Evidence that the GBV-C/hepatitis G virus is primarily a lymphotropic virus

Human pegivirus identified in severe myelitis and optic neuritis in immunocompromised patients: A pathogenic role for a forgotten virus?

The role of Human pegivirus (HPgV) in patients with encephalitis has been recently questioned. We present cases of 4 patients with similar clinical, biological, and radiological characteristics, including a past history of transplantation with long-term immunosuppression and a progressive course of severe and predominantly myelitis, associated in 3 cases with optic neuropathy causing blindness. Extensive workup was negative but analysis of the CSF by use of pan-microorganism DNA- and RNA-based shotgun metagenomics was positive for HPgV. This case series further supports the hypothesis of HPgV CNS infection and highlights the utility of metagenomic next-generation sequencing of CSF in immunocompromised patients.

Human Pegivirus Type 1: A Common Human Virus That Is Beneficial in Immune-Mediated Disease?

Two groups identified a novel human flavivirus in the mid-1990s. One group named the virus hepatitis G virus (HGV) and the other named it GB Virus type C (GBV-C). Sequence analyses found these two isolates to be the same virus, and subsequent studies found that the virus does not cause hepatitis despite sharing genome organization with hepatitis C virus. Although HGV/GBV-C infection is common and may cause persistent infection in humans, the virus does not appear to directly cause any other known disease state. Thus, the virus was renamed “human pegivirus 1” (HPgV-1) for “persistent G” virus. HPgV-1 is found primarily in lymphocytes and not hepatocytes, and several studies found HPgV-1 infection associated with prolonged survival in people living with HIV. Co-infection of human lymphocytes with HPgV-1 and HIV inhibits HIV replication. Although three viral proteins directly inhibit HIV replication in vitro, the major effects of HPgV-1 leading to reduced HIV-related mortality appear to result from a global reduction in immune activation. HPgV-1 specifically interferes with T cell receptor signaling (TCR) by reducing proximal activation of the lymphocyte specific Src kinase LCK. Although TCR signaling is reduced, T cell activation is not abolished and with sufficient stimulus, T cell functions are enabled. Consequently, HPgV-1 is not associated with immune suppression. The HPgV-1 immunomodulatory effects are associated with beneficial outcomes in other diseases including Ebola virus infection and possibly graft-versus-host-disease following stem cell transplantation. Better understanding of HPgV-1 immune escape and mechanisms of inflammation may identify novel therapies for immune-based diseases.

Review of human pegivirus: Prevalence, transmission, pathogenesis, and clinical implication

Human pegivirus (HPgV-1), previously known as GB virus C (GBV-C) or hepatitis G virus (HGV), is a single-stranded positive RNA virus belonging to the genus Pegivirus of the Flaviviridae family. It is transmitted by percutaneous injuries (PIs), contaminated blood and/or blood products, sexual contact, and vertical mother-to-child transmission. It is widely prevalent in general population, especially in high-risk groups. HPgV-1 viremia is typically cleared within the first 1–2 years of infection in most healthy individuals, but may persist for longer periods of time in immunocompromised individuals and/or those co-infected by other viruses. A large body of evidences indicate that HPgV-1 persistent infection has a beneficial clinical effect on many infectious diseases, such as acquired immunodeficiency syndrome (AIDS) and hepatitis C. The beneficial effects seem to be related to a significant reduction of immune activation, and/or the inhabitation of co-infected viruses (e.g. HIV-1). HPgV-1 has a broad cellular tropism for lymphoid and myeloid cells, and preferentially replicates in bone marrow and spleen without cytopathic effect, implying a therapeutic potential. The paper aims to summarize the natural history, prevalence and distribution characteristics, and pathogenesis of HPgV-1, and discuss its association with other human viral diseases, and potential use in therapy as a biovaccine or viral vector.

Detection of Virus-Related Sequences Associated With Potential Etiologies of Hepatitis in Liver Tissue Samples From Rats, Mice, Shrews, and Bats

Hepatitis is a major global health concern. However, the etiology of 10-20% hepatitis cases remains unclear. Some hepatitis-associated viruses, like the hepatitis E virus, are zoonotic pathogens. Rats, shrews, and bats are reservoirs for many zoonotic pathogens. Therefore, understanding the virome in the liver of these animals is important for the investigation of the etiologies of hepatitis and monitoring the emerging zoonotic viruses. In this study, viral metagenomics and PCR methods were used to investigate viral communities in rats, mice, house shrews, and bats livers. Viral metagenomic analysis showed a diverse set of sequences in liver samples, comprising: sequences related to herpesviruses, orthomyxoviruses, anelloviruses, hepeviruses, hepadnaviruses, flaviviruses, parvoviruses, and picornaviruses. Using PCR methods, we first detected hepatovirus sequences in Hipposideros larvatus (3.85%). We also reported the first detection of Zika virus-related sequences in rats and house shrews. Sequences related to influenza A virus and herpesviruses were detected in liver. Higher detection rates of pegivirus sequences were found in liver tissue and serum samples from rats (7.85% and 15.79%, respectively) than from house shrews. Torque teno virus sequences had higher detection rates in the serum samples of rats and house shrews (52.72% and 5.26%, respectively) than in the liver. Near-full length genomes of pegivirus and torque teno virus were amplified. This study is the first to compare the viral communities in the liver of bats, rats, mice, and house shrews. Its findings expand our understanding of the virome in the liver of these animals and provide an insight into hepatitis-related viruses.

Human Pegivirus Infection and Lymphoma Risk: A Systematic Review and Meta-analysis

BACKGROUND

Human pegivirus (HPgV) is a single-strand RNA virus belonging to the Flaviviridae. Although no definitive association between HPgV infection and disease has been identified, previous studies have suggested an association of HPgV viremia with risk of lymphomas.

METHODS

We conducted a systematic review and meta-analysis, including 1 cohort study and 14 case-control studies, assessing the association of HPgV viremia with adult lymphomas. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using a random-effects model, overall and by geographic region and lymphoma subtype.

RESULTS

The overall OR for lymphoma was 2.85 (95% CI, 1.98-4.11), with statistically significantly elevated ORs observed in 8 of 15 studies. There was a small amount of heterogeneity among studies (I2 = 28.9%; Q = 18.27, P = .16), and the funnel plot provided no evidence for publication bias. The strongest association with lymphoma risk was observed for studies from Southern Europe (OR, 5.68 [95% CI, 1.98-16.3]), whereas weaker ORs (with 95% CIs) were observed for studies from North America (2.24 [1.76-2.85]), Northern Europe (2.90 [.45-18.7), and the Middle East (2.51 [.87-7.27]), but all of similar magnitude. Participants with HPgV viremia had statistically significantly increased risks (OR [95% CI]) for developing diffuse large B-cell (3.29 [1.63-6.62]), follicular (3.01 [1.95-4.63]), marginal zone (1.90 [1.13-3.18]), and T-cell (2.11 [1.17-3.89]) lymphomas, while the risk for Hodgkin lymphoma (3.53 [.48-25.9]) and chronic lymphocytic leukemia (1.45 [.45-4.66]) were increased but did not achieve statistical significance.

