Mycobacterium tuberculosis antigen Rv1196 (PPE18)

Mycobacterium tuberculosis antigen Rv1196, also known as PPE family protein PPE18 or Mtb39A, is a 39-kDa cell wall-associated protein belonging to the PPE (Proline-Proline-Glutamic acid) family of the M. tuberculosis complex. It plays a critical role in the pathogen's interaction with the host immune system, notably by binding to Toll-like receptor 2 (TLR2) on macrophages. This interaction triggers an anti-inflammatory response through the induction of interleukin-10 (IL-10) and inhibits MHC class II-mediated antigen presentation, thereby aiding in immune evasion and the establishment of latent infection. Despite its role in suppressing host defenses during natural infection, Rv1196 is highly immunogenic and serves as a major component of the M72/AS01E tuberculosis vaccine candidate, where it is fused with the Rv0125 (Mtb32A) antigen. In the context of vaccination with the AS01E adjuvant, it is designed to elicit a robust Th1-type immune response, characterized by the activation of polyfunctional CD4+ T cells that produce protective cytokines like interferon-gamma and tumor necrosis factor-alpha. Although essential for mycobacterial virulence, its strategic use in vaccines aims to prevent the progression from latent infection to active pulmonary tuberculosis, though its efficacy may be challenged by significant genetic variability across clinical isolates.

Other names

Mtb39APPE family protein PPE18mtb39a

Induction of a Th1-skewed cell-mediated immune response characterized by the proliferation of polyfunctional CD4+ T cells and the production of antigen-specific IgG antibodies.