Tumor Necrosis Factor-Alpha Antagonist Interferes With the Formation of Granulomatous Multinucleated Giant Cells: New Insights Into Mycobacterium tuberculosis Infection

Disseminated, fatal reactivation of bovine tuberculosis in a patient treated with adalimumab: a case report and review of the literature

PURPOSE

Tumor necrosis factor inhibitors (TNFi) are known to increase the risk of tuberculosis (TB) reactivation, though cases involving Mycobacterium bovis are rarely reported.

CASE PRESENTATION/RESULTS

We describe a case of disseminated TB with M. bovis in a 78-year-old woman with a negative Interferon-Gamma-Release Assay (IGRA), taking adalimumab due to rheumatoid polyarthritis, which resulted in a fatal outcome. The atypical clinical and histopathological features were initially interpreted as sarcoidosis. The case occurred in Switzerland, an officially bovine tuberculosis-free country. The whole genome sequence of the patient's cultured M. bovis isolate was identified as belonging to the animal lineage La1.2, the main genotype in continental Europe, but showed significant genetic distance from previously sequenced Swiss cattle strains. In a literature review, four cases of bovine tuberculosis reactivation under TNFi treatment were identified, with pulmonal, oral and intestinal manifestations. Similar to our patient, two cases presented a negative IGRA before TNFi initiation, which later converted to positive upon symptomatic presentation of M. bovis infection.

CONCLUSION

This case highlights the diagnostic challenges of TB in immunosuppressed patients, the limited sensitivity of IGRA, and the importance of considering TB reactivation even in regions declared free of bovine tuberculosis. Detailed patient histories, including potential exposure to unpasteurized dairy products, are essential for guiding preventive TB treatment before TNFi initiation.

The rs11684747 and rs55790676 SNPs of ADAM17 influence tuberculosis susceptibility and plasma levels of TNF, TNFR1, and TNFR2

Introduction

The proteolytic activity of A Disintegrin and Metalloproteinase 17 (ADAM17) regulates the release of tumor necrosis factor (TNF) and TNF receptors (TNFRs) from cell surfaces. These molecules play important roles in tuberculosis (TB) shaping innate immune reactions and granuloma formation.

Methods

Here, we investigated whether single nucleotide polymorphisms (SNPs) of ADAM17 influence TNF and TNFRs levels in 224 patients with active TB (ATB) and 118 healthy close contacts. Also, we looked for significant associations between SNPs of ADAM17 and ATB status. TNF, TNFR1, and TNFR2 levels were measured in plasma samples by ELISA. Four SNPs of ADAM17 (rs12692386, rs1524668, rs11684747, and rs55790676) were analyzed in DNA isolated from peripheral blood leucocytes. The association between ATB status, genotype, and cytokines was analyzed by multiple regression models.

Results

Our results showed a higher frequency of rs11684747 and rs55790676 in close contacts than ATB patients. Coincidentally, heterozygous to these SNPs of ADAM17 showed higher plasma levels of TNF compared to homozygous to their respective ancestral alleles. Strikingly, the levels of TNF and TNFRs distinguished participant groups, with ATB patients displaying lower TNF and higher TNFR1/TNFR2 levels compared to their close contacts.

Conclusion

These findings suggest a role for SNPs of ADAM17 in genetic susceptibility to ATB.

Expression of a unique M. tuberculosis DNA MTase Rv1509 in M. smegmatis alters the gene expression pattern and enhances virulence

Mycobacterium tuberculosis (M. tb) genome encompasses 4,173 genes, about a quarter of which remain uncharacterized and hypothetical. Considering the current limitations associated with the diagnosis and treatment of tuberculosis, it is imperative to comprehend the pathomechanism of the disease and host-pathogen interactions to identify new drug targets for intervention strategies. Using in-silico comparative genome analysis, we identified one of the M. tb genes, Rv1509, as a signature protein exclusively present in M. tb. To explore the role of Rv1509, a likely methyl transferase, we constructed a knock-in Mycobacterium smegmatis (M. smegmatis) constitutively expressing Rv1509 (Ms_Rv1509). The Ms_Rv1509 led to differential expression of many transcriptional regulator genes as assessed by RNA-seq analysis. Further, in-vitro and in-vivo studies demonstrated an enhanced survival of Ms_Rv1509 inside the host macrophages. Ms_Rv1509 also promoted phagolysosomal escape inside macrophages to boost bacterial replication and dissemination. In-vivo infection studies revealed that Ms_Rv1509 survives better than BCG and causes pathological manifestations in the pancreas after intraperitoneal infection. Long-time survival of Ms_Rv1509 resulted in lymphocyte migration, increased T regulatory cells, giant cell formation, and likely granuloma formation in the pancreas, pointing toward the role of Rv1509 in M. tb pathogenesis.