CONCLUSIONS

This meta-analysis supports a positive association of HPgV viremia with lymphoma risk, overall and for the major lymphoma subtypes.

Discovery of a Novel Simian Pegivirus in Common Marmosets (Callithrix jacchus) with Lymphocytic Enterocolitis

From 2010 to 2015, 73 common marmosets (Callithrix jacchus) housed at the Wisconsin National Primate Research Center (WNPRC) were diagnosed postmortem with lymphocytic enterocolitis. We used unbiased deep-sequencing to screen the blood of deceased enterocolitis-positive marmosets for viruses. In five out of eight common marmosets with lymphocytic enterocolitis, we discovered a novel pegivirus not present in ten matched, clinically normal controls. The novel virus, which we named Southwest bike trail virus (SOBV), is most closely related (68% nucleotide identity) to a strain of simian pegivirus A isolated from a three-striped night monkey (Aotus trivirgatus). We screened 146 living WNPRC common marmosets for SOBV, finding an overall prevalence of 34% (50/146). Over four years, 85 of these 146 animals died or were euthanized. Histological examination revealed 27 SOBV-positive marmosets from this cohort had lymphocytic enterocolitis, compared to 42 SOBV-negative marmosets, indicating no association between SOBV and disease in this cohort (p = 0.0798). We also detected SOBV in two of 33 (6%) clinically normal marmosets screened during transfer from the New England Primate Research Center, suggesting SOBV could be exerting confounding influences on comparisons of common marmoset studies from multiple colonies.

Equine pegiviruses cause persistent infection of bone marrow and are not associated with hepatitis

Pegiviruses frequently cause persistent infection (as defined by >6 months), but unlike most other Flaviviridae members, no apparent clinical disease. Human pegivirus (HPgV, previously GBV-C) is detectable in 1–4% of healthy individuals and another 5–13% are seropositive. Some evidence for infection of bone marrow and spleen exists. Equine pegivirus 1 (EPgV-1) is not linked to disease, whereas another pegivirus, Theiler’s disease-associated virus (TDAV), was identified in an outbreak of acute serum hepatitis (Theiler’s disease) in horses. Although no subsequent reports link TDAV to disease, any association with hepatitis has not been formally examined. Here, we characterized EPgV-1 and TDAV tropism, sequence diversity, persistence and association with liver disease in horses. Among more than 20 tissue types, we consistently detected high viral loads only in serum, bone marrow and spleen, and viral RNA replication was consistently identified in bone marrow. PBMCs and lymph nodes, but not liver, were sporadically positive. To exclude potential effects of co-infecting agents in experimental infections, we constructed full-length consensus cDNA clones; this was enabled by determination of the complete viral genomes, including a novel TDAV 3’ terminus. Clone derived RNA transcripts were used for direct intrasplenic inoculation of healthy horses. This led to productive infection detectable from week 2–3 and persisting beyond the 28 weeks of study. We did not observe any clinical signs of illness or elevation of circulating liver enzymes. The polyprotein consensus sequences did not change, suggesting that both clones were fully functional. To our knowledge, this is the first successful extrahepatic viral RNA launch and the first robust reverse genetics system for a pegivirus. In conclusion, equine pegiviruses are bone marrow tropic, cause persistent infection in horses, and are not associated with hepatitis. Based on these findings, it may be appropriate to rename the group of TDAV and related viruses as EPgV-2.

Transmissible hepatitis in horses (Theiler’s disease) has been known for 100 years without knowledge of causative infectious agents. Recently, two novel equine pegiviruses (EPgV) were discovered. Whereas EPgV-1 was not associated to disease, the other was identified in an outbreak of acute serum hepatitis and therefore named Theiler’s disease-associated virus (TDAV). This finding was surprising since human and monkey pegiviruses typically cause long-term infection without associated clinical disease. Whereas no subsequent reports link TDAV to disease, the original association to hepatitis has not been formally examined. Here, we studied EPgV-1 and TDAV and found that their natural history of infection in horses were remarkably similar. Examination of various tissues identified the bone marrow as the primary site of replication for both viruses with no evidence of replication in the liver. To exclude potential effects of other infectious agents, we developed molecular full-length clones for EPgV-1 and TDAV and were able to initiate infection in horses using derived synthetic viral genetic material. This demonstrated long-term infection, but no association with hepatitis. These findings call into question the connection between TDAV, liver infection, and hepatitis in horses.

Human Pegivirus in Patients with Encephalitis of Unclear Etiology, Poland

Sequence analysis of human pegivirus from 3 patients indicates that the central nervous system constitutes a separate viral compartment from serum.

Human pegivirus (HPgV), previously called hepatitis G virus or GB virus C, is a lymphotropic virus with undefined pathology. Because many viruses from the family Flaviviridae, to which HPgV belongs, are neurotropic, we studied whether HPgV could infect the central nervous system. We tested serum and cerebrospinal fluid samples from 96 patients with a diagnosis of encephalitis for a variety of pathogens by molecular methods and serology; we also tested for autoantibodies against neuronal antigens. We found HPgV in serum and cerebrospinal fluid from 3 patients who had encephalitis of unclear origin; that is, all the markers that had been tested were negative. Single-strand confirmation polymorphism and next-generation sequencing analysis revealed differences between the serum and cerebrospinal fluid–derived viral sequences, which is compatible with the presence of a separate HPgV compartment in the central nervous system. It is unclear whether HPgV was directly responsible for encephalitis in these patients.

Human Pegivirus infection and lymphoma risk and prognosis: a North American study

We evaluated the association of Human Pegivirus (HPgV) viraemia with risk of developing lymphoma, overall and by major subtypes. Because this virus has also been associated with better prognosis in the setting of co-infection with human immunodeficiency virus, we further assessed the association of HPgV with prognosis. We used risk factor data and banked plasma samples from 2094 lymphoma cases newly diagnosed between 2002 and 2009 and 1572 frequency-matched controls. Plasma samples were tested for HPgV RNA by reverse transcription polymerase chain reaction (RT-PCR), and those with RNA concentrations <5000 genome equivalents/ml were confirmed using nested RT-PCR methods. To assess the role of HPgV in lymphoma prognosis, we used 2948 cases from a cohort study of newly diagnosed lymphoma patients (included all cases from the case-control study). There was a positive association of HPgV viraemia with risk of lymphoma overall (Odds ratio = 2·14; 95% confidence interval [CI] 1·63-2·80; P < 0·0001), and for all major subtypes except Hodgkin lymphoma and chronic lymphocytic leukaemia/small lymphocytic lymphoma, and this was not confounded by other lymphoma risk factors. In contrast, there was no association of HPgV viraemia with event-free survival (Hazard ratio [HR] = 1·00; 95% CI 0·85-1·18) or overall survival (HR = 0·97; 95% CI 0·79-1·20) for lymphoma overall, or any of the subtypes. These data support the hypothesis for a role of HPgV in the aetiology of multiple lymphoma subtypes.

