Antigen 85B of Mycobacterium tuberculosis: From Immunodominant Antigen to Vaccine Candidate

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), continues to pose a significant global health challenge despite the existence of effective treatments. The only licensed TB vaccine, Bacillus Calmette–Guérin (BCG), offers inconsistent and generally limited protection against adult pulmonary TB. As a result, the pursuit of more effective TB vaccines has intensified over the past two decades, prompting the evaluation of several immunodominant Mtb antigens as vaccines. Among these, antigen 85B (Ag85B) has emerged as a promising candidate due to its critical roles in mycobacterial cell wall biosynthesis, host cell adhesion, and the induction of immune responses. Ag85B has been incorporated into diverse vaccine platforms, including subunit, recombinant, DNA, and mRNA-based vaccines. Evidence from preclinical and clinical studies indicates that Ag85B-containing vaccine formulations elicit robust cellular immune responses, and in many instances, enhance protection against TB. Collectively, these findings position Ag85B as a central component in the development of next-generation TB vaccines. This review examines the biological properties and immunological significance of Ag85B and provides an overview of recent advances in Ag85B-based vaccine strategies.