Tuberculosis Immunity Research Articles

Construction of human MASP-2-CCP1/2SP, CCP2SP, SP plasmid DNA nanolipoplexes and the effects on tuberculosis in BCG-infected mice.

The lectin pathway, one of the complement cascade systems, provides the primary line of defense against invading pathogens. The serine protease of MASP-2 plays an essential role in complement activation of the lectin pathway. The C-terminal segment of MASP-2 is comprised of the CCP1-CCP2-SP domains, and is the crucial catalytic segment. However, what is the effect of CCP1-CCP2-SP domains in controlling chronic infection is unknown. In order to evaluate the potential impact of CCP1-CCP2-SP domains on tuberculosis, we constructed the human MASP-2 CCP1/2SP, CCP2SP and SP recombinant plasmids, and delivered these plasmids by DNA-DOTAP:cholesterol cationic nanolipoplexes to BCG-infected mice. After 21 days post DNA-DOTAP:chol nanolipoplexes application, we analyzed bacteria loads of pulmonary, pathology of granuloma, lymphocyte subpopulations. The C3a, C4a and MASP-2 levels in serum were measured with enzyme-linked immunosorbent assays. Compared to the control group that received GFP DNA-DOTAP:chol nanolipoplexes, MASP-2 CCP1/2SP DNA-DOTAP:chol nanolipoplexes treated group showed significantly enlarged pulmonary granulomas lesion (P<0.05) and did not reduce bacteria loads in the lung tissue (P<0.05). Furthermore, the levels of C3a in serum were decreased (P<0.05), the number and percentage of PD1+ and Tim3+ cells subgroups were increased in BCG-infected mice after treated with MASP-2 CCP1/2SP DNA-DOTAP:chol nanolipoplexes (P<0.05). But, there was no statistical difference in the serum C4a and MASP-2 level among DNA nanolipoplexes treated groups (P>0.05). These findings provided experimental evidence that MASP-2 CCP1/2SP DNA nanolipoplexes shown the negative efficacy in controlling Mycobacterium tuberculosis infection, and displayed a potential role of down-regulating T-cell-mediated immunity in tuberculosis.

Interactions between Type 1 Interferons and the Th17 Response in Tuberculosis: Lessons Learned from Autoimmune Diseases.

The classical paradigm of tuberculosis (TB) immunity, with a central protective role for Th1 responses and IFN-γ-stimulated cellular responses, has been challenged by unsatisfactory results of vaccine strategies aimed at enhancing Th1 immunity. Moreover, preclinical TB models have shown that increasing IFN-γ responses in the lungs is more damaging to the host than to the pathogen. Type 1 interferon signaling and altered Th17 responses have also been associated with active TB, but their functional roles in TB pathogenesis remain to be established. These two host responses have been studied in more detail in autoimmune diseases (AID) and show functional interactions that are of potential interest in TB immunity. In this review, we first identify the role of type 1 interferons and Th17 immunity in TB, followed by an overview of interactions between these responses observed in systemic AID. We discuss (i) the effects of GM-CSF-secreting Th17.1 cells and type 1 interferons on CCR2+ monocytes; (ii) convergence of IL-17 and type 1 interferon signaling on stimulating B-cell activating factor production and the central role of neutrophils in this process; and (iii) synergy between IL-17 and type 1 interferons in the generation and function of tertiary lymphoid structures and the associated follicular helper T-cell responses. Evaluation of these autoimmune-related pathways in TB pathogenesis provides a new perspective on recent developments in TB research.

Identification of Mycobacterial RplJ/L10 and RpsA/S1 Proteins as Novel Targets for CD4+ T Cells.

