Host genetics of mycobacterial diseases in mice and men: forward genetic studies of BCG-osis and tuberculosis

Immunological roads diverged: mapping tuberculosis outcomes in mice

The journey from phenotypic observation to causal genetic mechanism is a long and challenging road. For pathogens like Mycobacterium tuberculosis (Mtb), which causes tuberculosis (TB), host-pathogen coevolution has spanned millennia, costing millions of human lives. Mammalian models can systematically recapitulate host genetic variation, producing a spectrum of disease outcomes. Leveraging genome sequences and deep phenotyping data from infected mouse genetic reference populations (GRPs), quantitative trait locus (QTL) mapping approaches have successfully identified host genomic regions associated with TB phenotypes. Here, we review the ongoing optimization of QTL mapping study design alongside advances in mouse GRPs. These next-generation resources and approaches have enabled identification of novel host-pathogen interactions governing one of the most prevalent infectious diseases in the world today.

Polygenic TB control and the sequence of innate/adaptive immune responses to infection: MHC-II alleles determine the size of the S100A8/9-producing neutrophil population

Among several quantitative trait loci involved in tuberculosis (TB) control in mice, one was mapped within the chromosome 17 segment occupied by the H2 complex and another within the chromosome 3 segment comprising the S100A8/9 genes, which encode neutrophil inflammatory factor S100A8/9. Previously, we developed a panel of H2-congenic mouse strains differing by small segments of the major histocompatibility complex Class II (MHC-II) region from TB-susceptible H2j mice transferred onto the genetic background of the TB-resistant C57BL/6 (H2b) strain. Susceptible B6.I-9.3 mice differ from B6 progenitors by the alleles of their only classical MHC-II H2-Aβ gene. The goals of the present study were to: (i) comprehensively characterise the differences in TB-related phenotypes between mice of the two strains and (ii) decipher interactions between the H2-Aβ and S100A8/9 genes. Here, we describe the dynamics of TB-related phenotypes differentiating B6.I-9.3 and B6 mice (colony forming units counts, histopathology, lung immune cell infiltration and cytokine profiles). We show that disproportionally diminished CD4+ T-cell population, an enlarged S100A8/9-positive neutrophil population and higher S100A8/9 serum levels in B6.I-9.3 mice collectively form the 'susceptible' phenotype before infection. An increase in IL-17 and a decrease in intrferon-gamma production by CD4+ T-cells in these mice provide a mechanistic explanation of this phenotype. Using F2 segregation analysis, we show that the number of S100A8/9-producing neutrophils in lungs and spleens and the proportion of Th17 CD4+ T-cells in lungs are significantly lower in the presence of the MHC-II dominant 'resistant' b allele compared to the recessive 'susceptible' j/j genotype. This provides direct genetic evidence that MHC-II-regulated CD4+ T-cell landscapes determine neutrophil abundance before infection, an important pathogenic factor in TB immunity.

Increased serum interferon activity in sarcoidosis compared to that in tuberculosis: Implication for diagnosis?

Objectives

In this study, we measured serum interferon (IFN) levels and activity in patients with sarcoidosis and tuberculosis (TB) with and without uveitis. We aimed to understand the role of IFN in the pathophysiology of both conditions and explore its potential as a discriminating marker for these clinically similar diseases.

Methods

Sera from an Indonesian TB and a Dutch sarcoidosis cohort were used in the analysis. IFNα2 and IFNγ concentrations were measured using Simoa® and Luminex assays, respectively. Serum IFN activity was assessed by incubating THP-1 cells with patient serum and measuring IFN-stimulated gene transcription using qPCR. Anti-IFNα2 and IFNγ autoantibodies were detected via Luminex assay and tested for neutralizing capacity using a flow cytometry-based signal transducer and activator of transcription (STAT) 1 phosphorylation inhibition assay.

Results

IFNα2 was detected in 74 % and 64 % of patients with sarcoidosis and pulmonary TB, respectively, while IFNγ was found in 78 % and 23 % of patients with sarcoidosis and TB, respectively. For uveitis cases specifically, IFNα2 was detected in 85 % of sarcoid uveitis (SU) and 33 % of tubercular uveitis (TBU) cases. Similarly, IFNγ was detected in 69 % of SU and 17 % of TBU cases. IFNγ serum concentrations were higher in sarcoidosis than that in TB patients (p < 0.0001). Focusing on patients with uveitis, SU showed increased IFNα2 (p = 0.004) and IFNγ (p < 0.002) serum concentrations compared to that in TBU. Notably, TBU displayed significantly reduced IFNα2 concentrations compared to that in healthy controls (p = 0.006). These results align with the increased interferon stimulated gene (ISG) transcriptional upregulation observed in THP-1 cells stimulated with serum from patients with sarcoidosis. Elevated levels of non-neutralizing anti-IFN autoantibodies were observed in patients with TB; however, these levels were similar to those observed in geographically matched healthy Indonesian controls.

Conclusion

Our results suggest decreased serum levels and activity of type I and II IFN in TB compared to those in sarcoidosis. This is indicative of distinct pathophysiological processes in these highly clinically similar diseases. We propose that the assessment of serum IFN levels and IFN activity has the potential to distinguish between sarcoidosis/SU and TB/TBU.

Preclinical murine models for the testing of antimicrobials against Mycobacterium abscessus pulmonary infections: Current practices and recommendations

Mycobacterium abscessus, a rapidly growing nontuberculous mycobacterium, is increasingly recognized as an important pathogen of the human lung, disproportionally affecting people with cystic fibrosis (CF) and other susceptible individuals with non-CF bronchiectasis and compromised immune functions. M. abscessus infections are extremely difficult to treat due to intrinsic resistance to many antibiotics, including most anti-tuberculous drugs. Current standard-of-care chemotherapy is long, includes multiple oral and parenteral repurposed drugs, and is associated with significant toxicity. The development of more effective oral antibiotics to treat M. abscessus infections has thus emerged as a high priority. While murine models have proven instrumental in predicting the efficacy of therapeutic treatments for M. tuberculosis infections, the preclinical evaluation of drugs against M. abscessus infections has proven more challenging due to the difficulty of establishing a progressive, sustained, pulmonary infection with this pathogen in mice. To address this issue, a series of three workshops were hosted in 2023 by the Cystic Fibrosis Foundation (CFF) and the National Institute of Allergy and Infectious Diseases (NIAID) to review the current murine models of M. abscessus infections, discuss current challenges and identify priorities toward establishing validated and globally harmonized preclinical models. This paper summarizes the key points from these workshops. The hope is that the recommendations that emerged from this exercise will facilitate the implementation of informative murine models of therapeutic efficacy testing across laboratories, improve reproducibility from lab-to-lab and accelerate preclinical-to-clinical translation.

Antigen identification strategies and preclinical evaluation models for advancing tuberculosis vaccine development

In its myriad devastating forms, Tuberculosis (TB) has existed for centuries, and humanity is still affected by it. Mycobacterium tuberculosis (M. tuberculosis), the causative agent of TB, was the foremost killer among infectious agents until the COVID-19 pandemic. One of the key healthcare strategies available to reduce the risk of TB is immunization with bacilli Calmette-Guerin (BCG). Although BCG has been widely used to protect against TB, reports show that BCG confers highly variable efficacy (0-80%) against adult pulmonary TB. Unwavering efforts have been made over the past 20 years to develop and evaluate new TB vaccine candidates. The failure of conventional preclinical animal models to fully recapitulate human response to TB, as also seen for the failure of MVA85A in clinical trials, signifies the need to develop better preclinical models for TB vaccine evaluation. In the present review article, we outline various approaches used to identify protective mycobacterial antigens and recent advancements in preclinical models for assessing the efficacy of candidate TB vaccines.

Pathogenic Interleukin-10 Receptor Alpha Variants in Humans - Balancing Natural Selection and Clinical Implications

Balancing natural selection is a process by which genetic variants arise in populations that are beneficial to heterozygous carriers, but pathogenic when homozygous. We systematically investigated the prevalence, structural, and functional consequences of pathogenic IL10RA variants that are associated with monogenic inflammatory bowel disease. We identify 36 non-synonymous and non-sense variants in the IL10RA gene. Since the majority of these IL10RA variants have not been functionally characterized, we performed a systematic screening of their impact on STAT3 phosphorylation upon IL-10 stimulation. Based on the geographic accumulation of confirmed pathogenic IL10RA variants in East Asia and in Northeast China, the distribution of infectious disorders worldwide, and the functional evidence of IL-10 signaling in the pathogenesis, we identify Schistosoma japonicum infection as plausible selection pressure driving variation in IL10RA. Consistent with this is a partially augmented IL-10 response in peripheral blood mononuclear cells from heterozygous variant carriers. A parasite-driven heterozygote advantage through reduced IL-10 signaling has implications for health care utilization in regions with high allele frequencies and potentially indicates pathogen eradication strategies that target IL-10 signaling.

