purified immune globulin, they were protected against the lethal effect of the endotoxin lipopolysaccharide produced by Escherichia coli. The prophylactic effect was dose-dependent and was most effective when the antiserum was administered prior to the injection of the endotoxin. Antiserum to cachectin/TNF did not mitigate the febrile response of endotoxin-treated animals, and very high doses of endotoxin could overcome the protective effect. The median lethal dose of endotoxin in mice pretreated with 50 microliters of the specific antiserum was approximately 2.5 times greater the median lethal dose for controls given nonimmune serum. The data suggest that cachectin/TNF is one of the principal mediators of the lethal effect of endotoxin.
Several cytokines, in particular tumor necrosis factor-α (TNF;-α) and interferon-γ (IFN-γ), have been shown to be responsible for pathological reactions which may lead to shock and death observed in infection with Gram-negative bacteria and in response to endotoxins (lipopolysaccharides, LPS). Priming of mice with the avirulent Bacille Calmette Guerin (BCG) vaccine strain of Mycobacterium bovis increases the sensitivity of mice to the lethal effect of LPS and results in an efficient priming for cytokine production. In response to low doses (1 μg/mouse) of LPS, BCG-primed mice produce interleukin-12 (IL-12) which controls IFN-γ production, as demonstrated by the ability of neutralizing anti-IL-12 antibodies to suppress IFN-γ production. However, the concentration of the biologically active IL-12 p70 heterodimer is similar in the serum of both BCG-primed or unprimed mice, reaching levels of 1-3 ng/ml at 3-6 h after LPS injection, whereas IFN-γ production was observed only in BCG-primed mice. The priming effect of BCG on IFN-γ production appears to be mostly due to its ability to increase TNF-α production, which acts as cofactor with LPS-induced IL-12 in inducing IFN-γ production, as shown by the ability of injection of TNF-α and LPS (1 μg/mouse), but not LPS alone, to induce IFN-γ production. However, in addition to TNF-α, other LPS-induced cofactor(s) are required in cooperation with IL-12 to induce optimal IFN-γ production, because co-injection of TNF-α and IL-12, sufficient to induce serum concentrations of both cytokines higher and more persistent than those obtained by injection of LPS, was not sufficient to induce IFN-γ production in vivo. Neutralizing anti-IL-12 antibodies, in addition to inhibiting the in vivo LPS-induced IFN-γ production, also completely protect BCG-primed mice injected with up to 10 μg of LPS from shock-induced death. Thus, IL-12 is required for IFN-γ production and lethality in an endotoxic shock model in mice.
The multiple biological activities of tumor necrosis factor (TNF) are mediated by two distinct cell surface receptors of 55 kd (TNFRp55) and 75 kd (TNFRp75). Using gene targeting, we generated a TNFRp55-deficient mouse strain. Cells from TNFRp55-/-mutant mice lack expression of TNFRp55 but display normal numbers of high affinity TNFRp75 molecules. Thymocyte development and lymphocyte populations are unaltered, and clonal deletion of potentially self-reactive T cells is not impaired. However, TNF signaling is largely abolished, as judged by the failure of TNF to induce NF-kappa B in T lymphocytes from TNFRp55-deficient mice. The loss of TNFRp55 function renders mice resistant to lethal dosages of either lipopolysaccharides or S. aureus enterotoxin B. In contrast, TNFRp55-deficient mice are severely impaired to clear L. monocytogenes and readily succumb to infection. Thus, the 55 kd TNFR plays a decisive role in the host's defense against microorganisms and their pathogenic factors.
Signal transducers and activators of transcription (STATs) are activated by tyrosine phosphorylation in response to cytokines and mediate many of their functional responses. Stat4 was initially cloned as a result of its homology with Stat1 (refs 4, 5) and is widely expressed, although it is only tyrosine-phosphorylated after stimulation of T cells with interleukin (IL)-12 (refs 6,7). IL-12 is required for the T-cell-independent induction of the cytokine interferon (IFN)-gamma, a key step in the initial suppression of bacterial and parasitic infections. IL-12 is also important for the development of a Th1 response, which is critical for effective host defence against intracellular pathogens. To determine the function of Stat4 and its role in IL-12 signalling, we have produced mice that lack Stat4 by gene targeting. The mice were viable and fertile, with no detectable defects in haematopoiesis. However, all IL-12 functions tested were disrupted, including the induction of IFN-gamma, mitogenesis, enhancement of natural killer cytolytic function and Th1 differentiation.
