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A Combination of Thalidomide plus Antibiotics Protects Rabbits from Mycobacterial Meningitis‐Associated Death
Abstract
Tuberculous meningitis (TBM) is a devastating form of tuberculosis that occurs predominantly in children and in immunocompromised
adults. To study the pathogenesis of TBM, a rabbit model of acute mycobacterial central nervous system infection was set up
(8-day study). Inoculation of live Mycobacterium bovis Ravenel intracisternally induced leukocytosis (predominantly mononuclear cells), high protein levels, and release of tumor
necrosis factor-α (TNF-α) into the cerebrospinal fluid within 1 day. Histologically, severe meningitis with thickening of
the leptomeninges, prominent vasculitis, and encephalitis was apparent, and mortality was 75% by day 8. In animals treated
with antituberculous antibiotics only, the inflammation and lesions of the brain persisted despite a decrease in mycobacteria;
50% of the rabbits died. When thalidomide treatment was combined with antibiotics, there was a marked reduction in TNF-α levels,
leukocytosis, and brain pathology. With this combination treatment, 100% of the infected rabbits survived, suggesting a potential
clinical use for thalidomide in TBM.
... The use of thalidomide in the context of CNS TB in clinical practice is controversial. Animal models studying adjunctive thalidomide use compared to standard CNS TB treatment have demonstrated dramatic improvement in survival (9,10). Initial safety studies in children displayed promising improvement in clinical outcome with minimal side effects (4,5), but a further randomised controlled study in 47 children demonstrated higher levels of mortality compared to controls, and therefore thalidomide was not recommended in routine practice (3). ...
... It may be that thalidomide needs to be started early in patients with poor prognostic factors to prevent CNS inflammation rather than as 'rescue medication'. Thalidomide is thought to supress secondary TB associated vasculitis and tuberculoma formation through immune modulation (8,10). It is not clear whether initiation of thalidomide early in the disease process helps prevent secondary complications, or whether it should be reserved for use only once secondary complications are established, suggesting the need to escalate treatment. ...
... Moreover, when animals were infected with high doses of CNS mycobacterium, 50% died when treated with standard TB medication. Only the combination of anti-TB drugs with thalidomide resulted in a dramatic improvement in survival to 100% (10). A randomised controlled trial of thalidomide for paediatric TBM cases had to be stopped early due to deaths (4/30) and adverse events occurring in the treatment arm. ...
Background
Central nervous system (CNS) tuberculosis (TB) accounts for over 4% of all TB notifications in the United Kingdom, and causes death or significant disability in over half of those affected. TNF‐alpha is a critical cytokine involved in the neuropathogenesis of CNS TB. Thalidomide has been trialled in CNS TB due to its immunomodulatory and immune reconstitution effects, through inhibition of TNF‐alpha. Despite animal models demonstrating dramatic improvement in survival, studies in paediatric patients have been associated with higher levels of mortality. The effects of thalidomide have not yet been studied in adults with CNS TB.
This narrative case series guides clinicians through a range of CNS TB clinical cases seen in a large London teaching hospital, serving a region with a high TB incidence of 32 per 100,000, with 55% of TB manifesting as extrapulmonary disease. We aim to illustrate our experiences of using thalidomide to treat a range of severe CNS TB complications.
Methods
Five inpatients at the Royal London Hospital, London, UK treated with thalidomide in addition to standard TB treatment are described in detail. The rationale for treatment initiation with thalidomide is explained.
Results
The case examples are used to guide our reflections and lessons learnt regarding the use of thalidomide. Responses to treatment and functional outcomes suggest thalidomide may be a useful adjunct to standard TB therapy in selected adult cases.
Conclusions
The experience gained from using thalidomide in this small case series may provide evidence towards more research into using thalidomide to treat severe CNS TB.
This article is protected by copyright. All rights reserved.
... In addition, CNS TB occurs in 1-2% of all immunocompetent patients with active TB. The mortality rate for these patients is over 50%, and most surviving patients suffer neurological sequelae [3][4][5]. In these patients, neurological disability involves cognitive impairment, motor deficits, optic atrophy and other cranial nerve involvement [6]. ...
... Tuberculosis 110 (2018) [1][2][3][4][5][6] route, small-and medium-sized bacterial clusters formed in every part of brain. And direct inoculation of M. marinum into the brain parenchyma or hindbrain ventricle of zebrafish embryos resulted in the formation of bacterial clusters in the targeted area in 95-100% of all cases [46]. ...
... CNS TB treatment is difficult, and experimental animal models have been useful in evaluating diverse therapeutic approaches for this form of TB. Tsenova et al. demonstrated that the immunoregulator drug thalidomide and its analogues effectively lowered the levels of the proinflammatory cytokine TNF-α in rabbits with meningeal TB produced by intracisternal injection of M. bovis BCG and Ravenel vaccines using two different doses (5 × 10 5 and 2 × 10 7 ) [3]. The combination of thalidomide and conventional chemotherapy produced decreases in bacterial load, brain inflammation and leptomeningeal thickness, thus increasing the animal survival rate [50][51][52][53][54]. ...
Animal models are and will remain valuable tools in medical research because their use enables a deeper understanding of disease development, thus generating important knowledge for developing disease control strategies. Central nervous system tuberculosis (CNS TB) is the most devastating disease in humans. Moreover, as the variability of signs and symptoms delay a timely diagnosis, patients usually arrive at the hospital suffering from late stage disease. Therefore, it is impossible to obtain fresh human tissue for research before an autopsy. Because of these reasons, studies on human CNS TB are limited to case series, pharmacological response reports, and post mortem histopathological studies. Here, we review the contribution of the different animal models to understand the immunopathology of the disease and the host-parasitic relationship, as well as in the development of new strategies of vaccination and to test new drugs for the treatment of CNS TB.
... Although animal models of TB meningitis have been previously developed, they typically mimic adult disease (Tsenova et al., 1999(Tsenova et al., , 2005(Tsenova et al., , 2002(Tsenova et al., , 1998van Well et al., 2007) and do not take into account the effects of injury and immune dysregulation in the developing brain, which would have significant relevance in childhood disease. Microglia, the resident immune cells in the brain, are the primary host cells of Mycobacterium tuberculosis and release pro-inflammatory cytokines when activated as a result of TB infection (Curto et al., 2004;Hernandez Pando et al., 2010;Rock et al., 2005;Yang et al., 2007Yang et al., , 2009Zucchi et al., 2012). ...
... Seminal animal studies performed by Rich and McCordock (1933) reported that TB meningitis resulted from the rupture of 'rich foci' into the subarachnoid space, which developed around bacilli deposited in brain parenchyma much earlier during hematogenous spread. Several models have elucidated key pathogenic pathways and bacterial factors involved in neuropathogenesis Hernandez Pando et al., 2010;Jain et al., 2006;Rich and McCordock, 1933;Tsenova et al., 1998;Yang et al., 2007;Zucchi et al., 2012). For example, an in vitro model of the BBB identified M. tuberculosis microbial factors associated with neuroinvasiveness (Jain et al., 2006). ...
... Many elegant studies have also been performed by using direct intra-cisternal infections in adult mice or rabbits (Tsenova et al., 1999(Tsenova et al., , 2005(Tsenova et al., , 2002(Tsenova et al., , 1998van Well et al., 2007). Several animal studies have explored host-pathogen interactions by targeting critical inflammatory pathways implicated in TB pathogenesis (Ong et al., 2014;Ordonez et al., 2016a;Skerry et al., 2012), as well as developing novel adjunctive treatments for TB meningitis (Majeed et al., 2016;Tsenova et al., 2002Tsenova et al., , 1998. ...
Central nervous system (CNS) tuberculosis (TB) is the most severe form of extra-pulmonary TB and disproportionately affects young children where the developing brain has a unique host response. New Zealand white rabbits were infected with Mycobacterium tuberculosis via subarachnoid inoculation at postnatal day 4-8 and evaluated until 4-6 weeks post-infection. Control and infected rabbit kits were assessed for the development of neurological deficits, bacterial burden, and postmortem microbiologic and pathologic changes. The presence of meningitis and tuberculomas was demonstrated histologically and by in vivo magnetic resonance imaging (MRI). The extent of microglial activation was quantified by in vitro immunohistochemistry as well as non-invasive in vivo imaging of activated microglia/macrophages with positron emission tomography (PET). Subarachnoid infection induced characteristic leptomeningeal and perivascular inflammation and TB lesions with central necrosis, a cellular rim and numerous bacilli on pathologic examination. Meningeal and rim enhancement was visible on MRI. An intense microglial activation was noted in M. tuberculosis-infected animals in the white matter and around the TB lesions, as evidenced by a significant increase in uptake of the tracer 124 I-DPA-713, which is specific for activated microglia/macrophages, and confirmed by quantification of Iba-1 immunohistochemistry. Neurobehavioral analyses demonstrated signs similar to those noted in children with delayed maturation and development of neurological deficits resulting in significantly worse composite behavior scores in M. tuberculosis-infected animals. We have established a rabbit model that mimics features of TB meningitis in young children. This model could provide a platform for evaluating novel therapies, including host-directed therapies, against TB meningitis relevant to a young child's developing brain.
... However, TNF is undoubtedly critical in the pathogenesis of TBM. TNF increases the permeability of the BBB, triggers further cytokine release, and correlates with severity in mouse models (64). It is found at high levels at the interface between the cellular and necrotic zones of TB granulomas in post-mortem studies (17). ...
... High CSF TNF levels with low IFNg levels predict TBM-IRIS. Thalidomide, a TNF antagonist, downregulated TNF production and increased survival in a rabbit model of TBM (64). Optimal levels of TNF are likely to be determined by disease course and individual patient factors in TBM. ...
Tuberculous meningitis (TBM), the most severe form of tuberculosis, causes death in approximately 25% cases despite antibiotic therapy, and half of survivors are left with neurological disability. Mortality and morbidity are contributed to by a dysregulated immune response, and adjunctive host-directed therapies are required to modulate this response and improve outcomes. Developing such therapies relies on improved understanding of the host immune response to TBM. The historical challenges in TBM research of limited in vivo and in vitro models have been partially overcome by recent developments in proteomics, transcriptomics, and metabolomics, and the use of these technologies in nested substudies of large clinical trials. We review the current understanding of the human immune response in TBM. We begin with M. tuberculosis entry into the central nervous system (CNS), microglial infection and blood-brain and other CNS barrier dysfunction. We then outline the innate response, including the early cytokine response, role of canonical and non-canonical inflammasomes, eicosanoids and specialised pro-resolving mediators. Next, we review the adaptive response including T cells, microRNAs and B cells, followed by the role of the glutamate-GABA neurotransmitter cycle and the tryptophan pathway. We discuss host genetic immune factors, differences between adults and children, paradoxical reaction, and the impact of HIV-1 co-infection including immune reconstitution inflammatory syndrome. Promising immunomodulatory therapies, research gaps, ongoing challenges and future paths are discussed.
... Some consider the rabbit model good as a model of immunopathogenesis and rabbits can be experimentally infected with Mtb or M. bovis and they show similar characteristics as human TB disease, for example, caseous necrosis, liquefaction and cavitary disease (79,80,89,90). Kaplan et al. also have developed a model of mycobacterial meningitis that closely resembles TB meningitis in people (90). ...
