Klebsiella pneumoniae capsular polysaccharide (serotype K2) (K2 CPS)

The capsular polysaccharide (CPS) of Klebsiella pneumoniae, specifically serotype K2, is a high-molecular-weight carbohydrate structure that forms a protective capsule around the bacterial cell. This capsule is a major virulence factor, enabling the bacterium to evade host immune responses and contributing to its hypervirulent phenotype. The K2 CPS allows K. pneumoniae to resist phagocytosis by immune cells, avoid complement-mediated killing, and survive in hostile environments such as human serum. Serotype K2 is frequently associated with severe infections including pyogenic liver abscesses and bloodstream infections. The repeating unit of the K2 CPS consists of tetrasaccharides; O-acetylation of these units plays a crucial role in immunogenicity. The negative charge provided by carboxyl groups facilitates ionic interactions between the CPS and lipopolysaccharide (LPS) on the bacterial surface. Biosynthesis of the K2 capsular polysaccharide requires both rmpA regulatory gene function and an intact chromosomal cps gene cluster. O-acetylation patterns within the tetrasaccharide repeats are thought to be critical for recognition by host immune systems and may influence vaccine design strategies. Phage-derived tailspike proteins have been identified that specifically depolymerize K2 CPS into its constituent tetrasaccharides, providing insight into potential therapeutic or vaccine strategies.

Other names

K. pneumoniae K2 capsular polysaccharideK2 polysaccharideK2 capsule

Enzymatic depolymerization of the capsule; Neutralization of innate immune responses by homologous serotypes.