Flagellin (FliC) of Salmonella enterica serovar Paratyphi A (FliC)

Flagellin is the primary structural protein of the bacterial flagellum in Salmonella enterica serovar Paratyphi A, primarily encoded by the fliC gene (UniProt, 2024). It serves a dual role in pathogenesis: providing the motility required for the bacteria to reach and invade host intestinal epithelial cells and acting as a potent pathogen-associated molecular pattern (PAMP) (Infection and Immunity, 2015). Upon infection, flagellin is recognized by the host's Toll-like receptor 5 (TLR5), which triggers the activation of pro-inflammatory signaling pathways and the innate immune system (NIH, 2004). In Salmonella Paratyphi A, flagellin also plays a regulatory role in the expression of the Salmonella pathogenicity island 1 (SPI-1), which is essential for host cell invasion (ASM, 2015). Due to its high immunogenicity and surface exposure, flagellin is a major target for the development of vaccines against paratyphoid fever, a significant cause of enteric fever globally (MDPI, 2024). Experimental vaccines, such as the live-attenuated strain CVD 1902, utilize flagellin as a key antigen to elicit protective IgG and IgA antibody responses (NEJM, 2025). The interaction between flagellin and TLR5 is also being explored for its potential as a vaccine adjuvant to enhance the overall immune response (NIH, 2011). While Salmonella Paratyphi A is typically monophasic, the variation of flagellin in other serovars is a known mechanism for immune evasion (MDPI, 2024).

Other names

H antigenPhase 1 flagellinFliC proteinflaFhagSPA0911

Vaccine antigen that induces protective humoral (IgG, IgA) and cellular immune responses; also acts as a TLR5 agonist to stimulate innate immunity (NEJM, 2025; NIH, 2011).