The sequence and phylogenetic analysis of a novel hepatitis E virus isolated from a patient with acute hepatitis reported in the United States.

A variant of hepatitis E virus (HEV), designated HEV US-1, was identified in a hepatitis patient in the United States (US); the patient had no history of travel to areas where HEV is endemic. Nucleotide sequences were obtained from the 5' end of open reading frame (ORF) 1 (1418 nt), the 3' end of ORF1 (1359 nt), the entire ORF2 and ORF3 regions, and the 3'-untranslated region (2127 nt). The HEV US-1 strain is significantly divergent from other human HEV isolates with nucleotide identities ranging from 76.8 to 77.5%. Phylogenetic analyses indicate that HEV US-1 and a recently discovered HEV variant from swine may represent separate isolates of a new strain of HEV, significantly divergent from the Mexican and Burmese strains. Synthetic peptides derived from the carboxyl amino acids of ORF2 and ORF3 were shown to be useful for detecting exposure to HEV. In addition, IgM class antibodies directed against HEV US-1 synthetic peptides were detected in the US patient infected with HEV US-1, but were absent using synthetic peptides from the Burmese or Mexican strains of HEV. A preferential reactivity to HEV US-1 specific peptides has lead to the identification of a second isolate of this virus also from a patient with acute hepatitis from the US. The discovery of these HEV variants may be important in understanding the worldwide distribution of HEV infection.