Tuberculosis (TB) due to Mycobacterium tuberculosis remains a major global infectious disease problem, and a more efficacious vaccine is urgently needed for the control and prevention of disease caused by this organism. We previously reported that a genetically modified strain of Mycobacterium smegmatis called IKEPLUS is a promising TB vaccine candidate. Since protective immunity induced by IKEPLUS is dependent on antigen-specific CD4+ T cell memory, we hypothesized that the specificity of the CD4+ T cell response was a critical feature of this protection. Using in vitro assays of interferon gamma production (enzyme-linked immunosorbent spot [ELISPOT] assays) by splenocytes from IKEPLUS-immunized C57BL/6J mice, we identified an immunogenic peptide within the mycobacterial ribosomal large subunit protein RplJ, encoded by the Rv0651 gene. In a complementary approach, we generated major histocompatibility complex (MHC) class II-restricted T cell hybridomas from IKEPLUS-immunized mice. Screening of these T cell hybridomas against IKEPLUS and ribosomes enriched from IKEPLUS suggested that the CD4+ T cell response in IKEPLUS-immunized mice was dominated by the recognition of multiple components of the mycobacterial ribosome. Importantly, CD4+ T cells specific for mycobacterial ribosomes accumulate to significant levels in the lungs of IKEPLUS-immunized mice following aerosol challenge with virulent M. tuberculosis, consistent with a role for these T cells in protective host immunity in TB. The identification of CD4+ T cell responses to defined ribosomal protein epitopes expands the range of antigenic targets for adaptive immune responses to M. tuberculosis and may help to inform the design of more effective vaccines against tuberculosis.

Safety and immunogenicity of the novel H4:IC31 tuberculosis vaccine candidate in BCG-vaccinated adults: Two phase I dose escalation trials

BackgroundNovel vaccine strategies are required to provide protective immunity in tuberculosis (TB) and prevent development of active disease. We investigated the safety and immunogenicity of a novel TB vaccine candidate, H4:IC31 (AERAS-404) that is composed of a fusion protein of M. tuberculosis antigens Ag85B and TB10.4 combined with an IC31® adjuvant. MethodsBCG-vaccinated healthy subjects were immunized with various antigen (5, 15, 50, 150μg) and adjuvant (0, 100, 500nmol) doses of the H4:IC31 vaccine (n=106) or placebo (n=18) in two randomized, double-blind, placebo-controlled phase I studies conducted in a low TB endemic setting in Sweden and Finland. The subjects were followed for adverse events and CD4+ T cell responses. ResultsH4:IC31 vaccination was well tolerated with a safety profile consisting of mostly mild to moderate self-limited injection site pain, myalgia, arthralgia, fever and post-vaccination inflammatory reaction at the screening tuberculin skin test injection site. The H4:IC31 vaccine elicited antigen-specific CD4+ T cell proliferation and cytokine production that persisted 18weeks after the last vaccination. CD4+ T cell expansion, IFN-γ production and multifunctional CD4+ Th1 responses were most prominent after two doses of H4:IC31 containing 5, 15, or 50μg of H4 in combination with the 500nmol IC31 adjuvant dose. ConclusionsThe novel TB vaccine candidate, H4:IC31, demonstrated an acceptable safety profile and was immunogenic, capable of triggering multifunctional CD4+ T cell responses in previously BCG-vaccinated healthy individuals. These dose-escalation trials provided evidence that the optimal antigen-adjuvant dose combinations are 5, 15, or 50μg of H4 and 500nmol of IC31.Trial registration: ClinicalTrials.gov, NCT02066428 and NCT02074956.

