Enhancement of protective efficacy of recombinant attenuated Salmonella typhimurium delivering H9N2 avian influenza virus hemagglutinins(HA) antigen vaccine candidate strains by C-C motif chemokine ligand 5 in chickens(chCCL5).

The H9N2 inactivated avian influenza vaccine cannot induce cellular and mucosal immune responses, while the attenuated Salmonella vector as an intracellular bacterium can induce dominant cellular and mucosal immune responses. However, it provides low protection against the virus when delivering viral antigens and needs further optimization. Chicken C-C motif chemokine ligand 5 (chCCL5) is an important CC chemokine associated with immune cell chemotaxis, migration, and viral infection. This study connected the sequence of chCCL5 (CCL5) with the hemagglutinin sequence of the H9N2 avian influenza virus (yH9HA), utilizing the attenuated Salmonella typhimurium vector containing the delayed lysis system MazE/F regulated by arabinose as a carrier. A vaccine strain of recombinant attenuated Salmonella typhimurium and H9N2 avian influenza virus HA, rSC0130 (pS0017-yH9HA-CCL5), was successfully constructed. The experimental results indicate that yH9HA-CCL5 can be expressed in 293 T cells; compared to the strain without CCL5, rSC0130 (pS0017-yH9HA-CCL5) can induce significantly increased cellular immune responses and provide better protective effects in H9N2 virus challenge experiments. The above results indicate that chCCL5 can significantly enhance the protective effect of Salmonella delivering H9N2 avian influenza virus HA protein vaccine against H9N2 avian influenza virus infection, providing valuable theoretical support for further improving the protective efficiency of recombinant attenuated Salmonella vectors for delivering viral antigens.