Association of IFN-γ +874 A/T SNP and hypermethylation of the -53 CpG site with tuberculosis susceptibility

Introduction

Tuberculosis (TB) is now the 2nd leading infectious killer after COVID-19 and the 13th leading cause of death worldwide. Moreover, TB is a lethal combination for HIV-patients. Th1 responses and particularly IFN-γ are crucial for immune protection against Mycobacterium tuberculosis infection. Many gene variants for IFNG that confer susceptibility to TB have been described in multiple ethnic populations. Likewise, some epigenetic modifications have been evaluated, being CpG methylation the major epigenetic mark that makes chromatin inaccessible to transcription factors, thus avoiding the initiation of IFNG transcription.

Methods

We evaluated both genetic and epigenetic changes involved in IFN-γ production and TB susceptibility in Argentine population. Amplification refractory mutation system-polymerase chain reaction (ARMS-PCR) was performed for the IFN-γ +874 A/T polymorphism (rs2430561) genotyping in 199 healthy donors (HD) and 173 tuberculosis (TB) patients. IFN-γ levels from M. tuberculosis-stimulated PBMCs were measured by ELISA. The methylation status at the -53 CpG site of the IFNG promoter in individuals with latent infection (LTBI), TB and HD was determine by pyrosequencing.

Results

Using a case-control study, we found that A allele and, consequently, AA genotype were overrepresented in patients with active disease. Moreover, HD carrying T allele (AT or TT genotype) evidenced an augmented IFN-γ secretion compared to TB patients. Codominance was the genetic model that best fits our results according to the Akaike information criterion (AIC). In addition, increased methylation levels at the -53 CpG site in the IFN-γ promoter were observed in whole blood of patients with active TB compared to LTBI individuals.

Discussion

IFN-γ is regulated by genetic variants and epigenetic modifications during TB. Besides, AA genotype of the rs2430561 single nucleotide polymorphism could be considered as a potential TB susceptibility genetic biomarker in Argentina and the methylation of the -53 CpG site could result in a useful predictor of TB reactivation.

Mouse Models for Mycobacterium tuberculosis Pathogenesis: Show and Do Not Tell

Science has been taking profit from animal models since the first translational experiments back in ancient Greece. From there, and across all history, several remarkable findings have been obtained using animal models. One of the most popular models, especially for research in infectious diseases, is the mouse. Regarding research in tuberculosis, the mouse has provided useful information about host and bacterial traits related to susceptibility to the infection. The effect of aging, sexual dimorphisms, the route of infection, genetic differences between mice lineages and unbalanced immunity scenarios upon Mycobacterium tuberculosis infection and tuberculosis development has helped, helps and will help biomedical researchers in the design of new tools for diagnosis, treatment and prevention of tuberculosis, despite various discrepancies and the lack of deep study in some areas of these traits.

Re-engineered BCG overexpressing cyclic di-AMP augments trained immunity and exhibits improved efficacy against bladder cancer

In addition to its role as a TB vaccine, BCG has been shown to elicit heterologous protection against many other pathogens including viruses through a process termed trained immunity. Despite its potential as a broadly protective vaccine, little has been done to determine if BCG-mediated trained immunity levels can be optimized. Here we re-engineer BCG to express high levels of c-di-AMP, a PAMP recognized by stimulator of interferon genes (STING). We find that BCG overexpressing c-di-AMP elicits more potent signatures of trained immunity including higher pro-inflammatory cytokine responses, greater myeloid cell reprogramming toward inflammatory and activated states, and enhances epigenetic and metabolomic changes. In a model of bladder cancer, we also show that re-engineered BCG induces trained immunity and improved functionality. These results indicate that trained immunity levels and antitumor efficacy may be increased by modifying BCG to express higher levels of key PAMP molecules.

Evaluation of the effect of T regulatory cell depletion and donor BCG vaccination on Mycobacterium tuberculosis H37Ra infection using an in vitro model of human PBMC infection

This study evaluated the effect of T regulatory cells (Treg cells) and the impact of BCG vaccination history of donors using an in vitro model of Mycobacterium tuberculosis H37Ra infection of peripheral blood mononuclear cells (PBMCs). PBMCs from donors with or without prior BCG vaccination were depleted of Treg cells (PBMCs-Tregs) or not depleted with Treg cells (PBMCs + Tregs) were infected up to 8 days with Mtb H37Ra. Cell aggregates were smaller in PBMCs-Tregs compared to PBMCs + Tregs at day 8 post-infection. Mtb CFUs were higher in the PBMCs-Tregs compared to PBMCs + Tregs at days 3, 5 and 8. The levels of IL-17, IFN-γ (at days 3 and 5), and TNF-α and IL-6 (at day 3) were lower in PBMCs-Tregs compared to PBMCs + Tregs. In contrast, the levels of IL-10 and IL-4 cytokines were higher at day 3 in PBMCs-Tregs compared to PBMCs + Tregs. BCG vaccination status of donors had no impact on the mycobacterial culture, level of cytokines and immune cell populations. This study shows that depletion of Tregs in human PBMCs infected with Mtb H37Ra in vitro leads to a shift from a Th1 to a Th2 cytokine rich environment that supports the survival of Mtb in this model.

Channeling macrophage polarization by rocaglates increases macrophage resistance to Mycobacterium tuberculosis

Macrophages contribute to host immunity and tissue homeostasis via alternative activation programs. M1-like macrophages control intracellular bacterial pathogens and tumor progression. In contrast, M2-like macrophages shape reparative microenvironments that can be conducive for pathogen survival or tumor growth. An imbalance of these macrophages phenotypes may perpetuate sites of chronic unresolved inflammation, such as infectious granulomas and solid tumors. We have found that plant-derived and synthetic rocaglates sensitize macrophages to low concentrations of the M1-inducing cytokine IFN-gamma and inhibit their responsiveness to IL-4, a prototypical activator of the M2-like phenotype. Treatment of primary macrophages with rocaglates enhanced phagosome-lysosome fusion and control of intracellular mycobacteria. Thus, rocaglates represent a novel class of immunomodulators that can direct macrophage polarization toward the M1-like phenotype in complex microenvironments associated with hypofunction of type 1 and/or hyperactivation of type 2 immunity, e.g., chronic bacterial infections, allergies, and, possibly, certain tumors.

Sexual Dimorphism and Gender in Infectious Diseases

Epidemiological studies and clinical observations show evidence of sexual dimorphism in infectious diseases. Women are at less risk than men when it comes to developing most infectious diseases. However, understanding these observations requires a gender approach that takes into account an analysis of both biological and social factors. The host’s response to infection differs in males and females because sex differences have an impact on hormonal and chromosomal control of immunity. Estradiol appears to confer protective immunity, while progesterone and testosterone suppress anti-infectious responses. In addition, genetic factors, including those associated with sex chromosomes, also affect susceptibility to infections. Finally, differences in occupational activities, lifestyle, and comorbidities play major roles in exposure to pathogens and management of diseases. Hence, considering sexual dimorphism as a critical variable for infectious diseases should be one of the steps taken toward developing personalized therapeutic approaches.

Lethal Infectious Diseases as Inborn Errors of Immunity: Toward a Synthesis of the Germ and Genetic Theories

It was first demonstrated in the late nineteenth century that human deaths from fever were typically due to infections. As the germ theory gained ground, it replaced the old, unproven theory that deaths from fever reflected a weak personal or even familial constitution. A new enigma emerged at the turn of the twentieth century, when it became apparent that only a small proportion of infected individuals die from primary infections with almost any given microbe. Classical genetics studies gradually revealed that severe infectious diseases could be driven by human genetic predisposition. This idea gained ground with the support of molecular genetics, in three successive, overlapping steps. First, many rare inborn errors of immunity were shown, from 1985 onward, to underlie multiple, recurrent infections with Mendelian inheritance. Second, a handful of rare and familial infections, also segregating as Mendelian traits but striking humans resistant to other infections, were deciphered molecularly beginning in 1996. Third, from 2007 onward, a growing number of rare or common sporadicinfections were shown to result from monogenic, but not Mendelian, inborn errors. A synthesis of the hitherto mutually exclusive germ and genetic theories is now in view.