Arnold Rice Rich

Arnold Rice Rich

Early Secreted Antigenic Target of 6-kDa of Mycobacterium tuberculosis Stimulates IL-6 Production by Macrophages through Activation of STAT3

As early secreted antigenic target of 6 kDa (ESAT-6) of Mycobacterium tuberculosis (Mtb) is an essential virulence factor and macrophages are critical for tuberculosis infection and immunity, we studied ESAT-6 stimulated IL-6 production by macrophages. ESAT-6 stimulated significantly higher IL-6 secretion by murine bone marrow derived macrophages (BMDM) compared to culture filtrate protein 10 kDa (CFP10) and antigen 85A. Polymyxin B, an LPS blocker, did not affect ESAT-6 stimulated macrophage IL-6 production. ESAT-6 but not Pam3CSK4 induced IL-6 by TLR2 knockout BMDM. ESAT-6 induced phosphorylation and DNA binding of STAT3 and this was blocked by STAT3 inhibitors but not by rapamycin. STAT3 inhibitors suppressed ESAT-6-induced IL-6 transcription and secretion without affecting cell viability. This was confirmed by silencing STAT3 in macrophages. Blocking neither IL-6Rα/IL-6 nor IL-10 affected ESAT-6-induced STAT3 activation and IL-6 production. Infection of BMDM and human macrophages with Mtb with esat-6 deletion induced diminished STAT3 activation and reduced IL-6 production compared to wild type and esat-6 complemented Mtb strains. Administration of ESAT-6 but not CFP10 induced STAT3 phosphorylation and IL-6 expression in the mouse lungs, consistent with expression of ESAT-6, IL-6 and phosphorylated-STAT3 in Mtb-infected mouse lungs. We conclude that ESAT-6 stimulates macrophage IL-6 production through STAT3 activation.

Адаптивный иммунитет и генетические аспекты прогрессирования туберкулезной инфекции у детей

Адаптивный иммунитет и генетические аспекты прогрессирования туберкулезной инфекции у детей

"Suppressor Factor" of Neutrophils: A Short Story of a Long-Term Misconception.

A large body of evidence obtained during the last decade has demonstrated that neutrophils suppress T cell proliferation in different models of inflammation and cell interaction. The commonly used method for assessing cell proliferation and proliferation inhibition is measuring [3H]thymidine incorporation into cells. Earlier, we observed inhibition of [3H]thymidine uptake in experiments on neutrophil-mediated regulation of T cell response in tuberculosis immunity. Here, we used different types of proliferating cells to analyze the nature of the soluble "neutrophil factor" by a variety of methods (dialysis, HPLC, mass spectrometry, and NMR) and unambiguously demonstrated that neutrophils do not synthesize a specific factor inhibiting cell proliferation, but secrete high concentrations of extracellular thymidine that competitively inhibit [3H]thymidine incorporation. Although the physiological significance of thymidine secretion by neutrophils remains unknown, this phenomenon should be carefully considered when designing test systems for studying cell-cell interactions.

Combined Expression of IFN-γ, IL-17, and IL-4 mRNA by Recall PBMCs Moderately Discriminates Active Tuberculosis from Latent Mycobacterium tuberculosis Infection in Patients with Miscellaneous Inflammatory Underlying Conditions.

New biomarkers are needed for discriminating active tuberculosis (TB) from latent TB infection (LTBI), especially in vulnerable groups representing the major diagnostic challenge. This pilot study was carried out to explore the diagnostic potential of selected genes, IFN-γ, IL-17, IL-4, and FoxP3, associated with TB immunity and immunopathology. IFN-γ, IL-17, IL-4, and FoxP3 mRNA expression levels were measured by quantitative reverse transcription PCR (RT-qPCR) from antigen-stimulated peripheral blood mononuclear cells of patients with active TB (n = 25); patients with miscellaneous inflammatory disorders and concomitant LTBI (n = 20), rheumatoid arthritis (RA) being the most predominant in the group (n = 11); and in healthy Bacillus Calmette–Guérin (BCG) vaccinees (n = 8). While the levels of FoxP3 mRNA did not differ between the tested groups, the cumulative expression levels of purified protein derivative-stimulated IFN-γ, IL-17, and IL-4 mRNAs were found to distinguish active TB from the whole group of LTBI with 48% sensitivity and 85% specificity. When restricting the LTBI group to RA cases only, the sensitivity was 56% and specificity 100%. When interpreting the result as positive in at least one of the mRNAs IFN-γ, IL-17, or IL-4, sensitivity of 64% and specificities of 75% (heterogeneous group of LTBI) or 100% (LTBI with RA) were achieved. Moderate discrimination of active TB from LTBI with miscellaneous inflammatory underlying conditions by using combined quantitative expression of IFN-γ, IL-17, and IL-4 mRNA seems not to be of high diagnostic potential.

