Flagellin Enhances the Immunogenicity ofLipoprotein E Subunit Vaccine.

Abstract

Fowl cholera, caused byinfection, poses challenges for prevention because of its many serotypes. Bacterins are currently widely used for vaccination against fowl cholera, but protection is limited to homologous strains. Live attenuated vaccines ofprovide some heterologous protection, but side effects are considerable. More recently, protein-based antigens are promising subunit vaccines when their low immunogenicity has been addressed with effective adjuvants. Bacterial flagellin has been widely considered a promising adjuvant for vaccines. In this study, we tested the adjutancy of flagellin in a subunit vaccine againstin a mice and chicken models. For vaccine formulation, the antigen fPlpE (liporotein E) was combined with fFliC (Typhimurium flagellin). The recombinant proteins of fPlpE and fFliC were successfully expressed using thesystem as the expected sizes of 55 kDa and 70 kDa, respectively. The fFliC elicited strong expression levels of proinflammatory cytokine (IL-1β, IL-8, and IL-6) when stimulated in native chicken peripheral blood mononuclear cells. Immunization of mice and chickens with the subunit vaccines containing fFliC accelerated the antibody response. In the challenge tests, fFliC increased vaccine protective efficacy against the heterologous strainA1 and highly virulent strain Chu01 in mice and chickens, respectively. These data indicated potential possibilities of using fFliC as an immunostimulant adjuvant in developing a subunit vaccine against fowl cholera.