Transiently boosting Vγ9+Vδ2+ γδ T cells early in Mtb coinfection of SIV-infected juvenile macaques does not improve Mtb host resistance.

Children living with HIV have a higher risk of developing tuberculosis (TB), a disease caused by the bacterium Mycobacterium tuberculosis (Mtb). Gamma delta (γδ) T cells in the context of HIV/Mtb coinfection have been understudied in children, despite in vitro evidence suggesting γδ T cells assist with Mtb control. We investigated whether boosting a specific subset of γδ T cells, phosphoantigen-reactive Vγ9+Vδ2+ cells, could improve TB outcome using a nonhuman primate model of pediatric HIV/Mtb coinfection. Juvenile Mauritian cynomolgus macaques (MCM), equivalent to 4-8-year-old children, were infected intravenously (i.v.) with SIV. After 6 months, MCM were coinfected with a low dose of Mtb and then randomized to receive zoledronate (ZOL), a drug that increases phosphoantigen levels, (n=5; i.v.) at 3- and 17- days after Mtb accompanied by recombinant human IL-2 (s.c.) for 5 days following each ZOL injection. A similarly coinfected MCM group (n=5) was injected with saline as a control. Vγ9+Vδ2+ γδ T cell frequencies spiked in the blood, but not airways, of ZOL+IL-2-treated MCM following the first dose, however, were refractory to the second dose. At necropsy eight weeks after Mtb, ZOL+IL-2 treatment did not reduce pathology or bacterial burden. γδ T cell subset frequencies in granulomas did not differ between treatment groups. These data show that transiently boosting peripheral γδ T cells with ZOL+IL-2 soon after Mtb coinfection of SIV-infected MCM did not improve Mtb host defense.

Intravenous BCG induces a more potent airway and lung immune response than intradermal BCG in SIV-infected macaques.

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), is one of the leading causes of death due to an infectious agent. Coinfection with HIV exacerbates Mtb infection outcomes in people living with HIV (PLWH). Bacillus Calmette-Guérin (BCG), the only approved TB vaccine, is effective in infants, but its efficacy in adolescents and adults is limited. Here, we investigated the immune responses elicited by BCG administered via intravenous (IV) or intradermal (ID) routes in Simian Immunodeficiency Virus (SIV)-infected Mauritian cynomolgus macaques (MCM) without the confounding effects of Mtb challenge. We assessed the impact of vaccination on T cell responses in the airway, blood, and tissues (lung, thoracic lymph nodes, and spleen), as well as the expression of cytokines, cytotoxic molecules, and key transcription factors. Our results showed that IV BCG induces a robust and sustained immune response, including tissue-resident memory T (TRM) cells in lungs, polyfunctional CD4+ and CD8αß+ T cells expressing multiple cytokines, and CD8αß+ T cells and NK cells expressing cytotoxic effectors in airways. We also detected higher levels of mycobacteria-specific IgG and IgM in the airways of IV BCG-vaccinated MCM. Although IV BCG vaccination resulted in an influx of TRM cells in lungs of MCM with controlled SIV replication, MCM with high plasma SIV RNA (>105 copies/mL) typically displayed reduced T cell responses, suggesting that uncontrolled SIV or HIV replication would have a detrimental effect on IV BCG-induced protection against Mtb.

CD4 T cells and CD8α+ lymphocytes are necessary for intravenous BCG-induced protection against tuberculosis in macaques.

Tuberculosis (TB) is a major cause of morbidity and mortality worldwide despite widespread intradermal (ID) BCG vaccination in newborns. We previously demonstrated that changing the route and dose of BCG vaccination from 5×105 CFU ID to 5×107 CFU intravenous (IV) resulted in prevention of infection and disease in a rigorous, highly susceptible non-human primate model of TB. Identifying the immune mechanisms of protection for IV BCG will facilitate development of more effective vaccines against TB. Here, we depleted select lymphocyte subsets in IV BCG vaccinated macaques prior to Mtb challenge to determine the cell types necessary for that protection. Depletion of CD4 T cells or all CD8α expressing lymphoycytes (both innate and adaptive) resulted in loss of protection in most macaques, concomitant with increased bacterial burdens (~4-5 log10 thoracic CFU) and dissemination of infection. In contrast, depletion of only adaptive CD8αß+ T cells did not significantly reduce protection against disease. Our results demonstrate that CD4 T cells and innate CD8α+ lymphocytes are critical for IV BCG-induced protection, supporting investigation of how eliciting these cells and their functions can improve future TB vaccines.

