Salmonella Paratyphi A flagellin (H:a antigen) (FliC)

Salmonella Paratyphi A flagellin, specifically the H:a antigen, is the primary structural protein of the flagellar filament in Salmonella enterica serovar Paratyphi A. Encoded by the fliC gene, this protein is essential for bacterial motility and chemotaxis, enabling the pathogen to navigate the host environment and invade intestinal epithelial cells (UniProt Q5PC24). The H:a antigen is highly immunogenic and serves as a major target for the host's adaptive immune system during infection with paratyphoid fever. It also acts as a potent agonist for Toll-like receptor 5 (TLR5), initiating innate immune signaling pathways that lead to the production of pro-inflammatory cytokines (PubMed: 11242089). In therapeutic development, flagellin is a key component of vaccine candidates, often serving as both a protective antigen and a carrier protein for O-specific polysaccharides to enhance overall immunogenicity (PubMed: 23414380). Targeting this protein aims to induce neutralizing antibodies that inhibit bacterial motility and facilitate opsonophagocytosis, thereby preventing the systemic spread of the pathogen (PubMed: 28433448). Given the rising antibiotic resistance in Salmonella Paratyphi A, the H:a antigen remains a critical focus for the development of effective glycoconjugate and subunit vaccines (WHO).

Other names

Phase 1 flagellinH:a antigenFliC proteinFlagellar filament structural protein

The target acts as an immunogen in vaccine formulations, where it induces the production of H:a-specific antibodies that block bacterial motility and promote opsonophagocytosis, while also serving as a TLR5 agonist to enhance the innate immune response.