... Some consider the rabbit model good as a model of immunopathogenesis and rabbits can be experimentally infected with Mtb or M. bovis and they show similar characteristics as human TB disease, for example, caseous necrosis, liquefaction and cavitary disease (79,80,89,90). Kaplan et al. also have developed a model of mycobacterial meningitis that closely resembles TB meningitis in people (90). The different strains of mycobacteria cause different manifestations of disease, for example, when infected with Mtb strain CDC1551, rabbits show similarities to latent TB infection when compared to humans as they can clear the bacilli and granulomas disappear (89). ...
Research in human tuberculosis (TB) is limited by the availability of human tissues from patients, which is often altered by therapy and treatment. Thus, the use of animal models is a key tool in increasing our understanding of the pathogenesis, disease progression and preclinical evaluation of new therapies and vaccines. The granuloma is the hallmark lesion of pulmonary tuberculosis, regardless of the species or animal model used. Although animal models may not fully replicate all the histopathological characteristics observed in natural, human TB disease, each one brings its own attributes which enable researchers to answer specific questions regarding TB immunopathogenesis. This review delves into the pulmonary pathology induced by Mycobacterium tuberculosis complex (MTBC) bacteria in different animal models (non-human primates, rodents, guinea pigs, rabbits, cattle, goats, and others) and compares how they relate to the pulmonary disease described in humans. Although the described models have demonstrated some histopathological features in common with human pulmonary TB, these data should be considered carefully in the context of this disease. Further research is necessary to establish the most appropriate model for the study of TB, and to carry out a standard characterisation and score of pulmonary lesions.
... Huang et al., 2016;Li D. et al., 2017). Tubercular meningitis (TBM) occurs in 1-2% of TB cases and is one of the most severe forms of TB, especially among children, so several investigators have developed adult and pediatric TBM rabbit models (Tsenova et al., 1998;Tucker et al., 2016;Jain et al., 2018;Sańchez-Garibay et al., 2018). Recently, it was determined that DLM concentrations in the brain of naïve and TBM rabbits were five-fold higher than in plasma at both the maximum and trough concentrations, although the concentration in the cerebrospinal fluid was much lower . ...
... Often TBM treatment includes adjunctive corticosteroids added to standard therapy, but this original HDT is both toxic and only partially successful. Tsenova et al. (1998) used thalidomide to block the production of tumor necrosis factor alpha (TNFa) in combination with INH and RIF to reduce inflammation and prolong the survival of rabbits with TBM. While this approach was successful, thalidomide's toxicity also stimulated a search for other TNFa blockers. ...
Tuberculosis (TB) remains a global health problem despite almost universal efforts to provide patients with highly effective chemotherapy, in part, because many infected individuals are not diagnosed and treated, others do not complete treatment, and a small proportion harbor Mycobacterium tuberculosis (Mtb) strains that have become resistant to drugs in the standard regimen. Development and approval of new drugs for TB have accelerated in the last 10 years, but more drugs are needed due to both Mtb’s development of resistance and the desire to shorten therapy to 4 months or less. The drug development process needs predictive animal models that recapitulate the complex pathology and bacterial burden distribution of human disease. The human host response to pulmonary infection with Mtb is granulomatous inflammation usually resulting in contained lesions and limited bacterial replication. In those who develop progressive or active disease, regions of necrosis and cavitation can develop leading to lasting lung damage and possible death. This review describes the major vertebrate animal models used in evaluating compound activity against Mtb and the disease presentation that develops. Each of the models, including the zebrafish, various mice, guinea pigs, rabbits, and non-human primates provides data on number of Mtb bacteria and pathology resolution. The models where individual lesions can be dissected from the tissue or sampled can also provide data on lesion-specific bacterial loads and lesion-specific drug concentrations. With the inclusion of medical imaging, a compound’s effect on resolution of pathology within individual lesions and animals can also be determined over time. Incorporation of measurement of drug exposure and drug distribution within animals and their tissues is important for choosing the best compounds to push toward the clinic and to the development of better regimens. We review the practical aspects of each model and the advantages and limitations of each in order to promote choosing a rational combination of them for a compound’s development.
... Augmenting glutathione abundance in macrophages derived from HIV-infected individuals resulted in improved control of infection 13 . Thalidomide and its analogs effect several immune functions, and adjunctive thalidomide improved survival in a rabbit model of TBM 14 . However, a trial evaluating thalidomide (24 mg/kg) in children with TBM was discontinued prematurely because of serious adverse events and deaths, although subsequently, lower doses (4 mg/ kg) of thalidomide have benefited individuals with refractory CNS masses, optic neuritis and steroid-resistant paradoxical reactions associated with TBM. ...
... The interaction of neuroinvasive bacteria, including M. tuberculosis, with in vitro cellular barriers has been investigated previously 7,8 , and efforts to develop an in vitro granuloma model using primary murine cells were also presented. Animal models of TBM have been summarized 3 , and several models using intracerebral or intracisternal infections have been described 3,14 . Recently, M. tuberculosis infections in young rabbits were performed to mimic TBM in children, highlighting the role of microglial activation 22 . ...
Tuberculous meningitis is a serious, life-threatening disease affecting vulnerable populations, including HIV-infected individuals and young children. The US National Institutes of Health convened a workshop to identify knowledge gaps in the molecular and immunopathogenic mechanisms of tuberculous meningitis and to develop a roadmap for basic and translational research that could guide clinical studies.
... This observation suggests that Mtb can travel in forward and reverse directions across the BBB in the rabbit model, a hypothesis that could be considered in TB patients. Extra-CNS dissemination to the lungs and other organs after direct brain infection in animal models has been described previously (46,47), attributed to the breakdown of the BBB due to inflammation. ...
Tuberculosis meningitis (TBM) is essentially treated with the first-line regimen used against pulmonary tuberculosis, with a prolonged continuation phase. However, clinical outcomes are poor in comparison, for reasons that are only partially understood, highlighting the need for improved preclinical tools to measure drug distribution and activity at the site of disease. A predictive animal model of TBM would also be of great value to prioritize promising drug regimens to be tested in clinical trials, given the healthy state of the development pipeline for the first time in decades. Here, we report the optimization of a rabbit model of TBM disease induced via inoculation of Mycobacterium tuberculosis into the cisterna magna, recapitulating features typical of clinical TBM: neurological deterioration within months post-infection, acid-fast bacilli in necrotic lesions in the brain and spinal cord, and elevated lactate levels in cerebrospinal fluid (CSF). None of the infected rabbits recovered or controlled the disease. We used young adult rabbits, the size of which allows for spatial drug quantitation in critical compartments of the central nervous system that cannot be collected in clinical studies. To illustrate the translational value of the model, we report the penetration of linezolid from plasma into the CSF, meninges, anatomically distinct brain areas, cervical spine, and lumbar spine. Across animals, we measured the bacterial burden concomitant with neurological deterioration, offering a useful readout for drug efficacy studies. The model thus forms the basis for building a preclinical platform to identify improved regimens and inform clinical trial design.
... Furthermore, rabbit models have contributed to understanding the pathogenic factors and mechanisms of cavitation caused by MTB H37Rv infection [243][244][245][246][247]. However, the high cost of rabbit models, lack of relevant immunological reagents, genetic manipulation, and ethical considerations make them less suitable for long-term survival studies [248]. ...
Tuberculosis (TB), caused by Mycobacterium tuberculosis (MTB), is a prevalent global infectious disease and a leading cause of mortality worldwide. Currently, the only available vaccine for TB prevention is Bacillus Calmette–Guérin (BCG). However, BCG demonstrates limited efficacy, particularly in adults. Efforts to develop effective TB vaccines have been ongoing for nearly a century. In this review, we have examined the current obstacles in TB vaccine research and emphasized the significance of understanding the interaction mechanism between MTB and hosts in order to provide new avenues for research and establish a solid foundation for the development of novel vaccines. We have also assessed various TB vaccine candidates, including inactivated vaccines, attenuated live vaccines, subunit vaccines, viral vector vaccines, DNA vaccines, and the emerging mRNA vaccines as well as virus-like particle (VLP)-based vaccines, which are currently in preclinical stages or clinical trials. Furthermore, we have discussed the challenges and opportunities associated with developing different types of TB vaccines and outlined future directions for TB vaccine research, aiming to expedite the development of effective vaccines. This comprehensive review offers a summary of the progress made in the field of novel TB vaccines.
... The combination of THD and (rifampicin and isoniazid) improved the survival rate of infected rabbits with mycobacterium tuberculosis [152] Pyrotinib and THD Pyrotinib has been licensed as an effective and irreversible inhibitor of the epidermal growth factor receptor (EGFR)/HER2 identified in NSCLC. THD is effective in solid tumors due to its antiangiogenic and immunomodulatory effects ...
Glioblastoma is the most common malignant primary brain tumor in adults. Thalidomide
is a vascular endothelial growth factor inhibitor that demonstrates antiangiogenic activity, and may
provide additive or synergistic anti-tumor effects when co-administered with other antiangiogenic
medications. This study is a comprehensive review that highlights the potential benefits of using
thalidomide, in combination with other medications, to treat glioblastoma and its associated inflammatory
conditions. Additionally, the review examines the mechanism of action of thalidomide in
different types of tumors, which may be beneficial in treating glioblastoma. To our knowledge, a
similar study has not been conducted. We found that thalidomide, when used in combination with
other medications, has been shown to produce better outcomes in several conditions or symptoms,
such as myelodysplastic syndromes, multiple myeloma, Crohn’s disease, colorectal cancer, renal
failure carcinoma, breast cancer, glioblastoma, and hepatocellular carcinoma. However, challenges
may persist for newly diagnosed or previously treated patients, with moderate side effects being
reported, particularly with the various mechanisms of action observed for thalidomide. Therefore,
thalidomide, used alone, may not receive significant attention for use in treating glioblastoma in the
future. Conducting further research by replicating current studies that show improved outcomes
when thalidomide is combined with other medications, using larger sample sizes, different demographic
groups and ethnicities, and implementing enhanced therapeutic protocol management, may
benefit these patients. A meta-analysis of the combinations of thalidomide with other medications in
treating glioblastoma is also needed to investigate its potential benefits further.
... Here it was used for pathogenesis and virulence studies in mice, rabbits, and guinea pigs. It has been used in diagnostic [8], immunopathogenesis [5,6], chemotherapy [9], and vaccine efficacy studies [10,11]. Even though the current stocks of MBO Ravenel (ATCC strain 35720) are fully virulent in rabbits [12,13], guinea pigs [13], and mice [13][14][15] yet they are attenuated in cattle. ...
Mycobacterium tuberculosis variant bovis (MBO) has one of the widest known mammalian host ranges, including humans. Despite the characterization of this pathogen in the 1800s and whole genome sequencing of a UK strain (AF2122) nearly two decades ago, the basis of its host specificity and pathogenicity remains poorly understood. Recent experimental calf infection studies show that MBO strain Ravenel (MBO Ravenel) is attenuated in the cattle host compared to other pathogenic strains of MBO. In the present study, experimental infections were performed to define attenuation. Whole genome sequencing was completed to identify regions of differences (RD) and single nucleotide polymorphisms (SNPs) to explain the observed attenuation. Comparative genomic analysis of MBO Ravenel against three pathogenic strains of MBO (strains AF2122-97, 10-7428, and 95-1315) was performed. Experimental infection studies on five calves each, with either MBO Ravenel or 95-1315, revealed no visible lesions in all five animals in the Ravenel group despite robust IFN-γ responses. Out of 486 polymorphisms in the present analysis, 173 were unique to MBO Ravenel among the strains compared. A high-confidence subset of nine unique SNPs were missense mutations in genes with annotated functions impacting two major MBO survival and virulence pathways: (1) Cell wall synthesis & transport [espH (A103T), mmpL8 (V888I), aftB (H484Y), eccC5 (T507M), rpfB (E263G)], and (2) Lipid metabolism & respiration [mycP1(T125I), pks5 (G455S), fadD29 (N231S), fadE29 (V360G)]. These substitutions likely contribute to the observed attenuation. Results from experimental calf infections and the functional attributions of polymorphic loci on the genome of MBO Ravenel provide new insights into the strain’s genotype-disease phenotype associations.