Antibody glycosylation correlates with disease progression in SIV-Mycobacterium tuberculosis coinfected cynomolgus macaques.

Objectives: Tuberculosis (TB) remains a substantial cause of morbidity and mortality among people living with human immunodeficiency virus (HIV) worldwide. However, the immunological mechanisms associated with the enhanced susceptibility among HIV-positive individuals remain largely unknown. Methods: Here, we used a simian immunodeficiency virus (SIV)/TB-coinfection Mauritian cynomolgus macaque (MCM) model to examine humoral responses from the plasma of SIV-negative (n = 8) and SIV-positive (n = 7) MCM 8-week postinfection with Mycobacterium tuberculosis (Mtb). Results: Antibody responses to Mtb were impaired during SIV coinfection. Elevated inflammatory bulk IgG antibody glycosylation patterns were observed in coinfected macaques early at 8-week post-Mtb infection, including increased agalactosylation (G0) and reduced di-galactosylation (G2), which correlated with endpoint Mtb bacterial burden and gross pathology scores, as well as the time-to-necropsy. Conclusion: These studies suggest that humoral immunity may contribute to control of TB disease and support growing literature that highlights antibody Fc glycosylation as a biomarker of TB disease progression.

Intravenous Bacille Calmette-Guérin vaccination protects simian immunodeficiency virus-infected macaques from tuberculosis.

Tuberculosis, caused by Mycobacterium tuberculosis (Mtb), is the most common cause of death in people living with human immunodeficiency virus (HIV). Intra-dermal Bacille Calmette-Guérin (BCG) delivery is the only licensed vaccine against tuberculosis; however, it offers little protection from pulmonary tuberculosis in adults and is contraindicated in people living with HIV. Intravenous BCG confers protection against Mtb infection in rhesus macaques; we hypothesized that it might prevent tuberculosis in simian immunodeficiency virus (SIV)-infected macaques, a model for HIV infection. Here intravenous BCG-elicited robust airway T cell influx and elevated plasma and airway antibody titres in both SIV-infected and naive animals. Following Mtb challenge, all 7 vaccinated SIV-naive and 9 out of 12 vaccinated SIV-infected animals were protected, without any culturable bacteria detected from tissues. Peripheral blood mononuclear cell responses post-challenge indicated early clearance of Mtb in vaccinated animals, regardless of SIV infection. These data support that intravenous BCG is immunogenic and efficacious in SIV-infected animals.

Airway T cells are a correlate of i.v. Bacille Calmette-Guerin-mediated protection against tuberculosis in rhesus macaques.

Bacille Calmette-Guerin (BCG), the only approved Mycobacterium tuberculosis (Mtb) vaccine, provides limited durable protection when administered intradermally. However, recent work revealed that intravenous (i.v.) BCG administration yielded greater protection in macaques. Here, we perform a dose-ranging study of i.v. BCG vaccination in macaques to generate a range of immune responses and define correlates of protection. Seventeen of 34 macaques had no detectable infection after Mtb challenge. Multivariate analysis incorporating longitudinal cellular and humoral immune parameters uncovered an extensive and highly coordinated immune response from the bronchoalveolar lavage (BAL). A minimal signature predicting protection contained four BAL immune features, of which three remained significant after dose correction: frequency of CD4 T cells producing TNF with interferon γ (IFNγ), frequency of those producing TNF with IL-17, and the number of NK cells. Blood immune features were less predictive of protection. We conclude that CD4 T cell immunity and NK cells in the airway correlate with protection following i.v. BCG.

Host Immunity to Mycobacterium tuberculosis Infection Is Similar in Simian Immunodeficiency Virus (SIV)-Infected, Antiretroviral Therapy-Treated and SIV-Naïve Juvenile Macaques.