Human pegivirus (HPgV) infection in sub-Saharan Africa-A call for a renewed research agenda

The human pegivirus (HPgV)-formerly GB virus C-has a beneficial impact on HIV disease progression that has been described in multiple studies. Given the high prevalence of HIV in sub-Saharan Africa and the continuing need to suppress HIV replication, this review provides a comprehensive overview of the existing data on HPgV infection in sub-Saharan Africa, with a particular focus on studies of prevalence and the circulating HPgV genotypes. This review also highlights the need for additional studies of HPgV conducted on the African continent and proposes a research agenda for evaluation of HPgV.

Pegivirus avoids immune recognition but does not attenuate acute-phase disease in a macaque model of HIV infection

Human pegivirus (HPgV) protects HIV+ people from HIV-associated disease, but the mechanism of this protective effect remains poorly understood. We sequentially infected cynomolgus macaques with simian pegivirus (SPgV) and simian immunodeficiency virus (SIV) to model HIV+HPgV co-infection. SPgV had no effect on acute-phase SIV pathogenesis-as measured by SIV viral load, CD4+ T cell destruction, immune activation, or adaptive immune responses-suggesting that HPgV's protective effect is exerted primarily during the chronic phase of HIV infection. We also examined the immune response to SPgV in unprecedented detail, and found that this virus elicits virtually no activation of the immune system despite persistently high titers in the blood over long periods of time. Overall, this study expands our understanding of the pegiviruses-an understudied group of viruses with a high prevalence in the global human population-and suggests that the protective effect observed in HIV+HPgV co-infected people occurs primarily during the chronic phase of HIV infection.

Prevalence of human pegivirus-1 and sequence variability of its E2 glycoprotein estimated from screening donors of fetal stem cell-containing material

Background

Human pegivirus-1 (HPgV-1) is a member of the Flaviviridae family whose genomic organization and mode of cellular entry is similar to that of hepatitis C virus (HCV). The E2 glycoprotein of HPgV-1 is the principle mediator in the virus-cell interaction and as such harbors most of HPgV-1’s antigenic determinants. HPgV-1 persists in blood cell precursors which are increasingly used for cell therapy.

Methods

We studied HPgV-1 prevalence in a large cohort of females donating fetal tissues for clinical use. PCR was used for screening and estimation of viral load in viremic plasma and fetal samples. Sequence analysis was performed for portions of the 5′-untranslated and E2 regions of HPgV-1 purified from donor plasmas. Sequencing was followed by phylogenetic analysis.

Results

HPgV-1 was revealed in 13.7% of plasmas, 5.0% of fetal tissues, 5.4% of chorions, exceeding the prevalence of HCV in these types of samples. Transmission of HPgV-1 occurred in 25.8% of traceable mother-chorion-fetal tissues triads. For HPgV-1-positive donors, a high viral load in plasma appears to be a prerequisite for transmission. However, about one third of fetal samples acquired infection from non-viremic individuals. Sequencing of 5′-untranslated region placed most HPgV-1 samples to genotype 2a. At the same time, a portion of E2 sequence provided a much weaker support for this grouping apparently due to a higher variability. Polymorphisms were detected in important structural and antigenic motifs of E2.

Conclusion

HPgV-1 is efficiently transmitted to fetus at early embryonic stages. A high variability in E2 may pose a risk of generation of pathogenic subtypes. Although HPgV-1 is considered benign and no longer tested mandatorily in blood banks, the virus may have adversary effects at target niches if delivered with infected graft upon cell transplantation. This argues for the necessity of HPgV-1 testing of cell samples aimed for clinical use.

Human pegivirus-1 in the CSF of patients with HIV-associated neurocognitive disorder (HAND) may be derived from blood in highly viraemic patients

BACKGROUND

Human pegivirus-1 (HPgV-1) infection in the brain has not been extensively examined and its association with disease remains unconfirmed. In a high throughput sequencing study to look for infectious agents that could play a role in HIV-associated neurocognitive disorder (HAND), this virus was detected in 3 of 8 CSF samples.

OBJECTIVES

To determine the significance of this finding, additional patients were screened and the viral load and viral diversity in blood and CSF were examined.

STUDY DESIGN

Nested PCR of the viral 5'NCR region was performed on blood and CSF pairs from 16 HAND patients. PCR products were cloned, sequenced and analysed to determine viral diversity in blood and CSF. HPgV-1 viral loads were determined in paired blood and CSF of 2 patients by digital droplet PCR. Nested PCR was also performed on CSF samples from patients with other brain disorders.

RESULTS

Virus was detected in both blood and CSF in 3 of 16 HAND patients. Viral loads were very high in blood (8.81 and 10.56 log copies/ml) and 4-5 logs lower in CSF (4.68 and 5.84 log copies/ml). Sequence analysis of 5'NCR clones in blood and CSF showed limited variation. The dominant viral variant (based on clonal sequence identity) in blood and CSF was usually identical. HPgV-1 was detected in CSF from patients with other brain disorders at a similar frequency (15% versus 18.75% in HAND patients).

CONCLUSION

While several studies have reported HPgV-1 detection in CSF of patients with brain disease, this is the only study that has examined both blood and CSF compartments simultaneously. Our findings show that virus in CSF always coincided with viraemia and levels were 4-5 logs higher in blood. While a rare, but specific brain tropism cannot be excluded, blood is the more probable source of virus in HAND patients.

Durable sequence stability and bone marrow tropism in a macaque model of human pegivirus infection

Human pegivirus (HPgV)-formerly known as GB virus C and hepatitis G virus-is a poorly characterized RNA virus that infects about one-sixth of the global human population and is transmitted frequently in the blood supply. We create an animal model of HPgV infection by infecting macaque monkeys with a new simian pegivirus (SPgV) discovered in wild baboons. Using this model, we provide a high-resolution, longitudinal picture of SPgV viremia where the dose, route, and timing of infection are known. We detail the highly variable acute phase of SPgV infection, showing that the viral load trajectory early in infection is dependent on the infecting dose, whereas the chronic-phase viremic set point is not. We also show that SPgV has an extremely low propensity for accumulating sequence variation, with no consensus-level variants detected during the acute phase of infection and an average of only 1.5 variants generated per 100 infection-days. Finally, we show that SPgV RNA is highly concentrated in only two tissues: spleen and bone marrow, with bone marrow likely producing most of the virus detected in plasma. Together, these results reconcile several paradoxical observations from cross-sectional analyses of HPgV in humans and provide an animal model for studying pegivirus biology.

Human pegivirus detected in a patient with severe encephalitis using a metagenomic pan-virus array

•

Metagenomic microarray for unbiased detection of virus in patient samples.

•

Discovery of an occult viral infection, HPgV, in the spinal fluid of a patient with severe encephalitis.

•

HPgV can on rare occasions enter the CSF at high viral load, but uncertain if its presence in the CNS has any clinical implications.

