GB agents See GB viruses

GB viruses Isolated from a surgeon (George Barker) with acute non A-non B hepatitis, by injection of his serum into marmosets (tamarins) of Saguinus sp which then developed hepatitis. Could be serially passed in marmosets. Immunologically and structurally distinct from the Hepatitis A, B, C and E viruses. Two GB viruses (GBV-A and GBV-B) were isolated recently by representational difference analysis and molecular cloning from the serum of an infected marmoset, and have been shown to be new members of the Flaviviridae associated with GB agent hepatitis. A third virus, GB virus C, was identified in human sera by reverse-transcription and polymerase chain reaction using consensus primers based on the GBV-A, GBV-B and Hepatitis C helicase gene, and appears to be identical to Hepatitis G virus. For this reason the virus is usually called GB virus C/Hepatitis G virus. Although GBV-C/HGV has not been shown to cause hepatitis it seems to be able to infect liver as well as spleen cells without causing obvious disease symptoms. It is widely distributed in the human population worldwide.

Birkenmeyer LG et al (1998) J Med Virol 56, 44 Deinhardt F et al (1967) J Exp Med 125, 673 Mushahwar IK (2000) J Med Virol 62, 399

GB virus A An unassigned species in the family Flaviviridae. One of two fla-viviruses isolated from the serum of marmosets infected with GB virus. It has been identified in at least six species of New World monkeys since its discovery. The virus is transmissible via blood, but the natural mode of transmission is not known. Does not seem to cause hepatitis in the host species or other susceptible species. The positive-stranded RNA genome is related to the hepacivirus genome but lacks a complete capsid protein gene, and differs in the organization of the 3'-non-coding region.

Charrel RN et al (1999) J Gen Virol 80, 2329 Erker JC et al (1998) J Gen Virol 79, 41

GB virus B (GBV-B) An unassigned species in the family Flaviviridae. One of two fla-viviruses isolated from the serum of

GeLu cells marmosets infected with GB virus. It is transmissible via blood and causes hepatitis in several species of New World monkeys. It has not been detected in humans. Closely resembles Hepatitis C virus by sequence homology and organization.

GB virus-C/Hepatitis G virus (GBV-C/HGV) An unassigned species in the family Flaviviridae. A positive single-stranded RNA virus (genome 9.4 kb in length) of human origin. GBV-C was discovered by reverse transcription and PCR of human plasma using consensus primers based on the genomes of GBV-A, GBV-B and Hepatitis C viruses. Soon after, hepatitis G was discovered independently by cloning and expression of RNA amplified from human serum, but the genome sequences of the two isolates were almost identical, so they currently go under the clumsy name of GB virus C/hepatitis G virus. The viruses do not appear to cause hepatitis, even though they have been shown to infect the liver, and are widely distributed geographically, but much needs to be learned about their natural history and biology in humans. They can be transmitted experimentally to chimpanzees, without causing hepatitis. The viruses appear to be genetically heterogeneous, and distinct variants have been reported to differ in tropism for different organs. Some strains appear to be lym-photropic, not hepatotropic, viruses.

Fogeda M et al (2000) J Virol 74, 7936 Hadlock KG and Foung SKH (1997) Trans Med Rev 12, 94

GB virus-C troglodytes (GBV-Ctro) A virus genome amplified from the serum of a chimpanzee (Pan troglodytes). Probably a chimpanzee virus related to the GB viruses, with the highest homology to GBV-C/HGV. The significance of this virus in nature has yet to be determined.

Birkenmeyer LG et al (1998) J Med Virol 56, 44

GBB virus An isolate of Seoul virus in the genus Hantavirus obtained from laboratory rats in England.

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