To explore the immunoregulatory function of peony seed proteolysis product in mice, the protein from peony seed meal was extracted and hydrolyzed with bromelain. The peony seed proteolysis product was fed to mice at three different doses of 0.25, 0.5, and 1.0 g/kg for 21 days. The immunoregulation abilities of peony seed proteolysis product after each of these doses were evaluated in mice. Our results showed that all immune indices were higher in mice that had received a lavage with peony seed proteolysis product than in control mice. The immune indices of immune organs, delayed‐type hypersensitivity reaction (DTH), phagocytosis of peritoneal macrophages, serum hemolysin levels, lymphocyte proliferation (SI value), and levels of IFN‐γ and IL‐4 in the middle dose and high dose groups were significantly higher (p < .05) or extremely significant (p < .01) in comparison with the control group. These results indicate that the peony seed proteolysis product enhances immunological functions in mice. Practical applications Peony seed is rich in proteins and can be extracted and hydrolyzed using bromelain. The peony seed proteolysis product can enhance the nonspecific, humoral, and cellular immune responses. Thus, peony seed could be of potential value to obtain peony seed protein, which can be further developed and utilized in the manufacture of functional health products.

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.