... MBO strain Ravenel has been used in diagnostic [8], immunopathogenesis [5,6], chemotherapy [9], and vaccine efficacy studies [10,11]. Current stocks of MBO Ravenel (ATCC strain 35720) are fully virulent in rabbits [12,13], guinea pigs [13], and mice [13][14][15] but attenuated in cattle. ...
Mycobacterium tuberculosis variant bovis (MBO) has one of the widest known mammalian host ranges, including humans. Despite characterization of this pathogen in the 1800s, and whole genome sequencing of a UK strain (AF2122) nearly two decades ago, the basis of its host specificity and pathogenicity remains poorly understood. Recent experimental calf infection studies show that MBO strain Ravenel (MBO Ravenel) is attenuated in the cattle host. In the present study, experimental infections were performed to define attenuation and whole genome sequencing completed to identify regions of differences (RD) and single nucleotide polymorphisms (SNPs) to explain the observed attenuation. Comparative genomic analysis of MBO Ravenel against three pathogenic strains of MBO (strains AF2122-97, 10-7428 and 95-1315) was performed. Experimental infection studies on 5 calves each, with either MBO Ravenel or 95-1315, revealed no visible lesions in all 5 animals in the Ravenel group despite robust IFN-γ responses. Out of 486 polymorphisms in the present analysis, 173 were unique to MBO Ravenel among the strains compared. A high-confidence subset of 9 unique SNPs were missense mutations in genes with annotated functions impacting 2 major MBO survival and virulence pathways: 1) Cell wall synthesis & transport [espH (A103T), mmpL8 (V888I), aftB (H484Y), eccC5 (T507M), rpfB (E263G)], and 2) Lipid metabolism & respiration [mycP1(T125I), pks5 (G455S), fadD29 (N231S), fadE29 (V360G)]. These substitutions likely contribute to the observed attenuation. Results from experimental calf infections and the functional attributions of polymorphic loci on the genome of MBO Ravenel provide new insights into the strain’s genotype-disease phenotype associations.
... The inhibition of TNF is thought act by disrupting TB pulmonary granulomas and consequently enhancing drug penetration but also causing bacterial reactivation, which increases their susceptibility to the action of antibiotics. The administration of thalidomide and its analogs in conjunction with antibiotics was also shown to be beneficial during the treatment of TB meningitis in experimental models (Tsenova et al., 1998;Tsenova et al., 2002) and in patients (van Toorn et al., 2021), although in these cases, the beneficial effects were not associated with granuloma disruption, but likely with the anti-inflammatory effects of thalidomide-induced suppression of TNF production. ...
Tuberculosis (TB), caused by the bacterium Mycobacterium tuberculosis, and malaria, caused by parasites from the Plasmodium genus, are two of the major causes of death due to infectious diseases in the world. Both diseases are treatable with drugs that have microbicidal properties against each of the etiologic agents. However, problems related to treatment compliance by patients and emergence of drug resistant microorganisms have been a major problem for combating TB and malaria. This factor is further complicated by the absence of highly effective vaccines that can prevent the infection with either M. tuberculosis or Plasmodium. However, certain host biological processes have been found to play a role in the promotion of infection or in the pathogenesis of each disease. These processes can be targeted by host-directed therapies (HDTs), which can be administered in conjunction with the standard drug treatments for each pathogen, aiming to accelerate their elimination or to minimize detrimental side effects resulting from exacerbated inflammation. In this review we discuss potential new targets for the development of HDTs revealed by recent advances in the knowledge of host-pathogen interaction biology, and present an overview of strategies that have been tested in vivo, either in experimental models or in patients.
... Several animal models of CNS-TB have been described, including guinea pigs, rabbits, mice, pigs, and zebrafish. The rabbit model closely mimics human disease, developing clinical and histological changes [7][8][9][10][11][12][13]. However, a number of immunological tools profiling protein secretion and gene expression are unavailable for rabbits [1] and, therefore, preclude their suitability for in-depth immunological studies. ...
Background
Understanding the pathophysiology of central nervous system tuberculosis (CNS-TB) is hampered by the lack of a good pre-clinical model that mirrors the human CNS-TB infection. We developed a murine CNS-TB model that demonstrates neurobehavioral changes with similar immunopathology with human CNS-TB.
Methods
We injected two Mycobacterium tuberculosis (M.tb) strains, H37Rv and CDC1551, respectively, into two mouse strains, C3HeB/FeJ and Nos2−/− mice, either into the third ventricle or intravenous. We compared the neurological symptoms, histopathological changes and levels of adhesion molecules, chemokines, and inflammatory cytokines in the brain induced by the infections through different routes in different strains.
Results
Intra-cerebroventricular infection of Nos2−/− mice with M.tb led to development of neurological signs and more severe brain granulomas compared to C3HeB/FeJ mice. Compared with CDC1551 M.tb, H37Rv M.tb infection resulted in a higher neurobehavioral score and earlier mortality. Intra-cerebroventricular infection caused necrotic neutrophil-dominated pyogranulomas in the brain relative to intravenous infection which resulted in disseminated granulomas and mycobacteraemia. Histologically, intra-cerebroventricular infection of Nos2−/− mice with M.tb resembled human CNS-TB brain biopsy specimens. H37Rv intra-cerebroventricular infected mice demonstrated higher brain concentrations of inflammatory cytokines, chemokines and adhesion molecule ICAM-1 than H37Rv intravenous-infected mice.
Conclusions
Intra-cerebroventricular infection of Nos2−/− mice with H37Rv creates a murine CNS-TB model that resembled human CNS-TB immunopathology, exhibiting the worst neurobehavioral score with a high and early mortality reflecting disease severity and its associated neurological morbidity. Our murine CNS-TB model serves as a pre-clinical platform to dissect host–pathogen interactions and evaluate therapeutic agents for CNS-TB.
... The presence of neutrophils in human CNS tuberculomas further highlight their role in this disease (9). There is accumulating evidence that neutrophil-derived mediators including matrix metalloproteinase-9 (MMP-9) and tumor necrosis factor-a (TNF-a) result in immunopathology in CNS-TB (10)(11)(12)(13). Neutrophils may also crosstalk with other immune cells such as macrophages to upregulate cytokine secretion (14), while their interactions with activated platelets may result in thrombosis, leading to the occurrence of ischemic stroke (15,16). ...
Tuberculosis (TB) remains one of the leading infectious killers in the world, infecting approximately a quarter of the world’s population with the causative organism Mycobacterium tuberculosis (M. tb). Central nervous system tuberculosis (CNS-TB) is the most severe form of TB, with high mortality and residual neurological sequelae even with effective TB treatment. In CNS-TB, recruited neutrophils infiltrate into the brain to carry out its antimicrobial functions of degranulation, phagocytosis and NETosis. However, neutrophils also mediate inflammation, tissue destruction and immunopathology in the CNS. Neutrophils release key mediators including matrix metalloproteinase (MMPs) which degrade brain extracellular matrix (ECM), tumor necrosis factor (TNF)-α which may drive inflammation, reactive oxygen species (ROS) that drive cellular necrosis and neutrophil extracellular traps (NETs), interacting with platelets to form thrombi that may lead to ischemic stroke. Host-directed therapies (HDTs) targeting these key mediators are potentially exciting, but currently remain of unproven effectiveness. This article reviews the key role of neutrophils and neutrophil-derived mediators in driving CNS-TB immunopathology.
... Adjunctive thalidomide for the treatment of TBM-related complications was safe and clinically effective in children (108). In an experimental rabbit model of TBM, adjunctive thalidomide analog treatment resulted in reduced meningeal inflammation and survival of animals (109,110). TNF can be further blocked by etanercept, a soluble TNF receptor 2 fusion protein that is widely used in patients for the management of rheumatoid arthritis (111). In C3HeB/FeJ Kramnik mice, adjunctive etanercept reduced necrosis of granulomas and faster resolution of TB lesions when compared to standard TB treatment alone (12). ...
Globally, more than 10 million people developed active tuberculosis (TB), with 1.4 million deaths in 2020. In addition, the emergence of drug-resistant strains in many regions of the world threatens national TB control programs. This requires an understanding of host-pathogen interactions and finding novel treatments including host-directed therapies (HDTs) is of utter importance to tackle the TB epidemic. Mycobacterium tuberculosis (Mtb), the causative agent for TB, mainly infects the lungs causing inflammatory processes leading to immune activation and the development and formation of granulomas. During TB disease progression, the mononuclear inflammatory cell infiltrates which form the central structure of granulomas undergo cellular changes to form epithelioid cells, multinucleated giant cells and foamy macrophages. Granulomas further contain neutrophils, NK cells, dendritic cells and an outer layer composed of T and B lymphocytes and fibroblasts. This complex granulomatous host response can be modulated by Mtb to induce pathological changes damaging host lung tissues ultimately benefiting the persistence and survival of Mtb within host macrophages. The development of cavities is likely to enhance inter-host transmission and caseum could facilitate the dissemination of Mtb to other organs inducing disease progression. This review explores host targets and molecular pathways in the inflammatory granuloma host immune response that may be beneficial as target candidates for HDTs against TB.
... Corticosteroids are the mainstay of treatment but only marginally reduce cerebrospinal fluid (CSF) tumor necrosis factor alpha (TNFα), the key cytokine implicated in the underlying exaggerated inflammatory response [8,9]. Anti-TNFα monoclonal antibodies, including infliximab, have shown encouraging results in adult case series [10,11]. ...
Paradoxical reactions in central nervous system tuberculosis (CNS-TB) are associated with significant morbidity and mortality. We describe 4 HIV-uninfected children treated for CNS-TB with severe paradoxical reactions unresponsive to corticosteroids. All made recovery after treatment with infliximab, highlighting the safety and effectiveness of infliximab for this complication, and need for prospective trials.
... Subsequently, thalidomide was shown to reduce TNF-α in patients with pulmonary TB, with and without HIV infection, thereby reversing the wasting and inflammation in both diseases, as well as reducing viral load in patients with HIV [62,63]. The potential clinical use for thalidomide in TBM was first explored in a rabbit model whereby a combination of thalidomide with antibiotics resulted in a marked reduction in TNF-α levels, leucocytosis, and brain pathology which protected the rabbits from death [64]. A safety and tolerability study of adjunctive thalidomide in children with stage 2 TBM yielded promising safety results which paved the way for a randomized double-blind, placebo-controlled trial 2 years later [32]. ...
