Comparative immunogenicity study of two different types of tuberculosis vaccines based on a heterologous boosting strategy

BCG, one of the oldest vaccines in clinical use, has demonstrated well-documented safety, quality, and efficacy in preventing severe forms of tuberculosis (TB) in neonates. However, its protective efficacy declines significantly in adulthood, failing to prevent pulmonary the TB —a major driver of global TB transmission. To address this limitation, this study systematically evaluated two novel BCG-boosting strategies: a recombinant subunit protein vaccine targeting the Rv2074 antigen and a DNA vaccine encoding the same antigen, both evaluated in murine immunization. Antigen-specific cytokine levels in splenocyte supernatants and serum antibody titers were quantified by ELISA after euthanizing mice at 8 weeks (8w) and 16 weeks (16w) post-immunization. The results indicated that both vaccine types induced robust Th1-type immune responses in mice. Additionally, antigen-specific T cell cytokine secretion was analyzed using flow cytometry combined with intracellular cytokine staining. Experimental data revealed that the BCG + P group exhibited a significant increase in CD4⁺ T cells, while the BCG + D group showed a higher proportion of CD8⁺ T cells.Long-term immune effects surpassing short-term outcomes in both groups. These findings suggest that both vaccine types show promise as BCG-based booster vaccines.