Human pegivirus type 1 infection in Asia-A review of the literature.

The human pegivirus type 1 (HPgV-1)-as known as hepatitis G virus and GB virus C-is a common single-stranded RNA flavivirus. Because few studies have demonstrated an association between HPgV-1 infection and disease, screening for HPgV-1 is not performed routinely. Nonetheless, a beneficial impact of HPgV-1 infection on HIV disease progression has been reported in multiple studies. Given the burden of HIV in Asia and the complex interactions between viral co-infections and the host, we provide a comprehensive overview of the existing data from Asia on HPgV-1 infection, including the prevalence and circulating genotypes in all Asian countries with data reported. This review highlights the research conducted thus far and emphasizes the need for additional studies on HPgV-1 across the Asian continent.

Occurrence and molecular characterization of human pegivirus-1 (HPgV-1) viremia in healthy volunteer blood donors from Northern Portugal.

Human pegivirus-1 (HPgV-1) is a member of the Flaviviridae family and the Pegivirus genus. Despite having been discovered 25 years ago, there is still much to know regarding HPgV-1 clinical impact, as this virus is currently not associated with any pathology. Yet, HPgV-1 prevalence and molecular characterization are still unknown in many countries, including Portugal. To fill in this knowledge gap, this study aimed to determine the occurrence and molecular characterization of HPgV-1 in a group of healthy blood donors from the north of Portugal. Blood samples from 465 Portuguese blood donors were collected from a major Hospital Center in the north of Portugal. RNA was extracted and an initial nested RT-PCR was performed targeting the conserved 5'-untranslated region  region of the HPgV-1 genome. A second nested RT-PCR targeting the E2 region was performed for genotyping. Only one sample tested positive for HPgV-1 RNA, resulting in a prevalence of approximately 0.22%. Phylogenetic analyses confirmed the characterization as genotype 2, the most prevalent in Europe.

Tissue presentation of human pegivirus infection in liver transplanted recipients.

Human pegivirus-1 (HPgV-1) is known for its protective role in HIV co-infected individuals. This immunomodulatory effect raised questions concerning the possible role of HPgV-1 infection and the risk of rejection in liver transplanted patients. We aimed to evaluate the possible protective effect of HPgV-1 on graft outcome of liver transplanted patients. A total of 283 patients were recruited. Formalin-fixed paraffin-embedded tissue samples were collected from the explanted liver. HBV-DNA, HCV-RNA, and HPgV-1-RNA were determined using PCR and multiplex RT-PCR assays. The clinical course of patients including the occurrence of acute cellular rejection was compared between HPgV-1-infected vs. uninfected patients. HBV-DNA, HCV-RNA and HPgV-1-RNA were detected in 42.6%, 4.9%, and 7.8% of samples, respectively. None of the HPgV-1-infected patients experienced graft rejection. Group LASSO logistic regression revealed that HPgV-1 infection was the only factor which significantly reduced the odds of graft rejection (OR = 0.5, 95% CI = 0.29-0.89). No significant association was found between the presence of HPgV-1 with HBV and HCV infections. The lack of graft rejection in HPgV-1-infected liver transplanted patients might indicate a possible role of this virus for graft surveillance. Since these are still preliminary findings, prospective studies should further elucidate the role of HPgV-1 in liver transplantation outcomes.

Clinical and molecular aspects of human pegiviruses in the interaction host and infectious agent.

