Immunobiological features of an attenuated African swine fever virus strain FC-135 grown in a porcine bone marrow cell suspension

For many years, efforts of research scientists have been directed towards obtaining and testing of various attenuated variants of African swine fever (ASF) virus to develop specific methods for ASF prevention. Similar investigations were also carried out in the All-Russian Institute of Veterinary Virology and Microbiology which resulted in obtaining an attenuated ASF virus variant FC-135 through passaging a virulent strain France-32 of serotype 4 (V.A. Burlackov et al., 1979). The above strain grown in a porcine bone marrow (PBM) monolayer cell culture and taken at a 25-fold concentration provided 85 to 100 % protection from infection with a homologous virulent ASF virus. Because of higher manufacturability, performance and cost effectiveness of a suspension culture method as compared to those for a monolayer one, the investigation of antigenic and immunogenic activity of a virus-containing emulsified preparation produced in bioreactors from an ASF virus strain FC-135 grown in a PBM cell suspension was of some interest. The results of the reported research showed that when culturing the attenuated ASF virus strain FC-135 in PBM cell suspension in bioreactors, the highest virus accumulation levels of 7.50 to 8.00 lg HAU 50/cm 3 were observed after 4 day cultivation, and CF-antibody levels of 1:16 to 1:32 were indicated after 5 to 6 day cultivation. The titers of the virus grown in a PBM cell monolayer in mattresses were 0.25 to 0.50 lg HAU 50/cm 3 lower than those as seen in the previous case, although CF-antibody levels as observed within the same period were of 1:16. A concentrated emulsified preparation designed from the strain FC-135 grown in a PBM cell suspension using bioreactors provided protection of gilts against infection with a homologous virulent virus for 4 months (observation period). Also, we showed that the suspension method of the attenuated strain FC-135 culture in PBM cells using automated bioreactors, being more manufacturable, productive and cost-efficient as compared to the monolayer growth in mattresses, when applied under controlled conditions, provided production of homologous virus materials exhibiting high biological activity.