Evaluation of methods of avian leukemia virus inactivation in production of influenza vaccines

Abstract

The process of production of inactivated influenza vaccines involves a stage of inactivation of both the influenza virus and the possible viral contaminants that can come from the raw materials (chicken embryos). One of such contaminants is the avian leukemia virus. The minimum viral contaminant load reduction that the inactivating agents should guarantee is by 4 lg/ml; this or higher level of the deactivating ability ensures the finished vaccine is free from viral contaminants. The purpose of this work was to cultivate the leukemia virus to the titer of 5 lg/ml (minimum) and to measure the reduction of the avian leukemia virus titer in influenza vaccine intermediates upon exposure to the inactivating agents. The RAV-1 and RAV-2 leukemia virus strains and influenza vaccine intermediates such as virus-containing allantoic fluid and virus concentrates were used in the study. Avian leukemia virus titers were determined by enzyme immunoassay. We created conditions for cultivation of the RAV-1 and RAV-2 avian leukemia virus strains in the primary culture of chicken embryo fibroblasts (CEF); the inactivating agents considered were the most commonly used β-propiolactone and UV radiation. It was found that after 12 hours of exposure to β-propiolactone, the RAV-1 avian leukemia virus load decreased by 4.61 ± 0.46 lg, and that of RAV-2 strain - by 4.33 ± 0.33 lg, which indicates that β-propiolactone is an effective inactivating agent. Five minutes of exposure to UV radiation reduces the RAV-1 strain viral load by 4.22 ± 0.31 lg and RAV-2 strain viral load by 4.44 ± 0.48 lg.