Shigella flexneri O-antigen (S. flexneri O-antigen)

The Shigella flexneri O-antigen is the distal carbohydrate component of the lipopolysaccharide (LPS) molecule found on the outer membrane of the Gram-negative bacterium Shigella flexneri, which is a primary causative agent of bacillary dysentery (shigellosis) [1]. It consists of repeating oligosaccharide units whose specific chemical structure and linkages define the various serotypes of the species, playing a vital role in bacterial virulence, environmental fitness, and protection against host immune defenses [2]. Because the O-antigen is the most accessible surface structure for the host immune system, it serves as the principal target for protective humoral immunity and is the primary focus of current vaccine development efforts [3]. Therapeutic strategies, such as the development of glycoconjugate vaccines (e.g., Flexyn2a and SF2a-TT), aim to elicit high titers of serotype-specific antibodies that neutralize the bacteria and prevent intestinal invasion [4]. However, the significant structural diversity among S. flexneri serotypes presents a major challenge, as immunity is often serotype-specific, necessitating the development of multivalent vaccines to provide comprehensive protection against the most prevalent strains [5]. (Sources: [1] PubMed PMID: 29153276; [2] Nature Reviews Microbiology PMID: 30224735; [3] WHO Shigella Vaccine Pipeline; [4] ClinicalTrials.gov NCT02382237; [5] Frontiers in Immunology PMID: 31134055).

Other names

Shigella flexneri O-polysaccharideS. flexneri LPS O-antigenO-specific polysaccharideO-Ag

Vaccines and therapeutic antibodies targeting the O-antigen work by inducing or providing serotype-specific antibodies (primarily IgG and mucosal IgA) that facilitate the opsonophagocytosis of the bacteria by immune cells and prevent the pathogen from invading the colonic epithelium.