Shigella flexneri 2a O-antigen (Sf2a O-antigen) (Sf2a O-antigen)

The Shigella flexneri 2a O-antigen is a key polysaccharide component of the lipopolysaccharide (LPS) located on the outer membrane of Shigella flexneri serotype 2a, a major causative agent of bacillary dysentery (shigellosis) (1, 6). It is composed of a repeating tetrasaccharide unit consisting of rhamnose and N-acetylglucosamine residues, with specific glucose and O-acetyl modifications that determine its serological identity (4, 6). Biologically, the O-antigen is essential for bacterial virulence, providing resistance to the acidic environment of the stomach and protecting the pathogen from the host's innate immune system (8, 11). It is the primary target for vaccine-induced antibodies, which provide protection by neutralizing the bacteria and promoting complement-mediated killing (1, 2). Because natural immunity to Shigella is serotype-specific, this O-antigen is a critical antigen in the development of conjugate and bioconjugate vaccines, such as Flexyn2a and SF2a-TT (3, 9). These vaccines aim to elicit high titers of functional IgG and IgA antibodies to prevent infection and reduce the global burden of shigellosis, particularly in pediatric populations in developing countries (1, 3).

Other names

Shigella flexneri 2a O-polysaccharideSf2a O-SPShigella flexneri 2a O-specific polysaccharideSf2a OSPS. flexneri 2a LPS O-antigen

Induction of serotype-specific antibodies (IgG and IgA) that bind to the O-antigen, mediating complement-dependent bactericidal activity and preventing bacterial invasion of the colonic epithelium.