O-antigen of Shigella flexneri serotype 2a

The O-antigen of Shigella flexneri serotype 2a is a serotype-specific, highly immunogenic polysaccharide that constitutes the outermost domain of the bacterium’s lipopolysaccharide (LPS) layer[1][2][5]. It consists of a repeating tetrasaccharide unit, typically containing three L-rhamnose residues and one N-acetylglucosamine (GlcNAc), with critical modifications such as glucosylation and O-acetylation defining subtype-specific epitopes[1][2]. The O-antigen is the primary determinant of immune recognition and serotyping for Shigella flexneri, playing a key role in the induction of protective antibody responses as well as resistance to complement-mediated killing[1][2][5]. The structure provides a molecular basis for serotype 2a identification and underpins vaccine strategies, as targeting this antigen can confer serotype-specific immunity[4][6]. The O-antigen also serves as a receptor for certain bacteriophages and can influence virulence by modulating outer membrane stability and host cell invasion mechanisms[1][3]. The high variability and capacity for serotype conversion present both challenges and opportunities in disease control, vaccine design, and diagnostic approaches[5][6].

Other names

O-specific polysaccharide of Shigella flexneri 2aO-polysaccharide of S. flexneri 2aShigella flexneri 2a O-antigenS. flexneri 2a O-antigen

Antibodies bind to O-antigen, neutralizing bacteria and enhancing opsonization[4] Vaccines elicit O-antigen-specific immune responses, providing serotype-specific protection[4] Polysaccharide-based immunization induces functional antibodies, leading to bacterial killing by complement[6]