The Promotion of Peony Seed Proteolysis Product to the Immune Efficacy Induced by ptfA Gene DNA Vaccine of Avian Pasteurella multocida

Abstract

Background: Avian Pasteurella multocida is one of the pathogens that affect the health of poultry. The protective efficacy of traditional attenuated vaccine is not ideal. In previous study, we prepared ptfA gene DNA vaccine of avian P. multocida. However, the protective effect of ptfA gene DNA vaccine was inferior to the attenuated vaccine. Therefore, it is necessary to improve the immune efficacy of avian P. multocida DNA vaccine, such as screening for novel adjuvant. Methods: In this study, the peony seed proteolysis product was gavaged to chickens before DNA vaccination or was added to the ptfA gene DNA vaccine as adjuvant. These vaccines were administered to chickens and the serum antibody, lymphocyte proliferation levels, IFN-g, IL-2, IL-4 and IL-6 concentrations secreted by peripheral blood lymphocytes were determined. After challenging with virulent avian P. multocida, survival time and protective efficacy was evaluated. Result: Following vaccination, no significant differences in antibody levels and concentrations of IL-4 among the DNA vaccine group, adjuvant-DNA vaccine group and gavaged group were observed. The stimulation index (SI) values, concentrations of IFN-g, IL-2 and IL-6 in adjuvant-DNA vaccine group and gavaged group were significantly higher than those in the DNA vaccine group. The protective efficacy of live attenuated vaccine group, DNA vaccine group, adjuvant-DNA vaccine group and gavaged group were 92%, 52%, 72% and 60%, respectively. This study has laid a foundation for the design and application of future DNA vaccines of P. multocida and DNA vaccine adjuvant.