Shigella flexneri 2a and Shigella sonnei O-specific polysaccharide (O-SP)

The O-specific polysaccharide (O-SP) is the outermost carbohydrate domain of the lipopolysaccharide (LPS) molecule located on the surface of Gram-negative bacteria, including Shigella flexneri 2a and Shigella sonnei (PubMed: 29432011). It plays a crucial role in bacterial virulence and serves as the primary target for the host's adaptive immune system during infection (NCBI: PMC4324218). Immune-mediated recognition of the O-SP involves the production of antibodies that are highly specific to the repeating sugar units of the polysaccharide chain (PubMed: 18490741). Because Shigella species are major causes of moderate-to-severe diarrhea and dysentery worldwide, the O-SP is a primary candidate for vaccine development (WHO: Shigella Vaccine Pipeline). Current therapeutic approaches involve conjugating these O-SPs to carrier proteins to overcome the poor immunogenicity of pure polysaccharides and induce a T-cell dependent immune response (PubMed: 33450198). Successful recognition and response to these targets result in the generation of bactericidal antibodies that prevent the bacteria from invading the colonic mucosa (PubMed: 26183959).

Other names

O-antigenLPS O-side chainShigella O-polysaccharideLipopolysaccharide O-antigen

Induction of serotype-specific bactericidal antibodies (IgG and IgA) that recognize the O-antigen, leading to complement-mediated lysis or opsonophagocytosis of the bacteria.