BCG activation of trained immunity is associated with induction of cross reactive COVID-19 antibodies in a BCG vaccinated population

BACKGROUND

Pakistan is endemic to a diverse set of parasitic, mycobacterial and viral diseases. The recognition of BCG Trained Immunity (TI) led us to postulate that the continued presence of BCG-TI may play a protective role, previously reported for both infectious and noninfectious conditions. Most of the previous studies have addressed the issue of BCG-TI in the paediatric populations. This study addressed the key issue of maintenance of BCG-TI in a wider age range (adolescent and adults) to identify the strength and quality of the immune responses.

OBJECTIVE

To assess the BCG-induced recall responses in healthy individuals by cytokines secreted from the TI network and its potential role in providing cross-protection against COVID-19 and other viral infections.

STUDY DESIGN

In this cross-sectional study, healthy young adults and adolescents (n = 20) were recruited from 16-40 years of age, with no prior history of TB treatment, autoimmune, or chronic inflammatory condition.

METHODS

BCG-induced cytokine responses were assessed using prototypic markers for cells of the TI network [macrophages [M1 (TNFα, IFNγ), M2 (IL10)], NK (IL2), Gamma delta (γδ) T (IL17, IL4)] and SARS CoV2 IgG antibodies against RBD using short-term (12 hrs.) cultures assay.

RESULTS

Significant differences were observed in the magnitude of recall responses to BCG with macrophage cytokines showing the highest mean levels of TNFα (9148 pg/ml) followed by IL10 (488 pg/ml) and IFNγ (355 pg/ml). The ratio of unstimulated vs.BCG-stimulated cytokines was 132 fold higher for TNFα, 40 fold fo r IL10, and 27 fold for IFNγ. Furthermore, SARS-CoV-2 antibodies were also detected in unstimulated plasma which showed cross reactivity with BCG.

CONCLUSION

The presence of cross reactive antibodies to SARS-CoV-2 and the relative ratio of pro- and anti-inflammatory cytokines secreted by activated TI cellular network may play a pivotal role in protection in the early stages of infection as observed during the COVID-19 pandemic in the younger age groups resulting in lower morbidity and mortality.

TNF in Human Tuberculosis: A Double-Edged Sword

TNF, a pleiotropic proinflammatory cytokine, is important for protective immunity and immunopathology during Mycobacterium tuberculosis (Mtb) infection, which causes tuberculosis (TB) in humans. TNF is produced primarily by phagocytes in the lungs during the early stages of Mtb infection and performs diverse physiological and pathological functions by binding to its receptors in a context-dependent manner. TNF is essential for granuloma formation, chronic infection prevention, and macrophage recruitment to and activation at the site of infection. In animal models, TNF, in cooperation with chemokines, contributes to the initiation, maintenance, and clearance of mycobacteria in granulomas. Although anti-TNF therapy is effective against immune diseases such as rheumatoid arthritis, it carries the risk of reactivating TB. Furthermore, TNF-associated inflammation contributes to cachexia in patients with TB. This review focuses on the multifaceted role of TNF in the pathogenesis and prevention of TB and underscores the importance of investigating the functions of TNF and its receptors in the establishment of protective immunity against and in the pathology of TB. Such investigations will facilitate the development of therapeutic strategies that target TNF signaling, which makes beneficial and detrimental contributions to the pathogenesis of TB.

