Klebsiella pneumoniae capsular polysaccharide (CPS) (CPS)

Klebsiella pneumoniae capsular polysaccharide (CPS) is a complex, high-molecular-weight carbohydrate layer that serves as the outermost defense for the bacterium (Paczosa & Mecsas, 2016). Its primary biological function is to protect the pathogen from host immune defenses, specifically by inhibiting phagocytosis and preventing the activation of the complement system (Wyres et al., 2020). CPS is recognized as a major virulence factor, with hypercapsulated strains often causing severe, invasive diseases such as pyogenic liver abscesses, pneumonia, and neonatal sepsis (Martin & Bachman, 2018). Because it is surface-exposed, CPS is a key target for the development of conjugate vaccines and monoclonal antibodies designed to promote opsonophagocytic killing (PubMed: 32053475). Furthermore, research into phage-derived depolymerases focuses on the enzymatic degradation of this capsule to sensitize the bacteria to the host immune system and conventional antimicrobial agents (Frontiers in Microbiology, 2019). The existence of more than 80 distinct K-serotypes necessitates the development of multivalent or highly specific therapeutic strategies to achieve broad clinical efficacy (Nature Reviews Microbiology, 2020).

Other names

K-antigenK-capsuleCapsular polysaccharideK. pneumoniae CPS

Induction of opsonophagocytic killing (OPK) via antibody binding to the capsule, neutralization of immune evasion mechanisms, and enzymatic degradation of the polysaccharide structure by depolymerases to expose the bacterial cell surface.