IgM and IgG antibodies to hepatitis E virus (HEV) detected by an enzyme immunoassay based on an HEV-specific artificial recombinant mosaic protein

To develop an enzyme immunoassay (EIA) for IgM antibody to hepatitis E virus (HEV) (IgM anti‐HEV) and IgG antibody to HEV (IgG anti‐HEV), a synthetic gene encoding several liner immuno‐dominant antigenic epitopes from HEV structural proteins was assembled as a chimeric recombinant mosaic protein (Mpr) with glutathione S‐transferase and used as an immunodiagnostic target. In addition, a neutralization confirmation test was developed using individual synthetic peptides. Among 614 patients with acute hepatitis from 10 geographically distinct outbreaks, IgG anti‐HEV was found in 546 (88.9%), with a range of 77–100% depending on the outbreak. Of 130 patients tested for IgM anti‐HEV, 126 (96.9%) were positive. Among patients tested within 4 months of onset of jaundice, 37/37 (100%) were IgG anti‐HEV positive. For patients from whom sera were collected 1–16 days after onset of jaundice, the geometric mean IgG titer (GMT) was 1:47,000; the GMT increased to 1:70,710 30–40 days after onset of jaundice and decreased to 1:1,778 3–4 months after the onset of jaundice. For patients tested 6–8 months after onset of jaundice, 11/12 (92%) were IgG anti‐HEV positive, and the GMT was 1:2,908. IgM anti‐HEV was detected in 43/43 (100%) sera collected 1–40 days after onset of jaundice, and the GMT for IgM anti‐HEV was 1:10,000 at that time. For sera collected 3–4 and 6–12 months after onset of jaundice, 7/14 (50%) and 5/12 (40%) respectively, were IgM anti‐HEV positive. In conclusion, an artificial mosaic protein composed of linear antigenic epitopes from open reading frame 2 (ORF2) and ORF3 of HEV has been successfully applied to the development of a sensitive and specific EIA for the detection of IgG and IgM anti‐HEV activity. These assays were used for the verification of HEV infection in outbreak settings and for the diagnosis of HEV infection in sporadic cases. © 1996 Wiley‐Liss, Inc.