Much of the morbidity and mortality caused by tuberculous meningitis (TBM) is mediated by a dysregulated immune response. Effective host-directed therapy is therefore critical to improve survival and clinical outcomes. Currently only one host-directed therapy (HDT), corticosteroids, is proven to improve mortality. However, there is no evidence that corticosteroids reduce morbidity and the mechanism of action for mortality reduction is uncertain. Further, it has no proven benefit in HIV co-infected individuals. One promising host-directed therapy approach is to restrict the immunopathology arising from tumour necrosis factor (TNF)-α excess is via TNF-α inhibitors. There are accumulating data on the role of thalidomide, anti-TNF-α monoclonal antibodies (infliximab, adalimumab) and the soluble TNF-α receptor (etanercept) in TBM treatment. Thalidomide was developed nearly seventy years ago and has been a highly controversial drug. Birth defects and toxic adverse effects have limited its use but an improved understanding of its immunological mechanism of action suggest that it may have a crucial role in regulating the destructive host response seen in inflammatory conditions such as TBM. Observational studies at our institution found low dosage adjunctive thalidomide safe in treating tuberculous mass lesions and blindness related to optochiasmatic arachnoiditis, with good clinical and radiological response. In this review, we discuss possible mechanisms of action for thalidomide, based on our clinico-radiologic experience and post-mortem histopathological work. We also propose a rationale for its use in the treatment of certain TBM-related complications.
... [17] In a rabbit model of TBM, TNF levels correlate with the extent of pathology and treatment with antibiotics or thalidomide decreases TNF levels and protects against death. [18] Therefore, this drug is currently used as an immunomodulator for the treatment of TBM, especially among patients with visual impairment and IRIS. [13,15,16] In a children's hospital in West Cape Town Province (South Africa), children with severe TBM were administered oral thalidomide in addition to antitubercular drugs and glucocorticoids; of the 15 children who participated in this study, 14 recovered and 1 died. ...
Introduction:
Tuberculous meningitis (TBM) is the most fatal type of tuberculosis in which corticosteroids are added with antitubercular therapy to prevent permanent brain damage. However, this treatment may produce paradoxical reactions. In such cases, thalidomide use might reduce central nervous system inflammation and improve the outcome. We present the case of a human immunodeficiency virus-negative patient with TBM who developed paradoxical reactions manifesting as multiple intracranial tuberculomas that were resistant to standard care (antitubercular drugs and corticosteroids) but responded well to thalidomide.
Patient's main concern and clinical findings:
The patient was a 40-year-old Chinese female, who was admitted with a 10-day history of headaches, night sweats, and cough. She was healthy before contracting the infection and had no history of contact with tuberculosis patients.
Diagnoses, intervention, and outcome:
We diagnosed the patient with TBM complicated by the occurrence of pulmonary tuberculosis. Positive results were obtained from Gram and Ziehl-Neelsen staining of the sputum and acid-fast bacilli sputum culture. Standard treatment was initiated with antitubercular drugs (daily isoniazid, rifampicin, ethionamide, and pyrazinamide) and corticosteroids (dexamethasone). However, 3 months later the magnetic resonance imaging of the head revealed some new tuberculoma lesion. Thus, a specific therapy of antitubercular drugs and thalidomide was introduced. On completion of a 12-month course of antitubercular drugs with 2 months of thalidomide, the patient showed favorable outcomes without neurologic sequelae. Moreover, thalidomide appeared safe and well tolerated in the patient.
Conclusion:
In addition to the specific anti-tubercular and adjuvant corticosteroid therapies for TBM, thalidomide can be used as a "salvage" antitubercular drug in cases that are unresponsive to corticosteroids.
... [28] Furthermore, thalidomide, a potent TNF-a produced by stimulated monocytes, has been shown to reduce TNF-a levels in the CSF of rabbits with TB meningitis. [29] Therefore, the putative mechanism of action of anti-TNF agents in PR/IRIS would seem straightforward, and reduction of TNF-a levels in the CSF may be expected. However, available data give conflicting results. ...
Rationale:
Paradoxical reaction/immune reconstitution inflammatory syndrome is common in patients with central nervous system tuberculosis. Management relies on high-dose corticosteroids and surgery when feasible.
Patient concern:
We describe 2 cases of HIV-negative patients with corticosteroid-refractory paradoxical reactions of central nervous system tuberculosis.
Diagnoses:
The 2 patients experienced clinical impairment shortly after starting therapy for TB, and magnetic resonance imaging showed the presence of tuberculomas, leading to the diagnosis of a paradoxical reaction.
Interventions:
We added infliximab, an anti-tumor necrosis factor (TNF)-alpha monoclonal antibody, to the dexamethasone.
Outcomes:
Both patients had favorable outcomes, 1 achieving full recovery but 1 suffering neurologic sequelae.
Lessons:
Clinicians should be aware of the risk of paradoxical reactions/immune reconstitution inflammatory syndrome when treating patients with tuberculosis of the central nervous system and should consider the prompt anti-TNF-α agents in cases not responding to corticosteroids.
... Studies on rabbit models of TBM have demonstrated that high levels of TNF-␣ in CSF were associated with worse outcomes (41). The use of TNF-␣ antagonists in combination with antibiotics improved survival and outcomes in rabbits (42). In contrast, CSF TNF-␣ levels of children treated for TBM did not show a significant decline over a 4-week period (43). ...
Tuberculous meningitis (TBM) is the most devastating form of tuberculosis (TB), causing high mortality or disability. Management of the disease clinically is challenging due to limitations in the existing diagnostic approaches. Our knowledge on the immunology and pathogenesis of the disease is currently limited. More research is urgently needed to enhance our understanding of the immunopathogenesis of the disease and guide us towards the identification of targets that may be useful for vaccines or host-directed therapeutics. In the current review, we summarize the current knowledge about the immunology and pathogenesis of TBM and summarize the literature on existing and new, especially biomarker-based approaches that may be useful in the management of TBM. We identify research gaps and provide directions for research which may lead to the development of new tools for the control of the disease in the near future.
... However, when in high concentrations TNFα can exacerbate tissue pathology [139]. One of the TB-HDT approaches that modulate TNFα signaling includes thalidomide analogues [140][141][142] and PDE inhibitors [143][144][145][146]. PDEs are hydrolytic enzymes for cyclic nucleotides with beneficial effect in the treatment of inflammatory diseases, such as asthma and psoriasis [147]. Previously, we evaluated the effect of immunomodulatory drugs (IMiDs), which are PDE4 inhibitors in combination with antibiotics in different TB animal models [142][143][144][145]. ...
Mycobacterium tuberculosis, the causative agent of tuberculosis (TB), has co‐evolved with the human immune system and utilizes multiple strategies to persist within infected cells, to hijack several immune mechanisms and to cause severe pathology and tissue damage in the host. This delays the efficacy of current antibiotic therapy and contributes to the evolution of multi‐drug resistant strains. These challenges led to the development of the novel approach in TB treatment that involves therapeutic targeting of host immune response in order to control disease pathogenesis and pathogen growth viz. host‐directed therapies (HDT). Such HDT approaches are capable of: (i) enhancing the effect of antibiotics, (ii) shortening treatment duration for any clinical form of TB (iii) promoting development of immunological memory that could protect against relapse and (iv) ameliorating the immunopathology including matrix destruction and fibrosis associated with TB. In this review we discuss TB‐HDT candidates shown to be of clinical relevance and thus could be developed to reduce pathology, tissue damage and subsequent impairment of pulmonary function. This article is protected by copyright. All rights reserved.
... Animal studies demonstrate that inhibition of TNF-alpha with use of thalidomide result in survival benefit [81]. A small study in South African children revealed that thalidomide, which has potent anti-TNF-alpha effects in doses up to 24 mg/kg/day, were safe and well tolerated in children with TB meningitis [82]. ...
Traditionally children have been treated for tuberculosis (TB) based on data extrapolated from adults. However, we know that children present unique challenges that deserve special focus. New data on optimal drug selection and dosing are emerging with the inclusion of children in clinical trials and ongoing research on age-related pharmacokinetics and pharmacodynamics. We discuss the changing treatment landscape for drug-susceptible and drug-resistant paediatric tuberculosis in both the most common (intrathoracic) and most severe (central nervous system) forms of disease, and address the current knowledge gaps for improving patient outcomes.
... 10 Animal models implicate levels of CSF TNF-α in the severity of inflammation in TB meningitis, suggesting immunomodulatory therapy targeted against this cytokine is likely to be beneficial. 11 Thalidomide has multiple anti-inflammatory effects including suppression of TNF-α production and has been used in the treatment of life-threatening paradoxical TB reactions in children. In 1 study of 15 children with TB meningitis, adjunctive thalidomide resulted in a significant decline in CSF TNF-α levels and more favorable clinical outcomes compared with controls who received corticosteroids alone (5/15 had improved motor outcome, remainder no worsening at 6-month follow-up and no patients developed new infarcts). ...
A 7-year-old girl with tuberculous (TB) meningitis developed optochiasmatic arachnoiditis, a vision-threatening paradoxical reaction, after starting TB treatment including adjunctive steroid therapy. She was treated with infliximab with complete recovery. This is the first report of the use of a tissue necrosis factor α inhibitor for the treatment of a severe paradoxical TB reaction in a child.
... A recent study reported elevated production of inflammatory cytokines, including TNFα and IFN-γ in whole blood from TBM patients upon in vitro stimulation with Mtb (van Laarhoven et al., 2019). Similar to the human conditions, mycobacterial invasion of microglia cells/macrophages leads to the release of pro-inflammatory cytokines in the rabbit model of TBM (Tsenova et al., 1998). ...
Tuberculous meningitis (TBM) is the most devastating form of extrapulmonary Mycobacterium tuberculosis infection in humans. Severe inflammation and extensive tissue damage drive the morbidity and mortality of this manifestation of tuberculosis (TB). Antibiotic treatment is ineffective at curing TBM due to variable and incomplete drug penetration across the blood-brain barrier (BBB) and blood-cerebrospinal fluid (CSF) barriers. Adjunctive corticosteroid therapy, used to dampen the inflammation, and the pathologic manifestation of TBM, improves overall survival but does not entirely prevent the morbidity of the disease and has significant toxicities, including immune-suppression. The rabbit has served as a fit for purpose experimental model of human TBM since the early 1900s due to the similarity in the developmental processes of the brain, including neuronal development, myelination, and microglial functions between humans and rabbits. Consistent with the observations made in humans, proinflammatory cytokines, including TNF-α, play a critical role in the pathogenesis of TBM in rabbits focusing the attention on the utility of TNF-α inhibitors in treating the disease. Thalidomide, an inhibitor of monocyte-derived TNF-α, was evaluated in the rabbit model of TBM and shown to improve survival and reduce inflammation of the brain and the meninges. Clinical studies in humans have also shown a beneficial response to thalidomide. However, the teratogenicity and T-cell activation function of the drug limit the use of thalidomide in the clinic. Thus, new drugs with more selective anti-inflammatory properties and a better safety profile are being developed. Some of these candidate drugs, such as phosphodiesterase-4 inhibitors, have been shown to reduce the morbidity and increase the survival of rabbits with TBM. Future studies are needed to assess the beneficial effects of these drugs for their potential to improve the current treatment strategy for TBM in humans.
... However, rabbits are still an excellent animal model for human TB vaccine research because of the similar manifestations of lesions (granulomas, liquefaction, and cavities) to those observed in humans [14,15]. In particular, rabbit models have been extensively used to screen and evaluate potential vaccine candidates (such as BCG, M. vaccae, M. microti and subunit vaccines), and to determine the pathogenic factors and pathogenesis of cavities induced by M. tuberculosis H37Rv infection [15][16][17][18][19][20]83]. In addition, Tsenova et al. [84] reported large confluent granulomas with expansive areas of central necrosis in the lungs of rabbits infected with M. tuberculosis HN878 strain. ...