Antibodies as clinical tools for tuberculosis

Tuberculosis (TB) is a leading cause of morbidity and mortality worldwide. Global research efforts to improve TB control are hindered by insufficient understanding of the role that antibodies play in protective immunity and pathogenesis. This impacts knowledge of rational and optimal vaccine design, appropriate diagnostic biomarkers, and development of therapeutics. Traditional approaches for the prevention and diagnosis of TB may be less efficacious in high prevalence, remote, and resource-poor settings. An improved understanding of the immune response to the causative agent of TB, Mycobacterium tuberculosis (Mtb), will be crucial for developing better vaccines, therapeutics, and diagnostics. While memory CD4+ T cells and cells and cytokine interferon gamma (IFN-g) have been the main identified correlates of protection in TB, mounting evidence suggests that other types of immunity may also have important roles. TB serology has identified antibodies and functional characteristics that may help diagnose Mtb infection and distinguish between different TB disease states. To date, no serological tests meet the World Health Organization (WHO) requirements for TB diagnosis, but multiplex assays show promise for improving the sensitivity and specificity of TB serodiagnosis. Monoclonal antibody (mAb) therapies and serum passive infusion studies in murine models of TB have also demonstrated some protective outcomes. However, animal models that better reflect the human immune response to Mtb are necessary to fully assess the clinical utility of antibody-based TB prophylactics and therapeutics. Candidate TB vaccines are not designed to elicit an Mtb-specific antibody response, but evidence suggests BCG and novel TB vaccines may induce protective Mtb antibodies. The potential of the humoral immune response in TB monitoring and control is being investigated and these studies provide important insight into the functional role of antibody-mediated immunity against TB. In this review, we describe the current state of development of antibody-based clinical tools for TB, with a focus on diagnostic, therapeutic, and vaccine-based applications.

Effectiveness of Adjunctive High-Dose Infliximab Therapy to Improve Disability-Free Survival Among Patients With Severe Central Nervous System Tuberculosis: A Matched Retrospective Cohort Study

BACKGROUND

Few treatment options exist for patients with severe central nervous system (CNS) tuberculosis (TB) worsening due to inflammatory lesions, despite optimal antitubercular therapy (ATT) and steroids. Data regarding the efficacy and safety of infliximab in these patients are sparse.

METHODS

We performed a matched retrospective cohort study based on Medical Research Council (MRC) grading system and modified Rankin Scale (mRS) scores comparing 2 groups of adults with CNS TB. Cohort A received at least 1 dose of infliximab after optimal ATT and steroids between March 2019 and July 2022. Cohort B received only ATT and steroids. Disability-free survival (mRS score ≤2) at 6 months was the primary outcome.

RESULTS

Baseline MRC grades and mRS scores were similar between the cohorts. Median duration before initiation of infliximab therapy from start of ATT and steroids was 6 (IQR: 3.7-13) months and for neurological deficits was 4 (IQR: 2-6.2) months. Indications for infliximab were symptomatic tuberculomas (20/30; 66.7%), spinal cord involvement with paraparesis (8/30; 26.7%), and optochiasmatic arachnoiditis (3/30; 10%), worsening despite adequate ATT and steroids. Severe disability (5/30 [16.7%] and 21/60 [35%]) and all-cause mortality (2/30 [6.7%] and 13/60 [21.7%]) at 6 months were lower in cohort A versus cohort B, respectively. In the combined study population, only exposure to infliximab was positively associated (aRR: 6.2; 95% CI: 2.18-17.83; P = .001) with disability-free survival at 6 months. There were no clear infliximab-related side effects noted.

CONCLUSIONS

Infliximab may be an effective and safe adjunctive strategy among severely disabled patients with CNS TB not improving despite optimal ATT and steroids. Adequately powered phase 3 clinical trials are required to confirm these early findings.

Frequent Occurrence of Perianal Disease and Granuloma Formation in Patients with Crohn's Disease and Coexistent Orofacial Granulomatosis

BACKGROUND

Orofacial granulomatosis (OFG) is an inflammatory disorder of the perioral region and oral cavity. Crohn's disease (CD) in conjunction with OFG (CD-OFG), has been suggested to constitute a phenotype of CD with distinct features at diagnosis.

AIMS

The aim of this project was to investigate whether the distinct phenotypic features of CD-OFG persist in the years following the initial diagnosis of CD.

METHODS

Clinical data were extracted from medical records covering the first 5 years post-diagnosis for a cohort of patients with CD-OFG, and were compared to those of references with CD without OFG.

RESULTS

The clinical characteristics of our cohort of patients with CD-OFG (N = 25) were evaluated in comparison to references with CD without OFG (ratio 1:2). Five years post-diagnosis, more patients with CD-OFG had a phenotype with perianal disease (cumulative incidence: 16/25, 64% vs 13/50, 26%, P = 0.002) and intestinal granulomas (cumulative incidence: 22/25, 88% vs 24/50, 48%, P = 0.0009) than patients in the CD reference group. The patients with CD-OFG were also more likely to have undergone perianal surgery (12/25, 48% vs 4/50, 8%, P = 0.0002). At the end of the observation period, more of the patients with CD-OFG were receiving combination therapy, i.e., immunomodulators and tumor necrosis factor antagonists, than those in the CD reference group (9/25, 36% vs 5/50, 10%, P = 0.01).

