Antigen-Pulsed Dendritic Cell-Derived Dexosomes Induce a Robust Th1-Biased Antigen-Specific Humoral and Cellular Immunity in Mice against Latent Mycobacterium tuberculosis Antigen Rv2626c

Abstract

Tuberculosis (TB) continues to be a leading health crisis globally, with latent tuberculosis infection (LTBI) affecting approximately 1.7 billion people worldwide. The current BCG vaccine does not provide consistent protection against pulmonary TB in adults, underscoring the need for innovative vaccine strategies that target both active and latent Mycobacterium tuberculosis (Mtb) infections. In this study, we introduced a vaccine engineering approach to enhance the immunogenicity of candidate vaccine antigens by utilizing exosomes derived from antigen-pulsed dendritic cells (dexosomes). We focused on a representative latency-associated Mtb protein, Rv2626c, which immunoinformatics studies predicted to contain epitopes capable of eliciting a cell-mediated response biased toward Th1 cells. Rv2626c was cloned, purified, and the recombinant form (rRv2626c) was used to generate antigen-pulsed dexosomes. Rv2626c-pulsed dexosomes were successfully isolated, characterized, and evaluated for their immunomodulatory properties. In vitro studies demonstrated that dendritic cells treated with Rv2626c-pulsed dexosomes exhibited enhanced antigen uptake, improved antigen presentation, and increased expression of costimulatory signals. When immunized with Rv2626c-pulsed dexosomes, mice displayed robust antigen-specific CD8⁺ and CD4⁺ T-cell responses, marked by elevated production of IL-2 and IFN-γ compared to those receiving Rv2626c alone. Additionally, significant antigen-specific antibody responses were observed, with increased IgG2a/IgG1 and IgG2b/IgG1 ratios, indicating a Th1-biased immune response. The sustained antibody response suggests potential for long-lasting protection against latent Mtb bacilli. These findings represent an initial report on the use of dexosomes pulsed with a latency-associated antigen to elicit potent antigen-specific immunological responses. By enhancing both cellular and humoral immune responses, Rv2626c-pulsed dexosomes present a promising platform for the development of next-generation efficacious TB vaccines aimed at targeting LTBI and preventing the reactivation of latent Mtb infections. This research paves the way for further exploration of exosome-based delivery systems as immunomodulatory vehicles for TB vaccine development.