Early secretory antigenic target protein 6 (ESAT-6)

Early secretory antigenic target protein 6 (ESAT-6, EsxA) is a 6 kDa secretory protein encoded by the RD1 region of Mycobacterium tuberculosis, absent in BCG vaccine strains but present in virulent M. tuberculosis and M. bovis. ESAT-6 is a potent T-cell antigen, forming heterodimers with CFP-10 and secreted via the ESX-1/type VII secretion system. It drives host immune responses, participates in inflammation and lung pathology, functions as a dominant diagnostic antigen distinguishing TB infection from BCG exposure, and is under investigation as a vaccine candidate due to its role in both Th1 and Th17 immune activation. In pulmonary tissues, ESAT-6 induces pro-inflammatory cytokines/chemokines (e.g., IL-8), modulates apoptosis/necrosis, and contributes to granuloma formation and tissue damage, thereby amplifying chronic inflammation and pathogen virulence. The immune response to ESAT-6 is a key marker for TB diagnosis and helps differentiate active from latent disease states

Other names

Early secreted antigenic target 6 kDaESAT-6EsxA (gene name: RV3875)

Not a therapeutic target for direct drug binding; for diagnostics and vaccines, ESAT-6 acts as the antigen to trigger T-cell immune responses and antibody production