HIV Skews the Lineage-Defining Transcriptional Profile of Mycobacterium tuberculosis-Specific CD4+ T Cells.

HIV-infected persons are at greater risk of developing tuberculosis (TB) even before profound CD4 loss occurs, suggesting that HIV alters CD4(+) T cell functions capable of containing bacterial replication. An effective immune response to Mycobacterium tuberculosis most likely relies on the development of a balanced CD4 response, in which distinct CD4(+) Th subsets act in synergy to control the infection. To define the diversity of M. tuberculosis-specific CD4(+) Th subsets and determine whether HIV infection impacts such responses, the expression of lineage-defining transcription factors T-bet, Gata3, RORγt, and Foxp3 was measured in M. tuberculosis-specific CD4(+) T cells in HIV-uninfected (n = 20) and HIV-infected individuals (n = 20) with latent TB infection. Our results show that, upon 5-d restimulation in vitro, M. tuberculosis-specific CD4(+) T cells from healthy individuals have the ability to exhibit a broad spectrum of Th subsets, defined by specific patterns of transcription factor coexpression. These transcription factor profiles were skewed in HIV-infected individuals where the proportion of T-bet(high)Foxp3(+) M. tuberculosis-specific CD4(+) T cells was significantly decreased (p = 0.002) compared with HIV-uninfected individuals, a change that correlated inversely with HIV viral load (p = 0.0007) and plasma TNF-α (p = 0.027). Our data demonstrate an important balance in Th subset diversity defined by lineage-defining transcription factor coexpression profiles that is disrupted by HIV infection and suggest a role for HIV in impairing TB immunity by altering the equilibrium of M. tuberculosis-specific CD4(+) Th subsets.

Mycobacterium-Specific γ9δ2 T Cells Mediate Both Pathogen-Inhibitory and CD40 Ligand-Dependent Antigen Presentation Effects Important for Tuberculosis Immunity.

Numerous pathogens, including Mycobacterium tuberculosis, can activate human γ9δ2 T cells to proliferate and express effector mechanisms. γ9δ2 T cells can directly inhibit the growth of intracellular mycobacteria and may also act as antigen-presenting cells (APC). Despite evidence for γδ T cells having the capacity to function as APC, the mechanisms involved and importance of these effects on overall tuberculosis (TB) immunity are unknown. We prepared M. tuberculosis-specific γ9δ2 T cell lines to study their direct protective effects and APC functions for M. tuberculosis-specific αβ T cells. The direct inhibitory effects on intracellular mycobacteria were measured, and the enhancing effects on proliferative and effector responses of αβ T cells assessed. Furthermore, the importance of cell-to-cell contact and soluble products for γ9δ2 T cell effector responses and APC functions were investigated. We demonstrate, in addition to direct inhibitory effects on intracellular mycobacteria, the following: (i) γ9δ2 T cells enhance the expansion of M. tuberculosis-specific αβ T cells and increase the ability of αβ T cells to inhibit intracellular mycobacteria; (ii) although soluble mediators are critical for the direct inhibitory effects of γ9δ2 T cells, their APC functions do not require soluble mediators; (iii) the APC functions of γ9δ2 T cells involve cell-to-cell contact that is dependent on CD40-CD40 ligand (CD40L) interactions; and (iv) fully activated CD4(+) αβ T cells and γ9δ2 T cells provide similar immune enhancing/APC functions for M. tuberculosis-specific T cells. These effector and helper effects of γ9δ2 T cells further indicate that these T cells should be considered important new targets for new TB vaccines.