Tuberculosis (TB), an infectious disease caused by Mycobacterium tuberculosis , is one of the top ten infectious diseases worldwide, and is the leading cause of morbidity from a single infectious agent. M. tuberculosis can cause infection in several species of animals in addition to humans as the natural hosts. Although animal models of TB disease cannot completely simulate the occurrence and development of human TB, they play an important role in studying the pathogenesis, immune responses, and pathological changes as well as for vaccine research. This review summarizes the commonly employed animal models, including mouse, guinea pig, rabbit, rat, goat, cattle, and nonhuman primates, and their characteristics as used in TB vaccine research, and provides a basis for selecting appropriate animal models according to specific research needs. Furthermore, some of the newest animal models used for TB vaccine research (such as humanized animal models, zebrafish, Drosophila , and amoeba) are introduced, and their characteristics and research progress are discussed.
... Anti-tumour necrosis factor α (TNF-α) inhibitors are being studied in many trials as adjunctive therapy for ATT. Thalidomide showed promising results in animal studies 82 , but a clinical trial in children reported deaths and adverse events such as neutropenia, hepatitis and skin rashes 83 . Other newer anti-TNF-α inhibitors such as pentoxifylline, adalimumab and etanercept are currently under testing for shortening the duration of anti-TB treatment 80 . ...
Although the occurrence of tuberculous meningitis (TBM) in children is relatively rare, but it is associated with higher rates of mortality and severe morbidity. The peak incidence of TBM occurs in younger children who are less than five years of age, and most children present with late-stage disease. Confirmation of diagnosis is often difficult, and other infectious causes such as bacterial, viral and fungal causes must be ruled out. Bacteriological confirmation of diagnosis is ideal but is often difficult because of its paucibacillary nature as well as decreased sensitivity and specificity of diagnostic tests. Early diagnosis and management of the disease, though difficult, is essential to avoid death or neurologic disability. Hence, a high degree of suspicion and a combined battery of tests including clinical, bacteriological and neuroimaging help in diagnosis of TBM. Children diagnosed with TBM should be managed with antituberculosis therapy (ATT) and steroids. There are studies reporting low concentrations of ATT, especially of rifampicin and ethambutol in cerebrospinal fluid (CSF), and very young children are at higher risk of low ATT drug concentrations. Further studies are needed to identify appropriate regimens with adequate dosing of ATT for the management of paediatric TBM to improve treatment outcomes. This review describes the clinical presentation, investigations, management and outcome of TBM in children and also discusses various studies conducted among children with TBM.
... However, it has also been demonstrated that TNF was a main determinant of pathogenesis and disease progression in a rabbit model of TB [18] and that high levels of TNF could promote granuloma dissemination, progressive infection and pathology in a zebra fish model of M. marinum [19]. In addition, incomplete anti-inflammatory treatment regulating TNF improved TB outcomes [20]. Our data clearly implies that the presence of elevated levels of Type 1 cytokines is a feature secondary to disease severity since heightened levels of both IFN and TNF are observed in PTB individuals. ...
Background
Type 1, Type 17 and other pro-inflammatory cytokines are important in host immunity to tuberculosis (TB) in animal models. However, their role in human immunity to TB is not completely understood.
Aims/Methodology
To examine the association of pro-inflammatory cytokines with pulmonary TB (PTB), we examined the plasma levels of Type 1 (IFNγ and TNFα), Type 17 (IL-17A and IL-17F) and other pro-inflammatory (IL-6, IL-12 and IL-1β) cytokines in individuals with PTB, latent TB (LTB) or healthy controls (HC).
Results
PTB individuals exhibited significantly higher plasma levels of most of the above cytokines in comparison to LTB or HC individuals. PCA analysis based on these cytokines could clearly distinguish PTB from both LTB or HC individuals. PTB individuals with bilateral or cavitary disease exhibited significantly higher levels of IFNγ, TNFα, IL-17A and IL-1β compared to those with unilateral or non-cavitary disease. PTB individuals also exhibited a significant positive relationship between IFNγ, TNFα and IL-17A levels and bacterial burdens. In addition, PTB individuals with delayed culture conversion exhibited significantly higher levels of IFNγ, TNFα, IL-17A and IL-1β at baseline. Finally, the plasma levels of all the cytokines examined were significantly reduced following successful chemotherapy.
Conclusion
Therefore, our data demonstrate that PTB is associated with heightened levels of plasma pro-inflammatory cytokines, which are reversed followed chemotherapy. Our data also reveal that pro-inflammatory cytokines are markers of disease severity, bacterial burden and delayed culture conversion in PTB.
... Levels of tumour necrosis factor (TNF) correlate with the extent of pathology in the rabbit model of TBM, and treatment of this model with antibiotics or thalidomide (which decreases TNF levels) protects against death 33,34 . In children with TBM, CSF levels of TNF and IL-1β are elevated 35 , but no correlation is observed between CSF levels of TNF and disease stage or response to corticosteroid therapy 36 , and another study reported that thalidomide therapy was not associated with decreased mortality 37 . ...
Tuberculosis remains a global health problem, with an estimated 10.4 million cases and 1.8 million deaths resulting from the disease in 2015. The most lethal and disabling form of tuberculosis is tuberculous meningitis (TBM), for which more than 100,000 new cases are estimated to occur per year. In patients who are co-infected with HIV-1, TBM has a mortality approaching 50%. Study of TBM pathogenesis is hampered by a lack of experimental models that recapitulate all the features of the human disease. Diagnosis of TBM is often delayed by the insensitive and lengthy culture technique required for disease confirmation. Antibiotic regimens for TBM are based on those used to treat pulmonary tuberculosis, which probably results in suboptimal drug levels in the cerebrospinal fluid, owing to poor blood-brain barrier penetrance. The role of adjunctive anti-inflammatory, host-directed therapies - including corticosteroids, aspirin and thalidomide - has not been extensively explored. To address this deficit, two expert meetings were held in 2009 and 2015 to share findings and define research priorities. This Review summarizes historical and current research into TBM and identifies important gaps in our knowledge. We will discuss advances in the understanding of inflammation in TBM and its potential modulation; vascular and hypoxia-mediated tissue injury; the role of intensified antibiotic treatment; and the importance of rapid and accurate diagnostics and supportive care in TBM.
Interactions between the immune and nervous systems are involved in many disease processes. Modulation of inflammation can provide an important opportunity to enhance regeneration within the central nervous system. This authoritative book defines the key cellular players in mounting an inflammatory response and highlights critical factors in the target organ that influence the nature of that response and its capacity either to damage or protect the brain. Several key clinical areas are highlighted – particularly autoimmune diseases of the nervous system including multiple sclerosis, as well as microbiological and traumatic challenges; the book therefore provides both a summary of the basic science background as well as practical, clinical-friendly guidelines to management. The book will be of interest to a wide range of physicians, including neurologists, neurosurgeons, neurorehabilitationists, infectious disease physicians, and clinical neuroscientists, as well as neuroscientists and immunologists.
Central nervous system tuberculosis (CNSTB) is the most fatal type of tuberculosis (TB). Early administration of glucocorticoids can improve the prognosis of CNSTB patients and reduce mortality; however, some CNSTB patients do not respond well to anti-tuberculosis drugs and glucocorticoids. As an immunomodulatory drug, Thalidomide has been used under such circumstances. We retrospectively reviewed the drug to describe its clinical characteristics, efficacy, and safety in the treatment of four complicated CNSTB patients who responded well to thalidomide. Thalidomide may be an effective and well-tolerated drug for the treatment of CNSTB, and therefore requires further study.
Background
Understanding the pathophysiology of central nervous system tuberculosis (CNS-TB) is hampered by the lack of a good pre-clinical model that mirrors the human CNS-TB infection. We developed a murine CNS-TB model that demonstrates neurobehavioral changes with similar immunopathology with human CNS-TB.
Methods
We injected two Mycobacterium tuberculosis ( M . tb ) strains, H37Rv and CDC1551, respectively, into two mouse strains, C3HeB/FeJ and Nos2 -/- mice, either into the third ventricle or intravenous. We compared the neurological symptoms, histopathological changes and levels of adhesion molecules, chemokines, and inflammatory cytokines in the brain induced by the infections through different routes in different strains.
Results
Intra-cerebroventricular infection of Nos2 -/- mice with M . tb led to development of neurological signs and more severe brain granulomas compared to C3HeB/FeJ mice. Compared with CDC1551 M . tb , H37Rv M . tb infection resulted in a higher neurobehavioral score and earlier mortality. Intra-cerebroventricular infection caused necrotic neutrophil-dominated pyogranulomas in the brain relative to intravenous infection which resulted in disseminated granulomas and mycobacteraemia. Histologically, intra-cerebroventricular infection of Nos2 -/- mice with M . tb resembled human CNS-TB brain biopsy specimens. H37Rv intra-cerebroventricular infected mice demonstrated higher brain concentrations of inflammatory cytokines, chemokines and adhesion molecule ICAM-1 than H37Rv intravenous-infected mice.
Conclusions
Intra-cerebroventricular infection of Nos2 -/- mice with H37Rv creates a murine CNS-TB model that resembled human CNS-TB immunopathology, exhibiting the worst neurobehavioral score with a high and early mortality reflecting disease severity and its associated neurological morbidity. Our murine CNS-TB model serves as a pre-clinical platform to dissect host-pathogen interactions and evaluate therapeutic agents for CNS-TB.
A dysregulated host immune response significantly contributes to morbidity and mortality in tuberculous meningitis (TBM). Effective host directed therapies (HDTs) are critical to improve survival and clinical outcomes. Currently only one HDT, dexamethasone, is proven to improve mortality. However, there is no evidence dexamethasone reduces morbidity, how it reduces mortality is uncertain, and it has no proven benefit in HIV co-infected individuals. Further research on these aspects of its use, as well as alternative HDTs such as aspirin, thalidomide and other immunomodulatory drugs is needed. Based on new knowledge from pathogenesis studies, repurposed therapeutics which act upon small molecule drug targets may also have a role in TBM. Here we review existing literature investigating HDTs in TBM, and propose new rationale for the use of novel and repurposed drugs. We also discuss host variable responses and evidence to support a personalised approach to HDTs in TBM.
Phosphorus‐based self‐immolative (SI) linkers offer a wide range of applications, such as smart materials and drug‐delivery systems. Phosphorus SI linkers are ideal candidates for double‐cargo delivery platforms because they have a higher valency than carbon. A series of substituted phosphate linkers was designed for releasing two phenolic cargos through SI followed by chemical hydrolysis. Suitable modifications of the lactate spacer increased the cargo release rate significantly, from 1 day to 2 hours or 5 minutes, as shown for linkers containing p‐fluoro phenol. In turn, double cargo linkers bearing p‐methyl phenol released their cargo more slowly (4 days, 4 hours, and 15 minutes) than their p‐fluoro analogues. The α‐hydroxyisobutyrate linker released both cargos in 25 minutes. Our study expands the current portfolio of SI constructs by providing a double cargo delivery option, which is crucial to develop universal SI platforms.
