Pneumococcal surface antigen (Psa)

Pneumococcal surface antigens are a group of highly conserved proteins, including Pneumococcal surface antigen A (PsaA), Pneumococcal surface protein A (PspA), and Pneumococcal surface protein C (PspC), expressed on the surface of Streptococcus pneumoniae (UniProt P0A4G2). These proteins are critical for the pathogen's survival and virulence; for instance, PsaA is an essential component of the manganese transport system required for resistance to oxidative stress, while PspA and PspC facilitate immune evasion by inhibiting complement deposition and binding to host factors (PubMed: 10858233, PubMed: 11553240). Because these antigens are present across nearly all pneumococcal serotypes, they are being extensively researched as targets for next-generation vaccines to overcome the limitations of current polysaccharide-based vaccines, which only cover a subset of serotypes (PubMed: 25644337). Therapeutic strategies involve using these proteins as vaccine antigens to elicit protective antibodies that promote opsonophagocytosis or block bacterial adherence to the respiratory mucosa. Targeting these surface antigens aims to provide broad protection against both mucosal infections like otitis media and invasive diseases such as pneumonia and meningitis.

Other names

Pneumococcal surface proteinPsaAPspAPspCCbpACholine-binding protein

Induction of opsonophagocytic antibodies and T-cell mediated immunity to prevent bacterial colonization and invasive disease.