Innate immunity in tuberculosis: how the sensing of mycobacteria and tissue damage modulates macrophage death

The success of Mycobacterium tuberculosis as a human pathogen has been attributed to the ability of the bacillus to proliferate inside macrophages and to induce cell death. This review describes how the sensors of the innate immune system modulate the cell death pathways in infected macrophages and, consequently, the pathogenesis of tuberculosis.

The TB-specific CD4+ T cell immune repertoire in both cynomolgus and rhesus macaques largely overlap with humans

Non-human primate (NHP) models of tuberculosis (TB) immunity and pathogenesis, especially rhesus and cynomolgus macaques, are particularly attractive because of the high similarity of the human and macaque immune systems. However, little is known about the MHC class II epitopes recognized in macaques, thus hindering the establishment of immune correlates of immunopathology and protective vaccination. We characterized immune responses in rhesus macaques vaccinated against and/or infected with Mycobacterium tuberculosis (Mtb), to a panel of antigens currently in human vaccine trials. We defined 54 new immunodominant CD4(+) T cell epitopes, and noted that antigens immunodominant in humans are also immunodominant in rhesus macaques, including Rv3875 (ESAT-6) and Rv3874 (CFP10). Pedigree and inferred restriction analysis demonstrated that this phenomenon was not due to common ancestry or inbreeding, but rather presentation by common alleles, as well as, promiscuous binding. Experiments using a second cohort of rhesus macaques demonstrated that a pool of epitopes defined in the previous experiments can be used to detect T cell responses in over 75% of individual monkeys. Additionally, 100% of cynomolgus macaques, irrespective of their latent or active TB status, responded to rhesus and human defined epitope pools. Thus, these findings reveal an unexpected general repertoire overlap between MHC class II epitopes recognized in both species of macaques and in humans, showing that epitope pools defined in humans can also be used to characterize macaque responses, despite differences in species and antigen exposure. The results have general implications for the evaluation of new vaccines and diagnostics in NHPs, and immediate applicability in the setting of macaque models of TB.

Pulmonary tuberculosis with meningitis

We read with great interest the case report by GoicBarisic et al. [1] on “pulmonary tuberculosis with meningitis in a 7-month-old infant”. The case report provides an excellent overview of the pathogenesis and diagnosis of tuberculosis meningitis. It also rightly emphasizes the importance of screening and introducing chemoprophylaxis in infants exposed to patients with active tuberculosis as well as early discovery and therapy of the illness. We would like to share our views in this regard. Tuberculous meningitis though rare in Croatia, is seen commonly in developing countries like India. Other serious forms of extrapulmonary tuberculosis like spinal tuberculosis, abdominal tuberculosis are also frequently encountered. One of the reasons for this might be the increase in the number of human immunodeficiency virus cases, which causes decreased immunity and dissemination of tuberculosis to different parts of the body. Other factors contributing are overcrowding, delay in diagnosis and inadequate health facilities [2]. As per World Health Organization guidelines for treatment of tuberculous meningitis by Directly Observed Therapy Short Course, isoniazid, rifampin, pyrazinamide and streptomycin are given for 2 months followed by isoniazid and rifampicin for the next 4 months. Countries applying Directly Observed Thera-

Functional Heterogeneity and Antimycobacterial Effects of Mouse Mucosal-Associated Invariant T Cells Specific for Riboflavin Metabolites

