Shigella sonnei O-polysaccharide (Ss O-PS)

Shigella sonnei O-polysaccharide is the primary surface antigen and a critical virulence factor of the Gram-negative bacterium Shigella sonnei, which is a leading cause of bacillary dysentery worldwide. Unlike other Shigella species that exhibit high serotype diversity, S. sonnei exists as a single serotype characterized by a unique repeating disaccharide unit in its O-antigen: 4)-alpha-L-AltpNAcA-(1-3)-beta-D-FucpNAc4N-(1-. This polysaccharide chain is part of the lipopolysaccharide (LPS) layer and serves to protect the pathogen from host immune defenses, including complement-mediated lysis. Because antibodies against the O-polysaccharide are known to provide serotype-specific protection, it is the central target for vaccine development. Current therapeutic strategies focus on conjugate vaccines that link the O-polysaccharide to carrier proteins to enhance immunogenicity and induce long-term memory, particularly in pediatric populations in endemic regions.

Other names

Shigella sonnei O-antigenS. sonnei O-specific polysaccharideS. sonnei O-SPShigella sonnei lipopolysaccharide O-side chain

Induction of serum and mucosal antibodies (IgG and IgA) that recognize the O-antigen, leading to bacterial opsonization, phagocytosis, and complement-mediated killing to prevent intestinal invasion.