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 speci... More
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.