Interferon (IFN)-alpha/beta-mediated negative regulation of interleukin 12 (IL-12) and IFN-gamma proteins is reported here. Both IFN-alpha and IFN-beta inhibited fixed Staphylococcus aureus Cowan strain induction of IL-12 and IFN-gamma production by mouse splenic leukocytes in culture. Extended studies with IFN-alpha demonstrated that inhibition was at the level of biologically active IL-12 p70. Effects were selective, as induction of tumor necrosis factor was unaffected and induction of IL-6 was enhanced. Neutralization of IFN-alpha/beta expressed endogenously during infections with murine cytomegalovirus (MCMV) enhanced early IL-12 and IFN-gamma protein production. Furthermore, during infections of mice with lymphocytic choriomeningitis virus (LCMV), this treatment revealed a previously undetected early IL-12 and IFN-gamma protein expression, and mice deficient in IFN-alpha/beta receptor function, but not control mice, also expressed endogenous LCMV-induced IL-12. The effects of IFN-alpha/beta neutralization on production of IL-12 and IFN-gamma during the viral infections were detected in both serum samples and medium conditioned with splenic leukocytes isolated from infected animals. In vitro studies demonstrated that splenic leukocytes isolated from LCMV-infected mice were primed to produce IL-12 in response to stimulation with Staphylococcus aureus Cowan strain, but that this responsiveness was sensitive to added IFN-alpha. Moreover, endogenous IFN-alpha/beta induced by LCMV inhibited in vivo lipopolysaccharide stimulation of IL-12 production. These results demonstrate a new pathway for regulating cytokine responses, and suggest a mechanism for inhibition of IL-12-dependent immune responses during viral infections.
Innate cytokine responses are important mediators of early defense against infections. Certain of their effects can be delivered directly to activate protective mechanisms in infected cells. Others activate innate immune cells, including natural killer (NK) cells and macrophages, to mediate defense. Still others shape adaptive immune responses. The compositions and magnitudes of innate cytokine responses are modulated, by the nature of the infectious agent, to facilitate accessing of the anti-microbial defense functions most beneficial in defense against the particular infection. In the context of viral infections, interferons alpha and beta (IFN-alpha/beta) are induced to high levels, and help to mediate and regulate immune responses most effective against this class of agents. The cytokines induce anti-viral mechanisms in infected cells, negatively regulate interleukin 12 expression, and activate NK cell-mediated lysis. Protective development of adaptive immunity to viral infections includes prominent CD8 T cell expansion and activation, and IFN-alpha/beta can mediate functions with the potential to promote these T cell responses. Together, the characteristics define regulation of unique or unique prominent defense mechanisms in place to fight off viral infections.
An increase in the incidence of necrotizing fasciitis (NF) occurring in previously healthy children with primary varicella was noted in the Washington State area between December 1993 and June 1995. Our objective was to investigate ibuprofen use and other risk factors for NF in the setting of primary varicella.
Case-control study. Demographic information, clinical parameters, and potential risk factors for NF were compared for cases and controls. Cases of NF were analyzed to identify potential determinants of NF complicated by renal insufficiency and/or streptococcal toxic shock syndrome. Multivariate logistic regression was used to evaluate the association between ibuprofen use and NF. A case was defined as a child with NF hospitalized within 3 weeks of primary varicella (n = 19). Controls were children hospitalized with a soft tissue infection other than NF within 3 weeks of primary varicella (n = 29). Odds ratios (ORs) of ibuprofen, as well as other potential risk factors were evaluated. In addition, demographic and clinical data as well as other potential risk factors were compared between cases and controls.
After controlling for gender, age, and group A streptococcus isolation, cases were more likely than controls to have used ibuprofen before hospitalization (OR, 11. 5; 95% confidence interval, 1.4 to 96.9). In most children, ibuprofen was initiated after the onset of symptoms of secondary infection. Children with NF complicated by renal insufficiency and/or streptococcal toxic shock syndrome were more likely than children with uncomplicated NF to have used ibuprofen (OR, 16.0; 95% confidence interval, 1.0 to 825.0). Children with complicated NF also had a higher mean maximum temperature (40.9 degrees C vs 39.3 degrees C), and a longer mean duration of secondary symptoms (1.7 days vs 0.6 days) before admission than children with uncomplicated NF.
Ibuprofen use was associated with NF in the setting of primary varicella. Additional studies are needed to establish whether ibuprofen use has a causal role in the development of NF and its complications during varicella.