Visualization and characterization of GB virus-C particles: evidence for anucleocapsid

GB virus type C (GBV-C) is a member of the hepacivirus genus within the Fla viviradae. Persistent GBV-C infection is common in humans, yet it remains u nclear if GBV-C causes any disease, Although GBV-C infection has been assoc iated with acute non-A to non-E post-transfusion hepatitis, it does not app ear to cause chronic hepatitis, GBV-C is closely related to hepatitis C vir us (HCV), but indirect evidence suggests that it does not encode a core pro tein at the amino terminus of the open reading frame (ORF),This has led to speculation that GBV-C does not have a nucleocapsid, We evaluated the buoya nt density of GBV-C, and found very low density particles consistent with v irions, and intermediate density particles consistent with nucleocapsids in GBV-C-infected people, In addition, electron microscopy demonstrated an ap parent nucleocapsid within an enveloped particle. Although these biophysica l data strongly suggest that GBV-C utilizes a nucleocapsid, they do not ind icate the origin of the protein content of this particle. To assess this, w e evaluated patient plasma for reactivity with a synthetic oligopeptide rep resenting a conserved region near the amino terminus of the predicted ORE S pecific antibody was detected in some individuals, similar to data of Feuch t et al, who identified antibody against a recombinant core protein in GBV- C-infected people, These data indicate that GBV-C particles contain nucleoc apsids. RI least in some patients, the region upstream of the GBV-C E1 prot ein coding region appears to be expressed, and this region may represent th e structural protein of the nucleocapsid.