Publications

Mycobacterium tuberculosis (Mtb), bacteria causing tuberculosis (TB), is a leading cause of morbidity and mortality worldwide. Even though billions of individuals have evidence of past or present Mtb infection and millions develop TB yearly, most individuals exposed to Mtb do not progress to TB (active disease) and successfully control (and perhaps eliminate) the infection. Factors determining the likelihood of TB progression of Mtb-exposed individuals remains poorly understood, however. Mtb-exposed non-human primates (NHPs) such as rhesus macaques (RMs) also exhibit variable likelihood of developing active disease. Previous analysis of Mtb-exposed RMs suggested that blood proteins such as C-reactive protein (CRP), albumin to globulin (A/G), and kynurenine-to-tryptophan ratios and blood leukocytes (e.g., neutrophil frequency) were best correlated with TB diagnosis. We extended this previous work by using several machine learning (ML) techniques to further quantify the relative contribution of 20 features (and their derivatives) to predict development or diagnosis of active disease in Mtb-exposed RMs. We found that independent of the specific ML technique (random forest, linear support vector machine, or logistic regression), CRP and A/G ratio values and lung CFU were most informative at discriminating between animals with active disease or no disease; furthermore, when excluding endpoint measurements (measurements done at necropsy), CRP.peak and A/G.bottom dramatically outperformed all other features at determining progression to active disease. Top 5 (when including all features) or top 2 (when excluding endpoint measurements) features together had nearly as high discriminatory power (AUC ≥0.98) as all 20+ features. Importantly, in our analysis, frequency of blood leukocytes (e.g., percent of neutrophils or lymphocytes) or their ratios (e.g., neutrophil to lymphocyte ratio) had relatively poorer predictive or diagnostic value (AUC<0.8). Our results thus suggest that a combination of CRP and A/G ratio have a high power at predicting and/or diagnosing TB in Mtb-exposed RMs. Future studies will need to investigate if temporal changes in blood protein concentrations and leukocyte frequencies may further improve our ability to predict and/or diagnose TB in NHPs.

Granulomas, the hallmark of tuberculosis (TB) disease, can both restrict Mycobacterium tuberculosis (Mtb) dissemination and impede its clearance. Recent studies indicate that indoleamine 2,3-dioxygenase (IDO1), an immunosuppressive metabolic enzyme, limits infiltration of activated T cells and can contribute to TB disease progression. Treatment with 1-methyl-D-tryptophan (D-1MT), a small molecule inhibitor that restores mTOR signaling, has been shown to reduce IDO1 activity and improve immune responses in Mtb-infected rhesus macaques. Here, we investigated the impact of D-1MT treatment on TB granuloma architecture using 30-plex high-dimensional issue imaging in rhesus macaques. By spatially mapping 13 distinct cell populations, we found D-1MT treatment corresponded with significantly increased infiltration CD8+ T cells into granulomas compared to untreated controls. Notably, these CD8+ T cells expressed markers of cell proliferation and cytotoxicity. D-1MT enhanced CD8+ T cell infiltration throughout the granuloma, with particularly pronounced effects in the myeloid core, where we observed significantly enhanced spatial interactions between macrophages and CD8+ T cells, but not CD4+ T cells. Our results demonstrate that: i) effective intragranulomatous Mtb control is associated with the close spatial proximity between CD8+ T cells and macrophages, a feature less abundant in uncontrolled pulmonary TB; ii) IDO1 induction blocks CD8+ T cell infiltration and reduces T cell activation and proliferation; and iii) therapeutic strategies, including D-1MT, that improve intragranulomatous killing hold strong translational potential.

BACKGROUND: Aerosol exposure of non-human primates (NHPs) to Mycobacterium tuberculosis (Mtb) typically results in discrete sites of inflammation of the lung that is detectable by 2-deoxy-2-[fluorine-18]fluoro-D-glucose (18 F-FDG)-based PET/CT scans. Such scans are often analyzed using software such as Invicro VivoQuant or OsiriX as 3D images by manual labeling sites of PET signal using 2D slices and by reporting maximal standardized uptake value (SUV max) either of the whole lung or of individual lesions.

METHODS: Here we propose a pipeline for analysis of the same PET/CT scans using Imaris, a proprietary software typically used for analysis of fluorescent microscopy data.

RESULTS: We show that by using locations of spine vertebra (denoted as "landmarks") we can align serials scans of the same animal, and by using automated (with some manual corrections) image segmentation of PET scans in 3D as "surfaces", we can accurately define location of all sites of inflammation in the lung and lung-associated thoracic lymph nodes (LNs). We show that there is an excellent correlation between individual lesion's SUVmax determined by VivoQuant and maximum intensity determined by Imaris suggesting utility of this approach. Imaris also provides wealth of additional information for each of the identified lesions such as volume, location, shape, surface area, and others, and each lesion can be exported in Virtual Reality file format (.wrl).

CONCLUSION: Our novel methodology allows for detailed and rigorous analyses of how features of PET-defined lesions in Mtb-exposed monkeys evolve over time and correlate with the outcome of infection and/or treatment.