BACKGROUND: Human pegivirus 1 (HPgV-1) is a Positive-sense single-stranded RNA (+ ssRNA) virus, discovered in 1995 as a Flaviviridae member, and the closest human virus linked to HCV. In comparison to HCV, HPgV-1 seems to be lymphotropic and connected to the viral group that infects T and B lymphocytes. HPgV-1 infection is not persuasively correlated to any known human disease; nevertheless, multiple studies have reported a connection between chronic HPgV-1 infection and improved survival in HPgV-1/HIV co-infected patients with a delayed and favorable impact on HIV infection development. While the process has not been thoroughly clarified, different mechanisms for these observations have been proposed. HPgV-1 is categorized into seven genotypes and various subtypes. Infection with HPgV-1 is relatively common globally. It can be transferred parenterally, sexually, and through vertical ways, and thereby its co-infection with HIV and HCV is common. In most cases, the clearance of HPgV-1 from the body can be achieved by developing E2 antibodies after infection. MAIN BODY: In this review, we thoroughly discuss the current knowledge and recent advances in understanding distinct epidemiological, molecular, and clinical aspects of HPgV-1. CONCLUSION: Due to the unique characteristics of the HPgV-1, so advanced research on HPgV-1, particularly in light of HIV co-infection and other diseases, should be conducted to explore the essential mechanisms of HIV clearance and other viruses and thereby suggest novel strategies for viral therapy in the future.

Human pegivirus 1 in Cabo Verde: prevalence and genotypic distribution among HIV-infected individuals.

Human pegivirus 1 (HPgV-1) belongs to the genus Pegivirus, family Flaviviridae, and until now has been considered a non-pathogenic agent, despite being considered a risk factor for non-Hodgkin lymphoma. However, a beneficial impact of HPgV-1 on HIV disease progression has been extensively reported. Given the high prevalence of HIV in sub-Saharan Africa and the scarcity of epidemiological data for many countries of West Africa, we conducted the first study of HPgV-1 in HIV-infected individuals from Cabo Verde. To obtain new data regarding prevalence and genetic diversity of HPgV-1 in Africa, serum samples from 102 HIV-infected Cabo Verdeans were tested for the presence of viral RNA, and the circulating genotypes were identified by sequencing of the 5' untranslated region. HPgV-1 RNA was detected in 19.6% (20/102) of the samples. In 72.2% (13/18) of the samples, the virus was identified as genotype 2 (11/13 subtype 2a and 2/13 subtype 2b), and in 27.8% (5/18), it was identified as genotype 1. The estimated substitution rate of HPgV-1 genotype 2 was 5.76 × 10-4, and Bayesian analysis indicated the existence of inner clusters within subtypes 2a and 2b. The prevalence of HPgV-1 viremia in Cabo Verde agrees with that reported previously in Africa. Genotypes 1 and 2 cocirculate, with genotype 2 being more common, and HIV/HPgV-1 coinfection was not associated with higher CD4 T cell counts in the studied population. This finding contributes for the expansion of the pegivirus research agenda in African countries.

Human pegivirus (HPgV, GBV-C) RNA in volunteer blood donors from a public hemotherapy service in Northern Brazil.

BACKGROUND: Human pegivirus (HPgV)-formerly known as GBV-C-is a member of the Flaviviridae family and belongs to the species Pegivirus C. It is a non-pathogenic virus and is transmitted among humans mainly through the exposure to contaminated blood and is often associated with human immunodeficiency virus (HIV) infection, among other viruses. This study aimed to determine the prevalence of HPgV viremia, its association with HIV and clinical epidemiological factors, as well as the full-length sequencing and genome characterization of HPgV recovered from blood donors of the HEMOPA Foundation in Belém-PA-Brazil. METHODS: Plasma samples were obtained from 459 donors, tested for the presence of HPgV RNA by the RT-qPCR. From these, a total of 26 RT-qPCR positive samples were submitted to the NGS sequencing approach in order to obtain the full genome. Genome characterization and phylogenetic analysis were conducted. RESULTS: The prevalence of HPgV was 12.42%. We observed the highest prevalences among donors aged between 18 and 30 years old (16.5%), with brown skin color (13.2%) and men (15.8%). The newly diagnosed HIV-1 prevalence was 26.67%. The HPgV genotype 2 (2a and 2b) was identified. No data on viral load value was found to corroborate the protective effect of HPgV on HIV evolution. CONCLUSIONS: This study provided information regarding the HPgV infection among blood donors from HEMOPA Foundation. Furthermore, we genetically characterized the HPgV circulating strains and described by the first time nearly complete genomes of genotype 2 in Brazilian Amazon.

