Evaluation and Comparison of the Potential Immunogenicity of Two Commercial Inactivated Bivalent Newcastle and Avian Influenza Vaccines in SPF Chicken

In the present study, the potency and immunogenicity of the inactivated bivalent vaccine of Newcastle disease (ND) and avian influenza (AI) produced by Razi institute in Iran were compared with a similar imported vaccine administered by standard methods to specific-pathogen-free (SPF) chicken. A total of 150 twenty-one-day-old SPF chickens were used for evaluating Razi and imported inactivated H9N2/ND vaccines. The chickens were divided into eight groups. The subjects in groups 1 and 3 were vaccinated with 0.3 ml/bird by subcutaneous route in the back of the neck with Razi and imported vaccines, respectively. Chickens in group 2 received Razi vaccine based on the recommended dose of the manufacturer (0.2 ml/bird) by the same route. The birds in groups 4 and 5 received 0.01 ml/bird of Razi and imported vaccine, respectively. Groups 7 and 8 were considered for studying the safety of the two vaccines and received a double amount of the full dose of vaccines. Moreover, group6 was regarded as the negative control. Sera were collected weekly from each chicken for antibody analysis against Newcastle disease virus (NDV) and AI virus (AIV) and the study continued for 15 weeks after vaccination. An immunological evaluation was carried out using haemagglutination inhibition (HI) antibody test against NDV and AIV. The results showed that up to 15 weeks after vaccination, the Razi vaccine induced a higher level of protective antibody against AI and ND in comparison with the imported ones at the dose of 0.3 ml/bird. The mean HI titer was significantly different between Razi vaccine and imported vaccine at the dose of 0.3 ml/bird. There was no statically significant difference between Razi vaccine (0.2 ml/bird) and the imported vaccine (0.3 ml/bird) against NDV and AIV. According to the findings, 15 weeks after vaccination, HI titers were still detectable at a high level. The mean HI titer was found as 5.2 log2 against NDV and 5 log2 against H9N2 with Razi vaccine (0.3 ml/bird). In addition, the mean HI titer with Razi vaccine (0.2 ml/bird) was 4.1 log2 and 4.7 log2 against ND and AI, respectively. In summary, our results indicated that Razi inactivated vaccine (0.3 ml/bird) induced a strong and rapid antibody response in vaccinated chickens and is more effective in chicken against AIVs and NDVs, in comparison with the imported vaccine.