TB (Tuberculosis) and HIV co-infection remains a major global health challenge, with limited understanding of how these pathogens impact local immune responses in the lungs. This study is the first to investigate the modulation of IL-21 during LTBI and Mycobacterium tuberculosis (Mtb)/ Simian Immunodeficiency Virus (SIV) co-infection in non-human primates (NHP). We show that IL-21 expression, predominantly derived from CD4⁺ T cells, is significantly reduced in lungs of Mtb/SIV co-infected macaques, especially in the absence of cART. Although cART and cART with 3HP partially restore IL-21-producing CD4⁺ T cells, levels remain below those in LTBI, indicating ongoing immune impairment. Spatial transcriptomic analysis suggests localized alterations in immune signaling, including differences in STAT1- and STAT3-associated transcriptional profiles and reduced Mtb-specific IFN-γ responses in co-infected animals. Together, our findings indicate that IL-21-producing CD4⁺ T cells are selectively and persistently impaired in the lungs during Mtb/SIV co-infection despite antimicrobial and antiviral therapy. These results highlight a compartment-specific deficit in immune reconstitution and suggest that IL-21-associated pathways may warrant further investigation as potential targets for host-directed therapeutic strategies.

Most HIV-negative individuals exposed to Mycobacterium tuberculosis (Mtb) control infection as latent TB infection (LTBI), but HIV co-infection greatly increases progression to tuberculosis (TB), the leading cause of death in people living with HIV (PLHIV). Although combination antiretroviral therapy (cART) reduces LTBI reactivation, immune control of Mtb is not fully restored, as shown by persistent TB incidence in PLHIV on cART. In macaques, skewed pulmonary effector memory CD4⁺ T-cell (TEM) responses and new TB lesions persist despite cART. We hypothesize that concurrent anti-TB therapy with cART would improve bacterial control and immune restoration compared to cART alone. Using rhesus macaques (RM) with LTBI and Simian Immunodeficiency Virus (SIV) co-infection, we tested three months of weekly isoniazid and rifapentine (3HP) plus daily cART. Concurrent cART+3HP improves clinical and microbiological outcomes but fails to fully restore lung CD4⁺ T-cell immunity. Treated RMs retain caseous granulomas with high FDG uptake and incomplete CD4⁺ T-cell reconstitution, marked by persistent activation, exhaustion, and inflammation. CD4⁺ TEM cells remain depleted. Concurrent therapy induces Type I IFN signatures and enhances Mtb-specific TH1/TH17-but reduces TNFα-responses. These findings reveal persistent pulmonary immune defects underlying TB risk in HIV co-infection and identify potential targets for host-directed adjunctive therapies.

To radically diminish TB incidence and mortality by 2035, as set out by the WHO End TB Strategy, there is a desperate need for improved TB therapies and a more effective vaccine against the deadly pathogen Mycobacterium tuberculosis (Mtb). Aerosol vaccination with the MtbΔsigH mutant protects two different species of NHPs against lethal TB challenge by invoking vastly superior T and B cell responses in the lungs through superior antigen-presentation and interferon-conditioning. Since the Geneva consensus on essential steps towards the development of live mycobacterial vaccines recommends that live TB vaccines must incorporate at least two independent gene knock outs, we have now generated several rationally designed, double (DKO)- and triple (TKO) knock-out mutants in Mtb, each containing the ΔsigH deletion. Here, we report preclinical studies in the rhesus macaque model of aerosol infection and SIV/HIV co-infection, aimed at assessing the safety of these MtbΔsigH - based DKOs and TKOs. We found that most of these mutant strains are attenuated in both immunocompetent and SIV-co-infected macaques and combinatorial infection with these generated strong cellular immune responses in the lung, akin to MtbΔsigH. Aerosol infection with these KO strains elicited inducible Bronchus Associated Lymphoid Tissue (iBALT), which is a correlate of protection from TB.

Clinically relevant pediatric animal models are required to advance research and therapies for Mycobacterium tuberculosis (Mtb) infections in children. Utilizing infant rhesus macaques exposed to controlled doses of aerosolized Mtb CDC1551, we systematically monitored physical changes and assessed signs of tuberculosis, including physical examinations, clinical blood chemistry, radiography, and histopathology. Our results demonstrated that infant macaques exposed a physiologically relevant, low dose of aerosolized Mtb CDC1551 and exhibited immune control of infection similar to that observed in human infants, while those exposed to a higher dose experienced widespread dissemination, rapid disease progression, and mortality within six weeks after Mtb exposure. These findings suggest that pediatric rhesus macaques exposed to a low dose of Mtb via the aerosol route could serve as a translational model for natural Mtb infection in children, thereby allowing for the recapitulation of the immunopathogenesis and treatment of pediatric tuberculosis in a clinical setting.

