Rhodococcus equi virulence-associated protein A (VapA) (VapA)

Rhodococcus equi is a Gram-positive, facultative intracellular bacterium that is a major cause of severe pyogranulomatous pneumonia in foals and an opportunistic pathogen in immunocompromised humans [1]. The primary virulence factor and most significant antigen is the Virulence-associated protein A (VapA), a surface-expressed lipoprotein encoded on a highly conserved virulence plasmid [2]. VapA is essential for the bacterium's ability to survive and replicate within host macrophages by preventing the acidification of the phagosome and subsequent phagosome-lysosome fusion [3]. Because of its critical role in pathogenesis, VapA is the primary target for diagnostic assays, monoclonal antibody therapies, and vaccine development efforts [4]. Current therapeutic strategies include the use of hyperimmune plasma containing anti-VapA antibodies for prophylaxis in foals and the investigation of VapA-based subunit or DNA vaccines to induce protective Th1-type immune responses [5]. Sources: [1] Yamshchikov, A. V., et al. (2010). Clinical Infectious Diseases. [2] von Bargen, K., & Haas, A. (2009). Molecular Microbiology. [3] Benoit, S. C., et al. (2002). Microbiology. [4] Giguère, S., et al. (2011). Veterinary Microbiology. [5] Khan, M. A., et al. (2021). Vaccines.

Other names

Virulence-associated protein A15-17 kDa antigenpVAPA-encoded proteinRhodococcus equi antigens

Antibodies within hyperimmune plasma bind to surface antigens like VapA to opsonize the bacteria and neutralize their ability to inhibit phagosome-lysosome fusion, while vaccines prime the T-cell mediated immune response for intracellular clearance.