Hog cholera virus: identification and characterization of the viral RNA and the virus-specific RNA synthesized in infected swine kidney cells.

Virus-specific RNA in swine kidney cells infected with hog cholera virus and the RNA of gradient-purified virions were identified and characterized. The time curve for virus replication in SK-6 cells was established. The logarithmic phase of virus growth was between 4 and 12 h after virus adsorption. Virus production was maximum at 20 h after virus adsorption. Analysis of cytoplasmic RNA in a neutral agarose gel showed that the time curve for synthesis of a high molecular weight RNA in infected cells closely paralleled that for virus growth. Electrophoresis in an agarose-formaldehyde gel of [3H]uridine-labeled RNA, synthesized with actinomycin-D, showed that this high molecular weight RNA species was approximately 12 kilobases (kb) in length. RNA, extracted from virions purified in a glycerol-tartrate gradient, co-migrated in a neutral agarose gel with the 12 kb RNA species; moreover, it hybridized specifically with a cDNA clone prepared against the intracellular 12 kb RNA. These results confirm the virus-specific nature of the 12 kb RNA. Since no prominent subgenomic virus-specific RNA was identified in infected cells, an RNA species of this size may also act as a messenger RNA.