Capsular polysaccharide of Streptococcus pneumoniae serotype 8 (CPS8)

The **capsular polysaccharide of Streptococcus pneumoniae serotype 8** (CPS8) is a surface-expressed, high-molecular-weight carbohydrate polymer forming a thick capsule around the bacterium. This capsule is the major virulence determinant of S. pneumoniae, essential for resistance to phagocytosis and evasion of host immune responses[2][4][6]. The serotype 8 polysaccharide structure consists of repeating units of specific sugars (notably cellobiuronic acid) arranged in a precise sequence, and its biosynthesis depends on a dedicated set of enzymes encoded within the cap8 gene cluster[1][2]. CPS8 is immunogenic, eliciting type-specific antibody responses that form the basis for several pneumococcal vaccines[2][7]. Monoclonal antibodies against CPS8 confer protection by promoting complement-mediated opsonization and clearance of the bacterium[7]. The capsule’s structure and its metabolic cost influence both prevalence in human populations and resistance to immune clearance[4]. Serotype 8 is epidemiologically significant as it is commonly found in clinical isolates and is associated with invasive disease, which is why it is included in multivalent pneumococcal vaccines[2][4]. The antigen does not act as a receptor, enzyme, or classical drug target but is a pathogen-associated molecular pattern targeted by vaccines and antibodies.

Other names

Pneumococcal capsular polysaccharide serotype 8S. pneumoniae serotype 8 capsuleSerotype 8 CPSType 8 capsular polysaccharide

Vaccines/binding antibodies promote opsonization and complement activation, enhancing clearance of S. pneumoniae expressing serotype 8 capsule[7] Antibody binding to capsule inhibits immune evasion by the bacterium