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Target intelligence / Profile preview
O-antigen of Shigella species (O-antigen (OAg))
- Target
- O-antigen (OAg)
- Molecular classification
- Other (bacterial polysaccharide, not a protein, enzyme, or receptor), Surface antigen, Glycan/Lipopolysaccharide chain, Component of bacterial outer membrane
01
Overview
The O-antigen of Shigella species is a polysaccharide component of the lipopolysaccharide (LPS) located in the outer membrane of Shigella bacteria. It consists of repeating oligosaccharide units whose structure varies between serotypes, determining their immunological identity. O-antigen diversity underlies the multiple Shigella serotypes and is the basis for their serological classification. It is a major immune target, prompting production of protective antibodies during infection or vaccination. Structural modifications (e.g., glucosylation, acetylation) affect pathogenicity, immune evasion, and membrane stability. In Shigella sonnei, O-antigen forms a capsule that critically modulates virulence – enhancing resistance to complement and promoting persistence, though reducing invasion capability. The O-antigen is a primary focus for vaccine research, with successful candidates eliciting protective anti-OAg antibodies.
- Other names
- OAgShigella O-polysaccharideO-specific polysaccharideShigella LPS O-antigen capsuleO-antigen capsule (specifically for Shigella sonnei)
02
Mechanism of action
Vaccine-induced antibodies bind to O-antigen, promoting opsonization and complement-mediated lysis; Neutralization and prevention of bacterial invasion (by blocking surface O-antigen or its capsule); Enhancement of phagocytosis
03
Biological functions
Immune response induction (primary target of adaptive immune response)Evasion of host immunity (modulates bacterial visibility to immune system)Pathogenicity modulation (capsule affects invasion, complement resistance, and dissemination)Serotype determination (basis for Shigella serotyping)Outer membrane stability
04
Disease associations
Infection (essential factor in shigellosis, dysentery, and Shigella transmission)Virulence regulation (affects severity and persistence of infection)
05
Safety considerations
Serotype specificity limits broad protection; vaccines must cover multiple O-antigen variants due to high diversityPotential for serotype conversion and escape mutantsRisk of reactogenicity if too similar to host antigens or contaminated with LPSPossible modulation of host inflammation by capsule presence, resulting in differing safety profiles
06
Interacting drugs
Shigella GMMA vaccines (Generalized Modules for Membrane Antigens)
2 more in the full profile.
07
Biomarkers
Serological response against O-antigen (IgG titers to OAg indicate immunogenicity and protection)Presence of specific anti-O-antigen antibodies in blood post-vaccination
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