Interferon-gamma release assays (IGRAs) that evaluate an individual's T-cell activation response to Mycobacterium tuberculosis (M.tb)-specific peptides serve an important role in diagnosing tuberculosis (TB). However, there are substantial challenges to the use of IGRAs in resource-limited settings. Further, IGRA diagnostic performance can also be compromised in anergic individuals. Here we describe a microfluidic chip-based antigen-specific T-cell response assay (ASTRA) that automates the detection of M.tb-specific T-cell activation responses to facilitate screening for latent M.tb infection and TB. We observe that ASTRA demonstrates high specificity for M.tb infection in independent patient cohorts. Compared with IGRA, ASTRA shows greater diagnostic sensitivity in individuals with HIV-1 co-infections (93.8% versus 67%), comparable diagnostic sensitivity in HIV-negative individuals (92.8%) and faster detection (4 h versus 24-48 h). We also find that a self-powered ASTRA chip that analysed microsample ( 25 μl) whole-blood samples produced comparable results. ASTRA holds the potential to facilitate efforts to control the global TB epidemic and serve as a versatile platform for analysing T-cell responses across various infectious diseases and immunotherapeutic interventions.

The need for novel vaccination strategies to control tuberculosis (TB) is underscored by the limited and variable efficacy of the currently licensed vaccine, Bacille Calmette-Guerin (BCG). SigH is critical for Mycobacterium tuberculosis (Mtb) to mitigate oxidative stress, and in its absence Mtb is unable to scavenge host oxidative/nitrosative bursts. The MtbΔsigH (ΔsigH) isogenic mutant induces signatures of the innate immunity in macrophages and protects rhesus macaques from a lethal Mtb challenge. To understand the immune mechanisms of protection via mucosal vaccination with ΔsigH, we employed the resistant cynomolgus macaque model; and our results show that ΔsigH vaccination significantly protects against lethal Mtb challenge in this species. ΔsigH-vaccinated macaques are devoid of granulomas and instead generate inducible bronchus associated lymphoid structures, and robust antigen-specific CD4+ and CD8+ T cell responses, driven by a hyper-immune, trained immunity-like phenotype in host macrophages with enhanced antigen presentation. Correlates of protection in ΔsigH-vaccinated macaques include gene signatures of T cell activation, IFNG production, including IFN-responsive, activated T cells, concomitant with IFNG production, and suppression of IDO+ Type I IFN-responsive macrophage recruitment. Thus, ΔsigH is a promising lead candidate for further development as an antitubercular vaccine.

The majority of Human Immunodeficiency Virus (HIV) negative individuals exposed to Mycobacterium tuberculosis (Mtb) control the bacillary infection as latent TB infection (LTBI). Co-infection with HIV, however, drastically increases the risk to progression to tuberculosis (TB) disease. TB is therefore the leading cause of death in people living with HIV (PLWH) globally. Combinatorial antiretroviral therapy (cART) is the cornerstone of HIV care in humans and reduces the risk of reactivation of LTBI. However, the immune control of Mtb infection is not fully restored by cART as indicated by higher incidence of TB in PLWH despite cART. In the macaque model of co-infection, skewed pulmonary CD4+ TEM responses persist, and new TB lesions form despite cART treatment. We hypothesized that regimens that concurrently administer anti-TB therapy and cART would significantly reduce TB in co-infected macaques than cART alone, resulting in superior bacterial control, mitigation of persistent inflammation and lasting protective immunity. We studied components of TB immunity that remain impaired after cART in the lung compartment, versus those that are restored by concurrent 3 months of once weekly isoniazid and rifapentine (3HP) and cART in the rhesus macaque (RM) model of LTBI and Simian Immunodeficiency Virus (SIV) co-infection. Concurrent administration of cART + 3HP did improve clinical and microbiological attributes of Mtb/SIV co-infection compared to cART-naïve or -untreated RMs. While RMs in the cART + 3HP group exhibited significantly lower granuloma volumes after treatment, they, however, continued to harbor caseous granulomas with increased FDG uptake. cART only partially restores the constitution of CD4 + T cells to the lung compartment in co-infected macaques. Concurrent therapy did not further enhance the frequency of reconstituted CD4+ T cells in BAL and lung of Mtb/SIV co-infected RMs compared to cART, and treated animals continued to display incomplete reconstitution to the lung. Furthermore, the reconstituted CD4+ T cells in BAL and lung of cART + 3HP treated RMs exhibited an increased frequencies of activated, exhausted and inflamed phenotype compared to LTBI RMs. cART + 3HP failed to restore the effector memory CD4+ T cell population that was significantly reduced in pulmonary compartment post SIV co-infection. Concurrent therapy was associated with the induction of Type I IFN transcriptional signatures and led to increased Mtb-specific TH1/TH17 responses correlated with protection, but decreased Mtb-specific TNFa responses, which could have a detrimental impact on long term protection. Our results suggest the mechanisms by which Mtb/HIV co-infected individuals remain at risk for progression due to subsequent infections or reactivation due of persisting defects in pulmonary T cell responses. By identifying lung-specific immune components in this model, it is possible to pinpoint the pathways that can be targeted for host-directed adjunctive therapies for TB/HIV co-infection.