Streptococcus pneumoniae capsular and surface antigens (S. pneumoniae antigens)

Streptococcus pneumoniae capsular and surface antigens are the primary molecular structures used by the pneumococcus bacterium to establish infection and evade host defenses. The capsular polysaccharide (CPS) is the most critical virulence factor, forming a thick outer layer that prevents recognition and ingestion by host phagocytes (Source: NIH, StatPearls). In addition to the capsule, various surface proteins such as Pneumococcal surface protein A (PspA) and C (PspC) facilitate bacterial attachment to the respiratory epithelium and inhibit the host's complement system (Source: PubMed). These antigens are the fundamental components of modern vaccines, which utilize either purified polysaccharides or polysaccharides conjugated to carrier proteins to stimulate a protective immune response (Source: CDC). By inducing the production of specific antibodies, these vaccines enable the immune system to identify and destroy the bacteria, thereby preventing invasive diseases like pneumonia, meningitis, and sepsis (Source: WHO). However, the existence of over 100 distinct serotypes necessitates ongoing surveillance, as the use of vaccines can lead to serotype replacement, where non-targeted strains become more prevalent in the population (Source: Nature Reviews Microbiology).

Other names

Pneumococcal antigensCapsular polysaccharidesCPSPneumococcal surface proteinsPspAPspCPhtDPneumococcal histidine triad protein D

Induction of active immunity through the production of serotype-specific antibodies that facilitate opsonophagocytosis and bacterial clearance.