Hepatitis G virus (GB-C)
Last reviewed: 23.04.2024
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Hepatitis G virus (HGV) was discovered in 1995, belongs to the family Flaviviridae (genus Hepacivirus). The genome of the G virus is a single-stranded unfragmented positive RNA of 9500 bases in length. The structural organization of the genome of the G virus is similar to that of HVC. The genome contains one large reading frame that encodes a polyprotein precursor containing about 2,800 amino acid residues. It is cut by cellular and viral proteases with the formation of two structural and not less than five non-structural proteins. The genes encoding the structural proteins (cor and env) are adjacent to the 5 'end of the viral RNA, and the genes of the non-structural proteins (helicase, protease, polymerase) are at the 3' end. It was found that non-structural HGV genes are similar to the genes of the hepatitis C virus, as well as the GBV-A and GBV-B viruses. All these viruses are isolated in one genus of Hepacivirus family Flaviviridae.
According to the structure of structural HGV genes have nothing to do with GBV-A and HCV and only remotely resemble GBV-B. The hepatitis G virus was identical to the GBV-C virus, which was also isolated in the study of a subpopulation of GBV viruses from tamarin monkeys, through which the RNA virus was passed from a patient with acute hepatitis of unknown origin bearing GB initials; in honor of him, all these viruses and received the name of hepatitis viruses GBV-A, GBV-B, GBV-C. The HGV virus (GB-C) has a defective co-protein and has less pronounced variability than HCV. There are 3 types and 5 subtypes of the HGV genome. Genotype 2a dominates, including in Russia, Kazakhstan and Kyrgyzstan.
RNA of HGV is constructed according to the scheme characteristic for the entire family of flaviviruses: at the 5 'end there is a zone encoding structural proteins. At the 3 'end, a zone encoding non-structural proteins.
The RNA molecule contains one open reading frame (ORF); encodes the synthesis of a predecessor polyprotein, consisting of approximately 2900 amino acids. The virus has constant regions of the genome (used to create primers used in PCR), but it also differs by considerable variability, which is explained by low reliability of the reading function of the viral RNA polymerase. It is believed that the virus contains co-protein (a nucleocapsid protein) and surface proteins (super-capsid proteins). Various variants of capsid proteins were found in different isolates; it can also be assumed that defective capsid proteins exist. Different variants of nucleotide sequences of HGV in different isolates are regarded as different subtypes within a single genotype or as intermediate between genotypes and subtypes. However, some authors believe that there are different genotypes of HGV, referring to the latter and GBV-C and HGV-prototype.
Markers of the G virus are found in 2% of the population of these countries. The G virus is found in different countries of the world in 1-2% of blood donors, i.e., more often than the hepatitis C virus. Like the hepatocyte HBV / HCV virus, this virus is capable of persistence, but less often leads to chronic pathology, and this persistence occurs, probably, by the type of a healthy carrier. Acute clinical manifestations of hepatitis G are also less severe than in hepatitis B and C. For diagnosis of hepatitis G, use of CPR and IFM is used.
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