Streptococcus pneumoniae CPS

Streptococcus pneumoniae CPS (Capsular Polysaccharide) is a complex carbohydrate layer surrounding the cell wall of Streptococcus pneumoniae, a major cause of pneumonia, meningitis, and otitis media. The CPS is a key virulence factor: it protects the bacterium from phagocytosis by host immune cells (e.g., macrophages) by masking bacterial surface antigens that would otherwise trigger immune recognition. This protection allows Streptococcus pneumoniae to colonize the upper respiratory tract and spread to other tissues (e.g., lungs, brain). There are over 90 distinct serotypes of Streptococcus pneumoniae, each defined by unique CPS structures. The CPS is also highly immunogenic, and antibodies against a specific CPS serotype provide protective immunity against that serotype. This property forms the basis of pneumococcal vaccines, which contain purified CPS from the most common pathogenic serotypes. Vaccination induces the production of anti-CPS antibodies, enabling the immune system to recognize and clear Streptococcus pneumoniae before infection progresses. The CPS also serves as a target for diagnostic tests (e.g., latex agglutination assays) to identify Streptococcus pneumoniae serotypes in clinical samples.