Shigella sonnei O-specific polysaccharide antigen (O-SP)

The Shigella sonnei O-specific polysaccharide antigen (O-SP) is a critical component of the lipopolysaccharide (LPS) found on the outer membrane of the Gram-negative bacterium Shigella sonnei (PMID: 30243787). Unlike other Shigella species which have diverse O-antigen structures, S. sonnei possesses a unique, highly conserved O-antigen consisting of a repeating disaccharide unit of 4-amino-4,6-dideoxy-D-glucose and 2-acetamido-2-deoxy-L-altruronic acid (PMID: 26183943). This polysaccharide plays a vital role in the bacterium's survival within the host by providing a physical barrier against the host's innate immune system, particularly complement-mediated lysis. In the context of vaccine development, the O-SP is the primary target for inducing protective immunity, as antibodies directed against this structure are known to be bactericidal and correlate with protection against shigellosis (PMID: 29136439). Current therapeutic strategies focus on developing conjugate vaccines where the O-SP is chemically or enzymatically linked to a carrier protein to enhance immunogenicity, especially in young children. These vaccines, such as Flexyn2a, aim to reduce the global burden of bacillary dysentery, which remains a significant cause of morbidity and mortality in developing regions (PMID: 33516294). Successful targeting of the O-SP induces long-term memory B-cell responses that can prevent future infections by the same serotype.

Other names

Shigella sonnei O-antigenS. sonnei O-polysaccharideLipopolysaccharide O-side chainO-PS

Induction of O-antigen-specific bactericidal antibodies (IgG and IgA) that facilitate opsonophagocytosis and complement-mediated killing of Shigella sonnei bacteria (PMID: 26183943).