Shigella flexneri 2a O-antigen polysaccharide

The Shigella flexneri 2a O-antigen polysaccharide is a surface lipopolysaccharide component consisting of repeating tetrasaccharide units →2)-α-L-Rha-(1→2)-α-L-Rha-(1→3)-[α-D-Glc-(1→4)]-α-L-Rha-(1→3)-α-D-GlcNAc-(1→, with 3/4-O-acetylation on Rha residues and α-D-Glc branching on RhaIII defining the serotype. It exists in short (S-type) and very long (VL-type) chain lengths, influencing bacterial motility, host cell invasion, complement resistance, and phage susceptibility. It serves as the primary vaccine antigen due to its role in eliciting protective antibodies, as shown by mAb F22-4 binding a helical epitope across two repeat units.

Other names

Sf2a O-PSserotype 2a O-Ag[AB(E)CD] repeating unit polysaccharide

Antibody binding to conformational epitope spanning two repeat units (Rha-Rha-GlcNAc with branching Glc), involving hydrogen bonds and van der Waals contacts to six sugar residues for antigenic mimicry and protection Vaccine induction of serotype-specific protective immunity via O-antigen mimicry