We have used a metagenomic microarray to detect genomic RNA from human pegivirus in serum and cerebrospinal fluid from a patient suffering from severe encephalitis. No other pathogen was detected. HPgV in cerebrospinal fluid during encephalitis has never been reported before and its prevalence in cerebrospinal fluid needs further investigation.

Tropism of human pegivirus (formerly known as GB virus C/hepatitis G virus) and host immunomodulation: insights into a highly successful viral infection

Human pegivirus (HPgV; originally called GB virus C/hepatitis G virus) is an RNA virus within the genus Pegivirus of the family Flaviviridae that commonly causes persistent infection. Worldwide, ~750 million people are actively infected (viraemic) and an estimated 0.75-1.5 billion people have evidence of prior HPgV infection. No causal association between HPgV and disease has been identified; however, several studies described a beneficial relationship between persistent HPgV infection and survival in individuals infected with human immunodeficiency virus. The beneficial effect appeared to be related to a reduction in host immune activation. HPgV replicates well in vivo (mean plasma viral loads typically >1×107 genome copies ml-1); however, the virus grows poorly in vitro and systems to study this virus are limited. Consequently, mechanisms of viral persistence and host immune modulation remain poorly characterized, and the primary permissive cell type(s) has not yet been identified. HPgV RNA is found in liver, spleen, bone marrow and PBMCs, including T- and B-lymphocytes, NK-cells, and monocytes, although the mechanism of cell-to-cell transmission is unclear. HPgV RNA is also present in serum microvesicles with properties of exosomes. These microvesicles are able to transmit viral RNA to PBMCs in vitro, resulting in productive infection. This review summarizes existing data on HPgV cellular tropism and the effect of HPgV on immune activation in various PBMCs, and discusses how this may influence viral persistence. We conclude that an increased understanding of HPgV replication and immune modulation may provide insights into persistent RNA viral infection of humans.

GBV-C infection and risk of NHL among U.S. adults

Some retrospective studies suggest an association between infection with GB virus-C (GBV-C) and non-Hodgkin lymphoma (NHL). We evaluated this association prospectively in a nested case-control study within the U.S. Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial. Cases (N = 658) and controls (N = 1,316) were individually matched by age, sex, race/ethnicity, timing of study entry, and sample selection. Prediagnostic PLCO serum samples were tested for GBV-C RNA (as a measure of active infection) and E2 antibody (active or resolved infection). Logistic regression was used to estimate odds ratios (OR) for the association between GBV-C and NHL overall and NHL subtypes. Twelve cases (1.8%) and seven controls (0.5%) were GBV-C RNA-positive. GBV-C RNA positivity was associated with NHL overall [OR, 3.43; 95% confidence interval (CI), 1.35-8.71] and, based on small numbers, diffuse large B-cell lymphoma (OR, 5.31; 95% CI, 1.54-18.36). The association with NHL persisted when the interval between testing and selection was greater than 4 years (OR, 6.00; 95% CI, 1.21-29.73). In contrast, E2 antibody positivity was not associated with NHL risk (OR, 1.08; 95% CI, 0.74-1.58). Our study demonstrates that GBV-C infection precedes development of NHL. GBV-C infection may play an etiologic role in a small proportion of NHL cases, perhaps by causing chronic immune stimulation or impaired immunosurveillance.

Human pegivirus RNA is found in multiple blood mononuclear cells in vivo and serum-derived viral RNA-containing particles are infectious in vitro

Human pegivirus (HPgV; previously called GB virus C/hepatitis G virus) has limited pathogenicity, despite causing persistent infection, and is associated with prolonged survival in human immunodeficiency virus-infected individuals. Although HPgV RNA is found in and produced by T- and B-lymphocytes, the primary permissive cell type(s) are unknown. We quantified HPgV RNA in highly purified CD4(+) and CD8(+) T-cells, including naïve, central memory and effector memory populations, and in B-cells (CD19(+)), NK cells (CD56(+)) and monocytes (CD14(+)) using real-time reverse transcription-PCR. Single-genome sequencing was performed on viruses within individual cell types to estimate genetic diversity among cell populations. HPgV RNA was present in CD4(+) and CD8(+) T-lymphocytes (nine of nine subjects), B-lymphocytes (seven of ten subjects), NK cells and monocytes (both four of five). HPgV RNA levels were higher in naïve (CD45RA(+)) CD4(+) cells than in central memory and effector memory cells (P<0.01). HPgV sequences were highly conserved among subjects (0.117±0.02 substitutions per site; range 0.58-0.14) and within subjects (0.006±0.003 substitutions per site; range 0.006-0.010). The non-synonymous/synonymous substitution ratio was 0.07, suggesting a low selective pressure. Carboxyfluorescein succinimidyl ester (CFSE)-labelled HPgV RNA-containing particles precipitated by a commercial exosome isolation reagent delivered CSFE to uninfected monocytes, NK cells and T- and B-lymphocytes, and HPgV RNA was transferred to PBMCs with evidence of subsequent virus replication. Thus, HPgV RNA-containing serum particles including microvesicles may contribute to delivery of HPgV to PBMCs in vivo, explaining the apparent broad tropism of this persistent human RNA virus.

GB virus C infection in Indonesian HIV-positive patients

GB virus C (GBV-C), a human virus of the Flaviviridae family that is structurally and epidemiologically closest to hepatitis C virus (HCV), has been reported to confer beneficial outcomes in HIV-positive patients. However, the prevalence of GBV-C in HIV-positive individuals in Indonesia is unknown. Since GBV-C is more prevalent in anti-HCV positive patients than in anti-HCV negative subjects, transmission of GBV-C and HCV could be by the same method. This study examined the prevalence and molecular characteristics of GBV-C infection in HIV patients in Yogyakarta, Indonesia. The prevalence of GBV-C among HIV patients (n = 125, median age 31 years) based on the 5'UTR region was 111/125 (88.8%), including 39/48 (81.3%) and 72/77 (93.5%) HIV-infected patients with and without HCV infection, respectively. GBV-C isolates were of genotype 2a, 3 and 6 in 58.3%, 12.6% and 28.4% of patients, respectively. Patients with genotype 3 were significantly younger than those with genotypes 2a or 6 (P = 0.001 and P = 0.012, respectively). Genotypes 3 and 6 were significantly associated with injection drug use (P = 0.004 and P = 0.002, respectively) and HCV co-infection (P < 0.001 for both genotypes), indicating a shared transmission route with HCV. In conclusion, the prevalence of GBV-C among HIV-positive patients in Indonesia is high, and three genotypes were detected, namely genotype 2a, 3 and 6.

Hepatitis G virus/GBV-C in serum, peripheral blood mononuclear cells and bone marrow in patients with hematological malignancies

BACKGROUND

HGV/GBV-C is highly prevalent in the general population but its significance remains unclear. It is known that HGV/GBV-C is not primary hepatotropic and its replication was reported in PBMC, bone marrow and other tissues. To investigate a possible role of HGV/GBV-C 115 consecutive patients with hematological malignancies were analyzed for virus RNA presence and quasispecies composition in three compartments: serum, PBMC and bone marrow.