First insight into the whole-genome sequence variations in Mycobacterium bovis BCG-1 (Russia) vaccine seed lots and their progeny clinical isolates from children with BCG-induced adverse events

Background

The only licensed live Bacille Calmette-Guérin (BCG) vaccine used to prevent severe childhood tuberculosis comprises genetically divergent strains with variable protective efficacy and rates of BCG-induced adverse events. The whole-genome sequencing (WGS) allowed evaluating the genome stability of BCG strains and the impact of spontaneous heterogeneity in seed and commercial lots on the efficacy of BCG-vaccines in different countries. Our study aimed to assess sequence variations and their putative effects on genes and protein functions in the BCG-1 (Russia) seed lots compared to their progeny isolates available from immunocompetent children with BCG-induced disease (mainly, osteitis).

Results

Based on the WGS data, we analyzed the links between seed lots 361, 367, and 368 used for vaccine manufacture in Russia in different periods, and their nine progeny isolates recovered from immunocompetent children with BCG-induced disease. The complete catalog of variants in genes relative to the reference genome (GenBank: CP013741) included 4 synonymous and 8 nonsynonymous single nucleotide polymorphisms, and 3 frameshift deletions. Seed lot 361 shared variants with 2 of 6 descendant isolates that had higher proportions of such polymorphisms in several genes, including ppsC, eccD5, and eccA5 involved in metabolism and cell wall processes and reportedly associated with virulence in mycobacteria. One isolate preserved variants of its parent seed lot 361 without gain of further changes in the sequence profile within 14 years.

Conclusions

The background genomic information allowed us for the first time to follow the BCG diversity starting from the freeze-dried seed lots to descendant clinical isolates. Sequence variations in several genes of seed lot 361 did not alter the genomic stability and viability of the vaccine and appeared accumulated in isolates during the survival in the human organism. The impact of the observed variations in the context of association with the development of BCG-induced disease should be evaluated in parallel with the immune status and host genetics. Comparative genomic studies of BCG seed lots and their descendant clinical isolates represent a beneficial approach to better understand the molecular bases of efficacy and adverse events during the long-term survival of BCG in the host organism.

The human genetic determinism of life-threatening infectious diseases: genetic heterogeneity and physiological homogeneity?

Multicellular eukaryotes emerged late in evolution from an ocean of viruses, bacteria, archaea, and unicellular eukaryotes. These macroorganisms are exposed to and infected by a tremendous diversity of microorganisms. Those that are large enough can even be infected by multicellular fungi and parasites. Each interaction is unique, if only because it operates between two unique living organisms, in an infinite diversity of circumstances. This is neatly illustrated by the extraordinarily high level of interindividual clinical variability in human infections, even for a given pathogen, ranging from a total absence of clinical manifestations to death. We discuss here the idea that the determinism of human life-threatening infectious diseases can be governed by single-gene inborn errors of immunity, which are rarely Mendelian and frequently display incomplete penetrance. We briefly review the evidence in support of this notion obtained over the last two decades, referring to a number of focused and thorough reviews published by eminent colleagues in this issue of Human Genetics. It seems that almost any life-threatening infectious disease can be driven by at least one, and, perhaps, a great many diverse monogenic inborn errors, which may nonetheless be immunologically related. While the proportions of monogenic cases remain unknown, a picture in which genetic heterogeneity is combined with physiological homogeneity is emerging from these studies. A preliminary sketch of the human genetic architecture of severe infectious diseases is perhaps in sight.

Natural and trained innate immunity against Mycobacterium tuberculosis

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb) infection, remains a major global health emergency. It is estimated that one third of global population are affected, predominantly with latent granuloma form of the disease. Mtb co-evolved with humans, for its obligatory intra-macrophage phagosome habitat and slow replication, balanced against unique mycobacterial innate immunity, which appears to be highly complex. TB is transmitted via cough aerosol Mtb inhalation. Bovine TB attenuated Bacillus Calmette Guerin (BCG) live vaccine has been in practice for protection of young children from severe disseminated Mtb infection, but not sufficiently for their lungs, as obtained by trials in TB endemic community. To augment BCG vaccine-driven innate and adaptive immunity for neonates and better protection against adult pulmonary TB, a number of BCG pre-vaccination based, subset vaccine candidates have been tested via animal preclinical, followed by safe clinical trials. BCG also enhances innate macrophage trained immunity and memory, through primordial intracellular Toll-like receptors (TLRs) 7 and 9, which recognise distinct mycobacterial molecular pattern signature. This signature is transmitted by TLR signalling via nuclear factor-κB, for activating innate immune transcription and expression of gene profiling in a mycobacterial signature-specific manner. These are epigenetically imprinted in reprogramming of distinct chromatin areas for innate immune memory, to be recalled following lung reinfection. Unique TB innate immunity and its trained memory are considered independent from adaptive immune B and T cells. On the other hand, adaptive immunity is crucial in Mtb containment in granulomatous latency, supported by innate immune cell infiltration. In nearly 5-10 % of susceptible people, latent TB may be activated due to immune evasion by Mtb from intracellular phagosome within macrophage, perpetrating TB. However, BCG and new recombinant BCG vaccines have the capacity, as indicated in pre- and clinical trials, to overcome such Mtb evasion. Various strategies include pro-inflammatory-bactericidal type 1 polarisation (M1) phenotype of the infected macrophage, involving thrombospondin-TLR pathway. Saprophytic M. smegmatis-based recombinant vaccines are also promising candidates against TB. BCG vaccination of neonates/infants in TB endemic countries also reduced their pneumonia caused by various microbes independent of TB immunity. Here, we discuss host immune response against Mtb, its immune evasion strategies, and the important role innate immunity plays in the development of protection against TB.

The current state of animal models and genomic approaches towards identifying and validating molecular determinants of Mycobacterium tuberculosis infection and tuberculosis disease

Animal models are important in understanding both the pathogenesis of and immunity to tuberculosis (TB). Unfortunately, we are beginning to understand that no animal model perfectly recapitulates the human TB syndrome, which encompasses numerous different stages. Furthermore, Mycobacterium tuberculosis infection is a very heterogeneous event at both the levels of pathogenesis and immunity. This review seeks to establish the current understanding of TB pathogenesis and immunity, as validated in the animal models of TB in active use today. We especially focus on the use of modern genomic approaches in these models to determine the mechanism and the role of specific molecular pathways. Animal models have significantly enhanced our understanding of TB. Incorporation of contemporary technologies such as single cell transcriptomics, high-parameter flow cytometric immune profiling, proteomics, proteomic flow cytometry and immunocytometry into the animal models in use will further enhance our understanding of TB and facilitate the development of treatment and vaccination strategies.

Immunology of Mycobacterium tuberculosis Infections

Tuberculosis (TB) is a serious global public health challenge that results in significant morbidity and mortality worldwide. TB is caused by infection with the bacilli Mycobacterium tuberculosis (M. tuberculosis), which has evolved a wide variety of strategies in order to thrive within its host. Understanding the complex interactions between M. tuberculosis and host immunity can inform the rational design of better TB vaccines and therapeutics. This chapter covers innate and adaptive immunity against M. tuberculosis infection, including insights on bacterial immune evasion and subversion garnered from animal models of infection and human studies. In addition, this chapter discusses the immunology of the TB granuloma, TB diagnostics, and TB comorbidities. Finally, this chapter provides a broad overview of the current TB vaccine pipeline.

The monogenic basis of human tuberculosis

The pathogenesis of tuberculosis (TB) remains poorly understood, as no more than 5-10% of individuals infected with Mycobacterium tuberculosis go on developing clinical disease. The contribution of human genetics to TB pathogenesis has been amply documented by means of classic genetics since the turn of the twentieth century. Over the last 20 years, following-up on the study of Mendelian susceptibility to mycobacterial disease (MSMD), monogenic disorders have been found to underlie TB in some patients. Rare inborn errors of immunity, such as autosomal recessive, complete IL-12Rβ1 and TYK2 deficiencies, impairing the IL-12- and IL-23-dependent induction of IFN-γ, were initially identified in a few patients. More recently, homozygosity for a common variant of TYK2 (P1104A) that selectively disrupts cellular responses to IL-23 was found in two cohorts of TB patients. It shows high penetrance in areas endemic for TB and appears to be responsible for about 1% of TB cases in populations of European descent. Both rare and common genetic etiologies of TB affect IFN-γ immunity, providing a rationale for novel preventive and therapeutic approaches for TB control, including the use of recombinant IFN-γ.