Mucosal-associated invariant T (MAIT) cells have a semi-invariant TCR Vα-chain, and their optimal development is dependent upon commensal flora and expression of the nonpolymorphic MHC class I-like molecule MR1. MAIT cells are activated in an MR1-restricted manner by diverse strains of bacteria and yeast, suggesting a widely shared Ag. Recently, human and mouse MR1 were found to bind bacterial riboflavin metabolites (ribityllumazine [RL] Ags) capable of activating MAIT cells. In this study, we used MR1/RL tetramers to study MR1 dependency, subset heterogeneity, and protective effector functions important for tuberculosis immunity. Although tetramer(+) cells were detected in both MR1(+/+) and MR1(-/-) TCR Vα19i-transgenic (Tg) mice, MR1 expression resulted in significantly increased tetramer(+) cells coexpressing TCR Vβ6/8, NK1.1, CD44, and CD69 that displayed more robust in vitro responses to IL-12 plus IL-18 and RL Ag, indicating that MR1 is necessary for the optimal development of the classic murine MAIT cell memory/effector subset. In addition, tetramer(+) MAIT cells expressing CD4, CD8, or neither developing in MR1(+/+) Vα19i-Tg mice had disparate cytokine profiles in response to RL Ag. Therefore, murine MAIT cells are considerably more heterogeneous than previously thought. Most notably, after mycobacterial pulmonary infection, heterogeneous subsets of tetramer(+) Vα19i-Tg MAIT cells expressing CXCR3 and α4β1 were recruited into the lungs and afforded early protection. In addition, Vα19iCα(-/-)MR(+/+) mice were significantly better protected than were Vα19iCα(-/-)MR1(-/-), wild-type, and MR1(-/-) non-Tg mice. Overall, we demonstrate considerable functional diversity of MAIT cell responses, as well as that MR1-restricted MAIT cells are important for tuberculosis protective immunity.

Age at Mycobacterium bovis BCG Priming Has Limited Impact on Anti-Tuberculosis Immunity Boosted by Respiratory Mucosal AdHu5Ag85A Immunization in a Murine Model.

Tuberculosis (TB) remains a global pandemic despite the use of Bacillus Calmette-Guérin (BCG) vaccine, partly because BCG fails to effectively control adult pulmonary TB. The introduction of novel boost vaccines such as the human Adenovirus 5-vectored AdHu5Ag85A could improve and prolong the protective immunity of BCG immunization. Age at which BCG immunization is implemented varies greatly worldwide, and research is ongoing to discover the optimal stage during childhood to administer the vaccine, as well as when to boost the immune response with potential novel vaccines. Using a murine model of subcutaneous BCG immunization followed by intranasal AdHu5Ag85A boosting, we investigated the impact of age at BCG immunization on protective efficacy of BCG prime and AdHu5Ag85A boost immunization-mediated protection. Our results showed that age at parenteral BCG priming has limited impact on the efficacy of BCG prime-AdHu5Ag85A respiratory mucosal boost immunization-enhanced protection. However, when BCG immunization was delayed until the maturity of the immune system, longer sustained memory T cells were generated and resulted in enhanced boosting effect on T cells of AdHu5Ag85A respiratory mucosal immunization. Our findings hold implications for the design of new TB immunization protocols for humans.

Recruitment of IL-27-Producing CD4(+) T Cells and Effect of IL-27 on Pleural Mesothelial Cells in Tuberculous Pleurisy.

The numbers of IL-27-producing CD4(+) T cells and the concentration of soluble IL-27 have been found to be increased in tuberculous pleural effusion (TPE). The objective of the present study was to explore the mechanism by which IL-27(+)CD4(+) T cells are recruited into the pleural space, and to explore the impact of IL-27 on pleural mesothelial cells (PMCs). The expression profiles of chemokine receptor (CCR) were determined by flow cytometry. The chemoattractant activity of chemokines CCL20 and CCL22 for IL-27(+)CD4(+) T cells in vitro was observed. Effects of IL-27 on wound healing, proliferation and apoptosis of PMCs were also investigated. IL-27(+)CD4(+) T cells in TPE expressed high level of CCR6, medium level of CCR4, and low levels of CCR2, CCR3, CCR5, CCR7, CCR10, and CXCR3. Recruitment of IL-27(+)CD4(+) T cells into TPE could be induced by pleural CCL20 and CCL22. By activating STAT3 signaling, IL-27 significantly improved wound healing and promoted proliferation of PMCs, and completely prevented apoptosis of PMCs induced by IFN-γ. After being recruited into pleural space by CCL20 or/and CCL22, these pleural IL-27-producing CD4(+) T cells may play important roles in tuberculosis immunity by affecting PMC functions.

