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

SIMPLE SUMMARY: Camelpox is an important infectious viral disease of camels. This viral infectious disease is considered one of the major concerns for camel breeding countries, and the most effective way to solve this problem is to develop a vaccine. In this research, we developed a vaccine against camelpox. Our developed vaccine was tested in mice and camels, and it was found that the candidate vaccine was innocuous to mice and camels. This developed vaccine can be used in camel breeding farms in the future to prevent significant economic losses caused by camel pox. ABSTRACT: This article describes the preparation of 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 TCID(50)/(mL)) than in Vero cells (4.00 ± 0.14 log TCID(50)/(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 tested only in camels. In the safety evaluation of the inactivated vaccine, the vaccine was not observed to cause any adverse effects in mice and camels. During the immunogenicity study in camels, antibody formation started (0.2 ± 0.16 log2) at Day 21 post-vaccination (PV), and the antibody titer peaked (1.33 ± 0.21 log2) at Day 60 PV and decreased at Day 90 PV (0.50 ± 0.22 log2). Furthermore, no antibodies were detected in vaccinated camels from Days 180 to 365 PV. Camels that received vaccination and were subsequently exposed to wild-type virus evinced a healthy state despite lacking antibodies. In contrast, unvaccinated camels exhibited susceptibility to camelpox upon challenge.