The subgenomic RNA of feline calicivirus is packaged into viral particles during infection

During infection, feline calicivirus (FCV) produces an abundant subgenomic RNA of 2.4 kb that is the major template for translation of the single capsid protein. Feline cells infected with FCV (CFI/68 strain) at a high multiplicity of infection produced a population of lower density (ld) viral particles with a density of 1.35 g/cc as compared to the 1.39 g/cc density of the wild-type virus particle. The RNA isolated from the ld particles was 2.4 kb in size, the same as that of the intracellular subgenomic transcript that encodes the single capsid protein of the virus. Primer extension analysis revealed that the 5′ end of the RNA from the ld particles mapped to the same genomic location as the intracellular 2.4 kb RNA. RNA protection of the ld RNA using a FCV 4.2 kb minus strand cDNA containing 1984 bases of capsid protein coding sequences, protected an RNA fragment of approximately 2000 bases. The data presented here demonstrates that the ld particles contains the FCV subgenomic RNA and not a genomic RNA containing rearrangements or deletions.