Antigen-specific MAIT cell subsets involved in TB immunity (INC2P.420)

Abstract Mucosal associated invariant T (MAIT) cells have a semi-invariant TCRVα chain, and depend on riboflavin metabolites (ribityllumazines, RLAg) produced by commensal flora and presented by the nonpolymorphic class Ib molecule MR1 for optimal development. We used MR1/RLAg tetramers and TCR Vα19 transgenic mice to study MR1-dependency, subset heterogeneity and protective effector functions important for tuberculosis (TB) immunity. We found that Vβ6/8+NK1.1+ MAIT cell subsets maximally expand peripherally in mice expressing MR1. In addition, we show that MR1/RLAg tetramer+ MAIT cells expressing CD4, CD8 or neither contain populations variably co-expressing Vβ6/8 and/or NK1.1, indicating that MAIT cells are more heterogeneous than previously thought. Furthermore, NK1.1 (NKR-P1C) is minimally expressed on mature Vβ6/8+ tetramer+ MAIT cells in the thymus but progressively increases with peripheral activation. Importantly, after virulent mycobacterial pulmonary infection, heterogeneous subsets of tetramer+ MAIT cells (CD4-CD8-&amp;gt;CD4-CD8+&amp;gt;CD4+CD8-) co-expressing Vβ6/8 and NK1.1 and the homing molecules α4β1 and CXCR3, were recruited into the lungs and afforded maximal early protection in MR1-sufficient mice. Surprisingly, MAIT cells developing in the absence of MR1 were partially protective. Overall, we demonstrate diversity of MAIT cells, evidence that NK1.1 is an activation rather than developmental MAIT cell marker, and also that MAIT cells are important for TB protective immunity.

Co-evolution of Mycobacterium tuberculosis and Homo sapiens.

The causative agent of human tuberculosis (TB), Mycobacterium tuberculosis, is an obligate pathogen that evolved to exclusively persist in human populations. For M. tuberculosis to transmit from person to person, it has to cause pulmonary disease. Therefore, M. tuberculosis virulence has likely been a significant determinant of the association between M. tuberculosis and humans. Indeed, the evolutionary success of some M. tuberculosis genotypes seems at least partially attributable to their increased virulence. The latter possibly evolved as a consequence of human demographic expansions. If co-evolution occurred, humans would have counteracted to minimize the deleterious effects of M. tuberculosis virulence. The fact that human resistance to infection has a strong genetic basis is a likely consequence of such a counter-response. The genetic architecture underlying human resistance to M. tuberculosis remains largely elusive. However, interactions between human genetic polymorphisms and M. tuberculosis genotypes have been reported. Such interactions are consistent with local adaptation and allow for a better understanding of protective immunity in TB. Future ‘genome-to-genome’ studies, in which locally associated human and M. tuberculosis genotypes are interrogated in conjunction, will help identify new protective antigens for the development of better TB vaccines.

Tuberculosis interferon-gamma responses in the breast milk of human immunodeficiency virus infected mothers.

Tuberculosis (TB) cellular immune responses were examined in the breast milk of human immunodeficiency virus infected mothers using the T-SPOT. TB interferon-gamma release assay (IGRA). Positive TB interferon-gamma (IFN-γ) responses were detected in 6 of 8 (75%) valid breast milk assays. Among 7 mothers with paired breast milk and blood assays, TB IFN-γ responses were higher in breast milk than in blood (P = 0.02). The magnitude of TB IFN-γ responses in maternal breast milk and blood were correlated. Elucidating the influence of TB immune responses in breast milk on infant TB susceptibility and immunity may inform future maternal TB vaccine strategies.