Immunogenicity of a freeze-dried combined vaccine against Rift Valley fever and bovine ephemeral fever in cattle

Abstract

Background: The target of vaccination is to encourage a strong, covering and long-lasting immune response against antigens. For achieving these objectives; effective adjuvant and new vaccine strategies are demanded to make the vaccine sufficiently immunogenic to instigate a powerful immune response Aim: This study was completed for elaboration and evaluation of freeze-dried combined vaccine against both Rift Valley fever (RVF) and Bovine Ephemeral Fever (BEF) viruses using different stabilizers. Methods: Three formulae were prepared from such vaccine including: formula (1): stabilized with a mixture of 5% Lactalbumin Hydrolysate and 2.5% sucrose, formula (2): stabilized with a mixture of 50% the previous stabilizer and 50% of 1% Carbopol and formula (3): stabilized with 1% Carbopol solution. Samples of the three vaccine formulae were reconstituted on the time of experimental animal vaccination using saponin diluent which acts as an adjuvant for both RVFv and BEFv and as inactivator BEF virus. The ratio between both viruses in all vaccine formulae was 1:1. Results: All vaccine batches were proved to be free of any foreign contaminants and unharmed for experimentally vaccinated animals. Each of three groups of calves was vaccinated S/C with 2ml of a reconstituted vaccine formula and their immune response was evaluated using serum neutralization test (SNT). The gained results revealed that the prepared combined freeze-dried vaccine with Carbopol elicited better humoral immune response than the other two vaccine formulae. Conclusion: It could be recommended to use Carbopol as a stabilizer for preparation of the aimed vaccine.