Submitted to: Virus Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 2, 2002
Publication Date: July 1, 2002
Interpretive Summary: Emerging or newly discovered viruses are becoming more of a threat to both human and animal health. Some of these viruses belong to the calicivirus family of viruses. Two groups of caliciviruses, human enteric calicivirus (HECV) and porcine enteric calicivirus (PECV), do not grow in cell cultures. The HECV are a major cause of viral food poisoning. There is evidence that PECV may be involved in diarrhea outbreaks in swine herds. The inability to grow these viruses in the laboratory makes them difficult to study. To better understand the biology of the caliciviruses in general, feline caliciviruses (FCV) that grow well in the laboratory were studied. We examined a defective virus particle that has been shown to be associated with avirulent viruses. We found that the defective virus contained an RNA produced by FCV for production of virus coat protein. These particles are not able to infect a cell. This is the first step in understanding why some strains of FCV are virulent and some avirulent. This information will allow researchers to understand this mechanism and apply it to other caliciviruses.
Technical Abstract: 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. 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 dnot a genomic RNA containing rearrangements or deletions.