CONCLUSION

The results support the notion that CD in conjunction with OFG represents a specific phenotype of CD that is characterized by frequent perianal disease, pronounced intestinal granuloma formation and a need for extensive therapy.

Tuberculosis: The success tale of less explored dormant Mycobacterium tuberculosis

Mycobacterium tuberculosis (M.tb) is an intracellular pathogen that predominantly affects the alveolar macrophages in the respiratory tract. Upon infection, the activation of TLR2 and TLR4- mediated signaling pathways leads to lysosomal degradation of the bacteria. However, bacterium counteracts the host immune cells and utilizes them as a cellular niche for its survival. One distinctive mechanism of M.tb to limit the host stress responses such as hypoxia and nutrient starvation is induction of dormancy. As the environmental conditions become favorable, the bacteria resuscitate, resulting in a relapse of clinical symptoms. Different bacterial proteins play a critical role in maintaining the state of dormancy and resuscitation, namely, DevR (DosS), Hrp1, DATIN and RpfA-D, RipA, etc., respectively. Existing knowledge regarding the key proteins associated with dormancy and resuscitation can be employed to develop novel therapies. In this review we aim to highlight the current knowledge of bacterial progression from dormancy to resuscitation and the gaps in understanding the transition from dormant to active state. We have also focused on elucidating a few therapeutic strategies employed to prevent M.tb resuscitation.

Phenotypic adaptation of Mycobacterium tuberculosis to host-associated stressors that induce persister formation

Mycobacterium tuberculosis exhibits a remarkable ability to interfere with the host antimicrobial response. The pathogen exploits elaborate strategies to cope with diverse host-induced stressors by modulating its metabolism and physiological state to prolong survival and promote persistence in host tissues. Elucidating the adaptive strategies that M. tuberculosis employs during infection to enhance persistence is crucial to understanding how varying physiological states may differentially drive disease progression for effective management of these populations. To improve our understanding of the phenotypic adaptation of M. tuberculosis, we review the adaptive strategies employed by M. tuberculosis to sense and coordinate a physiological response following exposure to various host-associated stressors. We further highlight the use of animal models that can be exploited to replicate and investigate different aspects of the human response to infection, to elucidate the impact of the host environment and bacterial adaptive strategies contributing to the recalcitrance of infection.

Increased susceptibility to pneumonia due to tumour necrosis factor inhibition and prospective immune system rescue via immunotherapy

Immunomodulators such as tumour necrosis factor (TNF) inhibitors are used to treat autoimmune conditions by reducing the magnitude of the innate immune response. Dampened innate responses pose an increased risk of new infections by opportunistic pathogens and reactivation of pre-existing latent infections. The alteration in immune response predisposes to increased severity of infections. TNF inhibitors are used to treat autoimmune conditions such as rheumatoid arthritis, juvenile arthritis, psoriatic arthritis, transplant recipients, and inflammatory bowel disease. The efficacies of immunomodulators are shown to be varied, even among those that target the same pathways. Monoclonal antibody-based TNF inhibitors have been shown to induce stronger immunosuppression when compared to their receptor-based counterparts. The variability in activity also translates to differences in risk for infection, moreover, parallel, or sequential use of immunosuppressive drugs and corticosteroids makes it difficult to accurately attribute the risk of infection to a single immunomodulatory drug. Among recipients of TNF inhibitors, Mycobacterium tuberculosis has been shown to be responsible for 12.5-59% of all infections; Pneumocystis jirovecii has been responsible for 20% of all non-viral infections; and Legionella pneumophila infections occur at 13-21 times the rate of the general population. This review will outline the mechanism of immune modulation caused by TNF inhibitors and how they predispose to infection with a focus on Mycobacterium tuberculosis, Legionella pneumophila, and Pneumocystis jirovecii. This review will then explore and evaluate how other immunomodulators and host-directed treatments influence these infections and the severity of the resulting infection to mitigate or treat TNF inhibitor-associated infections alongside antibiotics.

