Shigella flexneri serotype 6 O-antigen (Sf6 O-antigen)

Shigella flexneri serotype 6 O-antigen is a critical carbohydrate component of the lipopolysaccharide (LPS) layer on the outer membrane of Shigella flexneri 6, a primary causative agent of bacterial dysentery (shigellosis) worldwide. Among the various S. flexneri serotypes, serotype 6 is distinct because it possesses a unique rhamnogalactan backbone structure (→2)-α-L-Rhap-(1→2)-α-L-Rhap-(1→4)-α-L-Galp-(1→3)-β-D-GalpNAc-(1→), whereas other serotypes share a common tetrasaccharide backbone. This structural divergence necessitates its specific inclusion in multivalent vaccine candidates to ensure broad protective coverage against the diverse range of Shigella pathogens. As a therapeutic target, the Sf6 O-antigen is typically developed as a glycoconjugate vaccine, where the polysaccharide is chemically linked to a carrier protein like Pseudomonas aeruginosa Exoprotein A (EPA) to convert the T-cell independent carbohydrate into a T-cell dependent antigen. This approach induces high-affinity IgG antibodies and immunological memory, providing a robust defense against enteric infection and reducing the global burden of diarrheal disease.

Other names

Shigella flexneri 6 lipopolysaccharideS. flexneri 6 O-polysaccharideShigella flexneri type 6 surface antigenSf6 LPS

Induction of O-antigen-specific bactericidal antibodies (IgG and IgA) that facilitate opsonophagocytosis and neutralize the pathogen in the intestinal lumen to prevent mucosal invasion.