Search

Currently, a variety of immunostimulatory molecules are used as adjuvants in combination with poor immunogenic recombinant infectious bursal disease virus (IBDV) vaccine antigen. TIR domain of Toll-like receptors (TLRs) triggers the interleukin-1 (IL-1) signaling cascade which plays a critical role in immune responses against infectious agents. For this study, the bacmid DNA pBac-VP2 of a field isolate was generated and transfected to Sf9 insect cells to produce recombinant VP2 (rVP2). In addition, based on in silico analysis, the cDNA encoding the conserved TIR domain of TLR7 (TIR-TLR7) contain the IL-1 receptor was synthesized and used as an adjuvant. We further evaluated the ability of rVP2/TIR-TLR7 vaccine candidate to induce specific immune responses in specific pathogen-free (SPF) chickens and compared the efficacy by challenging with the virulent IBDV. The results indicate that rVP2/TIR-TLR7-adjuvanted vaccine elicited humoral immune responses and protected chickens against IBDV infection. Higher levels of neutralizing IBDV antibody titers were observed in chickens intramuscularly immunized with rVP2/TIR-TLR7 than those injected with rVP2 alone. The antibody titers were higher in chickens which received booster injection. Furthermore, chickens immunized with rVP2/TIR-TLR7 in the prime and boost groups had significant protection against a virus challenge. The survival rate was 70 and 90% after the primary and booster rVP2/TIR-TLR7 vaccinations, respectively, and indicated that they were protected from virus challenge. Despite the unvaccinated control group, the immunized chickens with rVP2/TIR-TLR7 did not show any clinical signs and histopathological changes of the bursa. Our results demonstrate that TIR-TLR7 is a potential vaccine adjuvant and can induce antigen-specific immune responses induced by rVP2 for protection against IBDV infection. [ABSTRACT FROM AUTHOR]