Immunogenicity of HGV NS5 protein expressed from Sf9 insect cells

Abstract

Although reliable assays for the detection of hepatitis C virus and E virus became available, still 10%-20% hepatitis are not caused by hepatitisA-E virus[1-3]. In 1996, two research groups isolated this agent independently and almost simultaneously and named hepatitis G virus and GB virus C, respectively[4-7]. The nucleotide and amino acid homologies between GBV-C and hepatitis G virus (HGV) were 85% and 95%[5-7]. Therefore, GBV-C and HGV were considered as two different isolates of the same virus, referred to as HGV in this paper. HGV is a single-strand, positive sense RNA virus with approximately 9.4 kb in length, and classified as a member of Flaviviridae. HGV is mainly transmitted through transfusion and could be responsible for chronic liver infection. HGV RNA has been detected in the serum of intravenous drug users (IVDUs), volunteer and commercial blood donors, and patients with cryptogenic hepatitis[8-10]. Until now, RT-PCR is the most commonly used method for the diagnosis of HGV infection. It is necessary to develop a more convenient antibody detection assay. The baculovirus expression system is of a strong polyhedrin promoter[11], and can carry out many types of postranslation modification for a variety of proteins. Most of the expressed proteins were usually shown to be antigenic, immunological, and functionally similar to their authentic counterparts[12-16]. In this study, we used the baculovirus expression system to express HGV NS5 protein in Sf9 cells, and studied its immunogenecity.