Effect of human pegivirus route of transmission on the genetic distribution of the virus: an institution based cross-sectional study.

INTRODUCTION: Human pegivirus (HPgV), formally called GB virus C (GBV-C), is a member of the pegivirus genus in Flaviviridae family. High prevalence of HPgV infection is seen among sex workers, blood transfusion recipients and intravenous drug users (IDUs). So far, there are seven genotypes and many subtypes identified in different countries. The predominant genotype in Asia including China is genotype 3, although genotype 7 has been reported recently in China. The aim of this study was to evaluate the effect of the transmission routes of HPgV infection on the genotype distribution of the virus, to determine the prevalence rate, and identify the dominant genotype among men who have sex with men (MSM) and IDUs co-infected with human immunodeficiency virus type one (HIV-1) in Guangzhou, China. METHODS: A total of 131 MSM and 70 IDUs co-infected with HIV-1 were randomly selected in Guangdong Dermatology Hospital. HPgV RNA was detected by nested reverse transcriptase polymerase chain reaction (RT-PCR) using primers. The PCR products were sequenced and phylogenetically analyzed by using MEGA6.06 version software to determine the genotypes. Chi-square and Fisher exact test were implemented for comparing the proportion between different variables. RESULTS: The prevalence of HPgV infection was 32.9% among IDUs and 18.3% in MSM with a statistically significant difference between the two groups (p = 0.02). In IDU group, 82.6% infected with genotype 3 and the rest (17.4%) were categorized to genotype 7. Similarly, in MSM group, 83.3% belonged to genotype 3, and the remaining 16.7% were classified as sub-genotype 2a and 2b. CONCLUSION: In Guangzhou, China, the prevalence rate of HPgV infection in IDUs was higher than MSM. The dominant genotype in the two groups was genotype 3. Our results indicated that routes of transmission did not affect the genotype distribution but did affect the prevalence rate of HPgV infection.

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.

Discovery of a Novel Human Pegivirus in Blood Associated with Hepatitis C Virus Co-Infection.

Hepatitis C virus (HCV) and human pegivirus (HPgV), formerly GBV-C, are the only known human viruses in the Hepacivirus and Pegivirus genera, respectively, of the family Flaviviridae. We present the discovery of a second pegivirus, provisionally designated human pegivirus 2 (HPgV-2), by next-generation sequencing of plasma from an HCV-infected patient with multiple bloodborne exposures who died from sepsis of unknown etiology. HPgV-2 is highly divergent, situated on a deep phylogenetic branch in a clade that includes rodent and bat pegiviruses, with which it shares <32% amino acid identity. Molecular and serological tools were developed and validated for high-throughput screening of plasma samples, and a panel of 3 independent serological markers strongly correlated antibody responses with viral RNA positivity (99.9% negative predictive value). Discovery of 11 additional RNA-positive samples from a total of 2440 screened (0.45%) revealed 93-94% nucleotide identity between HPgV-2 strains. All 12 HPgV-2 RNA-positive cases were identified in individuals also testing positive for HCV RNA (12 of 983; 1.22%), including 2 samples co-infected with HIV, but HPgV-2 RNA was not detected in non-HCV-infected individuals (p<0.0001), including those singly infected by HIV (p = 0.0075) or HBV (p = 0.0077), nor in volunteer blood donors (p = 0.0082). Nine of the 12 (75%) HPgV-2 RNA positive samples were reactive for antibodies to viral serologic markers, whereas only 28 of 2,429 (1.15%) HPgV-2 RNA negative samples were seropositive. Longitudinal sampling in two individuals revealed that active HPgV-2 infection can persist in blood for at least 7 weeks, despite the presence of virus-specific antibodies. One individual harboring both HPgV-2 and HCV RNA was found to be seronegative for both viruses, suggesting a high likelihood of simultaneous acquisition of HCV and HPgV-2 infection from an acute co-transmission event. Taken together, our results indicate that HPgV-2 is a novel bloodborne infectious virus of humans and likely transmitted via the parenteral route.