Spontaneous Control of SIV Replication Does Not Prevent T Cell Dysregulation and Bacterial Dissemination in Animals Co-Infected with M. tuberculosis

Individuals co-infected with HIV and Mycobacterium tuberculosis (Mtb) are more likely to develop severe tuberculosis (TB) disease than HIV-naive individuals. To understand how a chronic pre-existing Simian immunodeficiency virus (SIV) infection impairs the early immune response to Mtb, we used the Mauritian cynomolgus macaque (MCM) model of SIV/Mtb co-infection. We examined the relationship between peripheral viral control and Mtb burden, Mtb dissemination, and T cell function between SIV+ spontaneous controllers, SIV+ non-controllers, and SIV-naive MCM who were challenged with a barcoded Mtb Erdman strain 6 months post-SIV infection and necropsied 6 weeks post-Mtb infection. Mycobacterial burden was highest in the SIV+ non-controllers in all assessed tissues. In lung granulomas, the frequency of TNF-α-producing CD4+ T cells was reduced in all SIV+ MCM, but IFNγ-producing CD4+ T cells were only lower in the SIV+ non-controllers. Further, while all SIV+ MCM had more PD1+ and TIGIT+ T cells in the lung granulomas relative to SIV-naive MCM, SIV+ controllers exhibited the highest frequency of cells expressing these markers. To measure the effect of SIV infection on within-host bacterial dissemination, we sequenced the molecular barcodes of Mtb present in each tissue and characterized the Mtb population complexity. While Mtb population complexity was not associated with SIV infection group, lymph nodes had increased complexity when compared with lung granulomas across all groups. These results provide evidence that SIV+ animals, independent of viral control, exhibit a dysregulated T cell immune response and enhanced dissemination of Mtb, likely contributing to the poor TB disease course across all SIV/Mtb co-infected animals. IMPORTANCE HIV and TB remain significant global health issues, despite the availability of treatments. Individuals with HIV, including those who are virally suppressed, are at an increased risk to develop and succumb to severe TB disease when compared with HIV-naive individuals. Our study aims to understand the relationship between the extent of SIV replication, mycobacterial growth, and T cell function in the tissues of co-infected Mauritian cynomolgus macaques during the first 6 weeks of Mtb infection. Here we demonstrate that increased viral replication is associated with increased bacterial burden in the tissues and impaired T cell responses, and that the immunological damage attributed to virus infection is not fully eliminated when animals spontaneously control virus replication.

Immunosuppressive Mechanisms in Brucellosis in Light of Chronic Bacterial Diseases

Brucellosis is considered one of the major zoonoses worldwide, constituting a critical livestock and human health concern with a huge socio-economic burden. Brucella genus, its etiologic agent, is composed of intracellular bacteria that have evolved a prodigious ability to elude and shape host immunity to establish chronic infection. Brucella’s intracellular lifestyle and pathogen-associated molecular patterns, such as its specific lipopolysaccharide (LPS), are key factors for hiding and hampering recognition by the immune system. Here, we will review the current knowledge of evading and immunosuppressive mechanisms elicited by Brucella species to persist stealthily in their hosts, such as those triggered by their LPS and cyclic β-1,2-d-glucan or involved in neutrophil and monocyte avoidance, antigen presentation impairment, the modulation of T cell responses and immunometabolism. Attractive strategies exploited by other successful chronic pathogenic bacteria, including Mycobacteria, Salmonella, and Chlamydia, will be also discussed, with a special emphasis on the mechanisms operating in brucellosis, such as granuloma formation, pyroptosis, and manipulation of type I and III IFNs, B cells, innate lymphoid cells, and host lipids. A better understanding of these stratagems is essential to fighting bacterial chronic infections and designing innovative treatments and vaccines.

Assessment of Experimental Techniques That Facilitate Human Granuloma Formation in an In Vitro System: A Systematic Review

The process of granuloma formation is complex, and due to species differences, the validity of animal studies is somewhat questioned. Moreover, the large number of animals needed to observe the different stages of development also raises ethical questions. Therefore, researchers have explored the use of human peripheral blood mononuclear cells (PBMCs), a heterogeneous population of immune cells, in an in vitro model. This review included in vitro studies that focused on exposing PBMCs—from healthy, sensitized, or diseased individuals—to antigens derived from infectious agents—such as mycobacteria or Schistosoma spp.—or inorganic antigens—such as beryllium. The reviewed studies mainly explored how human in vitro granuloma models can contribute towards understanding the pathogenesis of granulomatous diseases, especially during the early stages of granuloma formation. The feasibility of granuloma modelling was thus largely assessed via experimental techniques including (1) granuloma scoring indices (GI), (2) cell surface markers and (3) cytokine secretion profiling. While granuloma scoring showed some similarities between studies, a large variability of culture conditions and endpoints measured have been identified. The lack of any standardization currently impedes the success of a human in vitro granuloma model.

Insight into the Molecular Characteristics of Langhans Giant Cell by Combination of Laser Capture Microdissection and RNA Sequencing

Purpose

The presence of Langhans giant cell (LGC) is a hallmark of mycobacterium-induced granuloma. The molecular characteristics and functions of LGC remain unclear to date. The study aimed to systematically characterize the molecular characteristics of LGC and reveal the potential functions.