METHODS

RT-PCR was used to amplify 5'UTR HGV/GBV-C in serum, PBMC and bone marrow. Viral sequences obtained from three compartments were subjected for comparative molecular analysis performed by single strand conformational polymorphism (SSCP) and pyrosequencing.

RESULTS

HGV/GBV-C RNA was detected in 23 out of 115 (20.0%) patients, most often in bone marrow (18 patients), followed by PBMC (11 patients) and serum (10 patients). Differences in SSCP bands distribution corresponding to different viral variants and confirmed by direct sequencing were observed in three patients.

CONCLUSION

HGV/GBV-C infection is frequent in patients with hematological malignancies. Common detection of HGV/GBV-C in bone marrow supports the hypothesis that it is a major replication site of this virus.

Role of GB virus C in modulating HIV disease

GB virus C (GBV-C) is a member of the Flaviviridae family and the most closely related human virus to HCV. However, GBV-C does not replicate in hepatocytes, but rather in lymphocytes. GBV-C has a worldwide distribution and is transmitted sexually, parenterally and through mother-to-child transmission. Thus, co-infection with HCV and HIV is common. Until now, no human disease has been associated with GBV-C infection. However, there are several reports of a beneficial effect of GBV-C on HIV disease progression in vivo. Different mechanisms to explain these observations have been proposed, including modification of antiviral cytokine production, HIV co-receptor expression, direct inhibition of HIV-1 entry, T-cell activation and Fas-mediated apoptosis. Further understanding of these mechanisms may open new strategies for the treatment of HIV/AIDS.

Deep sequencing for the detection of virus-like sequences in the brains of patients with multiple sclerosis: detection of GBV-C in human brain

Multiple sclerosis (MS) is a demyelinating disease of unknown origin that affects the central nervous system of an estimated 400,000 Americans. GBV-C or hepatitis G is a flavivirus that is found in the serum of 1–2% of blood donors. It was originally associated with hepatitis, but is now believed to be a relatively non-pathogenic lymphotropic virus. Fifty frozen specimens from the brains of deceased persons affected by MS were obtained along with 15 normal control brain specimens. RNA was extracted and ribosomal RNAs were depleted before sequencing on the Illumina GAII. These 36 bp reads were compared with a non-redundant database derived from the 600,000+ viral sequences in GenBank organized into 4080 taxa. An individual read successfully aligned to the viral database was considered to be a “hit”. Normalized MS specimen hit rates for each viral taxon were compared to the distribution of hits in the normal controls. Seventeen MS and 11 control brain extracts were sequenced, yielding 4–10 million sequences (“reads”) each. Over-representation of sequence from at least one of 12 viral taxa was observed in 7 of the 17 MS samples. Sequences resembling other viruses previously implicated in the pathogenesis of MS were not significantly enriched in any of the diseased brain specimens. Sequences from GB virus C (GBV-C), a flavivirus not previously isolated from brain, were enriched in one of the MS samples. GBV-C in this brain specimen was confirmed by specific amplification in this single MS brain specimen, but not in the 30 other MS brain samples available. The entire 9.4 kb sequence of this GBV-C isolate is reported here. This study shows the feasibility of deep sequencing for the detection of occult viral infections in the brains of deceased persons with MS. The first isolation of GBV-C from human brain is reported here.

Influence of hepatitis G virus (GB virus C) on the prognosis of HIV-infected women

This study was undertaken to evaluate the prevalence of GB virus C (GBV-C) viraemia and anti-E2 antibody, and to assess the effect of co-infection with GBV-C and HIV during a 10-year follow-up of a cohort of 248 HIV-infected women. Laboratory variables (mean and median CD4 counts, and HIV and GBV-C viral loads) and clinical parameters were investigated. At baseline, 115 women had past exposure to GBV-C: 57 (23%) were GBV-C RNA positive and 58 (23%) were anti-E2 positive. There was no statistical difference between the groups (GBV-C RNA + /anti-E2 − , GBV-C RNA − /anti-E2 + and GBV-C RNA − /anti-E2 − ) regarding baseline CD4 counts or HIV viral loads ( P = 0.360 and 0.713, respectively). Relative risk of death for the GBV-C RNA + /anti-E2 − group was 63% lower than that for the GBV-C RNA − /anti-E2 − group. Multivariate analysis demonstrated that only HIV loads ≥ 100,000 copies/mL and AIDS-defining illness during follow-up were associated with shorter survival after AIDS development. It is likely that antiretroviral therapy (ART) use in our cohort blurred a putative protective effect related to the presence of GBV-C RNA.

The GB viruses: a review and proposed classification of GBV-A, GBV-C (HGV), and GBV-D in genus Pegivirus within the family Flaviviridae

In 1967, it was reported that experimental inoculation of serum from a surgeon (G.B.) with acute hepatitis into tamarins resulted in hepatitis. In 1995, two new members of the family Flaviviridae, named GBV-A and GBV-B, were identified in tamarins that developed hepatitis following inoculation with the 11th GB passage. Neither virus infects humans, and a number of GBV-A variants were identified in wild New World monkeys that were captured. Subsequently, a related human virus was identified [named GBV-C or hepatitis G virus (HGV)], and recently a more distantly related virus (named GBV-D) was discovered in bats. Only GBV-B, a second species within the genus Hepacivirus (type species hepatitis C virus), has been shown to cause hepatitis; it causes acute hepatitis in experimentally infected tamarins. The other GB viruses have however not been assigned to a genus within the family Flaviviridae. Based on phylogenetic relationships, genome organization and pathogenic features of the GB viruses, we propose to classify GBV-A-like viruses, GBV-C and GBV-D as members of a fourth genus in the family Flaviviridae, named Pegivirus (pe, persistent; g, GB or G). We also propose renaming 'GB' viruses within the tentative genus Pegivirus to reflect their host origin.

GB virus C genotype 2 predominance in a hepatitis C virus/HIV infected population associated with reduced liver disease

BACKGROUND AND AIM

GB virus C (GBV-C) infection in hepatitis C virus (HCV)/HIV co-infection is associated with a significant reduction in the severity of HCV-related liver disease. The role of GBV-C genotype in this association is unknown. It has been suggested that GBV-C genotype may influence CD4 positive T-cell counts in HCV/HIV co-infected patients. The aim of the present study was to identify the GBV-C genotype in a HCV/HIV co-infected population and determine if the GBV-C genotype contributes to a reduction in HCV-related liver disease.

METHODS

GBV-C RNA from 57 patients who were co-infected with HCV/HIV was analyzed. GBV-C RNA was detected by reverse transcription-polymerase chain reaction with primers to the NS5B gene and genotype determined by phylogenetic analysis after sequencing using E2 gene primers.

RESULTS

Genotype 2 was the predominant isolate in our population and was detected in 50/56 (89.3%) of patients, although sequences with similarity to genotypes 1, 3, 4 and 5 were also identified. There was no statistical difference between CD4 positive T-cell counts in the GBV-C genotype 2 and non-genotype 2 groups.