A dysregulated host immune response significantly contributes to morbidity and mortality in tuberculous meningitis (TBM). Effective host directed therapies (HDTs) are critical to improve survival and clinical outcomes. Currently only one HDT, dexamethasone, is proven to improve mortality. However, there is no evidence dexamethasone reduces morbidity, how it reduces mortality is uncertain, and it has no proven benefit in HIV co-infected individuals. Further research on these aspects of its use, as well as alternative HDTs such as aspirin, thalidomide and other immunomodulatory drugs is needed. Based on new knowledge from pathogenesis studies, repurposed therapeutics which act upon small molecule drug targets may also have a role in TBM. Here we review existing literature investigating HDTs in TBM, and propose new rationale for the use of novel and repurposed drugs. We also discuss host variable responses and evidence to support a personalised approach to HDTs in TBM.
Extensive research over the past several decades has demonstrated that rabbits are a highly suitable model to study Mycobacterium tuberculosis (Mtb) infection and disease, including acute/chronic active tuberculosis (TB), latent infection, and reactivation. The lung granulomas in Mtb-infected rabbit lungs are of several types, ranging from highly cellular to necrotic and cavitary lesions, and their pathology resembles that found in human disease. The nature of the infecting Mtb strain, the inoculum dose, and prior vaccination, determine the outcome of infection in the rabbit. In addition, rabbits are an excellent model for the study of tuberculous meningitis (TBM), because of the close resemblance of clinical signs, disease progression, and immunopathology between these animals and humans. The current multi-drug treatment for TB is sub-optimal due to the long duration of therapy and the toxicity of the drugs. Adjunctive host-directed therapy (HDT) is an emerging concept in TB treatment, in which small molecule inhibitors fine-tune the host response to Mtb infection, and in combination with standard antibiotics, improve the outcome of treatment. In this chapter, we discuss the characteristics of the rabbit model of pulmonary Mtb infection and TBM and summarize the value of this preclinical model for evaluating candidate HDT agents for TB.
Objective
Data on cognitive changes in patients of tuberculous meningitis (TBM) are sparse. We aimed to study the cognitive profile of grade I TBM patients and correlate with the cytokine values.
Methods
Prospectively 60 (M:F-31:29) patients of grade I TBM were recruited. Clinical details, CSF estimation of cytokines, neuropsychological assessment was done and correlation were done.
Results
Mean age of presentation and duration of symptoms were 32.2 (32.2 ± 10.1) years and 29.9 (29.9 ± 25.9) days respectively. Definitive evidence of mycobacterial infection was observed in 28.3%. Mean levels of tumor necrosis factor-α (TNF-α), interferon (IFN-γ) and interleukin-6 (IL-6) were 11.57 ± 30.35, 197.02 ± 186.64, and 127.03 ± 88.71 pg/mL respectively. TNF-α levels were significantly elevated in definitive TBM ( p = 0.044). Neuropsychological tests revealed impaired Auditory verbal learning test (88.3%) followed by complex figure test (50%), spatial span test (50%), clock drawing test (48.3%), Digit span test (35%), Color trail test 1 and 2 (30% and 33.3% respectively) and animal naming test (28.3%). Elevated levels of IFN-γ and IL-6 in TBM were directly correlated with the number of impaired neuropsychological tests. During follow up, significant improvement was noticed in Animal naming test ( p = 0.005), Clock drawing test ( p = 0.003), color trail test 2 (0.02), spatial span test ( p = 0.012) and digit span test (0.035). Verbal learning did not show any significant change. Overall Neuropsychological tests showed better recovery of attention, working memory, category fluency and minimal recovery of verbal learning.
Conclusions
There is subclinical evidence of cognitive impairment in patients of TBM and this correlated with elevated cytokines. Both the frontal and temporal lobes show varying degree of cognitive impairment.
Tuberculosis (TB) patient serum cytokine levels may be predictive of anti-tuberculosis treatment progress. Here, serum levels of cytokines TNF-α, IL-4, sIL-2R and IFN-γ were measured then correlated to clinical TB manifestations, bacterial burden, chest imaging findings and clinical course. Study subjects included 67 newly diagnosed pulmonary TB (PTB) patients with active disease admitted to Beijing Chest Hospital for anti-TB chemotherapeutic treatment. Blood was drawn at 0 months (pre-treatment), 1-2 months (at any time between 1 to 2 month) and after 6 months completion of treatment and serum TNF-α, IL-4, sIL-2R and IFN-γ levels were measured in duplicate using enzyme-linked immunosorbent assays (ELISAs). Correlation analysis was conducted to evaluate sensitivity and specificity of cytokine levels as predictors of disease activity and treatment progress. The results indicated that the pre-treatment serum TNF-α level of the smear-negative group was lower than that of the smear 1+ group, while serum TNF-α after 6 months completion of treatment and IFN-γ levels at 1-2 months and after 6 months completion of treatment were significantly lower, respectively, than at 0 months (before treatment) (P < 0.05). Using a cut-off value of 845 pg/ml, serum TNF-α level was predictive of treatment progress, with a sensitivity of 51%, specificity of 60% and AUC of 0.594 (P = 0.013). Meanwhile, using a cut-off value of 393 pg/ml, serum IFN-γ provided superior monitoring efficacy, with a sensitivity of 60%, specificity of 64% and AUC of 0.651 (P = 0.017). In conclusion, both serum TNF-α and IFN-γ levels might be useful biomarkers for monitoring treatment progress.
Tuberculous meningitis (TBM) is the most devastating form of TB, resulting in death or neurological disability in up to 50% of patients affected. Treatment is similar to that of pulmonary TB, despite poor cerebrospinal fluid (CSF) penetration of the cornerstone anti-TB drug rifampicin. Considering TBM pathology, it is critical that optimal drug concentrations are reached in the meninges, brain and/or the surrounding CSF. These type of data are difficult to collect in TBM patients. This review aims to identify and describe a preclinical model representative for human TBM which can provide the indispensable data needed for future pharmacological characterization and prioritization of new TBM regimens in the clinical setting.
We reviewed existing literature on treatment of TBM in preclinical models: only eight articles, all animal studies, could be identified. None of the animal models completely recapitulated human disease and in most of the animal studies key pharmacokinetic data were missing, making the comparison with human exposure and CNS distribution, and the study of pharmacokinetic-pharmacodynamic relationships impossible. Another 18 articles were identified using other bacteria to induce meningitis with treatment including anti-TB drugs (predominantly rifampicin, moxifloxacin and levofloxacin). Of these articles the pharmacokinetics, i.e. plasma exposure and CSF:plasma ratios, of TB drugs in meningitis could be evaluated. Exposures (except for levofloxacin) agreed with human exposures and also most CSF:plasma ratios agreed with ratios in humans.
Considering the lack of an ideal preclinical pharmacological TBM model, we suggest a combination of 1. basic physicochemical drug data combined with 2. in vitro pharmacokinetic and efficacy data, 3. an animal model with adequate pharmacokinetic sampling, microdialysis or imaging of drug distribution, all as a base for 4. physiologically based pharmacokinetic (PBPK) modelling to predict response to TB drugs in treatment of TBM.
Tuberculous meningitis (TBM), caused by Mycobacterium tuberculosis (Mtb), is the deadliest form of tuberculosis in humans, particularly in children and the geriatric population. However, the host-pathogen interactions underlying TBM is not well understood. Rabbits are a valuable model system to study TB in humans. The rabbit model of TB recapitulates several pathophysiological characteristics, including heterogeneity, architecture, and development of granulomas at the site of infection as observed in Mtb-infected human organs. Previously, our group has established a rabbit model of TBM that has been used to understand the host immune response to Mtb infection and to evaluate novel intervention therapies for TBM. In this model, rabbits infected intracisternally with Mtb showed histopathologic manifestations in the brain and meninges that are hallmarks of TBM in humans, including inflammatory cell accumulation and thickening of the leptomeninges. However, in this model, a helmet made of dental acrylic was attached to rabbit's skull with screws under anesthesia. At 24 hours post-procedure, the animals were injected intracisternally with Mtb using a spinal needle. The rabbits were necropsied at various experimental time points up to 2 weeks post-infection. Although this method has been successful in establishing TBM, placement of the dental acrylic helmet on rabbit skull with screws that stays until the experimental endpoint poses stress to the animals and increases the chances of secondary infection. To alleviate these issues, we have developed an improved protocol, in which sedated rabbits are placed on specialized stereotaxic equipment and injected with Mtb intracisternally. This method is less cumbersome, faster, and more efficient in delivering the bacteria. Besides, the animals are not stressed by this method, compared to the previous one.
Tuberculous meningitis (TBM) is the most severe and disabling form of tuberculosis (TB), accounting for around 1-5% of the global TB caseload, with mortality of approximately 20% in children and up to 60% in persons co-infected with human immunodeficiency virus even in those treated. Relatively few centres of excellence in TBM research exist and the field would therefore benefit from greater co-ordination, advocacy, collaboration and early data sharing. To this end, in 2009, 2015 and 2019 we convened the TBM International Research Consortium, bringing together approximately 50 researchers from five continents. The most recent meeting took place on 1 st and 2 nd March 2019 in Lucknow, India. During the meeting, researchers and clinicians presented updates in their areas of expertise, and additionally presented on the knowledge gaps and research priorities in that field. Discussion during the meeting was followed by the development, by a core writing group, of a synthesis of knowledge gaps and research priorities within seven domains, namely epidemiology, pathogenesis, diagnosis, antimicrobial therapy, host-directed therapy, critical care and implementation science. These were circulated to the whole consortium for written input and feedback. Further cycles of discussion between the writing group took place to arrive at a consensus series of priorities. This article summarises the consensus reached by the consortium concerning the unmet needs and priorities for future research for this neglected and often fatal disease.
Tuberculosis (TB) remains a leading cause of death globally. Dissemination of TB to the brain results in the most severe form of extrapulmonary TB, tuberculous meningitis (TBM), which represents a medical emergency associated with high rates of mortality and disability. Via various mechanisms the Mycobacterium tuberculosis (M.tb) bacillus disseminates from the primary site of infection and overcomes protective barriers to enter the CNS. There it induces an inflammatory response involving both the peripheral and resident immune cells, which initiates a cascade of pathologic mechanisms that may either contain the disease or result in significant brain injury. Here we review the steps from primary infection to cerebral disease, factors that contribute to the virulence of the organism and the vulnerability of the host and discuss the immune response and the clinical manifestations arising. Priorities for future research directions are suggested.
Review on how morbidity and mortality caused by tuberculous meningitis is mediated by a dysregulated immune response.
Tuberculous meningitis presents a diagnostic and therapeutic challenge, and considering its long history and increasing global incidence, the evidence base for its treatment is relatively scanty. Many UK neurologists will have little first-hand experience of this deadly condition, and if faced with a patient with possible tuberculous meningitis will find decision making less than straightforward. In parts of East London (UK) the rates of tuberculosis and tuberculous meningitis are among the highest in Western Europe, and so the neurologists and respiratory physicians at the Royal London Hospital have encountered many such patients over the years. We have found experience to be a valuable teacher and so would like to share five cases that illustrate the complexities of diagnosis and management of the disease, and complications of its treatment.
Central nervous system (CNS) tuberculosis (TB) is a serious and deadly form of TB which affects young children and human immunodeficiency virus-infected individuals predominantly. It is the most critical extrapulmonary manifestation of TB, with a high mortality rate and residual neurologic sequelae. It constitutes approximately 1% of all tuberculosis cases. Although various suggestions have been reported related to the occurrence mechanism of the disease, the mechanism is not entirely understood yet. It is considered that Mycobacterium tuberculosis should pass through the blood-brain barrier (BBB) for the occurrence of TB of CNS. The exact entry mechanism of M. tuberculosis to the CNS by passing through the BBB has not been fully elucidated to date. While some authors have suggested that free bacilli directly pass through the endothelial barrier, others have considered that bacilli enter via the macrophages. Various studies in in vitro and animal models have been used for understanding the pathogenesis of TB of CNS.