Methods

Human LGCs were purified through laser capture microdissection (LCM) in vitro. RNA sequencing and in-depth transcriptome analysis were performed for purified LGCs and macrophages in the same system. Skin samples from mycobacterial infection patients were used to confirm some of the transcriptional expression.

Results

Human LGCs have different expression pattern from macrophages in the same in vitro system. A total of 967 differentially expressed genes were found. Bioinformatics analysis showed that LGCs are is characterized by active cell shape regulation, increased cytoskeletal components, weakened energy metabolism level, and reduced immune response. CCL7 may be a specific molecular for LGC to communicate with CCR1-expression cells in granuloma.

Conclusion

LGCs have unique molecular characteristics different from that of macrophages. They may play a role in maintaining the hemostasis in granuloma.

Progress of the Art of Macrophage Polarization and Different Subtypes in Mycobacterial Infection

Mycobacteriosis, mostly resulting from Mycobacterium tuberculosis (MTb), nontuberculous mycobacteria (NTM), and Mycobacterium leprae (M. leprae), is the long-standing granulomatous disease that ravages several organs including skin, lung, and peripheral nerves, and it has a spectrum of clinical-pathologic features based on the interaction of bacilli and host immune response. Histiocytes in infectious granulomas mainly consist of infected and uninfected macrophages (Mφs), multinucleated giant cells (MGCs), epithelioid cells (ECs), and foam cells (FCs), which are commonly discovered in lesions in patients with mycobacteriosis. Granuloma Mφ polarization or reprogramming is the crucial appearance of the host immune response to pathogen aggression, which gets a command of endocellular microbe persistence. Herein, we recapitulate the current gaps and challenges during Mφ polarization and the different subpopulations of mycobacteriosis.

Pathogenetic role of tumor necrosis factor (TNF-α) for the development of peritoneal tuberculosis in an experiment

Currently tuberculosis is considered as a group of diseases united by one etiological factor. The pathogenesis of certain localizations of tuberculous inflammation, in particular peritoneum tuberculosis, hasn’t been sufficiently studied. The role of cytokine mechanisms in the development of the disease and the elaboration of non-sterile immunity requires further experimental studies, in particular the creation of a reproducible model on laboratory animals.

The aim: to study the effect of TNF-α on the development of tuberculosis of the serous coat of the abdominal cavity, as well as to evaluate the possibility of modeling tuberculous peritonitis in laboratory animals using infliximab.

Materials and methods. The studies were conducted on 18 male rabbits, which were simulated peritoneal tuberculosis by intra-abdominal administration of a suspension of Mycobacterium tuberculosis. 10 rabbits of the experimental group were intravenously injected with an infliximab solution and an iron (III) hydroxide sucrose complex intraperitoneally a day before infection.

Results. In the control group of animals, tuberculosis either didn’t develop, or in a third of cases it affected only the pulmonary parenchyma, while proliferative processes prevailed. On the contrary, in animals with inactivated TNF-α, in 100 % of observations, tuberculous peritonitis was detected with associated lung damage and the predominance of alterative caseous processes.

Conclusion. The created model of tuberculous peritonitis shows the leading role of TNF-α in the activation of macrophages, as well as in attracting cells to the site of infection. This is the primary signal necessary for the formation and stability of granulomas since the neutralization of this cytokine leads to a loss of control over the infection and the destruction of the granuloma with the development of destructive tuberculosis in the serous coat of the abdominal cavity. 

3D host cell and pathogen-based bioassay development for testing anti-tuberculosis (TB) drug response and modeling immunodeficiency

Tuberculosis (TB) is a global health threat that affects 10 million people worldwide. Human Immunodeficiency Virus (HIV) remains one of the major contributors to the reactivation of asymptomatic latent tuberculosis (LTBI). Over the recent years, there has been a significant focus in developing in-vitro 3D models mimicking early events of Mycobacterium tuberculosis (Mtb) pathogenesis, especially formation of the granuloma. However, these models are low throughput and require extracellular matrix. In this article, we report the generation of a matrix-free 3D model, using THP-1 human monocyte/macrophage cells and mCherry-expressing Mycobacterium bovis BCG (Bacilli Camille Guérin), henceforth referred as 3D spheroids, to study the host cell-bacterial interactions. Using mCherry-intensity-based tracking, we monitored the kinetics of BCG growth in the 3D spheroids. We also demonstrate the application of the 3D spheroids for testing anti-TB compounds such as isoniazid (INH), rifampicin (RIF), as well as a host-directed drug, everolimus (EVR) as single and combinational treatments. We further established a dual infection 3D spheroid model by coinfecting THP-1 macrophages with BCG mCherry and pseudotype HIV. In this HIV-TB co-infection model, we found an increase in BCG mCherry growth within the 3D spheroids infected with HIV pseudotype. The degree of disruption of the granuloma was proportional to the virus titers used for co-infection. In summary, this 3D spheroid assay is an useful tool to screen anti-TB response of potential candidate drugs and can be adopted to model HIV-TB interactions.

