Comparative Studies on the Diagnosis of Hepatitis E Virus Antibodies with ORF-2 and ORF-3 Proteins Expressed in Insect Cells.

Abstract

Hepatitis E is a worldwide health problem, especially in developing countries. The virus genome contains three different open reading frames (ORFs): ORF-1, which is believed to encode nonstructural proteins, and ORF-2 and ORF-3, which are believed to encode structural proteins. Presently, serologic tests for the detection of human antibodies to hepatitis E virus (HEV) infection are primarily based on the ORF-2 structural protein expressed in Escherichia coli, insect cells or synthetic peptides. We report here the comparative studies on the diagnosis of HEV infection with full-length ORF-2 and ORF-3 proteins expressed in insect cells. We found that 31 of 74 (42%) sera were positive for IgM antibody to HEV (anti-HEV) using the ORF-2 protein as an antigen, as compared to 6 of 74 sera (8%) using the ORF-3 protein as an antigen (p < 0.001). Similarly, 49 of 74 sera (66% were positive for IgG anti-HEV utilizing the ORF-2 protein versus 12 of 74 sera (16%) when the ORF-3 protein was used (p < 0.001). These results suggest that the recombinant ORF-2 protein is more sensitive as a diagnostic antigen for detecting antibodies to HEV in both acute-phase and convalescent-phase sera than ORF-3 protein. Copyright 1996 S. Karger AG, Basel