N-terminus of Flagellin Fused to an Antigen Improves Vaccine Efficacy against Pasteurella multocida Infection in Chickens.

Flagellin from bacteria elicits a proinflammatory immune response and may act as a vaccine adjuvant. In this study, we evaluated the adjuvant effect of the N-terminus of flagellin (residues 1-99) when linked to an antigen (a truncated, conserved domain of lipoprotein E of Pasteurella multocida). Immunization of chickens with the antigen-adjuvant chimeric protein showed that the N-terminus of flagellin accelerated the antibody response and enhanced the cellular immunity (CD8+ T cell expansion). Stimulation of peripheral blood mononuclear cells from vaccinated chickens showed both TH1 (IFN-γ and IL-12) and TH2 (IL-4)-type cytokine gene expressions. In a challenge test, the N-terminus of flagellin increased the survival rate to 75%, compared to 25% in the antigen-only group. In conclusion, our study found that the N-terminus of flagellin can increase the immune response and enhance vaccine protection.