MAL adaptor (TIRAP) S180L polymorphism and severity of disease among tuberculosis patients

OBJECTIVE

Though several genetic variants have been recognized to be associated with susceptibility to Tuberculosis (TB) infection and disease, a recent observation on the association of TIRAP C975T (S180L) variants with TB disease severity in mice model prompted us to assess their relevance in humans. In addition, TIRAP variants have also been reported to be associated with varied circulating Interferon-gamma induced protein (IP-10) levels. We investigated the association of TIRAP variants with severity of TB disease and IP-10 production in humans, which may be useful in predicting poor clinical outcome.

METHODS

Culture positive symptomatic adult pulmonary TB (PTB) patients enrolled between August 2014 and October 2017 were included in this investigation. Allelic discrimination PCR and conventional IP-10 quantification methods were employed for genotyping and IP-10 measurement followed by statistical investigations to analyse patients' variables.

RESULTS

Among 211 participants, C/C allele was identified in 70% (n = 147); 26% (n = 55) and 4% (n = 9) had C/T and T/T alleles respectively. There was no significant association between TIRAP variants and smear grade, chest-X-ray score, symptom severity score and circulating IP-10 levels. However, significant association was observed between i) circulating IP-10 levels and time to Mycobacterium Growth Indicator Tube (MGIT) culture conversion (p =0.032); ii) smear grade among active TB patients and circulating IP-10 levels (p =0 .032).

CONCLUSIONS

Although mice experiments showed promising results with more severe disease in C/C and T/T individuals, we did not observe any such association in humans.

The Non-synonymous rs763780 Single-Nucleotide Polymorphism in IL17F Gene Is Associated With Susceptibility to Tuberculosis and Advanced Disease Severity in Argentina

Th17 lymphocytes, that produce IL17A, IL17F, and IL22, play a crucial role during the immune response against Mycobacterium tuberculosis (Mtb) infection. Whereas, the contribution of IL17A in immunity to tuberculosis is usually accepted, the role of IL17F has been scarcely studied so far. The aim of this work was to evaluate the existence of a potential association of the non-synonymous variant rs763780 SNP of the IL17F gene with human tuberculosis. Accordingly, by comparing healthy donors (HD) and tuberculosis patients (TB) populations we demonstrated an association between the C allele of the SNP and the susceptibility to tuberculosis disease in Argentina. Furthermore, we found that peripheral blood mononuclear cells (PBMCs) from individuals with a more effective immune response against Mtb secreted the highest levels of IL17F when stimulated with a lysate of Mtb (Mtb-Ag). Besides, we evidenced that Mtb-Ag-stimulated PBMCs from HD carrying the C variant of the SNP displayed the lowest IFNG secretion, proliferation index, and SLAM expression as compared to TT carriers. Moreover, Mtb-Ag-stimulated PBMCs from TB carrying the C allele produced the lowest levels of IFNG, the highest level of IL17A, and the minimum proliferation indexes as compared to TT TB, suggesting a relationship between the C allele and tuberculosis severity. In fact, TB carrying the C allele presented a more severe disease, with the highest bacilli burden in sputum. Together, our findings identify the IL17F rs763780 SNP as a biomarker of tuberculosis susceptibility and advanced disease severity in Argentina, suggesting that IL17F could be a critical cytokine in tuberculosis immunity.

Revisiting hypoxia therapies for tuberculosis

The spectre of the coming post-antibiotic age demands novel therapies for infectious diseases. Tuberculosis (TB), caused by Mycobacterium tuberculosis, is the single deadliest infection throughout human history. M. tuberculosis has acquired antibiotic resistance at an alarming rate with some strains reported as being totally drug resistant. Host-directed therapies (HDTs) attempt to overcome the evolution of antibiotic resistance by targeting relatively immutable host processes. Here, I hypothesise the induction of hypoxia via anti-angiogenic therapy will be an efficacious HDT against TB. I argue that anti-angiogenic therapy is a modernisation of industrial revolution era sanatoria treatment for TB, and present a view of the TB granuloma as a 'bacterial tumour' that can be treated with anti-angiogenic therapies to reduce bacterial burden and spare host immunopathology. I suggest two complementary modes of action, induction of bacterial dormancy and activation of host hypoxia-induced factor (HIF)-mediated immunity, and define the experimental tools necessary to test this hypothesis.

Multidrug-resistant tuberculosis (MDR-TB) strain infection in macaques results in high bacilli burdens in airways, driving broad innate/adaptive immune responses

Tuberculosis (TB) has become the most deadly infectious diseases due to epidemics of HIV/AIDS and multidrug-resistant/extensively drug-resistant TB (MDR-/XDR-TB). Although person-to-person transmission contributes to MDR-TB, it remains unknown whether infection with MDR strains resembles infection with drug-sensitive (DS) TB strains, manipulating limited or broad immune responses. To address these questions, macaques were infected with MDR strain V791 and a drug-sensitive Erdman strain of TB. MDR bacilli burdens in the airway were significantly higher than those of the Erdman control after pulmonary exposure. This productive MDR strain infection upregulated the expression of caspase 3 in macrophages/monocytes and induced appreciable innate-like effector responses of CD3-negative lymphocytes and Ag-specific γδ T-cell subsets. Concurrently, MDR strain infection induced broad immune responses of T-cell subpopulations producing Th1, Th17, Th22, and CTL cytokines. Furthermore, MDR bacilli, like the Erdman strain, were capable of inducing typical TB disease characterized by weight loss, lymphocytopenia, and severe TB lesions. For the first time, our results suggest that MDR-TB infection acts like DS to induce high bacterial burdens in the airway (transmission advantage), innate/adaptive immune responses, and disease processes. Because nonhuman primates are biologically closer to humans than other species, our data may provide useful information for predicting the effects of primary MDR strain infection after person-to-person transmission. The findings also support the hypothesis that a vaccine or host-directed adjunctive modality that is effective for drug-sensitive TB is likely to also impact MDR-TB.

SP110 Polymorphisms Are Genetic Markers for Vulnerability to Latent and Active Tuberculosis Infection in Taiwan

One-fourth of the human population is estimated to have been exposed to Mycobacterium tuberculosis (Mtb) and carries the infection in its latent form. This latent infection presents a lifelong risk of developing active tuberculosis (TB) disease, and persons with latent TB infection (LTBI) are significant contributors to the pool of active TB cases. Genetic polymorphisms among hosts have been shown to contribute to the outcome of Mtb infection. The SP110 gene, which encodes an interferon-induced nuclear protein, has been shown to control host innate immunity to Mtb infection. In this study, we provide experimental data demonstrating the ability of the gene to control genetic susceptibility to latent and active TB infection. Genetic variants of the SP110 gene were investigated in the Taiwanese population (including 301 pulmonary TB patients, 68 LTBI individuals, and 278 healthy household contacts of the TB patients), and their association with susceptibility to latent and active TB infection was examined by performing an association analysis in a case-control study. We identified several SNPs (rs7580900, rs7580912, rs9061, rs11556887, and rs2241525) in the SP110 gene that are associated with susceptibility to LTBI and/or TB disease. Our studies further showed that the same SNPs may have opposite effects on the control of susceptibility to LTBI versus TB. In addition, our analyses demonstrated that the SP110 rs9061 SNP was associated with tumor necrosis factor-α (TNFα) levels in plasma in LTBI subjects. The results suggest that the polymorphisms within SP110 have a role in controlling genetic susceptibility to latent and active TB infection in humans. To the best of our knowledge, this is the first report showing that the SP110 variants are associated with susceptibility to LTBI. Our study also demonstrated that the identified SP110 SNPs displayed the potential to predict the risk of LTBI and subsequent TB progression in Taiwan.

Association of TLR8 and TLR9 polymorphisms with tuberculosis in a Chinese Han population: a case-control study

Background

Toll-like receptor (TLR) single nucleotide polymorphisms (SNPs) have been associated with regulation of TLR expression and development of active tuberculosis (TB). The objectives of this study were to determine whether TLR8 and TLR9 SNPs were associated with the development of latent TB infection (LTBI) and the subsequent pulmonary TB (PTB) in a Chinese Han population.

Methods

Two independent samples were enrolled. The first sample contained 584 TB cases and 608 controls; the second sample included 204 healthy controls, 201 LTBI subjects and 209 bacteria-confirmed active PTB patients. Three SNPs (rs3764880, rs187084 and rs5743836) were genotyped. The associations between the SNPs and risk of LTBI or PTB were investigated using unconditional logistic regression analysis.

