Mycobacterium tuberculosis antigen containing-exosomes reinforce BCG vaccine efficacy by augmenting long term protection and memory response against experimental tuberculosis in BALB-C mice.

Tuberculosis (TB), caused by Mycobacterium tuberculosis (M.tb.) , inflicts one third of the humanity. Despite the availability of effective drug regimens, complete eradication of M.tb. remains challenging due to prolong treatment duration. Additionally, MDR-TB and co-infection HIV further exacerbate disease severity. The Bacille Calmette–Guérin (BCG) has shown inconsistent efficacy due to absence of Th-1-antigens. Hence, there is a critical need for either a novel vaccine candidate or an efficient booster to enhance BCG’s prophylactic efficacy.In this study, in-house prepared M.tb. -infected alveolar macrophage-derived exosomes (Rv-Exo) and ESAT-6-containing exosomes (ESAT-6 Exo) were characterized based on size, purity, and pathogen-associated molecular patterns (PAMPs) and their epitope mapping was also performed. These M.tb. protein-containing exosomes (MPE) were utilized for immunization, either alone or as a booster to BCG, and evaluated in BALB/c mice against experimental M.tb. challenge.Our results demonstrate the ESAT-6 Exo and Rv-Exo, either alone or as a BCG booster, enhanced Th1-biased immune responses by activating CD4⁺ and CD8⁺ T cells, increasing memory T-cell populations, and significantly reducing the M.tb. burden in the lungs, spleen, and lymph nodes of infected mice. There finding highlights the potential of MPE as a promising strategy against TB specially in BCG vaccinated population.