GB virus C

GB virus C (GBV-C), formerly known as hepatitis G virus (HGV) and also known as Human pegivirus – HPgV is a virus in the family Flaviviridae and a member of the Pegivirus, is known to infect humans, but is not known to cause human disease. There have been reports that HIV patients coinfected with GBV-C can survive longer than those without GBV-C, but the patients may be different in other ways. There is current active research into the virus' effects on the immune system in patients coinfected with GBV-C and HIV. The majority of immune-competent individuals clear GBV-C viraemia, but in some individuals infection persists for decades. However, the time interval between GBV-C infection and clearance of viraemia (detection of GBV-C RNA in plasma) is not known. Approximately 2% of healthy US blood donors are viraemic with GBV-C, and up to 13% of blood donors have antibodies to E2 protein, indicating possible prior infection. Parenteral, sexual and vertical transmission of GBV-C have been documented. Because of shared modes of transmission, individuals infected with HIV are often coinfected with GBV-C; the prevalence of GBV-C viraemia in HIV patients ranges from 14 to 43%. Several but not all studies have suggested that coinfection with GBV-C slows the progression of HIV disease. In vitro models also demonstrated that GBV-C slows HIV replication. This beneficial effect may be related to action of several GBV-C viral proteins including NS5A phosphoprotein and E2 envelope protein. It has a single stranded positive RNA genome of about 9.3 kb and contains a single open reading frame (ORF) encoding two structural (E1 and E2) and five non-structural (NS2, NS3, NS4, NS5A, and NS5B) proteins. GB-C virus does not appear to encode a C (core or nucleocapsid) protein like, for instance, hepatitis C virus. Nevertheless, viral particles have been found to have a nucleocapsid. The source of the nucleocapsid protein remains unknown. GBV-C is a member of the Flaviviridae family and is phylogenetically related to hepatitis C virus, but replicates primarily in lymphocytes, and poorly, if at all, in hepatocytes. GBV-A and GBV-B are probably tamarin viruses, while GBV-C infects humans. The GB viruses have been tentatively assigned to a fourth genus within the Flaviviridae named 'Pegivirus', but this has yet to be formally endorsed by The International Committee on Taxonomy of Viruses. Another member of this clade, GBV-D, has been isolated from a bat (Pteropus giganteus). GBV-D may be ancestral to GBV-A and GBV-C.