Tumor Necrosis Factor Inhibitors Exacerbate Whipple's Disease by Reprogramming Macrophage and Inducing Apoptosis

Tropheryma whipplei is the agent of Whipple’s disease, a rare systemic disease characterized by macrophage infiltration of the intestinal mucosa. The disease first manifests as arthralgia and/or arthropathy that usually precede the diagnosis by years, and which may push clinicians to prescribe Tumor necrosis factor inhibitors (TNFI) to treat unexplained arthralgia. However, such therapies have been associated with exacerbation of subclinical undiagnosed Whipple’s disease. The objective of this study was to delineate the biological basis of disease exacerbation. We found that etanercept, adalimumab or certolizumab treatment of monocyte-derived macrophages from healthy subjects significantly increased bacterial replication in vitro without affecting uptake. Interestingly, this effect was associated with macrophage repolarization and increased rate of apoptosis. Further analysis revealed that in patients for whom Whipple’s disease diagnosis was made while under TNFI therapy, apoptosis was increased in duodenal tissue specimens as compared with control Whipple’s disease patients who never received TNFI prior diagnosis. In addition, IFN-γ expression was increased in duodenal biopsy specimen and circulating levels of IFN-γ were higher in patients for whom Whipple’s disease diagnosis was made while under TNFI therapy. Taken together, our findings establish that TNFI aggravate/exacerbate latent or subclinical undiagnosed Whipple’s disease by promoting a strong inflammatory response and apoptosis and confirm that patients may be screened for T. whipplei prior to introduction of TNFI therapy.

Distinguishing Blau Syndrome from Systemic Sarcoidosis

PURPOSE OF REVIEW

The purpose of this review is to provide a framework to distinguish Blau syndrome/Early Onset Sarcoidosis and Sarcoidosis clinically. We also discuss relevant differences in genetics, pathogenesis, and management of these diseases.

RECENT FINDINGS

Blau syndrome and Sarcoidosis share the characteristic histologic finding of noncaseating granulomas as well as some similar clinical characteristics; nevertheless, they are distinct entities with important differences between them. Blau syndrome and Early Onset Sarcoidosis are due to one of numerous possible gain-of-function mutations in NOD2, commonly presenting before age 5 with a triad of skin rash, arthritis, and uveitis. However, as more cases are reported, expanded clinical manifestations have been described. In systemic Sarcoidosis, there are numerous susceptibility genes that have been identified, and disease is thought to result from an environmental exposure in a genetically susceptible host. It most often presents with constitutional symptoms and pulmonary involvement and typically affects adolescents and adults. This paper reviews the similarities and differences between Blau syndrome and Sarcoidosis. We also discuss the importance of distinguishing between them, particularly with regard to prognosis and outcomes.

The Potential for Repurposing Anti-TNF as a Therapy for the Treatment of COVID-19

Coronavirus disease 2019 (COVID-19) currently has few effective treatments. Given the uncertainty surrounding the effectiveness and uptake of a vaccine, it is important that the search for treatments continue. An exaggerated inflammatory state is likely responsible for much of the morbidity and mortality in COVID-19. Elevated levels of tumor necrosis factor (TNF), a key pro-inflammatory cytokine, have been shown to be associated with increased COVID-19 mortality. In patients with rheumatoid arthritis, TNF blockade reduces not only biologically active TNF but other pro-inflammatory cytokines important in COVID-19 hyperinflammation. Observational data from patients already on anti-TNF therapy show a reduced rate of COVID-19 poor outcomes and death compared with other immune-suppressing therapies. Anti-TNF has a long history of safe use, including in special at-risk populations, and is widely available. The case to adequately assess anti-TNF as a treatment for COVID-19 is compelling.