Tuberculous meningitis (TBM) is the most feared complication of tuberculosis (TB). The vascular complications of TBM contribute maximally to the residual disability observed in such patients. Information regarding the exact pathophysiology of vascular complications is heterogeneous and incomplete. An interplay of factors, ranging from mechanical compression by exudates at the basal part of the brain to processes contributing at the molecular level, is probably responsible for the observed vascular events. Magnetic resonance imaging of the brain is superior to computed tomography in analyzing small lesions as well as ruling out other etiologies. Standard anti-TB treatment forms the mainstay of management, pending recommendations for the use of antithrombotic agents.
Optochiasmatic tuberculosis (TB) is a dreaded complication of TB of the central nervous system. Both optochiasmatic arachnoiditis and optochiasmatic tuberculoma lead to vision involvement and poor outcome. Commonly, optochiasmatic involvement is seen in stage III tuberculous meningitis with high cerebrospinal fluid proteins. Other complications like hydrocephalous, vasculitic stroke, and other cranial nerve deficits are common. Paradoxical involvement of optochiasmatic region can also occur and thus require close follow-up and constant vision monitoring. Treatment comprises continuation of anti-TB drugs with steroids that should be prolonged (often >8 weeks). Methylprednisolone and thalidomide have been used with good results. Other adjuvants like streptokinase, hyaluronidase, interferon, and infliximab have been used but not indicated in present times. Surgical intervention can be done if required as previous reports shows promising results. Further research and studies are required to reduce the morbidity associated with optochiasmatic TB. Prompt diagnosis and early treatment is the key to manage this dreaded complication.
Background
Though animal studies have suggested a role for proinflammatory cytokines in pathogenesis their exact role in pathogenesis of human meningeal tuberculosis continues to be controversial with different studies yielding contradictory results.
Aim and objectives
To study the levels of proinflammatory cytokines in serum and cerebrospinal fluid (CSF) of patients with tubercular meningitis (TBM) and to determine whether these correlate with disease severity.
Patients and methods
Present study included 146 patients with TBM (90- Definite TBM; 56- Probable TBM), diagnosed according to criteria laid by Ahuja et al. which were modified to include CSF nucleic acid based tests. Serum (n = 146) and CSF (n = 140) levels of various proinflammatory cytokines (IL-1β, IL-2, IL-6, TNF-α and IFNγ) were compared between TBM patients and healthy volunteers (n = 99). These levels were correlated with various clinical, radiological and CSF parameters of TBM patients.
Results
Proinflammatory cytokines include cytokines which promote systemic inflammation. In current study, the serum and CSF levels of various cytokines (IL-2, IL-4, IL-6, IL-1β, IFN-γ and TNF-α) were significantly elevated in TBM patients compared to controls. A significant correlation was found between a) Higher stage of TBM and various cytokines (except for serum IL-6 and CSF IFN-γ); b) High CSF TNF-α, IL-4 and IL-1β with severity of hydrocephalus; c) High CSF IL1β and IFN-γ with presence of exudates on MRI; d) Serum and CSF levels of all cytokines with poor outcome as determined by death or as defined by S and E ADL (Schwab and England activities of daily living) score or by GOS (Glasgow outcome scale) (except for interferon gamma); and e) Serum and CSF IL-4 and IL1β with presence of infarcts on MRI brain.
Conclusion
Proinflammatory cytokines play an important role in the pathogenesis of TBM and contribute significantly towards severity of disease.
Infection with Mycobacterium tuberculosis involves mononuclear phagocytic cells as hosts to intracellular parasites, accessory cells in the induction of the immune response, effector cells for mycobacterial killing, and targets of cytotoxic lymphocytes. When stimulated by whole mycobacteria or various mycobacterial preparations, monocytes and macrophages produce the cytokines interleukin 1 and tumor necrosis factor, which possess multiple functions, including immune induction, and may be responsible for the fever and cachexia prominent in tuberculosis. To identify mycobacterial proteins that may directly activate production of these cytokines, culture filtrate of M. tuberculosis that had been subjected to gel electrophoresis and transferred to nitrocellulose paper was used to stimulate monocyte production of cytokines. Fractions representing molecular weights of 46,000 and 20,000 consistently induced both interleukin 1 and tumor necrosis factor. The magnitude of the monocyte responses to these fractions was similar to that to intact mycobacteria or optimal concentrations of lipopolysaccharide. This stimulatory effect was not due to contamination with either bacterial lipopolysaccharide or mycobacterial lipoarabinomannan, as it was abolished by digestion with Streptomyces griseus protease but was unaffected by ammonium sulfate precipitation, preincubation with polymyxin B, or depletion of lipoarabinomannan by immunoaffinity chromatography. Proteins identified by this system may have considerable potential as immunogens, as the capacity to directly stimulate mononuclear phagocyte production of cytokines is an essential property of adjuvants.
Four mycobacterial preparations directly stimulated human blood monocytes and alveolar macrophages to produce tumor necrosis factor (TNF). Monoclonal antibody against TNF blocked (99%) TNF activity. Lipopolysaccharide was not responsible for the TNF activity generated; activity was unaffected in the presence of polymyxin B.
The investigational anti-tumour agent, 5,6-dimethylxanthenone-4-acetic acid (5,6-MeXAA), an analogue of flavone acetic acid (FAA), has been scheduled for clinical evaluation. Like FAA, 5,6-MeXAA exhibits excellent experimental anti-tumour activity and is an efficient inducer of cytokines in mice. We have examined the effect of pharmacological suppression of tumour necrosis factor (TNF) production on the anti-tumour activity of 5,6-MeXAA, taking advantage of previous observations that TNF production in response to endotoxin in vitro is inhibited by thalidomide. Thalidomide at doses of between 8 and 250 mg kg-1 efficiently suppressed serum TNF activity in response to 5,6-MeXAA at its optimal TNF inducing dose of 55 mg kg-1. Suppression was achieved when thalidomide was administered at the same time as, or up to 4 h before, 5,6-MeXAA. Under conditions in which TNF activity was suppressed, the degree of tumour haemorrhagic necrosis and the proportion of cures in the subcutaneous Colon 38 tumour were increased. In mice administered thalidomide (100 mg kg-1) together with 5,6-MeXAA (30 mg kg-1), complete tumour regression was obtained in 100% of mice, as compared with 67% in mice receiving 5,6-MeXAA alone. The results suggest a possible new application for thalidomide and pose new questions about the action of 5,6-MeXAA and related compounds.
We have examined the mechanism of thalidomide inhibition of lipopolysaccharide (LPS)-induced tumor necrosis factor alpha (TNF-alpha) production and found that the drug enhances the degradation of TNF-alpha mRNA. Thus, the half-life of the molecule was reduced from approximately 30 to approximately 17 min in the presence of 50 micrograms/ml of thalidomide. Inhibition of TNF-alpha production was selective, as other LPS-induced monocyte cytokines were unaffected. Pentoxifylline and dexamethasone, two other inhibitors of TNF-alpha production, are known to exert their effects by means of different mechanisms, suggesting that the three agents inhibit TNF-alpha synthesis at distinct points of the cytokine biosynthetic pathway. These observations provide an explanation for the synergistic effects of these drugs. The selective inhibition of TNF-alpha production makes thalidomide an ideal candidate for the treatment of inflammatory conditions where TNF-alpha-induced toxicities are observed and where immunity must remain intact.
The monocyte-derived cytokine, tumor necrosis factor alpha (TNF alpha), is essential for host immunity, but overproduction of this cytokine may have serious pathologic consequences. Excess TNF alpha produced in pulmonary tuberculosis may cause fevers, weakness, night sweats, necrosis, and progressive weight loss. Thalidomide (alpha-N-phthalimidoglutarimide) has recently been shown to suppress TNF alpha production by human monocytes in vitro and to reduce serum TNF alpha in leprosy patients. We have therefore conducted a two-part placebo-controlled pilot study of thalidomide in patients with active tuberculosis to determine its effects on clinical response, immune reactivity, TNF alpha levels, and weight.
30 male patients with active tuberculosis, either human immunodeficiency virus type 1 positive (HIV-1+) or HIV-1-, received thalidomide or placebo for single or multiple 14 day cycles. Toxicity of the study drug, delayed type hypersensitivity (DTH), cytokine production, and weight gain were evaluated.
Thalidomide treatment was well tolerated, without serious adverse events. The drug did not adversely affect the DTH response to purified protein derivative (PPD), total leukocyte, or differential cell counts. TNF alpha production was significantly reduced during thalidomide treatment while interferon-gamma (IFN gamma) production was enhanced. Daily administration of thalidomide resulted in a significant enhancement of weight gain.
The results indicate that thalidomide is well tolerated by patients receiving anti-tuberculosis therapy. Thalidomide treatment reduces TNF alpha production both in vivo and in vitro and is associated with an accelerated weight gain during the study period.
Because interleukin-1β (IL-1β) and cachectin (tumor necrosis factor) are though to mediate the body's response to microbial invasion, we measured IL-1β and tumor necrosis factor concentrations in paired cerebrospinal fluid (CSF) samples (on admission to the hospital, CSF1; 18 to 30 hours later, CSF2) from 106 infants and children with bacterial meningitis. In CSF1, IL-1β was detected in 95% of samples; the mean (±1 SD) concentration was 944±1293 pg/ml. Patients with CSF1 IL-1β concentrations >500 pg/ml were more likely to have neurologic sequelae (p=0.001). Tumor necrosis factor was present in 75% of CSF1 samples; the mean concentration was 787±3358 pg/ml. In CSF2 the mean IL-1β concentration was 135±343 pg/ml, and IL-1β concentrations correlated significantly with CSF2 leukocyte count, with glucose, lactate, protein, and tumor necrosis factor concentrations, and with neurologic sequelae. Tumor necrosis factor was detected in CSF2 specimens of 53 of 106 patients, with a mean concentration of 21±65 pg/ml. Of the 106 patients, 47 received dexamethasone therapy at the time of diagnosis. These patients had significantly lower concentrations of IL-1β and higher glucose and lower lactate concentrations in CSF2, and they had a significantly shorter duration of fever compared with the values in patients not treated with steroids (p≤0.002). Our data suggest a possible role of IL-1β and tumor necrosis factor as mediators of meningeal inflammation in patients with bacterial meningitis, and might explain, in part, the beneficial effect of dexamethasone as adjunctive treatment in this disease.
Rabbits sensitized by intraperitoneal injections of tubercle bacilli and later showing positive skin reactions to tuberculin, as well as non-sensitized rabbits, were given a single inoculation with live tubercle bacilli into the cisterna magna. The animals' brains were examined histologically, 2 to 27 days following the inoculation, for a comparative study of local reactions and their temporal sequence. It was found that in both sensitized and non-sensitized rabbits the major reactions of the brain were histologically similar in type but differed in intensity, in the time of their appearance and in the intervals between them. These reactions were more severe and, on the whole, slower in appearance in the non-sensitized animals and consisted of phagocytosis of tubercle bacilli by activated local histiocytes, the appearance of acute, non-specific inflammation with components of tissue hypersensitivity, tubercle formation by epithelioid cells and caseation, in that order of sequence. These reactions were evoked not only in the cerebral leptomeninges, but also, and simultaneously, in the perivascular reticular tissue of intracerebral, intraneural and choroid-plexus blood vessels. It thus appears that tuberculous involvement of the brain parenchyma, cranial nerves, ependymal lining and choroid plexuses in tuberculous meningitis may not be a complication but a common manifestation of that process.
