The ΔfbpA attenuated candidate vaccine from Mycobacterium tuberculosis, H37Rv primes for a stronger T-bet dependent Th1 immunity in mice

Abstract

Summary The ΔfbpA candidate vaccine derived from Mycobacterium tuberculosis (H37Rv) protects mice better than BCG against tuberculosis, and we investigated the hypothesis that ΔfbpA may induce a stronger Th1 immunity. Since T-bet transcription factor regulates Th1 immunity, mice infected with ΔfbpA, BCG vaccine and related mycobacteria were analyzed for T-bet positive T cells. Mouse dendritic cells (DCs) or macrophages were also pulsed with excretory-secreted antigens (ES; Antigen-85B, ESAT-6 and CFP10) and cocultured with T cells from immunized or naïve mice and tested for in vitro induction of T-bet and IFN-γ. In both models, ΔfbpA mutant induced a stronger response of T-bet+CD4 T cells, which correlated with an increased expansion of IFN-γ+CD4 T cells in vivo and in vitro. When DCs pulsed with ES antigens were allowed to stimulate T cells, ESAT-6 and CFP-10 failed to induce a recall expansion of T-bet+IFN-γ+CD4 T cells from BCG vaccinated mice. Thus, deletion of RD1 in BCG seems to reduce its ability to induce T-bet and induce stronger Th1 immunity. Finally, mice were vaccinated with ΔfbpA and BCG and challenged with virulent Mtb for evaluation of protection and T cell expansion. ΔfbpA vaccinated mice showed a rapid and stronger expansion of CD4+CXCR3+ IFN-γ+ T cells in the lungs of Mtb challenged mice, compared to those which had BCG vaccine. ΔfbpA immunized mice also showed a better decline of the Mtb bacterial counts of the lungs. Mtb derived ΔfbpA candidate vaccine therefore induces qualitatively better T-bet dependent Th1 immunity than BCG vaccine.

Immunoevasion and immunosuppression of the macrophage by Mycobacterium tuberculosis

“…Given the major role, it plays in eliciting protective adaptive immunity , autophagy induction is being examined as a novel strategy to enhance the efficacy of TB vaccines currently under development. In mice immunized with DCs infected with vaccine candidate Δ fbpA attenuated Mtb and treated with rapamycin, T‐helper cell‐mediated protection was induced in response to virulent Mtb . The same study showed that enhanced immunogenicity of BCG overexpressing Ag85B is associated with increased macrophage autophagy.…”

An autophagy-inducing and TLR-2 activating BCG vaccine induces a robust protection against tuberculosis in mice

“…T cells from spleens were also stained for multifunctional cytokines after they were re-stimulated with a soluble protein antigen from Mtb Erdman as described before. 124 Purified protein antigens used for recall immune responses (ESAT-6, CFP-10, antigen-85B were from BEI (NIH). IFN-γ assays were performed by stimulating splenocytes using specific protein antigens added at 1 µg/mL and 18 h supernatants assayed for IFN-γ using sandwich ELISA.…”

Live Attenuated Vaccines against Tuberculosis: Targeting the Disruption of Genes Encoding the Secretory Proteins of Mycobacteria

“…Similar to BCG vaccine manipulations, using the Mtb platform to derive vaccines deleting secretory products appears encouraging. The ∆secA-∆lysA and ∆fbpA-sapM and mutants were more effective than BCG [116,152,183] and are potential booster vaccines for BCG-vaccinated infants. Among these, the ∆secA-lysA strain has an excellent safety profile in mice [183] compared to ∆fbpA-sapM, qualifying it for clinical trials.…”

“…To our knowledge, this is the first study demonstrating that an Mtb mutant lacking a secretory protein antigen is effective as a vaccine against TB. The ∆fbpA candidate vaccine induced high levels of phagosome maturation, proinflammatory cytokines, and Th1 immune response and an increased expansion of CD4+ CXCR3+ IFN-γ+ cells in mice after vaccination [116]. Although recombinant mycobacterial strains over-expressing Ag85B (FbpB) and Ag85C (FbpC) also protect mice against TB [106,117], thus far, Mtb mutants 'lacking' these proteins have not been tested for vaccine efficacy.…”