Live-attenuated auxotrophic mutant of Salmonella Typhimurium expressing immunogenic HA1 protein enhances immunity and protective efficacy against H1N1 influenza virus infection

Aim: To evaluate the efficacy of attenuated Salmonella Typhimurium (JOL912) as a live bacterial vaccine vector. Materials & methods: The JOL912 engineered to deliver HA1 protein from influenza A/Puerto Rico/8/1934 (H1N1; PR8) virus was coined as JOL1635 and further evaluated for immunogenicity and protective efficacy. Results: The JOL1635 stably harbored the HA1 gene within pMMP65 plasmid with periplasmic expression and effective delivery of HA1 protein to RAW264.7 cells. The JOL1635 immunized chickens showed the significant increase in HA1-specific IgG, sIgA antibody, IFN-gamma, IL-6 cytokine and cellular immune responses. The postoral challenge, the JOL1635-immunized chickens showed a faster clearance of PR8 virus cloacal shedding than the control group. Conclusion: Generated JOL1635 can establish specific immunogenicity and protection against the PR8 virus in chickens.