Empty virus-like particle-based enzyme-linked immunosorbent assay for antibodies to hepatitis E virus

Hepatitis E, an enterically transmitted non-A, non-B hepatitis, is a seriou s viral infection that occasionally causes large epidemics in developing co untries. In developed countries, the disease only appears sporadically due to the transmission routes, and it is considered to be less important. The hepatitis E virus (HEV) cannot grow in cultured cells and no reliable assay system has ever been developed. In addition, the present diagnostic are no t perfect, and actual rates of HEV infection may be underestimated. Highly purified empty virus-like particles (VLPs) of HEV have been produced by the use of a recombinant baculovirus vector in insect cells. Using these VLPs as an antigen, an enzyme-linked immunosorbent assay (ELISA) for antibodies to HEV was developed. A panel of 164 sera that were randomized and coded, a nd sera collected periodically from three patients with hepatitis E were us ed for the evaluation. The sensitivity of the assay was shown to be equal t o or better than that obtained in previous research that used the same seru m panel. The ELISA demonstrated that the serum IgM level of the patients wa s highest at the onset of the clinical illness and then rapidly decreased. In contrast, a high level of circulating IgG antibody titers lasted for mor e than 4 years. In Japan, a non-endemic country, the prevalence of the IgG class antibody to HEV in healthy individuals was found to range from 1.9% t o 14.1%, depending on the geographical area. Only one out of 900 (0.1%) ser um samples was IgM-positive. The IgM class antibody to HEV was detected in 10.8% of non-A, non-B, and non-C acute hepatitis patients in northeast Chin a, whereas none of the patients in Korea had the IgM antibody. The ELISA ut ilizing the VLPs is sensitive and specific in its detection of the IgM and IgG antibodies to HEV. The ELISA is therefore useful for diagnosing HEV inf ection and for seroepidemiological study of hepatitis E. J. Med. Virol. 62: 327-333, 2000. (C) 2000 Wiley-Liss, Inc.