Pre-existing HIV infection increases tuberculosis (TB) risk in children. Antiretroviral therapy (ART) reduces, but does not abolish, this risk in children with HIV. The immunologic mechanisms involved in TB progression in both HIV-naive and HIV-infected children have not been explored. Much of our current understanding is based on human studies in adults and adult animal models. In this study, we sought to model childhood HIV/Mycobacterium tuberculosis (Mtb) coinfection in the setting of ART and characterize T cells during TB progression. Macaques equivalent to 4 to 8 year-old children were intravenously infected with SIVmac239M, treated with ART 3 months later, and coinfected with Mtb 3 months after initiating ART. SIV-naive macaques were similarly infected with Mtb alone. TB pathology and total Mtb burden did not differ between SIV-infected, ART-treated and SIV-naive macaques, although lung Mtb burden was lower in SIV-infected, ART-treated macaques. No major differences in frequencies of CD4+ and CD8+ T cells and unconventional T cell subsets (Vγ9+ γδ T cells, MAIT cells, and NKT cells) in airways were observed between SIV-infected, ART-treated and SIV-naive macaques over the course of Mtb infection, with the exception of CCR5+ CD4+ and CD8+ T cells which were slightly lower. CD4+ and CD8+ T cell frequencies did not differ in the lung granulomas. Immune checkpoint marker levels were similar, although ki-67 levels in CD8+ T cells were elevated. Thus, ART treatment of juvenile macaques, 3 months after SIV infection, resulted in similar progression of Mtb and T cell responses compared to Mtb in SIV-naive macaques.

Vaccination with intravenous BCG protects macaques with pre-existing SIV infection from tuberculosis.

Tuberculosis (TB) is the most common cause of death in people living with HIV. BCG delivered intradermally (ID) is the only licensed vaccine to prevent TB. However, it offers little protection from pulmonary TB in adults. Intravenous (IV) BCG, but not ID BCG, confers striking protection against Mycobacterium tuberculosis (Mtb) infection and disease in rhesus macaques. We investigated whether IV BCG could protect against TB in macaques with a pre-existing SIV infection. There was a robust influx of airway T cells following IV BCG in both SIV-infected and SIV-naïve animals, with elevated antibody titers in plasma and airways. Following Mtb challenge, all 7 SIV-naïve and 9 out of 12 SIV-infected vaccinated animals were completely protected, without any culturable bacilli in their tissues. PBMC responses post-challenge indicated early clearance of Mtb in vaccinated animals regardless of SIV infection. These data support that IV BCG is immunogenic and efficacious in SIV-infected animals.

Characterizing the Spectrum of Latent Mycobacterium tuberculosis in the Cynomolgus Macaque Model: Clinical, Immunologic, and Imaging Features of Evolution.

Mycobacterium tuberculosis infection outcomes have been described as active tuberculosis or latent infection but a spectrum of outcomes is now recognized. We used a nonhuman primate model, which recapitulates human infection, to characterize the clinical, microbiologic, and radiographic patterns associated with developing latent M. tuberculosis infection. Four patterns were identified. "Controllers" had normal erythrocyte sedimentation rate (ESR) without M. tuberculosis growth in bronchoalveolar lavage or gastric aspirate (BAL/GA). "Early subclinicals" showed transient ESR elevation and/or M. tuberculosis growth on BAL/GA for 60 days postinfection, "mid subclinicals" were positive for 90 days, and "late subclinicals" were positive intermittently, despite the absence of clinical disease. Variability was noted regarding granuloma formation, lung/lymph node metabolic activity, lung/lymph node bacterial burden, gross pathology, and extrapulmonary disease. Like human M. tuberculosis infection, this highlights the heterogeneity associated with the establishment of latent infection, underscoring the need to understand the clinical spectrum and risk factors associated with severe disease.

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

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

Pre-existing Simian Immunodeficiency Virus Infection Increases Expression of T Cell Markers Associated with Activation during Early Mycobacterium tuberculosis Coinfection and Impairs TNF Responses in Granulomas.