Multinucleated Giant Cell Formation as a Portal to Chronic Bacterial Infections

This review provides a snapshot of chronic bacterial infections through the lens of Burkholderia pseudomallei and detailing its ability to establish multi-nucleated giant cells (MNGC) within the host, potentially leading to the formation of pyogranulomatous lesions. We explore the role of MNGC in melioidosis disease progression and pathology by comparing the similarities and differences of melioidosis to tuberculosis, outline the concerted events in pathogenesis that lead to MNGC formation, discuss the factors that influence MNGC formation, and consider how they fit into clinical findings reported in chronic cases. Finally, we speculate about future models and techniques that can be used to delineate the mechanisms of MNGC formation and function.

T-Bet Controls Susceptibility of Mice to Coxiella burnetii Infection

T-bet is a transcription factor known to initiate and coordinate the gene expression program during Th1 differentiation, which is crucial for clearance of intracellular pathogens. Q fever is a worldwide zoonosis caused by Coxiella burnetii. This bacterium is transmitted to humans by aerosol. Indeed, the inhibition of the Coxiella-specific adaptive Th1 immune response leads to persistent infection and organ injury. How deficiency of T-bet affects host infection by C. burnetii has not been investigated. Here, using mice with a deletion of the T-bet gene and an airborne mode of infection to reproduce the natural conditions of C. burnetii infection, we show that infected T-bet^–/– mice were more affected than wild-type mice. The lack of T-bet leads to defective bacterial control, intense replication, persistent infection, and organ injury manifesting as an increased number of granulomas. The absence of T-bet was also associated with an impaired immune response. Indeed, the production of the immunomodulatory cytokines interleukin (IL)-6 and IL-10 was increased, whereas the expression of microbicidal genes by splenocytes was impaired. Moreover, the absence of T-bet exhibited impaired production of interferon-γ, the principal cytokine released by Th1 effector cells. Thus, our study highlights the key role of T-bet in the control of C. burnetii infection in mice and leads to a reappraisal of granulomas in the pathogenesis of Q fever disease.

Defective Granuloma Formation in Elderly Infected Patients

Granulomas are compact structures formed in tissues by the immune system in response to aggressions. The in vitro formation of granulomas using circulating mononuclear cells is an innovative method to easily assess the immune response of patients. Monitoring the efficiency of mononuclear cells from patients to form granulomas in vitro would help improve their therapeutic management. Circulating mononuclear cells from 23 elderly patients with sepsis and 24 elderly controls patients were incubated with Sepharose beads coated with either BCG or Coxiella burnetii extracts. The formation of granulomas was measured over 9 days. Most healthy elderly patients (92%) were able to form granulomas in response to BCG and Coxiella burnetii extracts compared to only 48% of infected elderly patients. Undernutrition was significantly associated with impaired granuloma formation in healthy and infected patients. Granulomas typically comprise epithelioid cells and multinucleated giant cells, however, these cells were not detected in samples obtained from patients unable to form granulomas. We also found that the impairment of granuloma formation was associated with reduced production of tumor necrosis factor without overproduction of interleukin-10. Finally, all genes specifically modulated in granulomatous cells were down-modulated in patients with defective granuloma formation. TNFSF10 was the only M1 gene markedly upregulated in patients who did not form granulomas. Our study suggest that defective granuloma formation may be a measurement of altered activation of immune cells which can predispose to nosocomial infections in elderly patients.

How mycobacteria take advantage of the weakness in human immune system in the modern world

Tuberculosis (TB) infection remains a global health threat in recent decades partly due to a marked increase in the number of susceptible patients, including those with diabetes mellitus (DM) and who receive biologics. Immunity in TB infection is complex as Mycobacterium tuberculosis (MTB) is a highly adaptive pathogen and may evade the immune defense through various ways. Recent advances in TB immunity have revealed that granulomatous inflammation in TB infection is highly dynamic and the early influx of neutrophils may lead to excessive inflammation and pulmonary cavitation, which provide niches for MTB not only to survive but also to spread to other sites. Furthermore, reactive oxygen species have been found to play a crucial role among pathogenesis of TB infection in diabetics (DM-TB) through regulating inflammasome activation and the production of IL-1β, which in turn modulates the inflammatory network in TB infection, leading to dysfunctional inflammatory responses and tissue remodeling. To understand the exact immunological mechanisms underlying TB infection hence is essential for developing novel adjunctive host-directed therapy (HDT) aiming to alleviate excessive inflammation and tissue destruction and, at the same time, enhance the efficacy of currently available choices of anti-mycobacterial agents. Here we reviewed current epidemiological challenges of global TB control, novel immunological mechanisms underlying dysregulated inflammation in TB infection, especially in DM-TB, and some potential applications of adjunctive HDT in TB treatment.