CONCLUSIONS

The GBV-C genotype distribution in our HCV/HIV patient group was consistent with that reported in other developed countries. The predominance of genotype 2 in this study meant that we could not draw a conclusion for the role of GBV-C genotype in the reduced severity of liver disease in co-infected patients but CD4 positive T-cell counts appeared to be unaffected by GBV-C genotype.

What you need to know about GB virus C

GB virus C (GBV-C) is a nonpathogenic member of the Flaviviridae family most closely related to hepatitis C virus (HCV). Infection is common in healthy and immunocompromised people and may persist for years. GBV-C infection is associated with improved survival, improved AIDS-free survival, higher CD4(+) T-cell counts, and lower HIV viral loads in HIV-infected people compared with people infected with HIV but not GBV-C. The mechanism of this effect is not yet clear, but GBV-C has been shown to inhibit HIV replication in vitro through increased synthesis and secretion of anti-HIV b-chemokines MIP-1a, MIP-1b, RANTES, SDF-1, and SDF-2 and downregulation of CCR5 receptor expression. GBV-C also inhibits apoptosis of its host cell, similar to HCV. GBV-C E2 protein in serum has also been associated with prolonged survival in HIV infection; recent evidence indicates that GBV-C E2 protein may neutralize HIV infection in vitro.

Reduction in hepatitis C-related liver disease associated with GB virus C in human immunodeficiency virus coinfection

BACKGROUND & AIMS

It has been reported that GB virus C infection (GBV-C) leads to improved morbidity and mortality in patients with human immunodeficiency virus (HIV) infection. However, GBV-C has no effect on the course of liver disease in hepatitis C virus (HCV) monoinfection. The aim of the study was to determine the influence of GBV-C infection on liver disease in patients with HCV/HIV coinfection.

METHODS

Data on 158 HCV/HIV patients were collected from January 1996 to October 2005. Two plasma specimens, collected at least 18 months apart, were tested for GBV-C RNA by reverse transcription-polymerase chain reaction with primers to the NS5B gene and confirmed using E2 gene primers and sequencing. Antibodies to GBV-C E2 protein were also determined. Liver-related morbidity and mortality were assessed from patient records.

RESULTS

Fifty-seven of 158 (36%) patients had GBV-C RNA and 94 (59%) had evidence of exposure to GBV-C based on combined polymerase chain reaction and antibody results. Thirty-four (21%) patients had features of cirrhosis, with 20 having compensated and 14 having decompensated cirrhosis. Active GBV-C RNA was significantly associated with a reduction in cirrhosis, both compensated and decompensated in multivariate analysis (hazard ratio, 0.27; 95% confidence interval, 0.08-0.88; P = .03), as well as in analysis for cirrhosis-free survival vs duration of HCV infection (P = .006). No significant effect on liver-related or overall survival was observed.

CONCLUSIONS

In these HCV/HIV-coinfected patients, GBV-C RNA was associated with a significant reduction in the severity of HCV-related liver disease.

GB virus C and HIV-1 RNA load in single virus and co-infected West African individuals

BACKGROUND

Investigations on the impact of GB virus C (GBV-C) co-infection on HIV disease progression relied essentially on clinical follow-up but not on virologic parameters.

OBJECTIVES

To detect and quantify GBV-C RNA in West African populations co-infected or not with HIV-1 and to correlate the RNA load of HIV-1 and GBV-C in co-replicating patients with different clinical conditions.

METHODS

Three Ghanaian populations (blood donors, pregnant women and HIV-infected patients) were subdivided into six groups according to HIV-1 and clinical status and GBV-C and HIV-1 RNA load was tested by quantitative real time reverse transcriptase-polymerase chain reaction. In one population with HIV-1 disease, CD4+ cell count was also measured.

RESULTS

Prevalence of GBV-C markers in HIV-1-infected groups and HIV-1 non-infected pregnant women were significantly higher than in healthy blood donors. Similar levels and distribution of GBV-C RNA load were found in each population irrespective of HIV-1 status except for a lower GBV-C RNA load in AIDS patients. There was a significant shift of HIV-1 load towards lower value when GBV-C RNA was present and a trend towards an inverse correlation between HIV-1 and GBV-C RNA load. A positive correlation between CD4+ cell count and GBV-C RNA load in symptomatic HIV-1-infected patients was observed.

CONCLUSIONS

The moderate impact of GBV-C on HIV-1 viremia is unlikely to entirely account for a favourable clinical outcome of replicating co-infections.

Comparison of GB virus C, HIV, and HCV infection markers in hemophiliacs exposed to non-inactivated or inactivated factor concentrates

BACKGROUND

Until the mandatory introduction of viral inactivation techniques of blood plasma products in the early 1980s many recipients of these products were infected with various viral pathogens.

OBJECTIVES

To determine the rate of transmission of GB virus C/hepatitis G virus (GBV-C/HGV) HCV, and HIV through non-virus-inactivated clotting factor concentrates in hemophiliacs, as well as the relation between amount of administered clotting factor and risk for GBV-C/HGV infection.

STUDY DESIGN

In this cross-sectional study, we determined retrospectively the rates of infection markers for GBV-C/HGV, HCV, and HIV in a German cohort of hemophiliacs treated with documented amounts of non-virus-inactivated clotting factor concentrates (group A) and in a second group of hemophiliacs who were treated exclusively with virus-inactivated clotting factor (group B). The presence of anti-virus antibodies was determined by ELISA. Viral RNA was detected by RT-PCR. Markers for viral infections were compared to amounts of administered non-virus-inactivated clotting factor.

RESULTS

Among hemophiliacs treated with documented amounts of non-virus-inactivated clotting factor the prevalence for GBV-C/HGV, HCV, and HIV was 40.3%, 98.6%, and 56.3%, respectively. In contrast to HIV, the rate of GBV-C/HGV infections did not increase with increasing amounts of consumed non-inactivated clotting factor. Even in the subgroup of heavily treated hemophiliacs the rate of GBV-C/HGV infection markers did not exceed 45%.

CONCLUSIONS

The amount of non-virus-inactivated clotting factor is not predictive for the risk of GBV-C/HGV infection in hemophiliacs. Despite repeated parenteral exposure more than 55% of hemophiliacs were not infected with GBV-C/HGV. Our findings indicate a high frequency of host factors preventing parenteral transmission of GBV-C/HGV.

