Mycobacterium tuberculosis antigen 85A (Ag85A)

Mycobacterium tuberculosis antigen 85A (Ag85A) is a major secreted protein of the Ag85 complex, which also includes Ag85B and Ag85C. It functions as a mycolyltransferase essential for the synthesis of trehalose dimycolate (TDM), also known as cord factor, which is a vital component of the mycobacterial cell wall and a key virulence factor helping the bacterium maintain structural integrity [1, 4, 15]. Beyond its role in the cell wall, Ag85A possesses diacylglycerol acyltransferase activity involved in the formation of lipid storage bodies that facilitate bacterial survival during dormancy and persistent infection [6, 10, 19]. Due to its high immunogenicity, Ag85A is a primary target for new-generation tuberculosis vaccines, such as the recombinant viral vector MVA85A, which was designed to boost BCG-induced immunity [7, 11, 14]. It is also being explored as a therapeutic target for small-molecule inhibitors and repurposed drugs intended to disrupt mycolic acid metabolism, particularly against multidrug-resistant (MDR) and extensively drug-resistant (XDR) tuberculosis strains [15, 16]. Understanding the dual enzymatic and immunological properties of Ag85A is central to developing more effective countermeasures against the global tuberculosis epidemic [3, 13].

Other names

fbpASecreted antigen 85AMycolyltransferase Ag85AFibronectin-binding protein AAntigen 85 complex A

Ag85A serves as an immunogen in vaccine formulations to elicit protective T-cell immunity and as an enzymatic target for small-molecule inhibitors that block its mycolyltransferase activity, leading to the disruption of cell wall integrity and trehalose dimycolate (TDM) synthesis.