Construction and characterization of infectious cDNA clones of a chicken strain of hepatitis E virus (HEV), avian HEV.

Hepatitis E virus (HEV), the causative agent of hepatitis E, is an important human pathogen. Increasing evidence indicates that hepatitis E is a zoonosis. Avian HEV was recently discovered in chickens with hepatitis-splenomegaly syndrome in the USA. Like swine HEV from pigs, avian HEV is also genetically and antigenically related to human HEV. The objective of this study was to construct and characterize an infectious cDNA clone of avian HEV for future studies of HEV replication and pathogenesis. Three full-length cDNA clones of avian HEV, pT7-aHEV-5, pT7G-aHEV-10 and pT7G-aHEV-6, were constructed and their infectivity was tested by in vitro transfection of leghorn male hepatoma (LMH) chicken liver cells and by direct intrahepatic inoculation of specific-pathogen-free (SPF) chickens with capped RNA transcripts from the three clones. The results showed that the capped RNA transcripts from each of the three clones were replication competent when transfected into LMH cells as demonstrated by detection of viral antigens with avian HEV-specific antibodies. SPF chickens intrahepatically inoculated with the capped RNA transcripts from each of the three clones developed active avian HEV infections as evidenced by seroconversion to avian HEV antibodies, viraemia and faecal virus shedding. The infectivity was further confirmed by successful infection of naïve chickens with the viruses recovered from chickens inoculated with the RNA transcripts. The results indicated that all three cDNA clones of avian HEV are infectious both in vitro and in vivo. The availability of these infectious clones for a chicken strain of HEV now affords an opportunity to study the mechanisms of HEV cross-species infection and tissue tropism by constructing chimeric viruses among human, swine and avian HEVs.