GB virus C: insights into co-infection

GB virus C (GBV-C) is a single stranded positive sense RNA virus, which is a member of the Flaviviridae. It has a close sequence homology and genomic organisation to hepatitis C virus (HCV). However, unlike HCV it is not hepatotrophic. GBV-C replicates within cells of the haemopoietic lineage, in particular lymphocytes. No disease has been associated with GBV-C infection but co-infection with human immunodeficiency virus (HIV) leads to improved morbidity and mortality for the HIV infected individual and slows progression to acquired immunodeficiency syndrome. This potential benefit of GBV-C has been demonstrated in the pre and post highly active anti-retroviral treatment (HAART) eras. GBV-C has been found to decrease HIV replication in in vitro models. The mechanism of the beneficial effect of GBV-C appears to be mediated by alterations in the cellular immune response, the details of which remain unclear. Despite this, there continues to be controversy regarding the influence of GBV-C on HIV as several reports have questioned the beneficial effect. GBV-C does not appear to influence liver related disease in subjects co-infected with HCV or hepatitis B virus (HBV). Combination of HIV and HCV leads to accelerated liver disease. The influence of GBV-C in this situation is yet to be determined. Elucidation of the putative protective effect of GBV-C in HIV co-infection could potentially identify novel targets for anti-HIV therapeutics and lead to the development of disease modifying vaccines.

GB virus type C NS5A sequence polymorphisms: association with interferon susceptibility and inhibition of PKR-mediated eIF2alpha phosphorylation

GB virus type C (GBV-C) causes persistent infection in humans, although the mechanism by which the virus avoids clearance by the host is unknown. To determine if amino acid polymorphisms in the GB virus type C (GBV-C) NS5A and E2 proteins alter response to interferon (IFN) therapy, we studied the sequence of GBVC NS5A and E2 obtained from people receiving IFN therapy. In addition, we expressed recombinant GBVC NS5A protein to determine if it interferes with RNA-activated protein kinase (PKR) function in vitro. GBVC NS5A amplified from a person whose virus was cleared by IFN therapy (IFN sensitive) demonstrated unique amino acid changes occurring in the region that aligns with the hepatitis C virus (HCV) IFN sensitivity-determining region (ISDR) compared with NS5A sequences from individuals who did not clear GBV-C (IFN resistant). There were no differences in the E2 sequences obtained from IFN-sensitive and IFN-resistant isolates. Using a yeast genetic system, IFN-resistant NS5A inhibited PKR-mediated phosphorylation of eukaryotic initiation factor 2alpha (eIF2alpha) in yeast, whereas IFN-sensitive NS5A did not inhibit PKR function. GBV-C NS5A amino acid polymorphisms appear to be involved in response to IFN therapy, and IFN-resistant GBV-C NS5A inhibited PKR-mediated eIF2alpha phosphorylation in a yeast genetic system, suggesting a mechanism by which GBV-C may evade clearance by naturally occurring host antiviral responses.

Detection and genotyping of GBV-C virus in the United Arab Emirates

GB virus-C/Hepatitis G virus (GBV-C/HGV), collectively known as GBV-C, is spread widely and has been reported to be associated with non A-E hepatitis. The aim of the current project was to determine the rate of infection and genotypic characteristics of GBV-C in the United Arab Emirates (UAE). A total of 379 plasma/serum samples representing different populations in the UAE and comprising healthy as well as patients positive for HBV and HCV were screened using RT-PCR/nested PCR of the 5'-untranslated region (UTR). National subjects (n=168) and non-nationals residing in the UAE (n=211) were tested. The results obtained showed that the rate of GBV-C infection in healthy nationals, and those positive for HCV or HBV were 11.1%, 14.3%, and 5.7%, respectively, compared to 8.3%, 33.3%, and 8.6%, respectively, in non-nationals. No statistically significant correlation between infection with GBV-C and HCV or HBV (P>0.05) was found. Sequence analysis of the 5'-UTR using 37 and 46 clones from 8 and 6 healthy nationals and non-nationals, respectively, revealed the prevalence of the European/North American genotype 2 when compared to the five reference genotypes in GenBank.

[Hepatitis G virus and labile blood products: role of transfusional transmission]

The GBV-C/HGV (HGV) virus was discovered a few years ago. This virus is known to be parenterally as well as sexually transmitted. However, no study has found some pathogenic roles for HGV so far. In the present study, we aimed to investigate the transmission of HGV by blood components transfused to 284 patients hospitalized in surgery unit in 1995. We tested two parameters of infection in blood components transfused to infected recipients: viral RNA by PCR and anti-E2 antibodies by ELISA. We tried to suspect some potent hepatocyte impacts by assessing the levels of two enzymes in serums: alanine aminotransferase (ALT) and alpha-glutathion S-transferase (alpha-GST). We found that HGV-RNA was detectable in 3.6% of recipients prior to transfusion and 7.5% post-transfusion. For each infected recipient, we retrospectively did a search for HGV-RNA in each transfused blood component, and we found at least one blood component as HGV-RNA-positive for each transfusional infected recipient. Anti-E2 antibody prevalence standing for a former and cured infection was 39.6% in all the recipients. In viremic recipients, ALT levels were mostly normal, while alpha-GST levels were found more commonly elevated than in non-viremic recipients although non-significantly (20% vs. 6.3%; P = 0.07). The present study underlines that HGV transmission is mostly transfusional in surgery units, and that infectiosity of blood components can be anticipated by detection of the viral RNA by PCR. Furthermore, the possible relationship between the serum activity of alpha-GST and the hepatotropism of HGV, although non-admitted as pathogenic, should be investigated.

GB virus type C coinfection in HIV-infected African mothers and their infants, KwaZulu Natal, South Africa

GB virus type C (GBV-C) infection was studied in a convenience sample of 75 antiretroviral (ART)-naive African mothers with human immunodeficiency virus infection and their infants. GBV-C RNA was extracted from serum and amplified by reverse-transcriptase polymerase chain reaction. Twenty-seven (36%) of these 75 HIV-infected women tested positive for GBV-C RNA. To study transmission dynamics, we chose a random subsample of 20 of these women and their infants. In this cohort, there was evidence of postnatal transmission of GBV-C; however, it was not possible to demonstrate evidence of in utero or intrapartum transmission. In this pilot observational study, transmission of HIV from mother-to-infant occurs independently of the GBV-C infection status of the mother. The immunological indices measured tend to suggest an association with protection and or delayed progression of HIV disease in GBV-C-infected mothers.

[Is GB virus C alias "hepatitis" G virus involved in human pathology?]

GB virus-C alias "hepatitis" virus G was discovered in 1995 as a putative causative virus of non A-E hepatitis. It is a very common virus found in 1 to 5% of eligible blood donors in developed countries. Numerous studies over seven years led to the exclusion of its role as a significant etiological agent of hepatitis. Its in vivo replication site is still unknown. Its direct involvement in the induction of significant hepatic or extra-hepatic diseases could not be demonstrated. However, coinfections with other viruses may contribute to changes in the evolution of both liver disease (negatively) and HIV/AIDS (favourably). Today, no country has decided to screen GBV-C in blood donors. However, more studies are necessary before the absence of influence of GBV-C infection on human health in the context of other viral infections could be confirmed definitely. This article is a review of the literature on a possible involvement of GBV-C in pathologies whether associated or not to other infections.

HGV/GB virus C transmission by blood components in patients undergoing open-heart surgery

BACKGROUND

To establish the rate of HGV/GB virus C (GBV-C) transmission by blood components in open-heart surgery patients.

