Construction of an infectious cDNA clone of genotype 1 avian hepatitis Evirus: characterization of its pathogenicity in broiler breeders and demonstration ofits utility in studying the role of the hypervariable region in virusreplication

摘要

A full-length infectious cDNA clone of the genotype 1 Korean avian hepatitis E virus(avian HEV) (pT11-aHEV-K) was constructed and its infectivity and pathogenicity wereinvestigated in leghorn male hepatoma (LMH) chicken cells and broiler breeders. Wedemonstrated that capped RNA transcripts from the pT11-aHEV-K clone were translationcompetent when transfected into LMH cells and infectious when injectedintrahepatically into the livers of chickens. Gross and microscopic pathologicallesions underpinned the avian HEV infection and helped characterize its pathogenicityin broiler breeder chickens. The avian HEV genome contains a hypervariable region(HVR) in ORF1. To demonstrate the utility of the avian HEV infectious clone, severalmutants with various deletions in and beyond the known HVR were derived from thepT11-aHEV-K clone. The HVR-deletion mutants were replication competent in LMH cells,although the deletion mutants extending beyond the known HVR were non-viable. Byusing the pT11-aHEV-K infectious clone as the backbone, an avian HEV luciferasereporter replicon and HVR-deletion mutant replicons were also generated. Theluciferase assay results of the reporter replicon and its mutants support the dataobtained from the infectious clone and its derived mutants. To further determine theeffect of HVR deletion on virus replication, the capped RNA transcripts from thewild-type pT11-aHEV-K clone and its mutants were injected intrahepatically intochickens. The HVR-deletion mutants that were translation competent in LMH cellsdisplayed in chickens an attenuation phenotype of avian HEV infectivity, suggestingthat the avian HEV HVR is important in modulating the virus infectivity andpathogenicity.