Abstract
At present, there is no vaccine available against Pseudomonas aeruginosa, a common zoonotic pathogenic bacterium. In a previous study, the authors prepared a divalent combination DNA vaccine, pOPRL+pOPRF, which exhibited good protective efficacy. To explore the optimal immunization dose of this divalent combination DNA vaccine, in the present study, chickens were vaccinated with 25, 50, 100, and 200 µg doses. The levels of serum antibody, interferon-γ (IFN-γ), and interleukin-2 (IL-2) were determined, and lymphocyte proliferation assays were performed. After challenge with virulent P. aeruginosa, the protective efficacy was evaluated. Following vaccination, the serum antibodies, stimulation index values, and concentrations of IFN-γ and IL-2 were significantly higher in chickens vaccinated with 100 and 200 µg vaccines than in those vaccinated with 25 and 50 µg doses (P<0.05). IFN-γ and IL-2 concentrations in chickens immunized with 100 µg vaccine were slightly higher than those in chickens immunized with 200 µg vaccine, although the difference was not statistically significant. The protective rates were 55%, 65%, 85%, and 85% with 25, 50, 100, and 200 µg of the pOPRL+pOPRF DNA vaccine, respectively. Thus, the immune efficacy of the pOPRL+pOPRF DNA vaccine increased with an increase in immunization dose, but this does not imply that a higher dose necessarily achieves a better outcome. The optimal immunization dose of pOPRL+pOPRF DNA vaccine in chickens was 100 µg.