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

Abstract

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.

Keywords: BCG vaccine; DNA vaccine; Immunogenicity; Protein vaccine; Tuberculosis.