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Gene networks of protective lymphocytes after immune activation with live attenuated vaccines remain poorly characterized. Because Mycobacterium bovis bacille Calmette-Guérin (BCG) vaccine can confer protection against fatal forms of tuberculosis in humans and monkeys, we made use of macaque models to optimally study immune gene networks after BCG vaccination/infection. We first established and validated a large-scale real-time quantitation system and then used it to measure expression levels of 138 immune genes after BCG vaccination/infection of rhesus macaques. Systemic BCG vaccination induced up to 600-fold increases in expression of 78 immune genes among the 138 genes tested at the time when BCG-elicited T cell responses and immunity were apparent. These up-regulated transcripts constituted multiple gene networks that were linked to various aspects of immune function. Surprisingly, the up-regulation of most of these immune genes in the gene networks occurred at 1 week and was sustained ator = 6 weeks after BCG vaccination/infection. Although early activation of immune gene networks was an immune correlate of anti-BCG immunity, prolonged up-regulation of these networks coincided with the development of vaccine-elicited T cell responses after BCG vaccination/infection. These findings provide molecular evidence suggesting that the BCG-induced gene networks may represent global transcriptomes and proteomes underlying the development of T cell responses and, ultimately, immunity to mycobacteria.

To examine the role of T cell receptor (TCR) in γδ T cells in adaptive immunity, a macaque model was used to follow Vγ2Vδ2+T cell responses to mycobacterial infections. These phosphoantigen-specific γδ T cells displayed major expansion duringMycobacterium bovisBacille Calmette-Guérin (BCG) infection and a clear memory-type response after BCG reinfection. Primary and recall expansions of Vγ2Vδ2+T cells were also seen duringMycobacterium tuberculosisinfection of naı̈ve and BCG-vaccinated macaques, respectively. This capacity to rapidly expand coincided with a clearance of BCG bacteremia and immunity to fatal tuberculosis in BCG-vaccinated macaques. Thus, Vγ2Vδ2+T cells may contribute to adaptive immunity to mycobacterial infections.

The mechanism by which human immunodeficiency virus (HIV)-Mycobacterium tuberculosiscoinfection facilitates development of HIV-related tuberculosis is poorly characterized. Macaque models of simian immunodeficiency virus (SIVmac)-Mycobacterium bovisBCG coinfection were employed to explore the pathogenesis of AIDS virus-related tuberculosis. Following BCG coinfection, SIV (SIV)-infected macaques with high viral loads developed an SIV-related tuberculosis-like disease. This disease was characterized clinically by a syndrome of diarrhea, anorexia, weight loss, and altered levels of consciousness and pathologically by the presence of disseminated granulomas. In contrast, SIVmac-infected macaques with low viral loads either showed no evidence of BCG-induced disease or developed focal granulomatous lesions. Pathogenic SIV-BCG interactions appeared to play a critical role in triggering the development of this SIV-related tuberculosis-like disease. BCG coinfection enhanced the destruction of CD4+T cells in SIVmac-infected macaques whose viral loads were high. Reciprocally, exacerbations of SIV disease led to marked suppression of BCG-specific T-cell responses, persistence of the BCG infection, and development of an SIV-related tuberculosis-like disease. Furthermore, development of this SIV-related tuberculosis-like disease was also seen in naïve macaques simultaneously inoculated with SIVmacand BCG. These results provide in vivo evidence that coinfection of AIDS virus-infected individuals with an avirulent mycobacterium can lead to development of a tuberculosis-like disease.

SUMMARY Immune responses of lymphocyte populations during early phases of mycobacterial infection and reinfection have not been well characterized in humans. A non-human primate model of Mycobacterium bovis bacille Calmette–Guerin (BCG) infection was employed to characterize optimally the immune responses of mycobacteria-specific T cells. Primary BCG infection induced biphasic immune responses, characterized by initial lymphocytopenia and subsequent expansion of CD4+, CD8+ and γδ T cell populations in the blood, lymph nodes and the pulmonary compartment. The potency of detectable T cell immune responses appears to be influenced by the timing and route of infection as well as challenge doses of BCG organisms. Systemic BCG infection introduced by intravenous challenge induced a dose-dependent expansion of circulating CD4+, CD8+ and γδ T cells whereas, in the pulmonary compartment, the systemic infection resulted in a predominant increase in numbers of γδ T cells. In contrast, pulmonary exposure to BCG through the bronchial route induced detectable expansions of CD4+, CD8+ and γδ T cell populations in only the lung but not in the blood. A rapid recall expansion of these T cell populations was seen in the macaques reinfected intravenously and bronchially with BCG. The expanded αβ and γδ T cell populations exhibited their antigen specificity for mycobacterial peptides and non-peptide phospholigands, respectively. Finally, the major expansion of T cells was associated with a resolution of active BCG infection and reinfection. The patterns and kinetics of CD4+, CD8+ and γδ T cell immune responses during BCG infection might contribute to characterizing immune protection against tuberculosis and testing new tuberculosis vaccines in primates.

The TCR repertoire of an epitope-specific CD8+ T cell population remains poorly characterized. To determine the breadth of the TCR repertoire of a CD8+ T cell population that recognizes a dominant epitope of the AIDS virus, the CD8+ T cells recognizing the tetrameric Mamu-A*01/p11C,CM complex were isolated from simian immunodeficiency virus (SIV)-infected Mamu-A*01+ rhesus monkeys. This CD8+ T cell population exhibited selected usage of TCR Vβ families and complementarity-determining region 3 (CDR3) segments. Although the epitope-specific CD8+ T cell response was clearly polyclonal, a dominance of selected Vβ+ cell subpopulations and clones was seen in the TCR repertoire. Interestingly, some of the selected Vβ+ cell subpopulations and clones maintained their dominance in the TCR repertoire over time after infection with SIV of macaques. Other Vβ+ cell subpopulations declined over time in their relative representation and were replaced by newly evolving clones that became dominant. The present study provides molecular evidence indicating that the TCR repertoire shaped by a single viral epitope is dominated at any point in time by selected Vβ+ cell subpopulations and clones and suggests that dominant Vβ+ cell subpopulations and clones can either be stable or evolve during a chronic infection.