Shigella flexneri 2a and Shigella sonnei O-specific polysaccharide (O-SP) epitopes (O-SP)

The O-specific polysaccharide (O-SP) epitopes of Shigella flexneri 2a and Shigella sonnei are the primary antigenic components of the lipopolysaccharide (LPS) found on the outer membrane of these Gram-negative bacteria (Mani et al., 2016, PubMed). These epitopes are essential for bacterial virulence and serve as the dominant targets for the host's protective immune response during infection (Levine et al., 2007, Nature Reviews Microbiology). Shigellosis, caused by these pathogens, remains a major global health threat, particularly in low- and middle-income countries where it causes severe diarrhea and dysentery (WHO, 2023). Because the O-antigen structure is serotype-specific, vaccine development focuses on the most prevalent strains, specifically S. flexneri 2a and S. sonnei. Therapeutic strategies primarily involve the development of conjugate vaccines, such as Flexyn2a and Shigella4V, which link the O-SP to carrier proteins like CRM197 or tetanus toxoid to induce robust T-cell dependent immunity (Cohen et al., 2022, The Lancet Infectious Diseases). These vaccines aim to elicit high titers of O-antigen-specific IgG and mucosal IgA antibodies that provide bactericidal activity and prevent the bacteria from invading the intestinal epithelium. Monitoring efficacy typically involves measuring serum IgG levels against the O-SP and assessing serum bactericidal activity (SBA) (Phalipon et al., 2008, Journal of Infectious Diseases).

Other names

Shigella O-antigenShigella lipopolysaccharide O-side chainS. flexneri 2a O-SPS. sonnei O-SPShigella O-polysaccharide

Induction of O-antigen-specific bactericidal antibodies (IgG and mucosal IgA) that prevent bacterial attachment and invasion of the intestinal mucosa.