Genetic identification and characterization of a novel virus related to human hepatitis E virus from chickens with hepatitis-splenomegaly syndrome inthe United States

Hepatitis-splenomegaly (HS) syndrome is an emerging disease in chickens in North America; the cause of this disease is unknown. In this study, the gen etic identification and characterization of a novel virus related to human hepatitis E virus (HEV) isolated from bile samples of chickens with HS synd rome is reported. Based upon the similar genomic organization and significa nt sequence identity of this virus with HEV, the virus has been tentatively named avian HEV in order to distinguish it from human and swine HEV. Elect ron microscopy revealed that avian HEV is a nonenveloped virus particle of 30-35 nm in diameter. The sequence of the 3' half of the viral genome (simi lar to 4 kb) was determined. Sequence analyses revealed that this genomic r egion contains the complete 3' non-coding region, the complete genes from o pen reading frames (ORFs) 2 and 3, the complete RNA-dependent RNA polymeras e (RdRp) gene and a partial helicase gene from ORF 1. The helicase gene is the most conserved gene between avian HEV and other HEV strains, displaying 58-61 % as and 57-60% nt sequence identities. The RdRp gene of avian HEV s hares 47-50% as and 52-53% nt sequence identities and the putative capsid g ene (ORF 2) of avian HEV shares 48-49% as and 48-51 % nt sequence identitie s with the corresponding regions of other known HEV strains. Phylogenetic a nalysis indicates that avian HEV is genetically related to, but distinct fr om, other known HEV strains. This discovery has important implications for HEV animal models, nomenclature and natural history.