Capsular polysaccharide antigen (CPS)

Capsular polysaccharide antigens are high-molecular-weight carbohydrate structures that form a dense, hydrated gel (capsule) on the surface of many bacterial pathogens. They are intrinsically diverse, with structure and antigenicity often varying between bacterial species and even among strains of the same species (e.g., more than 80 K-antigens in *E. coli*). The term is broad, referring to a large class of surface carbohydrate antigens rather than a single molecule or protein. More specificity (e.g., organism and serotype) may be needed for structured data. Their primary biological roles include evasion of host immune responses, inhibition of complement activation and phagocytosis, protection from environmental stresses, and facilitation of adherence to host tissues. Because they are essential for virulence and surface-exposed, these antigens are important targets for vaccine development, notably in conjugate vaccines against *Streptococcus pneumoniae*, *Neisseria meningitidis*, *Haemophilus influenzae* type b, and Group B *Streptococcus*. Challenges with these targets include serotype variability, potential immune evasion through antigenic mimicry, and variable immunogenicity depending on host age and immune status[1][2][3][4][5][6][7].

Other names

Capsule antigenCapsular antigenK antigenCPS

Vaccines: Induce production of antibodies targeting the capsule, promoting opsonization, complement-mediated killing, and phagocytosis. Small molecule inhibitors: Interfere with biosynthesis or assembly of the capsule, thereby reducing bacterial virulence and resistance to immune effectors.