Immunogenicity and protective efficacy of Salmonella enterica serovar Pullorum pathogenicity island 2 mutant as a live attenuated vaccine candidate

Background: Salmonella enterica serovar Pullorum (S. Pullorum) causes Pullorum disease (PD), a severe systemic disease of poultry and results in considerable economic losses in developing countries. In order to develop a safe and immunogenic vaccine, the immunogenicity and protective efficacy of S06004 Delta SPI2, a Salmonella pathogenicity island 2 (SPI2) deleted mutant of S. Pullorum was evaluated in 2-day old chickens. Results: Single intramuscular vaccination with S06004 Delta SPI2 (2 x 10(7) CFU) of chickens revealed no differences in body weight or clinical symptoms compared to control group. S06004 Delta SPI2 bacteria can colonize and persistent in liver and spleen of vaccinated chickens approximately 14 days, and specific humoral and cellular immune responses were significantly induced. Vaccination of chickens offered efficient protection against S. Pullorum strain S06004 and S. Gallinarum strain SG9 challenge, respectively, at 10 days post vaccination (dpv) based on mortality and clinical symptoms compared to control group. Conclusions: These findings suggest that S06004 Delta SPI2 appears to be a highly immunogenic and efficient live attenuated vaccine candidate.