Effect of flagellin on inhibition of infectious mechanisms by activating opsonization and salmonella flagellum disruption

Abstract

Some serovars of salmonella cause huge global diseases such as enteric fever and invasive non typhoidal Salmonella disease. Flagellin as a key antigenic component of salmonella, can induce humoral and cellular immunity responses. In this research, we performed an opsonophagocytic killing assay (OPKA) as an important mechanism of the host-defense system, for salmonella to study the activity of anti-sera of native FliC, truncated modified recombinant FliC (tmFliC) and full length recombinant FliC proteins (flFliC). Also, the potency of antibodies for inhibiting bacterial movement was evaluated by traditional and newly-designed motility inhibition assay methods. Results showed both recombinant FliC anti-sera and native FliC (nFliC) anti-serum had the ability to opsonize Salmonella typhimurim, which led to bacterial clearance by mice macrophages. Also, inhibition of bacterial motility was observed for all anti-sera. Anti-nFliC and anti-flFliC sera showed higher effects on Salmonella typhimurim motility than that of tmFliC. In traditional method, about 88%, 86% and 80% inhibition were observed by using 5% nFliC, anti-flFliC and anti-tmFliC sera, respectively. In the newly-designed method using SIM (Sulfide indole motility) medium, results confirmed the traditional method for motility inhibition. Our findings suggest that salmonella fliC as a protective antigen may disrupt the flagellum apparatus activity.