Results

The A-allele of TLR8 rs3764880 SNP was protective against the development of TB in males (A vs G, OR = 0.58, 95%CI = 0.37–0.91). The AA genotype of rs3764880 SNP was found to increase the risk of PTB among females with an OR of 4.81 (1.11–20.85). The G allele of TLR9 SNP rs187084 was found to increase the risk of PTB (G vs A, P = 0.01, OR = 1.48, 95% CI = 1.10–2.00), the significance was also observed under dominant genetic models. The GA-genotype of TLR9 rs187084 SNP was found to increase the risk of PTB with an OR of 1.68 (1.07–2.65), but was found to decrease the risk of MTB infection with an OR = 0.64 (0.41–0.98). TLR9_rs5743836 SNP was excluded from the data analyses, because the minimum allele frequency was< 1%.

Conclusions

Our findings in two independent samples indicated that SNPs in TLR8 and TLR9 were associated with the development of TB, and highlight that SNPs may have different effects on disease pathogenesis and progression.

Early Resistance of Non-virulent Mycobacterial Infection in C57BL/6 Mice Is Associated With Rapid Up-Regulation of Antimicrobial Cathelicidin Camp

Early clearance of tuberculosis is the successful eradication of inhaled bacteria before the development of an adaptive immune response. We previously showed, by utilizing a non-virulent mycobacteria infection model, that C57BL/6 mice are more efficient than BALB/c in their control of bacterial growth in the lungs during the first weeks of the infection. Here, we assessed early (within 1–3 days) innate immune events locally in the lungs to identify factors that may contribute to the control of non-virulent mycobacterial burden. We confirmed that C57BL/6 mice are more resistant to infection compared with BALB/c after intranasal inoculation with mycobacterium. Transcriptomic analyses revealed a remarkably silent signature in C57BL/6 mice despite effective control of bacterial growth. In contrast, BALB/c mice up-regulated genes associated with neutrophil and myeloid cell chemotaxis and migration. Flow cytometry analyses corroborated the transcriptomic analyses and demonstrated influx of both neutrophil and myeloid cell populations in BALB/c mice, while these did not increase in C57BL/6 mice. We further detected increased release of TNF-α from BALB/c lung cells but limited release from C57BL/6-derived cells. However, C57BL/6 mice showed a marked early up-regulation of the Camp gene, encoding the cathelicidin CRAMP peptide, post-mycobacterial exposure. CRAMP (LL-37 in human) expression in the lungs was confirmed using immunofluorescence staining. Altogether, these findings show that C57BL/6 mice can clear the mycobacterial infection early and that this early control is associated with high CRAMP expression in the lungs without concomitant influx of immune cells. The role of CRAMP/LL-37 during mycobacterial infection may be relevant for novel protective strategies, and warrants further studies of human cohorts.

A modular transcriptional signature identifies phenotypic heterogeneity of human tuberculosis infection

Whole blood transcriptional signatures distinguishing active tuberculosis patients from asymptomatic latently infected individuals exist. Consensus has not been achieved regarding the optimal reduced gene sets as diagnostic biomarkers that also achieve discrimination from other diseases. Here we show a blood transcriptional signature of active tuberculosis using RNA-Seq, confirming microarray results, that discriminates active tuberculosis from latently infected and healthy individuals, validating this signature in an independent cohort. Using an advanced modular approach, we utilise the information from the entire transcriptome, which includes overabundance of type I interferon-inducible genes and underabundance of IFNG and TBX21, to develop a signature that discriminates active tuberculosis patients from latently infected individuals or those with acute viral and bacterial infections. We suggest that methods targeting gene selection across multiple discriminant modules can improve the development of diagnostic biomarkers with improved performance. Finally, utilising the modular approach, we demonstrate dynamic heterogeneity in a longitudinal study of recent tuberculosis contacts.

Type I interferons in tuberculosis: Foe and occasionally friend

Tuberculosis remains one of the leading causes of mortality worldwide, and, despite its clinical significance, there are still significant gaps in our understanding of pathogenic and protective mechanisms triggered by Mycobacterium tuberculosis infection. Type I interferons (IFN) regulate a broad family of genes that either stimulate or inhibit immune function, having both host-protective and detrimental effects, and exhibit well-characterized antiviral activity. Transcriptional studies have uncovered a potential deleterious role for type I IFN in active tuberculosis. Since then, additional studies in human tuberculosis and experimental mouse models of M. tuberculosis infection support the concept that type I IFN promotes both bacterial expansion and disease pathogenesis. More recently, studies in a different setting have suggested a putative protective role for type I IFN. In this study, we discuss the mechanistic and contextual factors that determine the detrimental versus beneficial outcomes of type I IFN induction during M. tuberculosis infection, from human disease to experimental mouse models of tuberculosis.

Functional domains of SP110 that modulate its transcriptional regulatory function and cellular translocation

Background

SP110, an interferon-induced nuclear protein, belongs to the SP100/SP140 protein family. Very recently, we showed that SP110b, an SP110 isoform, controls host innate immunity to Mycobacterium tuberculosis infection by regulating nuclear factor-κB (NF-κB) activity. However, it remains unclear how the structure of SP110 relates to its cellular functions. In this study, we provide experimental data illustrating the protein domains that are responsible for its functions.

Methods

We examined the effects of SP110 isoforms and a series of deletion mutants of SP110 on transcriptional regulation by luciferase reporter assays. We also employed confocal microscopy to determine the cellular distributions of enhanced green fluorescent protein-tagged SP110 isoforms and SP110 mutants. In addition, we performed immunoprecipitation and Western blotting analyses to identify the regions of SP110 that are responsible for protein interactions.

Results

Using reporter assays, we first demonstrated that SP110 isoforms have different regulatory effects on NF-κB-mediated transcription, supporting the notion that SP110 isoforms may have distinct cellular functions. Analysis of deletion mutants of SP110 showed that the interaction of the N-terminal fragment (amino acids 1–276) of SP110 with p50, a subunit of NF-κB, in the cytoplasm plays a crucial role in the down-regulation of the p50-driven tumor necrosis factor-α (TNFα) promoter activity in the nucleus, while the middle and C-terminal regions of SP110 localize it to various cellular compartments. Surprisingly, a nucleolar localization signal (NoLS) that contains one monopartite nuclear localization signal (NLS) and one bipartite NLS was identified in the middle region of SP110. The identification of a cryptic NoLS in the SP110 suggests that although this protein forms nuclear speckles in the nucleoplasm, it may be directed into the nucleolus to carry out distinct functions under certain cellular conditions.

Conclusions

The findings from this study elucidating the multidomain structure of the SP110 not only identify functional domains of SP110 that are required for transcriptional regulation, cellular translocation, and protein interactions but also implicate that SP110 has additional functions through its unexpected activity in the nucleolus.

Electronic supplementary material

The online version of this article (10.1186/s12929-018-0434-4) contains supplementary material, which is available to authorized users.

Targeting Mycobacterium tuberculosis Antigens to Dendritic Cells via the DC-Specific-ICAM3-Grabbing-Nonintegrin Receptor Induces Strong T-Helper 1 Immune Responses

Tuberculosis remains a major global health problem and efforts to develop a more effective vaccine have been unsuccessful so far. Targeting antigens (Ags) to dendritic cells (DCs) in vivo has emerged as a new promising vaccine strategy. In this approach, Ags are delivered directly to DCs via antibodies that bind to endocytic cell-surface receptors. Here, we explored DC-specific-ICAM3-grabbing-nonintegrin (DC-SIGN) targeting as a potential vaccine against tuberculosis. For this, we made use of the hSIGN mouse model that expresses human DC-SIGN under the control of the murine CD11c promoter. We show that in vitro and in vivo delivery of anti-DC-SIGN antibodies conjugated to Ag85B and peptide 25 of Ag85B in combination with anti-CD40, the fungal cell wall component zymosan, and the cholera toxin-derived fusion protein CTA1-DD induces strong Ag-specific CD4⁺ T-cell responses. Improved anti-mycobacterial immunity was accompanied by increased frequencies of Ag-specific IFN-γ⁺ IL-2⁺ TNF-α⁺ polyfunctional CD4⁺ T cells in vaccinated mice compared with controls. Taken together, in this study we provide the proof of concept that the human DC-SIGN receptor can be efficiently exploited for vaccine purposes to promote immunity against mycobacterial infections.