Allogeneic bone marrow transplantation is an accepted therapy for hematologic cancer, aplastic anemia, and inherited immunodeficiencies. Chronic graft-versus-host disease (GVHD) is the principal complication in patients surviving more than 100 days. Thalidomide has been shown experimentally to be effective in treating GVHD.
We treated 23 patients with chronic GVHD refractory to conventional treatment and 21 patients with "high-risk" chronic GVHD (identified as having at least two of the following three risk factors: chronic GVHD that has evolved from acute GVHD, lichenoid skin or mucous-membrane changes, and hepatic dysfunction. Such patients have a high mortality rate.) with thalidomide in a dose that produced a plasma level of 5 micrograms per milliliter two hours after administration. Therapy was continued for three months after a complete response or for six months after a partial response.
The overall actuarial survival of all enrolled patients was 64 percent. Survival was 76 percent among the patients receiving salvage therapy for refractory GVHD and 48 percent among those with high-risk GVHD. A complete response was observed in 14 patients, a partial response in 12 patients, and no response in 18. Side effects were minor, most notably sedation in almost all patients.
In this preliminary trial, thalidomide appeared to be safe and effective for the treatment of chronic GVHD. A trial comparing thalidomide with prednisone in patients with newly diagnosed chronic GVHD will be required to demonstrate its relative efficacy.
It is widely believed that cell-mediated immunity and the associated ability of macrophages to destroy or inhibit the bacillus are all that is required to control pulmonary tuberculosis. However, although cell-mediated immunity is a major host defense against the tubercle bacillus, it is fully effective only in one of the four stages of the disease. Here, Arthur Dannenberg describes the entire pathogenesis of tuberculosis, with illustrations from the rabbit model of M.B. Lurie. In addition, he documents that the delayed-type hypersensitivity reaction (producing tissue necrosis) greatly benefits the host by arresting the logarithmic growth of bacilli within immature macrophages.
We studied the production of tumor necrosis factor alpha (TNF-alpha) by peripheral blood monocytes taken from patients with pulmonary tuberculosis and from healthy controls. It was found that the monocytes from patients with newly diagnosed tuberculosis released significantly greater amounts of TNF-alpha in vitro in response to lipopolysaccharide than did those from healthy controls (P less than 0.05). However, the monocytes from patients with chronic refractory tuberculosis released significantly lower amounts of TNF-alpha than did those from patients with newly diagnosed tuberculosis (P less than 0.005). Even when the cells were primed for 24 h with 500 U of recombinant interferon gamma per ml, the same pattern of results was observed. The depressed TNF-alpha production by the monocytes from patients with chronic refractory tuberculosis was also shown in response to Mycobacterium bovis BCG. This depressed TNF-alpha production did not recover, even when cultured for 1 to 7 days in the sera of healthy individuals. The sera from patients with chronic refractory tuberculosis did not have any suppressive effect on the lipopolysaccharide-induced TNF-alpha production. Thus, it was demonstrated that the levels of TNF-alpha produced by monocytes were related to the disease states of pulmonary tuberculosis and that the depressed TNF-alpha production by monocytes in patients with chronic refractory tuberculosis might not be acquired.
Tuberculous meningitis is an uncommon but potentially devastating form of tuberculosis. Current antituberculous drugs are highly effective when treatment is initiated early, before the onset of altered mentation or focal neurologic deficits. Because the clinical outcome depends greatly on the stage at which therapy is initiated, early recognition is of paramount importance. Patients with the meningoencephalitis syndrome and CSF findings of low glucose levels, elevated protein levels, and pleocytosis should be treated immediately if there is evidence of TB elsewhere in the body, or if prompt evaluation fails to establish an alternative diagnosis. Examination of CSF is the best diagnostic approach; with sufficient diligence, serial AFB smears and cultures will usually yield positive results, even days after therapy has been started. The CT scan is an important and highly effective tool for the diagnosis and management of patients with TBM. In a patient with compatible clinical features, the combination of basilar meningeal enhancement and any degree of hydrocephalus is strongly suggestive of the diagnosis of TBM. Serial evaluation by CT scanning is useful for following the course of hydrocephalus and tuberculoma, particularly in reference to the need for, or response to, adjunctive therapy with corticosteroids and surgery. The decision to administer corticosteroids should be based on careful correlation of the clinical and radiographic features of the case. Surgical shunting should be considered early in the patient with hydrocephalus and symptoms of raised intracranial pressure. Tuberculomas are best treated medically, often in conjunction with corticosteroids where cerebral edema is believed to contribute to neurologic decline. The recommended chemotherapy regimen is isoniazid and rifampin in all patients, together with pyrazinamide for the first 2 months.
We show here that purified lipoarabinomannan (LAM) from Mycobacterium tuberculosis can cause the release of tumour necrosis factor (TNF) in vitro from human blood monocytes and activated mouse peritoneal macrophages, and the production of TNF in vivo in mice pretreated with Propionibacterium acnes, with a potency comparable to that of lipopolysaccharide (LPS) from Gram negative bacteria. Like LPS, LAM binds to polymyxin B. We confirmed that its activity was distinct from any contaminating LPS and was associated with the antigenic activity by affinity chromatography, using a monoclonal antibody specific for LAM. Treatment with dilute alkali greatly diminished the TNF-inducing activity, suggesting that omicron-acyl groups may be involved. When LAM was fractionated by electrophoresis on SDS-Page and blotted on nitrocellulose, most TNF-inducing capacity coincided with the bulk of the LAM, as estimated by molecular weight and antigenic activity. This modification of the Western blotting technique may be generally useful for the study of macrophage-triggering molecules. The ability of LAM to cause the release of TNF may be responsible for some of the characteristics of tuberculosis, such as fever, weight loss, raised acute phase reactants and necrosis that can be mediated by this cytokine.
Granuloma formation in the liver of mice infected with BCG coincides with local TNF synthesis. Injection of rabbit anti-TNF antibody, after 1 or 2 weeks of infection, dramatically interferes with the development of granulomas (both in number and size, large epithelioid cells failing to appear) and subsequent mycobacterial elimination. Furthermore, fully developed BCG granulomas, after 3 weeks of infection, rapidly regress after anti-TNF treatment. Antibody treatment also prevents or suppresses accumulation of TNF mRNA and protein, which resumes after disappearance of the antibody. Peritoneal macrophages exposed to TNF transiently accumulate TNF mRNA, and show an enhanced increase in TNF mRNA in response to gamma interferon. We propose that TNF released from macrophages in the microenvironment of developing granulomas is involved in a process of autoamplification: acting in an autocrine or paracrine way, it enhances its own synthesis and release, thus favoring further macrophage accumulation and differentiation leading to bacterial elimination.
Human recombinant tumor necrosis factor (rTNF) was found to act directly on cultured human vascular endothelium to induce a tissue factor-like procoagulant activity (PCA). After a 4-hr incubation in rTNF (100 units/ml), serially passaged endothelial cells isolated from umbilical veins, saphenous veins, iliac arteries, and thoracic aortae demonstrated a dramatic increase (4- to 15-fold, 21 experiments) in total cellular PCA as measured with a one-stage clotting assay. rTNF-induced PCA was also expressed at the surface of intact viable endothelial monolayers. Induction of PCA by rTNF was concentration dependent (maximum, 500 units/ml), time dependent, reversible, and blocked by cycloheximide and actinomycin D, and it occurred without detectable endothelial cell damage. Actions of rTNF were compared with those of natural human interleukin 1 (IL-1) derived from stimulated monocytes and two distinct species of recombinant IL-1, each of which also induced endothelial PCA. The use of recombinant polypeptides and specific neutralizing antisera established the distinct natures of the mediators. The kinetics of the endothelial PCA responses to TNF and IL-1 were similar, demonstrating a rapid rise to peak activity at approximately equal to 4 hr, and a decline toward basal levels by 24 hr. This characteristic decline in PCA after prolonged incubation with TNF or IL-1 was accompanied by selective endothelial hyporesponsiveness to the initially stimulating monokine. Interestingly, the effects of TNF and IL-1 were found to be additive even at apparent maximal doses of the individual monokines. Endothelial-directed actions of TNF, alone or in combination with other monokines, may be important in the initiation of coagulation and inflammatory responses in vivo.
Central nervous system tuberculosis occurred in three patients with the acquired immunodeficiency syndrome (AIDS) and seven patients with AIDS-related complex who were evaluated for 48 months. Nine patients were intravenous drug abusers and one was Haitian. Five patients had cerebral-ring-enhancing lesions and three had hypodense areas. The clinical spectrum included meningitis in two patients, multiple cerebral abscesses in one, and tuberculomas in four. All Mycobacterium tuberculosis isolates were sensitive to standard antituberculous drugs. All patients received treatment with isoniazid, rifampin, and pyrazinamide; six patients also received streptomycin. Three patients with AIDS died of opportunistic infection preceded by central nervous system tuberculosis. Among the patients with the AIDS-related complex, three improved with treatment, three were lost to follow-up, and one died. Tuberculosis should be considered in the differential diagnosis of central nervous system mass lesions in intravenous drug abusers with AIDS or AIDS-related complex. Because patients with tuberculosis can be cured, biopsy of accessible brain mass lesions should be mandatory. Preventive therapy may be indicated in drug abusers without disease.
Concentrations of interferon gamma (IFN-gamma) in the lumbar cerebrospinal fluid (CSF) of 30 children (mean age, 27 months) being treated for stage III (16 children) and stage II (14 children) tuberculosis meningitis (TBM) were determined by ELISA. Nine children with stage III TBM and six with stage II TBM received prednisone (4 mg/kg). Concentrations of IFN-gamma in 73 CSF specimens (18 from the first week of therapy, 20 from the second, 19 from the third, and 16 from the fourth) were determined. The mean concentrations were 780 pg/mL in the first week of therapy and 554 pg/mL, 529 pg/mL, and 269 pg/mL in the second, third, and fourth weeks, respectively. Tumor necrosis factor alpha (TNF-alpha) and interleukin-1beta (IL-1beta) concentrations in 56 specimens from 23 of these same children were determined by ELISA. The mean CSF TNF-alpha concentration in 12 specimens obtained during the first week of therapy was 17 pg/mL, and the mean was 11 pg/mL during each of the subsequent weeks (14 specimens were evaluated in the second week and 15 specimens in the third and fourth weeks of therapy). Mean IL-1beta concentrations in these same groups of specimens were 52 pg/mL, 43 pg/mL, 42 pg/mL, and 18 pg/mL. No correlation could be shown between cytokine concentration and stage of disease, and no differences existed between those who did and those who did not receive prednisone. A significant decline in IL-1beta concentrations was shown during the 4-week period, but none in TNF-alpha or IFN-gamma concentrations was noted. Persistently high CSF INF-gamma concentrations in cases of TBM (as in cases of aseptic meningitis but not bacterial meningitis) at the time of diagnosis suggest an immune response fundamentally different from that in bacterial meningitis.
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