Virus-like particles and GB agent hepatitis

Sequence analysis of hepatitis GB virus C (GBV-C) isolates from 14 patients

In 1995, a new human hepatitis virus belonging to the family Flaviviridae was described and designated hepatitis GBV-C. To investigate variations within the genome of GBV-C and to study the relationship of GBV-C to GBV-A/B or hepatitis C virus (HCV), we established a detection system using reverse transcriptase polymerase chain reaction (RT-PCR) of the putative helicase region (NS3). So far, isolates derived from 14 different GBV-C-positive sera were analyzed (GBV-C/S3-36), showing 80.1-89.4% (mean: 85%) identical nucleotides. The deduced amino acid sequences revealed 97.3% homology. Nucleotide sequences of GBV-C/S3-36 revealed about 60% identity to GBV-A as well as to HCV, but only 56% identity to GBV-B. Amino acid sequences revealed 73.4 and 68.6% similarity to GBV-A and GBV-B, respectively, but a slightly higher percentage of 78.5% to HCV sequences. Thus, according to the putative GBV-C helicase sequence, a subtyping of GBV-C into different genotypes may be necessary.

GB virus C/hepatitis G virus and other putative hepatitis non A-E viruses

The identification of the major agents causing human hepatitis (Hepatitis A, B, C, D and E Viruses) was achieved during the last 30 years. These viruses are responsible for the vast majority of human viral hepatitis cases, but there are still some cases epidemiologically related to infectious agents without any evidence of infection with known virus, designated as hepatitis non A-E. Those cases are considered to be associated with at least three different viruses: 1--Hepatitis B Virus mutants expressing its surface antigen (HBsAg) with altered epitopes or in low quantities; 2--Another virus probably associated with enteral transmitted non A-E hepatitis, called Hepatitis F Virus. Still more studies are necessary to better characterize this agent; 3--Hepatitis G Virus or GB virus C, recently identified throughout the world (including Brazil) as a Flavivirus responsible for about 10% of parenteral transmitted hepatitis non A-E. Probably still other unknown viruses are responsible for human hepatitis cases without evidence of infection by any of these viruses, that could be called as non A-G hepatitis.

Hepatitis G virus/GB virus C in Brazil. Preliminary report

Hepatitis G virus/GB virus C is a novel flavivirus recently detected in hepatitis non A-E cases. In this study, the presence of this virus in chronic non-B, non-C hepatitis patients was evaluated using GBV-C specific PCR and this virus was detected in one out of thirteen patients. This patient has presented a severe liver failure, has lived for a long time in the Western Amazon basin and no other cause for this clinical picture was reported. The impact of the discovery of this new agent is still under evaluation throughout the world. The study of the prevalence of this virus among chronic hepatitis patients and healthy individuals (as blood donors) will furnish subside to evaluate its real pathogenicity.

The GB hepatitis viruses

The genomes of three new flavi-like viruses, GBV-A, GBV-B and GBV-C have been identified. Nucleic acid molecules corresponding to the genomes of GBV-A and GBV-B were isolated from tamarins with hepatitis which had been infected with the GB agent. RNA sequences corresponding to GBV-C have been shown to be present in sera from humans with non-A-E hepatitis. Sequence comparisons show that these three viruses are more closely related to each other and to hepatitis C virus (HCV) than to any other known viruses. Together with HCV they appear to form a discrete cluster of related viruses within the larger genus of flaviviridae. The pathological significance of these viruses and their association with hepatitis is currently emerging.

Studies of GB hepatitis agent in tamarins

Three tamarins (Saguinus labiatus), two of which had previously been infected with hepatitis A virus and parenteral non-A, non-B hepatitis, were inoculated intravenously with the agent of GB hepatitis. All three animals developed alanine aminotransferase abnormalities 2 weeks after inoculation. Peak alanine aminotransferase levels were recorded 4 weeks postinoculation. These declined thereafter but continued to fluctuate at abnormal levels for 32 weeks. Liver biopsies showed liver cell swelling and inflammation with focal necrosis. Portal tracts and areas around central veins were heavily infiltrated with mononuclear cells. A fourth animal (no previous exposure to hepatitis viruses) inoculated with GB was killed on Day 15 postinoculation. Serum and extracts of liver and feces from this day were used as inocula for three other animals. Only the serum and liver extract transmitted GB hepatitis. The fecal specimen did not transmit and a fecal extract taken at a later date from another animal was also noninfectious. GB hepatitis virus is distinct from the viruses causing Type A and blood-borne non-A, non-B-hepatitis. Although the virus is present in serum and has previously been transmitted per os, it is not shed in feces.

Diagnostic virology using electron microscopic techniques

This chapter illustrates the development of the use of electron microscopy in viral diagnosis. The field covered is confined to medical viral diagnosis, but parallel developments have taken place in both veterinary and botanical fields and techniques derived from both these sources are also included where relevant. It is reported that the scanning transmission mode of operation, which can induce image contrast changes electronically, may enhance studies with unstained sections and perhaps facilitate thin section immune electron microscopy (IEM). The application of negative stain IEM has been particularly useful for the study of the antigenic nature of some of the newly discovered noncultivable viruses. Viral antigens can also be detected in thin sections of infected cells by IEM with suitably labeled specific antibodies. Confirmation of viral infection by electron microscopy on tissues originally processed for light microscopy is also frequently useful.

Circulating immune complexes in non-A, non-B hepatitis. Possible masking of viral antigen

Serial serum samples from 22 patients with transfusion-associated non-A, non-B hepatitis and 2 chimpanzees with the experimentally induced disease were tested for circulating immune complexes by Raji-cell radioimmunoassay. 13 patients (59%) and 1 chimpanzee had circulating immune complexes immediately before, coincident with, or during the return to normal of raised aminotransferase activity. 7 of the 10 patients with chronic non-A, non-B hepatitis had detectable complexes at levels which waxed and waned in parallel with changes in serum aminotransferase activity. Immune complexes may contain and mask viral antigens, and their presence may explain the failure of conventional immunological techniques to detect virus antigens.