The IFNG rs1861494 Single Nucleotide Polymorphism Is Associated with Protection against Tuberculosis Disease in Argentina

Interferon gamma (IFNG) plays a key role during Mycobacterium tuberculosis (Mtb) infection, and several polymorphisms located in its gene are associated with risk of tuberculosis in diverse populations. Nevertheless, the genetic resistance/susceptibility to tuberculosis in Argentina is unknown. The IFNG rs1861494 polymorphism (G→A) was reported to alter the binding of transcription factors to this region, influencing IFNG production. Using a case-control study, we found an association between the AA and AG genotypes and tuberculosis resistance (AA vs. GG: odds ratio (OR) = 0.235, p-value = 0.012; AG vs. GG: OR = 0.303, p-value = 0.044; AA vs. AG: OR = 0.776, p-value = 0.427; AA + AG vs. GG: OR = 0.270, p-value = 0.022). Moreover, Mtb-antigen stimulated peripheral blood mononuclear cells (PBMCs) from healthy donors and AA carriers secreted the highest amounts of IFNG in culture supernatants (p-value = 0.034) and presented the greatest percentage of CD4⁺IFNG⁺ lymphocytes (p-value = 0.035), in comparison with GG carriers. No association between the polymorphism and clinical parameters of tuberculosis severity was detected. However, our findings indicate that the rs1861494 single nucleotide polymorphism (SNP) could be considered as a biomarker of tuberculosis resistance in the Argentinean population.

Thioaptamer targeted discoidal microparticles increase self immunity and reduce Mycobacterium tuberculosis burden in mice

Worldwide, tuberculosis (TB) remains one of the most prevalent infectious diseases causing morbidity and death in >1.5 million patients annually. Mycobacterium tuberculosis (Mtb), the etiologic agent of TB, usually resides in the alveolar macrophages. Current tuberculosis treatment methods require more than six months, and low compliance often leads to therapeutic failure and multidrug resistant strain development. Critical to improving TB-therapy is shortening treatment duration and increasing therapeutic efficacy. In this study, we sought to determine if lung hemodynamics and pathological changes in Mtb infected cells can be used for the selective targeting of microparticles to infected tissue(s). Thioaptamers (TA) with CD44 (CD44TA) targeting moiety were conjugated to discoidal silicon mesoporous microparticles (SMP) to enhance accumulation of these agents/carriers in the infected macrophages in the lungs. In vitro, CD44TA-SMP accumulated in macrophages infected with mycobacteria efficiently killing the infected cells and decreasing survival of mycobacteria. In vivo, increased accumulations of CD44TA-SMP were recorded in the lung of M. tuberculosis infected mice as compared to controls. TA-targeted carriers significantly diminished bacterial load in the lungs and caused recruitment of T lymphocytes. Proposed mechanism of action of the designed vector accounts for a combination of increased uptake of particles that leads to infected macrophage death, as well as, activation of cellular immunity by the TA, causing increased T-cell accumulation in the treated lungs. Based on our data with CD44TA-SMP, we anticipate that this drug carrier can open new avenues in TB management.

Host genetics in susceptibility to and severity of mycobacterial diseases

The genetic analysis of susceptibility to infections has proven to be extremely useful for identification of key cells, molecules, pathways, and genes involved in the battle between two genomes - the essence of the infectious process. This is particularly true for tuberculosis and other mycobacterial infections which traditionally attracted much attention from both immunologists and geneticists. In this short review, we observe results of genetic studies performed in human populations and in animal models and compare relative input of forward and reverse genetic approaches in our knowledge about genetic control of and immune responses to mycobacterial infections.

SP110b Controls Host Immunity and Susceptibility to Tuberculosis

RATIONALE

How host genetic factors affect Mycobacterium tuberculosis (Mtb) infection outcomes remains largely unknown. SP110b, an IFN-induced nuclear protein, is the nearest human homologue to the mouse Ipr1 protein that has been shown to control host innate immunity to Mtb infection. However, the function(s) of SP110b remains unclear.

OBJECTIVES

To elucidate the role of SP110b in controlling host immunity and susceptibility to tuberculosis (TB), as well as to identify the fundamental immunological and molecular mechanisms affected by SP110b.

METHODS

Using cell-based approaches and mouse models of Mtb infection, we characterized the function(s) of SP110b/Ipr1. We also performed genetic characterization of patients with TB to investigate the role of SP110 in controlling host susceptibility to TB.

MEASUREMENTS AND MAIN RESULTS

SP110b modulates nuclear factor-κB (NF-κB) activity, resulting in downregulation of tumor necrosis factor-α (TNF-α) production and concomitant upregulation of NF-κB-induced antiapoptotic gene expression, thereby suppressing IFN-γ-mediated monocyte and/or macrophage cell death. After Mtb infection, TNF-α is also downregulated in Ipr1-expressing mice that have alleviated cell death, less severe necrotic lung lesions, more efficient Mtb growth control in the lungs, and longer survival. Moreover, genetic studies in patients suggest that SP110 plays a key role in modulating TB susceptibility in concert with NFκB1 and TNFα genes.

CONCLUSIONS

These results indicate that SP110b plays a crucial role in shaping the inflammatory milieu that supports host protection during infection by fine-tuning NF-κB activity, suggesting that SP110b may serve as a potential target for host-directed therapy aimed at manipulating host immunity against TB.

The IL-17A rs2275913 single nucleotide polymorphism is associated with protection to tuberculosis but related to higher disease severity in Argentina

Mycobacterium tuberculosis (Mtb) causes nearly 10 millions of new tuberculosis disease cases annually. However, most individuals exposed to Mtb do not develop tuberculosis, suggesting the influence of a human genetic component. Here, we investigated the association of the rs2275913 SNP (G → A) from IL-17A and tuberculosis in Argentina by a case-control study. Furthermore, we evaluated in vitro the functional relevance of this SNP during the immune response of the host against Mtb and analyzed its impact on clinical parameters of the disease. We found an association between the AA genotype and tuberculosis resistance. Additionally, within the healthy donors population, AA cells stimulated with a Mtb lysate (Mtb-Ag) produced the highest amounts of IL-17A and IFN-γ, which further support the genetic evidence found. In contrast, within the tuberculosis patients population, AA Mtb-Ag stimulated cells showed the lowest immunological parameters and we evidenced an association between the AA genotype and clinical parameters of disease severity, such as severe radiological lesions and higher bacilli burden in sputum. Overall, our findings demonstrated that the AA genotype from the IL-17A rs2275913 SNP is positively associated with protection to active tuberculosis but related to higher disease severity in the Argentinean population.

Fine-tuning of macrophage activation using synthetic rocaglate derivatives

Drug-resistant bacteria represent a significant global threat. Given the dearth of new antibiotics, host-directed therapies (HDTs) are especially desirable. As IFN-gamma (IFNγ) plays a central role in host resistance to intracellular bacteria, including Mycobacterium tuberculosis, we searched for small molecules to augment the IFNγ response in macrophages. Using an interferon-inducible nuclear protein Ipr1 as a biomarker of macrophage activation, we performed a high-throughput screen and identified molecules that synergized with low concentration of IFNγ. Several active compounds belonged to the flavagline (rocaglate) family. In primary macrophages a subset of rocaglates 1) synergized with low concentrations of IFNγ in stimulating expression of a subset of IFN-inducible genes, including a key regulator of the IFNγ network, Irf1; 2) suppressed the expression of inducible nitric oxide synthase and type I IFN and 3) induced autophagy. These compounds may represent a basis for macrophage-directed therapies that fine-tune macrophage effector functions to combat intracellular pathogens and reduce inflammatory tissue damage. These therapies would be especially relevant to fighting drug-resistant pathogens, where improving host immunity may prove to be the ultimate resource.

Differences between Mycobacterium-Host Cell Relationships in Latent Tuberculous Infection of Mice Ex Vivo and Mycobacterial Infection of Mouse Cells In Vitro

The search for factors that account for the reproduction and survival of mycobacteria, including vaccine strains, in host cells is the priority for studies on tuberculosis. A comparison of BCG-mycobacterial loads in granuloma cells obtained from bone marrow and spleens of mice with latent tuberculous infection and cells from mouse bone marrow and peritoneal macrophage cultures infected with the BCG vaccine in vitro has demonstrated that granuloma macrophages each normally contained a single BCG-Mycobacterium, while those acutely infected in vitro had increased mycobacterial loads and death rates. Mouse granuloma cells were observed to produce the IFNγ, IL-1α, GM-CSF, CD1d, CD25, CD31, СD35, and S100 proteins. None of these activation markers were found in mouse cell cultures infected in vitro or in intact macrophages. Lack of colocalization of lipoarabinomannan-labeled BCG-mycobacteria with the lysosomotropic LysoTracker dye in activated granuloma macrophages suggests that these macrophages were unable to destroy BCG-mycobacteria. However, activated mouse granuloma macrophages could control mycobacterial reproduction in cells both in vivo and in ex vivo culture. By contrast, a considerable increase in the number of BCG-mycobacteria was observed in mouse bone marrow and peritoneal macrophages after BCG infection in vitro, when no expression of the activation-related molecules was detected in these cells.