Prevalence and genotypes of GBV-C and its associations with HIV infection among persons who inject drugs in Eastern Europe.

We aimed to determine the rate of GBV-C viremia, seropositivity, and genotypes among people who inject drugs (PWID) and healthy volunteers in Estonia and to evaluate associations between GBV-C and sociodemographic factors, intravenous drug use, co-infections. The study included 345 Caucasian PWID and 118 healthy volunteers. The presence of GBV-C RNA (viremia) was determined by reverse transcriptase-nested PCR in 5' long terminal repeat. PCR products were sequenced and genotyped by phylogenetic analysis. GBV-C seropositivity was determined by ELISA. One third of PWID (114/345) and 6% (7/118) of healthy volunteers (OR = 7.8, 95% CI = 3.5-20.5, P < 0.001) were GBV-C viremic. In PWID group, 79% of sequences belonged to subtype 2a, 19% to subtype 2b, and two remained unclassified. In healthy volunteers, six out of seven sequences belonged to subtype 2a and one to subtype 2b. We found HIV+ PWID to have two times increased odds of being GBV-C viremic compared to HIV- PWID (62% vs. 38%; OR = 2.13, 95% CI = 1.34-3.36, P = 0.001). In addition, odds of being GBV-C viremic decreased with increasing age (OR = 0.94, 95% CI = 0.90-0.98, P = 0.001). HIV positivity remained associated with GBV-C viremia in multivariate analysis after adjustment for age (OR = 2.23, 95% CI = 1.39-3.58, P = 0.001). GBV-C seropositivity was similar among PWID and healthy volunteers (2.3% vs. 1.7%, respectively; OR = 1.4, 95% CI =0.3-13.5, P = 1). In an Eastern European country we demonstrated that GBV-C viremia is common among PWID, but uncommon among healthy volunteers, and GBV-C seropositivity is infrequent among both groups. Similarly to other European countries and USA, GBV-C 2a is the most common genotype in Estonia. J. Med. Virol. 89:632-638, 2017. © 2016 Wiley Periodicals, Inc.

Recombination among GB virus C (GBV-C) isolates in the United States.

GB virus C (GBV-C) is a non-pathogenic flavivirus that may play a role in modulating HIV disease. Multiple genotypes of GBV-C that have been identified to date that may differentially regulate HIV; however, the number of complete GBV-C sequences published to date is very limited. We sequenced full-length GBV-C genomes from four individuals with HIV/HCV co-infection in the United States. Intergenotypic recombination was evident in two of these individuals. Evaluation of additional full-length GBV-C genomes would facilitate the creation of full-length, replication-competent molecular clones of GBV-C to evaluate the phenotypic diversity of GBV-C genotypes and provide important molecular data on this understudied virus.

GB virus C coinfections in west African Ebola patients.

In 49 patients with known Ebola virus disease outcomes during the ongoing outbreak in Sierra Leone, 13 were coinfected with the immunomodulatory pegivirus GB virus C (GBV-C). Fifty-three percent of these GBV-C(+) patients survived; in contrast, only 22% of GBV-C(-) patients survived. Both survival and GBV-C status were associated with age, with older patients having lower survival rates and intermediate-age patients (21 to 45 years) having the highest rate of GBV-C infection. Understanding the separate and combined effects of GBV-C and age on Ebola virus survival may lead to new treatment and prevention strategies, perhaps through age-related pathways of immune activation.

Detection of GB virus C genomic sequence in the cerebrospinal fluid of a HIV-infected patient in China: a case report and literature review.

