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Novel tuberculosis (TB)-vaccines preferably should (i) boost host immune responses induced by previous BCG vaccination and (ii) be directed against Mycobacterium tuberculosis (Mtb) proteins expressed throughout the Mtb infection-cycle. Human Mtb antigen-discovery screens identified antigens encoded by Mtb-genes highly expressed during in vivo murine infection (IVE-TB antigens). To translate these findings towards animal models, we determined which IVE-TB-antigens are recognised by T-cells following Mtb challenge or BCG vaccination in three different mouse strains. Eleven Mtb-antigens were recognised across TB-resistant and susceptible mice. Confirming previous human data, several Mtb-antigens induced cytokines other than IFN-γ. Pulmonary cells from susceptible C3HeB/FeJ mice produced less TNF-α, agreeing with the TB-susceptibility phenotype. In addition, responses to several antigens were induced by BCG in C3HeB/FeJ mice, offering potential for boosting. Thus, recognition of promising Mtb-antigens identified in humans validates across multiple mouse TB-infection models with widely differing TB-susceptibilities. This offers translational tools to evaluate IVE-TB-antigens as diagnostic and vaccine antigens. [ABSTRACT FROM AUTHOR]

The only tuberculosis vaccine currently available, bacille Calmette-Guérin (BCG) is a poor inducer of CD8+ T cells, which are particularly important for the control of latent tuberculosis and protection against reactivation. As the induction of strong CD8+ T cell responses is a hallmark of DNA vaccines, a combination of BCG with plasmid DNA encoding a prototype TB antigen (Ag85A) was tested. As an alternative animal model, pigs were primed with BCG mixed with empty vector or codon-optimized pAg85A by the intradermal route and boosted with plasmid delivered by intramuscular electroporation. Control pigs received unformulated BCG. The BCG-pAg85A combination stimulated robust and sustained Ag85A specific antibody, lymphoproliferative, IL-6, IL-10 and IFN-γ responses. IgG1/IgG2 antibody isotype ratio reflected the Th1 helper type biased response. T lymphocyte responses against purified protein derivative of tuberculin (PPD) were induced in all (BCG) vaccinated animals, but responses were much stronger in BCG-pAg85A vaccinated pigs. Finally, Ag85A-specific IFN-γ producing CD8+ T cells were detected by intracellular cytokine staining and a synthetic peptide, spanning Ag85A131-150 and encompassing two regions with strong predicted SLA-1*0401/SLA-1*0801 binding affinity, was promiscuously recognized by 6/6 animals vaccinated with the BCG-pAg85A combination. Our study provides a proof of concept in a large mammalian species, for a new Th1 and CD8+ targeting tuberculosis vaccine, based on BCG-plasmid DNA co-administration. [ABSTRACT FROM AUTHOR]

Abstract: DNA vaccination is a potent means for inducing strong CD4+ (Th1) and particularly CD8+ mediated immune responses and protective immunity against tuberculosis infection in mice. Here we have analyzed the potential of a DNA vaccine encoding the immunodominant mycolyl-transferase Ag85A for increasing the efficacy of the current tuberculosis vaccine Mycobacterium bovis Bacille Calmette-Guérin (BCG) in three long-term survival experiments. BALB/c mice were vaccinated with BCG either following DNA priming or prior to DNA boosting. Ag85A specific CD4+ and CD8+ mediated IFN-γ responses were increased in mice primed with DNA prior to BCG, and in BCG vaccinated mice subsequently boosted with DNA. In the latter immunization protocol, antigenic stimulation also induced significant levels of IL-17. Mice were monitored for cachexia and survival following a low dose intravenous challenge with M. tuberculosis H37Rv. Priming with Ag85A but not control DNA increased significantly the protective efficacy of the BCG vaccine as indicated by reduced cachexia and prolonged survival time: 32 weeks versus 23 weeks in one experiment and 33 weeks versus 26 weeks in another experiment (MST in control, TB infected mice: 17 weeks in both experiments). On the other hand, boosting of BCG by subsequent Ag85A DNA in saline or vaxfectin™ – or recombinant 85A protein or MVA-85A for that matter – did not augment the efficacy of BCG (MST 19–21 weeks in all vaccinated groups versus 11 weeks in control, TB infected mice). Our results demonstrate that Ag85A DNA priming can increase efficacy of BCG and that boosting protocols of BCG may possibly be hampered by the induction of ThIL-17 cells. [Copyright &y& Elsevier]