Hepatitis E Virus ORF3 Antigens Derived From Genotype 1 and 4 Viruses are Detected With Varying Efficiencies by an Anti-HEV Enzyme Immunoassay

The function of the hepatitis E virus (HEV) open reading frame 3 (ORF3) protein product remains unclear but it is able to induce a strong antibody response following HEV infection. Therefore, it has been used in some enzyme immunoassays (EIAs) for detecting anti-HEV antibody. In order to evaluate the difference in antigenicity of HEV ORF3 polypeptides derived from genotypes 1 and 4, two EIAs were developed, based on ORF3 polypeptides from genotypes 1 and 4 HEV. Serial weekly serum samples from two rhesus monkeys vaccinated with ORF3 antigens derived from the genotype 4 ORF3 protein and nine rhesus monkeys experimentally infected with genotypes 1 and 4 HEV were tested for anti-HEV using the assays. HEV ORF3 antigens derived from viruses of genotypes 1 and 4 showed different patterns of reactivity with sera obtained from monkeys immunized with ORF3 antigens or infected experimentally with HEV. The genotype 1 ORF3 polypeptide exhibited stronger reactivity with the sera from monkeys infected with genotype 1 than the genotype 4 ORF3 polypeptide. The genotype 4 ORF3 polypeptide demonstrated stronger reactivity with the sera from monkeys infected with genotype 4 than did the genotype 1 ORF3 polypeptide. The HEV ORF3 polypeptide contains genotype-specific antigens and the antigen-antibody reactions between the same genotypes were stronger than those between different genotypes. J. Med. Virol. 83: 827-832, 2011. (C) 2011 Wiley-Liss, Inc.