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.

Construction of a ptfA chitosan nanoparticle DNA vaccine against Pasteurella multocida and the immune response in chickens

The aim of this study was to evaluate the effect of chitosanon the immune response induced by a DNA vaccine based on the ptfA gene of avian Pasteurella multocida. Naked DNA vaccine was packed with chitosanmolecules, resulting in a chitosannanoparticle DNA vaccine. The encapsulation efficiency, shape, size and resistance to DNA degradation were determined. The vaccine was administered to chickens and serum antibody, interferon-γ (IFN-γ), interleukin-2 (IL-2) and interleukin-4 (IL-4) concentrations were determined and lymphocyte proliferation assays were performed. After challenge with virulent avian P. multocida, protective efficacy was evaluated. The encapsulation efficiency of the chitosan nanoparticle DNA vaccine was 95.3%. The particle size was approximately 200nm and close to spherical in shape and it could effectively resist degradation by DNases. Following vaccination, serum antibodies, stimulation index (SI) value and concentrations of IFN-γ and IL-2 in chickens vaccinated with the chitosan nanoparticle DNA vaccine were significantly higher than those that were vaccinated with the naked DNA vaccine (P-values are 0.026, 0.045, 0.039 and 0.024, respectively). However, the concentrations of IL-4 in the two DNA vaccines group were no significant difference (P=0.157). The protective efficacy rate provided by naked DNA vaccine, chitosan nanoparticle DNA vaccine and the attenuated live vaccine were 56%, 68% and 88%, respectively. The results indicated that chitosan was able to enhance the immune response to a naked DNA vaccine based on the ptfA gene of P. multocida.