EXPRESSION OF THE GB VIRUS-C E2 GLYCOPROTEIN USING THE SEMLIKI-FOREST-VIRUS VECTOR SYSTEM AND ITS UTILITY AS A SEROLOGIC MARKER

A 336-amino-acid segment of the GB virus C second envelope protein (E2 ) has been produced in BHK-21 cells using the Semliki Forest virus vec tor system. Secretion of this protein was facilitated by deletion of a hydrophobic region at the C-terminus that may represent the membrane anchoring domain. The E2 protein recovered from the culture supernatan t exhibited a molecular mass of approximately 52 kDa, with the increas e in size relative to the polyprotein backbone being contributed by N- linked glycosylation. A radioimmunoprecipitation assay using GBV-C E2 was developed to test for the presence of antibodies against this prot ein in human sera. The prevalence of antibodies to E2 was high among i njection drug users and other individuals at risk for acquiring parent erally transmitted agents. There was a much higher percentage of anti- E2 seropositivity in GBV-C RT-PCR negative compared to GBV-C RT-PCR po sitive samples from these populations. In addition, serial samples fro m patients transfused with blood containing GBV-C showed seroconversio n to anti-E2 positivity and loss of GBV-C viremia as measured by RT-PC R within 11 months of transfusion in five of seven individuals. Thus, this system provided a rapid means to identify GBV-C E2 as a useful an tigen for the study of GBV-C exposure. (C) 1996 academic Press, Inc.