Research Note: The immune enhancement ability of inulin on ptfA gene DNA vaccine of avian Pasteurella multocida

To evaluate the ability of inulin to enhance the immune response of a ptfA gene DNA vaccine for avian Pasteurella multocida, inulin was added as an adjuvant to the ptfA-DNA vaccine, obtaining an inulin-adjuvant DNA vaccine. The DNA vaccine was administered to chickens; a fimbria protein vaccine and an attenuated live vaccine were used as positive controls. The levels of the serum antibody and concentrations of interferon-γ (IFN-γ), interleukin-2 (IL-2), and interleukin-4 (IL-4) were determined, and a lymphocyte proliferation assay was performed. After being challenged with virulent P. multocida, the protective efficacy was evaluated. The results showed that the serum antibodies induced by the ptfA-DNA vaccine were not enhanced by inulin. The stimulation index values and the concentrations of IL-2 and IFN-γ in chickens vaccinated with inulin-adjuvant DNA vaccine were significantly higher than those in chickens vaccinated with the DNA vaccine, those with the fimbria protein vaccine, and the chickens gavaged with inulin. The concentrations of IL-4 in the inulin-adjuvant DNA vaccine group and the fimbria protein vaccine group were higher than those in the DNA vaccine group and the inulin-gavage group. The protective efficacy rates of the attenuated live vaccine group, the fimbria protein vaccine group, the DNA vaccine group, the inulin-adjuvant DNA vaccine group, and the inulin-gavage group were 90, 70, 55, 65, and 55%, respectively.