Early secretory antigenic target 6 kDa protein (ESAT-6)

Early secretory antigenic target 6 kDa protein (ESAT-6) is a small secreted protein produced by *Mycobacterium tuberculosis* and related pathogenic mycobacteria[1][2][10]. Encoded by the esxA (Rv3875) gene, ESAT-6 is critical for mycobacterial virulence and is absent in non-virulent BCG vaccine strains[7]. ESAT-6 is secreted through the ESX-1 (type VII) secretion system, acts as a potent antigen stimulating T-cell responses, and is widely used in the immunodiagnosis of tuberculosis infection[1][2][7]. ESAT-6 forms a complex with CFP-10 (culture filtrate protein 10), and together they modulate host immune responses, promote host cell death, induce IL-8 and IL-6 expression in lung epithelial cells, and contribute to granuloma formation and lung pathogenesis in tuberculosis[1][2][5][7][9]. Direct therapeutics targeting ESAT-6 are lacking; instead, it is exploited as a biomarker and antigen in TB vaccines and diagnostic tests[2][7].

Other names

esxAESAT6Esat-6esaT6Rv3875

When used as an antigen (e.g., in diagnostics or vaccines such as QuantiFERON-TB Gold), induces T-cell mediated immune response