Th17-related cytokines contribute to recall-like expansion/effector function of HMBPP-specific Vγ2Vδ2 T cells after Mycobacterium tuberculosis infection or vaccination: Immunity to infection

Whether cytokines can influence the adaptive immune response by antigen-specific γδ T cells during infections or vaccinations remains unknown. We previously demonstrated that, during BCG/Mycobacterium tuberculosis (Mtb) infections, Th17-related cytokines markedly upregulated when phosphoantigen-specific VγVδ2 T cells expanded. In this study, we examined the involvement of Th17-related cytokines in the recall-like responses of Vγ2Vδ2 T cells following Mtb infection or vaccination against TB. Treatment with IL-17A/IL-17F or IL-22 expanded phosphoantigen 4-hydroxy-3-methyl-but-enyl pyrophosphate (HMBPP)-stimulated Vγ2Vδ2 T cells from BCG-vaccinated macaques but not from naïve animals, and IL-23 induced greater expansion than the other Th17-related cytokines. Consistently, Mtb infection of macaques also enhanced the ability of IL-17/IL-22 or IL-23 to expand HMBPP-stimulated Vγ2Vδ2 T cells. When evaluating IL-23 signaling as a prototype, we found that HMBPP/IL-23-expanded Vγ2Vδ2 T cells from macaques infected with Mtb or vaccinated with BCG or Listeria ΔactA prfA*-ESAT6/Ag85B produced IL-17, IL-22, IL-2, and IFN-γ. Interestingly, HMBPP/IL-23-induced production of IFN-γ in turn facilitated IL-23-induced expansion of HMBPP-activated Vγ2Vδ2 T cells. Furthermore, HMBPP/IL-23-induced proliferation of Vγ2Vδ2 T cells appeared to require APC contact and involve the conventional and novel protein kinase C signaling pathways. These findings suggest that Th17-related cytokines can contribute to recall-like expansion and effector function of Ag-specific γδ T cells after infection or vaccination

Role of Isoprenoid Biosynthesis in Listeria-based Tuberculosis Vaccine Efficacy

Tuberculosis is a leading infectious cause of death worldwide. Antibiotics are increasingly ineffective in treatment, and the only approved vaccine shows minimal protection against disease in children and no protection against disease in adults. Thus, improved treatment and vaccination strategies are needed. Using the gastrointestinal pathogen, Listeria monocytogenes, we deliver immunogenic proteins to the cytoplasm of antigen presenting cells, producing strong antigen-specific Helper and Killer T cell responses. The current studies focus on the examination of the T cell responses generated by respiratory administration of this Listeria-based Tuberculosis Vaccine, and the potential protective effect it generates against primary progressive Tuberculosis infection. In the studies describe here, we examine the protective effect of respiratory administration of a Listeria-based Tuberculosis vaccine, and demonstrate that 1 intratracheal dose provides significant improvement of bacterial burden and pulmonary pathology following respiratory Mycobacterium tuberculosis challenge, while 3 doses of the same vaccine provide minimal protection against Tuberculosis-mediated pathology. Examination of the T cell responses generated by the vaccine demonstrated that CD4 and CD8 T cells specific for select Mycobacterim tuberculosis proteins accumulate in both the blood and airways following vaccination. T cells specific for isoprenoid synthesis pathway intermediates accumulate in massive numbers in the blood and airways after a single administration of the vaccine, but the number and activity of these cells declines following repeated administration of the vaccine. In addition, these isoprenoid-sensitive T cells demonstrate markers of exhaustion and apoptosis following repeated stimulation with the vaccine, suggesting that repeated high dose vaccination could be inducing activation-induced T cell exhaustion and cell death. Using molecular biology techniques, we decrease production of isoprenoids by our vaccine, decreasing the hyper-secretion of isoprenoids recovering the vaccine’s ability to protect against pulmonary Tuberculosis. Collectively, these data support the hypothesis that Listeria-based vaccines given in repeated high doses induce exhaustion and cell death of isoprenoid-sensitive T cells. As these T cells have been demonstrated to be important components of the early response to Tuberculosis and other infections this may provide a mechanism through which repeated bacterial infection or repeated BCG infection result in poorer outcomes of Tuberculosis infection

Intranasal Vaccination with the Recombinant Listeria monocytogenes ΔactA prfA* Mutant Elicits Robust Systemic and Pulmonary Cellular Responses and Secretory Mucosal IgA ▿

We previously showed that recombinant (r) Listeria monocytogenes carrying ΔactA and a selected prfA* mutation (r-Listeria ΔactA prfA*) secreted >100-fold more immunogen in broth culture than wild-type r-Listeria or r-Listeria ΔactA and elicited much greater cellular and humoral immune responses than r-Listeria ΔactA after intravenous vaccination of mice. Here, we conducted comparative studies evaluating vaccine-elicited immune responses in systemic and mucosal sites after intranasal, intravenous, intraperitoneal, or subcutaneous immunization of mice with r-Listeria ΔactA prfA* vaccine candidates. Intranasal vaccination of mice with r-Listeria ΔactA prfA* vaccine candidates elicited a robust gamma interferon-positive (IFN-γ+) cellular response in systemic sites, although intravenous or intraperitoneal immunization was more efficient. Surprisingly, intranasal vaccination elicited an appreciable pulmonary IFN-γ+ cellular response that was nonstatistically higher than the magnitude induced by the intravenous route but was significantly greater than that elicited by subcutaneous immunization. Furthermore, although intranasal r-Listeria ΔactA prfA* delivery induced poor systemic IgG responses, intranasal vaccination elicited appreciable secretory immunogen-specific IgA titers that were similar to or higher in mucosal fluid than those induced by subcutaneous and intravenous immunizations. Thus, intranasal vaccination with r-Listeria ΔactA prfA* appears to be a useful approach for eliciting robust systemic and pulmonary cellular responses and measurable secretory mucosal IgA titers