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.

Protectivity of Freeze Dried Inactivated Rift Valley Fever Vaccine

“…Clinical examination of sheep vaccinated with the two different reconstitutions of lyophilized inactivated RVF vaccines reconstitution (1) with saponin and reconstitution (2) with normal saline) showed no observable symptoms of disease or local reactivity at the injection site during the course of the examination. Similarly, [13] observed that inoculated animals did not experience any unfavorable post-vaccinal reactions after receiving the inactivated lyophilized RVF vaccine diluted with saponin and [26] reported that calves vaccinated with lyophilized inactivated RVF vaccine using Carbopol showing no any abnormal local or systemic clinical signs.…”

“…They found that the immunological response in sheep given two doses of the lyophilized RVF vaccine, stabilized with lactalbumin and sucrose and diluted with saponin, remained within the protective range until the end of the ninth month after vaccination. Also, these results related to the use of saponin as adjuvant where [26] showed that a superior humoral immune response was induced by the produced freeze-dried vaccine containing both BEF and RVF along with carbopol. The results that were obtained seem to coincide with [19], who revealed that saponin-based adjuvants have the advantage of just requiring a little dose to have an adjuvant effect and can alter the cell-mediated immune response as well as improve the production of antibodies, and [46] who reported that Saponin-based adjuvants (SBAs) are promising new adjuvants that stand out as they not only enforce CD4+T cellmediated immunity but also motivate the antibody response.…”

“…The produced solution was autoclaved at 121˚C for 20 minutes for heat sterilization. It was then kept at 4˚C until it was needed as a stabilizer again [26].…”

“…On the other hand, trials were done to produce a lyophilized inactivated vaccines, one of these trials that was done by [11] using different adjuvants like skimmed milk, gelatin and sucrose lactalbumin. Another trial was carried out by [12] who reported that the prepared combined BEF and RVF freeze-dried vaccine with Carbopol elicited a better humoral immune response. Also [13] concluded that the lyophilized inactivated RVF vaccine using Saponin as a diluent is more highly immunogenic and economic than the ALOH inactivated RVF vaccine so they recommended using lyophilized inactivated RVF Carbopol is a synthetic polymer that finds extensive use in the pharmaceutical industry.…”