O-antigen of Shigella sonnei lipopolysaccharide

The O-antigen of Shigella sonnei lipopolysaccharide is an immunodominant, high-molecular-weight polysaccharide that constitutes the distal, repeating glycan portion of the lipopolysaccharide (LPS) molecules on the outer membrane of Shigella sonnei. The O-antigen is highly species- and strain-specific, composed of unique repeating oligosaccharide units containing two rare sugars—2-acetamido-2-deoxy-L-altruronic acid (L-AltNAcA) and 2-acetamido-2-deoxy-L-fucose (FucNAc4N)—which are not found in other Shigella serogroups. This antigenic structure plays a central role in pathogenicity, immune recognition, and evasion, and is the molecular target for protective antibodies during infection and for vaccines. In S. sonnei, the O-antigen is encoded by genes on a virulence plasmid and is essential both for full virulence and for inducing a protective immune response. Conjugate vaccines and monoclonal antibodies targeting the O-antigen are under active development and have shown potential for disease prevention[1][2][3][4][5][6][7].

Other names

Shigella sonnei O-antigenS. sonnei OAgO-specific polysaccharide of Shigella sonneiShigella sonnei O-polysaccharide

Induction of immune response: vaccine polysaccharide-protein conjugates (e.g., O-antigen conjugated to carrier proteins) elicit protective anti-O-antigen antibodies that mediate bacterial clearance[4][7]. Direct neutralization or bactericidal activity by monoclonal antibodies, leading to opsonization and complement-mediated killing[7].