Shigella O-specific polysaccharide (O-SP)

The Shigella O-specific polysaccharide (O-SP) is the distal carbohydrate component of the lipopolysaccharide (LPS) located on the outer membrane of Shigella bacteria (Morona et al., 2003, Journal of Bacteriology). It consists of repeating oligosaccharide units that define the serotype of the organism, which is a major determinant of the host immune response (Phalipon et al., 2008, Journal of Experimental Medicine). Biologically, the O-SP acts as a critical virulence factor by protecting the pathogen from the host's innate immune system, specifically by inhibiting complement-mediated lysis and phagocytosis (Hong and Payne, 1997, Molecular Microbiology). Because it is highly immunogenic and accessible on the bacterial surface, it serves as the primary target for vaccine development and therapeutic monoclonal antibodies (Cohen et al., 2022, The Lancet Infectious Diseases). Most current clinical strategies utilize O-SP conjugated to carrier proteins to induce robust, T-cell-dependent immunity (Riddle et al., 2021, Vaccine). Effective targeting of the O-SP is vital for preventing shigellosis, a leading cause of severe diarrheal disease and mortality in children worldwide (WHO, 2023).

Other names

Shigella O-antigenO-polysaccharideLPS O-side chainShigella lipopolysaccharide O-antigen

Induction of serotype-specific bactericidal and neutralizing antibodies (IgG and IgA) that bind to the bacterial surface, preventing attachment and invasion of the colonic epithelium.