The QTL within the H2 Complex Involved in the Control of Tuberculosis Infection in Mice Is the Classical Class II H2-Ab1 Gene

The level of susceptibility to tuberculosis (TB) infection depends upon allelic variations in numerous interacting genes. In our mouse model system, the whole-genome quantitative trait loci (QTLs) scan revealed three QTLs involved in TB control on chromosomes 3, 9, and in the vicinity of the H2 complex on chromosome 17. For the present study, we have established a panel of new congenic, MHC-recombinant mouse strains bearing differential small segments of chromosome 17 transferred from the TB-susceptible I/St (H2^j) strain onto the genetic background of TB-resistant C57BL/6 (B6) mice (H2^b). This allowed narrowing the QTL interval to 17Ch: 33, 77–34, 34 Mb, containing 36 protein-encoding genes. Cloning and sequencing of the H2^j allelic variants of these genes demonstrated profound polymorphic variations compare to the H2^b haplotype. In two recombinant strains, B6.I-249.1.15.100 and B6.I-249.1.15.139, recombination breakpoints occurred in different sites of the H2-Aβ 1 gene (beta-chain of the Class II heterodimer H2-A), providing polymorphic variations in the domain β1 of the Aβ-chain. These variations were sufficient to produce different TB-relevant phenotypes: the more susceptible B6.I-249.1.15.100 strain demonstrated shorter survival time, more rapid body weight loss, higher mycobacterial loads in the lungs and more severe lung histopathology compared to the more resistant B6.I-249.1.15.139 strain. CD4⁺ T cells recognized mycobacterial antigens exclusively in the context of the H2-A Class II molecule, and the level of IFN-γ-producing CD4⁺ T cells in the lungs was significantly higher in the resistant strain. Thus, we directly demonstrated for the first time that the classical H2- Ab1 Class II gene is involved in TB control. Molecular modeling of the H2-A^j product predicts that amino acid (AA) substitutions in the Aβ-chain modify the motif of the peptide–MHC binding groove. Moreover, unique AA substitutions in both α- and β-chains of the H2-A^j molecule might affect its interactions with the T-cell receptor (TCR).

Many genes of the host regulate interactions with Mycobacterium tuberculosis and determine the level of susceptibility to, and severity of, tuberculosis (TB). Identification of these genes and their alleles is continuing and contributes new knowledge about the host-pathogen interactions. So far, forward genetic approaches (from phenotype to gene) have identified several chromosomal segments involved in genetic control of TB in mice (quantitative trait loci—QTL), but only one particular gene, Ipr1, has been identified. Here, we report the identification of a second TB-controlling gene. On the basis of a pair of mouse inbred strains with polar susceptibility to TB infection (susceptible I/St and more resistant C57BL/6) we established a panel of recombinant strains carrying small segments of Chromosome 17 from I/St on the genetic background of C57BL/6. A combination of genetic mapping, gene sequencing, TB phenotypes assessment and immunological approaches demonstrates that the H2-Ab1 gene encoding the beta-chain of the Class II heterodimer H2-A determines susceptibility to TB infection. The importance of allelic polymorphisms in Class II genes encoding antigen-presenting molecules in susceptibility to infection has been suspected. This is the first prove of this role obtained by the methods of classical forward genetics.

Inherited and acquired immunodeficiencies underlying tuberculosis in childhood

Tuberculosis (TB), caused by Mycobacterium tuberculosis (M.tb) and a few related mycobacteria, is a devastating disease, killing more than a million individuals per year worldwide. However, its pathogenesis remains largely elusive, as only a small proportion of infected individuals develop clinical disease either during primary infection or during reactivation from latency or secondary infection. Subacute, hematogenous, and extrapulmonary disease tends to be more frequent in infants, children, and teenagers than in adults. Life-threatening primary TB of childhood can result from known acquired or inherited immunodeficiencies, although the vast majority of cases remain unexplained. We review here the conditions conferring a predisposition to childhood clinical diseases caused by mycobacteria, including not only M.tb but also weakly virulent mycobacteria, such as BCG vaccines and environmental mycobacteria. Infections with weakly virulent mycobacteria are much rarer than TB, but the inherited and acquired immunodeficiencies underlying these infections are much better known. Their study has also provided genetic and immunological insights into childhood TB, as illustrated by the discovery of single-gene inborn errors of IFN-γ immunity underlying severe cases of TB. Novel findings are expected from ongoing and future human genetic studies of childhood TB in countries that combine a high proportion of consanguineous marriages, a high incidence of TB, and an excellent clinical care, such as Iran, Morocco, and Turkey.

Versatile myeloid cell subsets contribute to tuberculosis-associated inflammation

Tuberculosis (TB), a chronic bacterial infectious disease caused by Mycobacterium tuberculosis (Mtb), typically affects the lung and causes profound morbidity and mortality rates worldwide. Recent advances in cellular immunology emphasize the complexity of myeloid cell subsets controlling TB inflammation. The specialization of myeloid cell subsets for particular immune processes has tailored their roles in protection and pathology. Among myeloid cells, dendritic cells (DCs) are essential for the induction of adaptive immunity, macrophages predominantly harbor Mtb within TB granulomas and polymorphonuclear neutrophils (PMNs) orchestrate lung damage. However, within each myeloid cell population, diverse phenotypes with unique functions are currently recognized, differentially influencing TB pneumonia and granuloma functionality. More recently, myeloid-derived suppressor cells (MDSCs) have been identified at the site of Mtb infection. Along with PMNs, MDSCs accumulate within the inflamed lung, interact with granuloma-residing cells and contribute to exuberant inflammation. In this review, we discuss the contribution of different myeloid cell subsets to inflammation in TB by highlighting their interactions with Mtb and their role in lung pathology. Uncovering the manifold nature of myeloid cells in TB pathogenesis will inform the development of future immune therapies aimed at tipping the inflammation balance to the benefit of the host.

The innate immune response in human tuberculosis

Mycobacterium tuberculosis (Mtb) infection can be cleared by the innate immune system before the initiation of an adaptive immune response. This innate protection requires a variety of robust cell autonomous responses from many different host immune cell types. However, Mtb has evolved strategies to circumvent some of these defences. In this mini-review, we discuss these host-pathogen interactions with a focus on studies performed in human cells and/or supported by human genetics studies (such as genome-wide association studies).

Abnormal Mammary Development in 129:STAT1-Null Mice is Stroma-Dependent

Female 129:Stat1-null mice (129S6/SvEvTac-Stat1^tm1Rds homozygous) uniquely develop estrogen-receptor (ER)-positive mammary tumors. Herein we report that the mammary glands (MG) of these mice have altered growth and development with abnormal terminal end buds alongside defective branching morphogenesis and ductal elongation. We also find that the 129:Stat1-null mammary fat pad (MFP) fails to sustain the growth of 129S6/SvEv wild-type and Stat1-null epithelium. These abnormalities are partially reversed by elevated serum progesterone and prolactin whereas transplantation of wild-type bone marrow into 129:Stat1-null mice does not reverse the MG developmental defects. Medium conditioned by 129:Stat1-null epithelium-cleared MFP does not stimulate epithelial proliferation, whereas it is stimulated by medium conditioned by epithelium-cleared MFP from either wild-type or 129:Stat1-null females having elevated progesterone and prolactin. Microarrays and multiplexed cytokine assays reveal that the MG of 129:Stat1-null mice has lower levels of growth factors that have been implicated in normal MG growth and development. Transplanted 129:Stat1-null tumors and their isolated cells also grow slower in 129:Stat1-null MG compared to wild-type recipient MG. These studies demonstrate that growth of normal and neoplastic 129:Stat1-null epithelium is dependent on the hormonal milieu and on factors from the mammary stroma such as cytokines. While the individual or combined effects of these factors remains to be resolved, our data supports the role of STAT1 in maintaining a tumor-suppressive MG microenvironment.

