Development of a live cell culture camelpox vaccine.

A Saudi isolate of camel orthopoxvirus was serially propagated on monolayers of camel kidney cell cultures. The attenuation of the 78th passage was tested in two susceptible camels. Two other susceptible camels were inoculated with vaccinia virus four times propagated in camel kidney cell cultures. The four inoculated camels showed no postinoculation clinical symptoms and formed neutralizing antibodies against both the camel orthopox and vaccinia viruses. No postchallenge clinical symptoms were observed in these four camels, while two non-inoculated contact control camels showed typical symptoms of generalized camelpox. These results indicated the safety and potency of the 78th passage of the Saudi isolate of camel orthopoxvirus (designated Jouf-78) to be used for production of live attenuated cell culture camelpox vaccine. The field testing of the vaccine was carried out on two farms using at least 10(3) TCID50 as a recommended field dose. None of the inoculated camels showed any postvaccination reaction and the serological tests showed seroconversion of many vaccinated field camels. The relationship between camel orthopoxvirus and vaccinia virus as well as the advantages of the live attenuated camelpox vaccine are discussed.