Development of an Inactivated Vaccine from Attenuated Camelpox Virus Strain: Safety and Protection in Camels

This article describes the technology of preparing an inactivated vaccine from an attenuated strain of camelpox. The attenuated camelpox virus (CMLV) was grown in lamb kidney cells and in Vero cells. CMLV was accumulated to a significantly higher (p≤0.05) titer in lamb kidney cells (7.75±0.08 log TCID50/ml) than in Vero cells (4.00±0.14 log TCID50/ml). During virus inactivation, a concentration of 0.05% beta-propiolactone (BPL) completely inactivated the virus in 6 h at a temperature of 22 ± 1 °C, while a concentration of 0.2% formaldehyde inactivated the virus in 8 h. However, a viral antigen inactivated by BPL was used for vaccine preparation. The inactivated viral antigen was adsorbed with aluminum hydroxide gel, and as a result, an inactivated candidate vaccine was prepared. While the safety of the candidate vaccine was tested in camels and white mice, the protective efficacy of the vaccine was only tested in camels. In the safety evaluation of the inactivated vaccine, the vaccine did not cause any adverse effects in mice and camels. During the immunogenicity study in camels, antibody formation started (0.2 ± 0.16 log2) from the 21st day post-vaccination (DPV), the antibody titer peaked (1.33 ± 0.21 log2) at the 60th DPV and decreased at the 90th DPV (0.50 ± 0.22 log2). Furthermore, no antibodies were detected in vaccinated camels from 180 to 365 DPV. Vaccinated camels challenged with wild-type virus remained healthy even though they did not have antibodies, whereas at that time, unvaccinated camels were affected by camel pox during the challenge.