Tuberculosis (TB) is the leading infectious cause of death among people living with HIV. People living with HIV are more susceptible to contracting Mycobacterium tuberculosis and often have worsened TB disease. Understanding the immunologic defects caused by HIV and the consequences it has on M. tuberculosis coinfection is critical in combating this global health epidemic. We previously showed in a model of SIV and M. tuberculosis coinfection in Mauritian cynomolgus macaques (MCM) that SIV/M. tuberculosis-coinfected MCM had rapidly progressive TB. We hypothesized that pre-existing SIV infection impairs early T cell responses to M. tuberculosis infection. We infected MCM with SIVmac239, followed by coinfection with M. tuberculosis Erdman 6 mo later. Although similar, TB progression was observed in both SIV+ and SIV-naive animals at 6 wk post-M. tuberculosis infection; longitudinal sampling of the blood (PBMC) and airways (bronchoalveolar lavage) revealed a significant reduction in circulating CD4+ T cells and an influx of CD8+ T cells in airways of SIV+ animals. At sites of M. tuberculosis infection (i.e., granulomas), SIV/M. tuberculosis-coinfected animals had a higher proportion of CD4+ and CD8+ T cells expressing PD-1 and TIGIT. In addition, there were fewer TNF-producing CD4+ T cells in granulomas of SIV/M. tuberculosis-coinfected animals. Taken together, we show that concurrent SIV infection alters T cell phenotypes in granulomas during the early stages of TB disease. As it is critical to establish control of M. tuberculosis replication soon postinfection, these phenotypic changes may distinguish the immune dysfunction that arises from pre-existing SIV infection, which promotes TB progression.

MAIT cells are functionally impaired in a Mauritian cynomolgus macaque model of SIV and Mtb co-infection.

Mucosal-associated invariant T (MAIT) cells can recognize and respond to some bacterially infected cells. Several in vitro and in vivo models of Mycobacterium tuberculosis (Mtb) infection suggest that MAIT cells can contribute to control of Mtb, but these studies are often cross-sectional and use peripheral blood cells. Whether MAIT cells are recruited to Mtb-affected granulomas and lymph nodes (LNs) during early Mtb infection and what purpose they might serve there is less well understood. Furthermore, whether HIV/SIV infection impairs MAIT cell frequency or function at the sites of Mtb replication has not been determined. Using Mauritian cynomolgus macaques (MCM), we phenotyped MAIT cells in the peripheral blood and bronchoalveolar lavage (BAL) before and during infection with SIVmac239. To test the hypothesis that SIV co-infection impairs MAIT cell frequency and function within granulomas, SIV+ and -naïve MCM were infected with a low dose of Mtb Erdman, and necropsied at 6 weeks post Mtb-challenge. MAIT cell frequency and function were examined within the peripheral blood, BAL, and Mtb-affected lymph nodes (LN) and granulomas. MAIT cells did not express markers indicative of T cell activation in response to Mtb in vivo within granulomas in animals infected with Mtb alone. SIV and Mtb co-infection led to increased expression of the activation/exhaustion markers PD-1 and TIGIT, and decreased ability to secrete TNFα when compared to SIV-naïve MCM. Our study provides evidence that SIV infection does not prohibit the recruitment of MAIT cells to sites of Mtb infection, but does functionally impair those MAIT cells. Their impaired function could have impacts, either direct or indirect, on the long-term containment of TB disease.

Prevention of tuberculosis in macaques after intravenous BCG immunization.

Mycobacterium tuberculosis (Mtb) is the leading cause of death from infection worldwide1. The only available vaccine, BCG (Bacillus Calmette-Guérin), is given intradermally and has variable efficacy against pulmonary tuberculosis, the major cause of mortality and disease transmission1,2. Here we show that intravenous administration of BCG profoundly alters the protective outcome of Mtb challenge in non-human primates (Macaca mulatta). Compared with intradermal or aerosol delivery, intravenous immunization induced substantially more antigen-responsive CD4 and CD8 T cell responses in blood, spleen, bronchoalveolar lavage and lung lymph nodes. Moreover, intravenous immunization induced a high frequency of antigen-responsive T cells across all lung parenchymal tissues. Six months after BCG vaccination, macaques were challenged with virulent Mtb. Notably, nine out of ten macaques that received intravenous BCG vaccination were highly protected, with six macaques showing no detectable levels of infection, as determined by positron emission tomography-computed tomography imaging, mycobacterial growth, pathology and granuloma formation. The finding that intravenous BCG prevents or substantially limits Mtb infection in highly susceptible rhesus macaques has important implications for vaccine delivery and clinical development, and provides a model for defining immune correlates and mechanisms of vaccine-elicited protection against tuberculosis.