ICOS and Bcl6-dependent pathways maintain a CD4 T cell population with memory-like properties during tuberculosis

Protective CD4 T cells specific for M. tuberculosis (Mtb) are maintained in the lungs during active Mtb infection. Similar to memory CD4 T cells, persistence of these Mtb-specific cells requires intrinsic expression of Bcl6 and ICOS.

Immune control of persistent infection with Mycobacterium tuberculosis (Mtb) requires a sustained pathogen-specific CD4 T cell response; however, the molecular pathways governing the generation and maintenance of Mtb protective CD4 T cells are poorly understood. Using MHCII tetramers, we show that Mtb-specific CD4 T cells are subject to ongoing antigenic stimulation. Despite this chronic stimulation, a subset of PD-1⁺ cells is maintained within the lung parenchyma during tuberculosis (TB). When transferred into uninfected animals, these cells persist, mount a robust recall response, and provide superior protection to Mtb rechallenge when compared to terminally differentiated Th1 cells that reside preferentially in the lung-associated vasculature. The PD-1⁺ cells share features with memory CD4 T cells in that their generation and maintenance requires intrinsic Bcl6 and intrinsic ICOS expression. Thus, the molecular pathways required to maintain Mtb-specific CD4 T cells during ongoing infection are similar to those that maintain memory CD4 T cells in scenarios of antigen deprivation. These results suggest that vaccination strategies targeting the ICOS and Bcl6 pathways in CD4 T cells may provide new avenues to prevent TB.

Mutations in genes underlying atypical familial mycobacteriosis are not found in tuberculosis patients from Siberian populations

OBJECTIVES

Atypical familial mycobacteriosis (AFM, OMIM #209950) is caused by mutations in genes regulating IL12/IFNG pathway. Some of the mutations exhibit incomplete penetrance, and they have been proposed to be involved in the common (polygenic) predisposition to tuberculosis (TB). We set out to test this hypothesis in two populations from Siberian region of Russia with high prevalence of TB.

MATERIAL AND METHODS

The prevalence of twelve mutations in IL12/IFNG pathway genes of were analysed in 331 Russians and 238 Tuvinians TB patients and in 279 healthy Russians and 265 healthy Tuvinians. A screening for new mutations and rare polymorphisms was carried out in 10 children with severe generalized TB and severe BCG-vaccine complications using Sanger's bidirectional sequencing.

RESULTS

Twelve mutations most commonly identified in AFM patients appeared to be "wild-type" monomorphic in the studied groups. No new mutations or rare polymorphisms were identified by sequencing. However, 15 common single nucleotide polymorphisms were found, none of which was associated with TB after correction for multiple testing.

CONCLUSION

The results of the study contradict with a hypothesis that mutations underlying AFM syndrome are involved in the predisposition to TB.

Advancing the understanding of behaviors associated with Bacille Calmette Guérin infection using multivariate analysis

Behavioral indicators in the murine Bacille Calmette Guérin (BCG) model of inflammation have been studied individually; however, the variability of the behaviors across BCG levels and the mouse-to-mouse variation within BCG-treatment group are only partially understood. The objectives of this study were: (1) to gain a comprehensive understanding of sickness and depression-like behaviors in a BCG model of inflammation using multivariate approaches, and (2) to explore behavioral differences between BCG-treatment groups and among mice within group. Adult mice were challenged with either 0mg (saline), 5mg or 10mg of BCG (BCG-treatment groups: BCG0, BCG5, or BCG10, respectively) at Day 0 of the experiment. Sickness indicators included body weight changes between Day 0 and Day 2 and between Day 2 and Day 5, and horizontal locomotor activity and vertical activity (rearing) measured at Day 6. Depression-like indicators included duration of immobility in the forced swim test and in the tail suspension test at Day 6 and sucrose consumption in the sucrose preference test at Day 7. The simultaneous consideration of complementary sickness and depression-like indicators enabled a more precise characterization of behavioral changes associated with BCG-treatment and of mouse-to-mouse variation, relative to the analysis of indicators individually. Univariate and multivariate analyses confirmed differences between BCG-treatment groups in weight change early on the trial. Significant differences between BCG-treatment groups in depression-like behaviors were still measurable after Day 5. The potential for multivariate models to account for the correlation between behavioral indicators and to augment the analytical precision relative to univariate models was demonstrated both for sickness and for depression-like indicators. Unsupervised learning approaches revealed the complementary information provided by the sickness and depression-like indicators considered. Supervised learning approaches using cross-validation confirmed subtle differences between BCG-treatment groups and among mice within group identified by the consideration of sickness and depression-like indicators. These findings support the recommendation for multivariate and multidimensional analyses of sickness and depression-like indicators to augment the systemic understanding of the behavioral changes associated with infection.

Interferon γ and Tumor Necrosis Factor Are Not Essential Parameters of CD4+ T-Cell Responses for Vaccine Control of Tuberculosis

BACKGROUND

Mycobacterium tuberculosis infects one third of the world's population and causes >8 million cases of tuberculosis annually. New vaccines are necessary to control the spread of tuberculosis. T cells, interferon γ (IFN-γ), and tumor necrosis factor (TNF) are necessary to control M. tuberculosis infection in both humans and unvaccinated experimental animal models. However, the immune responses necessary for vaccine efficacy against M. tuberculosis have not been defined. The multifunctional activity of T-helper type 1 (TH1) cells that simultaneously produce IFN-γ and TNF has been proposed as a candidate mechanism of vaccine efficacy.

METHODS

We used a mouse model of T-cell transfer and aerosolized M. tuberculosis infection to assess the contributions of TNF, IFN-γ, and inducible nitric oxide synthase (iNOS) to vaccine efficacy.

RESULTS

CD4(+) T cells were necessary and sufficient to transfer protection against aerosolized M. tuberculosis, but neither CD4(+) T cell-produced TNF nor host cell responsiveness to IFN-γ were necessary. Transfer of Tnf(-/-) CD4(+) T cells from vaccinated donors to Ifngr(-/-) recipients was also sufficient to confer protection. Activation of iNOS to produce reactive nitrogen species was not necessary for vaccine efficacy.

CONCLUSIONS

Induction of TH1 cells that coexpress IFN-γ and TNF is not a requirement for vaccine efficacy against M. tuberculosis, despite these cytokines being essential for control of M. tuberculosis in nonvaccinated animals.

Understanding and overcoming the barriers to T cell-mediated immunity against tuberculosis

Despite the overwhelming success of immunization in reducing, and even eliminating, the global threats posed by a wide spectrum of infectious diseases, attempts to do the same for tuberculosis (TB) have failed to date. While most effective vaccines act by eliciting neutralizing antibodies, T cells are the primary mediators of adaptive immunity against TB. Unfortunately, the onset of the T cell response after aerosol infection with Mycobacterium tuberculosis (Mtb), the bacterium that causes TB, is exceedingly slow, and systemically administered vaccines only modestly accelerate the recruitment of effector T cells to the lungs. This delay seems to be orchestrated by Mtb itself to prolong the period of unrestricted bacterial replication in the lung that characterizes the innate phase of the response. When T cells finally arrive at the site of infection, multiple layers of regulation have been established that limit the ability of T cells to control or eradicate Mtb. From this understanding, emerges a strategy for achieving immunity. Lung resident memory T cells may recognize Mtb-infected cells shortly after infection and confer protection before regulatory networks are allowed to develop. Early studies using vaccines that elicit lung resident T cells by targeting the lung mucosa have been promising, but many questions remain. Due to the fundamental nature of these questions, and the need to understand and manipulate the early events in the lung after aerosol infection, only coordinated approaches that utilize tractable animal models to inform human TB vaccine trials will move the field toward its goal.

Host genetic factors in susceptibility to mycobacterial disease

Primary immunodeficiencies (PID) are a group of rare inherited disorders that manifest as heightened susceptibility to infection, autoimmunity and/or malignancy. By exploring their genetic and cellular aetiology, we can learn much about the basis of pathogen-specific immunity in humans. This is exemplified by mycobacterial susceptibility, which occurs across several types of PID, either as an isolated problem or as part of a broader pattern of susceptibility to infection. These experiments of nature have contributed to our understanding of the central role of T cells in activating infected macrophages to eliminate phagosomal mycobacteria through mutually activating, cytokine-dependent interactions. In recent years, the discovery of novel forms of PID has emphasised the important role of dendritic cells and monocytes in mycobacterial defence in humans. Here, we provide a brief overview of these new disorders alongside other genetic causes of susceptibility to mycobacterial disease.