A hepatitis E virus variant from the United States: molecular characterization and transmission in cynomolgus macaques.

The partial sequence of a hepatitis E virus (HEV-US1) isolated from a patient in the United States (US), suffering from acute viral hepatitis with no known risk factors for acquiring HEV, has been reported. These sequences were significantly different from previously characterized HEV isolates, alluding to the existence of a distinct human variant. In this paper, we report the near full-length sequences of HEV-US1 and a second US isolate (HEV-US2). HEV-US2 was identified in a US patient suffering from acute viral hepatitis. These sequences verify the presence of a new HEV strain in North America and provide information as to the degree of variability between variants. The HEV-US nucleotide sequences are 92% identical to each other and only 74% identical to the Burmese and Mexican strains. Amino acid and phylogenetic analyses also demonstrate that the US isolates are genetically distinct, suggesting the presence of three genotypes of HEV. Serum from the second US patient induced hepatitis following inoculation into a cynomolgus macaque. Within 2-4 weeks, HEV-US2 RNA was detectable in both the serum and faecal material coinciding with elevated serum alanine transaminase levels. Infection resolved as antibody titres increased 8 weeks post-inoculation.