Boosting BCG with proteins or rAd5 does not enhance protection against tuberculosis in rhesus macaques.

Tuberculosis (TB) is the leading cause of death from infection worldwide. The only approved vaccine, BCG, has variable protective efficacy against pulmonary TB, the transmissible form of the disease. Therefore, improving this efficacy is an urgent priority. This study assessed whether heterologous prime-boost vaccine regimens in which BCG priming is boosted with either (i) protein and adjuvant (M72 plus AS01E or H56 plus CAF01) delivered intramuscularly (IM), or (ii) replication-defective recombinant adenovirus serotype 5 (Ad5) expressing various Mycobacterium tuberculosis (Mtb) antigens (Ad5(TB): M72, ESAT-6/Ag85b, or ESAT-6/Rv1733/Rv2626/RpfD) administered simultaneously by IM and aerosol (AE) routes, could enhance blood- and lung-localized T-cell immunity and improve protection in a nonhuman primate (NHP) model of TB infection. Ad5(TB) vaccines administered by AE/IM routes following BCG priming elicited ~10-30% antigen-specific CD4 and CD8 T-cell multifunctional cytokine responses in bronchoalveolar lavage (BAL) but did not provide additional protection compared to BCG alone. Moreover, AE administration of an Ad5(empty) control vector after BCG priming appeared to diminish protection induced by BCG. Boosting BCG by IM immunization of M72/AS01E or H56:CAF01 elicited ~0.1-0.3% antigen-specific CD4 cytokine responses in blood with only a transient increase of ~0.5-1% in BAL; these vaccine regimens also failed to enhance BCG-induced protection. Taken together, this study shows that boosting BCG with protein/adjuvant or Ad-based vaccines using these antigens, by IM or IM/AE routes, respectively, do not enhance protection against primary infection compared with BCG alone, in the highly susceptible rhesus macaque model of tuberculosis.

Preexisting Simian Immunodeficiency Virus Infection Increases Susceptibility to Tuberculosis in Mauritian Cynomolgus Macaques.

Tuberculosis (TB), caused by Mycobacterium tuberculosis, is the leading cause of death among human immunodeficiency virus (HIV)-positive patients. The precise mechanisms by which HIV impairs host resistance to a subsequent M. tuberculosis infection are unknown. We modeled this coinfection in Mauritian cynomolgus macaques (MCM) using simian immunodeficiency virus (SIV) as an HIV surrogate. We infected seven MCM with SIVmac239 intrarectally and 6 months later coinfected them via bronchoscope with ∼10 CFU of M. tuberculosis Another eight MCM were infected with M. tuberculosis alone. TB progression was monitored by clinical parameters, by culturing bacilli in gastric and bronchoalveolar lavages, and by serial [18F]fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) imaging. The eight MCM infected with M. tuberculosis alone displayed dichotomous susceptibility to TB, with four animals reaching humane endpoint within 13 weeks and four animals surviving >19 weeks after M. tuberculosis infection. In stark contrast, all seven SIV+ animals exhibited rapidly progressive TB following coinfection and all reached humane endpoint by 13 weeks. Serial PET/CT imaging confirmed dichotomous outcomes in MCM infected with M. tuberculosis alone and marked susceptibility to TB in all SIV+ MCM. Notably, imaging revealed a significant increase in TB granulomas between 4 and 8 weeks after M. tuberculosis infection in SIV+ but not in SIV-naive MCM and implies that SIV impairs the ability of animals to contain M. tuberculosis dissemination. At necropsy, animals with preexisting SIV infection had more overall pathology, increased bacterial loads, and a trend towards more extrapulmonary disease than animals infected with M. tuberculosis alone. We thus developed a tractable MCM model in which to study SIV-M. tuberculosis coinfection and demonstrate that preexisting SIV dramatically diminishes the ability to control M. tuberculosis coinfection.

Rhesus Macaques Are More Susceptible to Progressive Tuberculosis than Cynomolgus Macaques: a Quantitative Comparison.