STUDY DESIGN AND METHODS

From 55 patients receiving blood components, sera were collected before and 2, 4, 6, 8, 10, 12, 16, 20, 26, and 32 weeks after heart surgery. Serum samples from patients and implicated blood donations were tested for HGV/GBV-C RNA by PCR. Recipients of RNA-positive blood components were also tested for the presence of E2 antibodies (E2Ab) by ELISA.

RESULTS

Of 55 recipients, 18 received RNA-positive blood components. Of 14 recipients of RNA-positive blood components, who were negative for RNA or E2Ab before transfusion, 8 became RNA positive and one developed E2Ab after transfusion. Three recipients of RNA-positive blood components had E2Ab before transfusion, and none of these became RNA positive after transfusion. One of 18 recipients was RNA positive before and after transfusion. Of 55 recipients, 37 received RNA-negative blood components: 34 were RNA negative before and after transfusion. Of 37 recipients, 3 were RNA positive before and after transfusion.

CONCLUSION

Of susceptible patients, 64 percent became infected with HGV/GVC-C when transfused with RNA-positive blood components. E2Ab-positive patients were protected against HGV/GBV-C infection.

Genotyping of GB virus C by restriction pattern analysis of the 5' untranslated region

GB virus C (GBV-C) is a virus that has been proposed as a member of the Flaviviridae family, distantly related to hepatitis C virus (HCV). The virus is able to infect humans parenterally and perinatally, although its true pathogenicity remains unknown. The 5' terminal region of GBV-C is the most highly conserved region of the virus genome. Comparison of 5' untranslated region (5' UTR) sequences from GBV-C infected individuals shows that variation is limited to particular sites that are often covariant and associated with different virus genotypes. Extensive sequence analysis of the GBV-C genome provides evidence for the existence of at least five major genotypes, some of which can be further divided into subtypes. For genotyping by restriction fragment length polymorphism (RFLP), it is essential to identify genomic positions that not only reflect genotype differences, but that also harbor restriction sites that allow recognition of these differences. Restriction site analysis of type-specific sequence motifs predicted that endonucleases BsmFI, HaeII, HinfI, and ScrFI could be used for the identification all known genotypes (types 1-5) with 99.6% accuracy. The method was applied to serum samples from 46 chronic GBV-C carriers of heterogeneous geographical and ethnic origin, comparing observed cleavage patterns of GBV-C variants amplified by reverse transcriptase-polymerase chain reaction (RT-PCR) of the 5' UTR with the RFLP predicted from sequences deposited in GenBank database. cDNA sequencing and subsequent alignment of the 46 GBV-C isolates confirmed RFLP profiles predicted theoretically. The observed geographical distribution of genotypes is also in agreement with previous reports. This method may be useful for rapid and reliable characterization of GBV-C isolates when either epidemiological or transmission studies are carried out.

Interactions Between GB Virus Type C and HIV

GB virus C (GBV-C, also known as hepatitis G virus) commonly causes human infection. Genetically, it is closely related to hepatitis C virus, but GBV-C appears to grow primarily in lymphocytes, not hepatocytes. Although it causes persistent infection in about 25% to 50% of infected individuals, numerous studies have failed to connect GBV-C with any disease process. GBV-C is transmitted sexually, parenterally, and vertically, and due to these shared modes of transmission, coinfection is common among HIV-infected individuals. Of 10 studies done of HIV-GBV-C coinfection, eight found a beneficial effect of GBV-C viremia on HIV-related mortality or response to therapy. The mechanism by which GBV-C may improve survival of HIV-positive people is not known; however, in vitro studies suggest that GBV-C inhibits HIV replication, and preliminary data also point toward alterations in cytokine and/or chemokine expression by GBV-C-infected cells.

GB virus C/hepatitis G virus

GB virus C (GBV-C), or hepatitis G virus (HGV), is a recently discovered enveloped RNA virus belonging to the Flaviviridae family. GBV-C/HGV is transmitted by contaminated blood and/or blood products, intravenous drug use, from mother to child, sexually, and possibly through close social contacts. Several reports indicate a high prevalence of GBV-C/HGV viremia (1-4%) within healthy populations in Europe and North America, and an even higher prevalence (10-33%) among residents in South America and Africa. GBV-C/HGV has been suggested to be a causative agent for non-A-non-E hepatitis. However, several contradictory observations suggest that its ability to cause hepatitis is questionable. Taken together most data suggest that GBV-C/HGV is not a major cause of liver disease despite recent data indicating that it may infect and replicate in hepatocytes.

GB virus B as a model for hepatitis C virus

GB viruses A and B (GBV-A and GBV-B) are members of the Flaviviridae family and are isolated from tamarins injected with serum from a human hepatitis patient. Along with a related human virus, GB virus C, or alternatively, hepatitis G virus (GBV-C/HGV), the three viruses represent the GB agents. Of the three viruses, GBV-B has been proposed as a potential surrogate model for the study of hepatitis C virus (HCV) infections of humans. GBV-B is phylogenetically most closely related to HCV and causes an acute, self-resolving hepatitis in tamarins as indicated by an increase in alanine aminotransferase and changes in liver histology. Similarities between GBV-B and HCV are found at the nucleotide sequence level with the two viruses sharing 28% amino acid homology over the lengths of their open reading frames. Short regions have even higher levels of homology that are functionally significant as shown by the ability of the GBV-B NS3 protease to cleave recombinant HCV polyprotein substrates. The shared protease substrate specificities suggest that GBV-B may be useful in testing antiviral compounds for activity against HCV. Although there are numerous similarities between GBV-B and HCV, there are important differences in that HCV frequently causes chronic infections in people, whereas GBV-B appears to cause only acute infections. The acute versus chronic course of infection may point to important differences between the two viruses that, along with the numerous similarities, will make GBV-B in tamarins a good surrogate model for HCV.

GB virus C/hepatitis G virus (GBV-C/HGV): still looking for a disease

GB Virus C and Hepatitis G Virus (GBV-C/HGV) are positive, single-stranded flaviviruses. GBV-C and HGV are independent isolates of the same virus. Transmission via the blood-borne route is the commonest mode, although vertical and sexual transmission is well documented. GBV-C/HGV is distributed globally; its prevalence in the general population is 10 fold higher in African countries than in non-African countries. High prevalences of GBV-C/HGV have been found in subjects with frequent parenteral exposure and in groups at high risk of exposure to blood and blood products. The clinical significance of human infection with GBV-C/HGV is currently unclear. The virus can establish both acute and chronic infection and appears to be sensitive to interferon. Only some 12-15% of chronic Non-A, B, C hepatitis cases are infected with GBV-C/HGV. A direct association with liver pathology is still lacking and it is not yet clear as to whether GBV-C/HGV is indeed a hepatotropic virus. Current evidence suggests that the spectrum of association of GBV-C/HGV infection with extrahepatic diseases ranges from haematalogical diseases, aplastic anaemia, human immunodeficiency virus (HIV)-positive idiopathic thrombocytopenia and thalassemia, through to common variable immune deficiency and cryoglobunemia.