In the past 2 decades, it has become increasingly clear that nonhuman primates, specifically macaques, are useful models for human tuberculosis (TB). Several macaque species have been used for TB studies, and questions remain about the similarities and differences in TB pathogenesis among macaque species, which can complicate decisions about the best species for a specific experiment. Here we provide a quantitative assessment, using serial positron emission tomography and computed tomography (PET-CT) imaging and precise quantitative determination of bacterial burdens of low-dose Mycobacterium tuberculosis infection in cynomolgus macaques of Chinese origin, rhesus macaques of Chinese origin, and Mauritian cynomolgus macaques. This comprehensive study demonstrates that there is substantial variability in the outcome of infection within and among species. Overall, rhesus macaques have higher rates of disease progression, more lung, lymph node, and extrapulmonary involvement, and higher bacterial burdens than Chinese cynomolgus macaques. The small cohort of Mauritian cynomolgus macaques assessed here indicates that this species is more similar to rhesus macaques than to Chinese cynomolgus macaques in terms of M. tuberculosis infection outcome. These data provide insights into the differences among species, providing valuable data to the field for assessing macaque studies of TB.

PET CT Identifies Reactivation Risk in Cynomolgus Macaques with Latent M. tuberculosis.

Mycobacterium tuberculosis infection presents across a spectrum in humans, from latent infection to active tuberculosis. Among those with latent tuberculosis, it is now recognized that there is also a spectrum of infection and this likely contributes to the variable risk of reactivation tuberculosis. Here, functional imaging with 18F-fluorodeoxygluose positron emission tomography and computed tomography (PET CT) of cynomolgus macaques with latent M. tuberculosis infection was used to characterize the features of reactivation after tumor necrosis factor (TNF) neutralization and determine which imaging characteristics before TNF neutralization distinguish reactivation risk. PET CT was performed on latently infected macaques (n = 26) before and during the course of TNF neutralization and a separate set of latently infected controls (n = 25). Reactivation occurred in 50% of the latently infected animals receiving TNF neutralizing antibody defined as development of at least one new granuloma in adjacent or distant locations including extrapulmonary sites. Increased lung inflammation measured by PET and the presence of extrapulmonary involvement before TNF neutralization predicted reactivation with 92% sensitivity and specificity. To define the biologic features associated with risk of reactivation, we used these PET CT parameters to identify latently infected animals at high risk for reactivation. High risk animals had higher cumulative lung bacterial burden and higher maximum lesional bacterial burdens, and more T cells producing IL-2, IL-10 and IL-17 in lung granulomas as compared to low risk macaques. In total, these data support that risk of reactivation is associated with lung inflammation and higher bacterial burden in macaques with latent Mtb infection.

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.

Variability in tuberculosis granuloma T cell responses exists, but a balance of pro- and anti-inflammatory cytokines is associated with sterilization.

Lung granulomas are the pathologic hallmark of tuberculosis (TB). T cells are a major cellular component of TB lung granulomas and are known to play an important role in containment of Mycobacterium tuberculosis (Mtb) infection. We used cynomolgus macaques, a non-human primate model that recapitulates human TB with clinically active disease, latent infection or early infection, to understand functional characteristics and dynamics of T cells in individual granulomas. We sought to correlate T cell cytokine response and bacterial burden of each granuloma, as well as granuloma and systemic responses in individual animals. Our results support that each granuloma within an individual host is independent with respect to total cell numbers, proportion of T cells, pattern of cytokine response, and bacterial burden. The spectrum of these components overlaps greatly amongst animals with different clinical status, indicating that a diversity of granulomas exists within an individual host. On average only about 8% of T cells from granulomas respond with cytokine production after stimulation with Mtb specific antigens, and few "multi-functional" T cells were observed. However, granulomas were found to be "multi-functional" with respect to the combinations of functional T cells that were identified among lesions from individual animals. Although the responses generally overlapped, sterile granulomas had modestly higher frequencies of T cells making IL-17, TNF and any of T-1 (IFN-γ, IL-2, or TNF) and/or T-17 (IL-17) cytokines than non-sterile granulomas. An inverse correlation was observed between bacterial burden with TNF and T-1/T-17 responses in individual granulomas, and a combinatorial analysis of pair-wise cytokine responses indicated that granulomas with T cells producing both pro- and anti-inflammatory cytokines (e.g. IL-10 and IL-17) were associated with clearance of Mtb. Preliminary evaluation suggests that systemic responses in the blood do not accurately reflect local T cell responses within granulomas.