Hepatitis G virus or GB virus C (GBV-C) is a human virus of the Flaviviridae family that is structurally and epidemiologically closest to hepatitis C virus, but replicates primarily in lymphocytes. Co-infection with GBV-C has been reported to confer beneficial outcomes in some HIV-positive patients. Up to now, however, studies on GBV-C infection in the central nervous system (CNS) of HIV-infected patient have rarely been reported. Herein, we report on a 32-year-old HIV-1-infected patient with cerebral toxoplasmosis and fungal encephalitis. GBV-C viral loads were detected in CSF by quantitative real-time reverse transcription polymerase chain reaction (RT-PCR), and the results showed that GBV-C viral load was 6·5 log copies/ml. We amplified and sequenced the E2 and 5'-untranslated regions from the purified viral RNA from CSF by RT-PCR. Both sequences belong to genotype 3 and there were some minor nucleotide divergence among the E2 sequences from the CSF of the patient. These data suggest that GBV-C may be able to penetrate the blood-brain barrier and colonize the CNS of HIV-infected patients. However, the exact mechanisms and potential effect of the infected GBV-C in CNS on HIV-associated neuropathy needs to be further explored.

Detection and phylogenetic analysis of human pegivirus (GBV-C) among blood donors and patients infected with hepatitis B virus (HBV) in Qatar.

Human Pegivirus (HPgV), formerly GB virus-C/Hepatitis G virus (GBV-C/HGV), collectively known as GBV-C, is widely spread and has been reported to be associated with non-A-E hepatitis. To our knowledge, no previous study was conducted about HPgV in Qatar. Thus, the objectives of this study were as follows: (i) to determine the rates of HPgV infection in Qatar among healthy blood donors and HBV-infected patients, and (ii) to determine the most predominant HPgV genotype in Qatar. A total of 714 blood plasma samples from healthy donors (612) and HBV-infected patients (102) were collected. RNA was extracted, reversed transcribed, and then subjected for HPgV detection by two round-nested PCR using primers amplifying a 208 bp of 5'-UTR of the HPgV. For genotyping, the 5'-UTR PCR products (from 25 randomly picked samples) were cloned and sequenced. The overall infection rate of HPgV in Qatar was 13.3%. There was no significant difference (P = 0.41) in the infection rates between healthy donor (13.7%) and in HBV-infected patients (10.7%). Moreover, we did not find any significant association between HPgV infection rates and nationality, sex, or age (P > 0.05). Sequence analysis of 40 5'-UTR PCR amplicons yielded the European genotype 2 as most predominant in Qatar, although other genotypes (5 and 7) were also present. Our results indicate that there is no strong correlation between HPgV infection rate, condition, nationality, age, and sex, and genotype 2 is most predominant in Qatar.

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.

Host and viral determinants of the outcome of exposure to HCV infection genotype 4: a large longitudinal study.

OBJECTIVES: The objective of this study was to characterize the factors that influence the outcome of exposure to hepatitis C virus (HCV) genotype 4 (HCV-G4) and the course of recent infection. METHODS: In this longitudinal study, we prospectively assessed the clinical, genetic, virological, and immunological parameters and retrospectively determined single-nucleotide polymorphisms at interleukin-28B (IL-28B) rs12979860 in a well-characterized large cohort recently exposed to HCV-G4. RESULTS: A total of 136 subjects with acute HCV (new viremia, seroconversion, and HCV-specific T-cell responses) were identified. Forty-eight subjects (35%) had spontaneous viral clearance and 88 subjects developed chronic HCV of which 42 subjects were treated with pegylated interferon monotherapy, with a sustained virologic response (SVR) rate of 88%. Twenty-six subjects developed HCV-specific T-cell immune responses without detectable viremia or seroconversion. IL-28B-CC (odds ratio (OR) 14.22; P<0.0001), multispecific T-cell responses (OR=11.66; P<0.0001), >300 IU/l alanine aminotransferase (ALT) decline within 4 weeks (OR=6.83; P<0.0001), jaundice (OR=3.54; P=0.001), female gender (OR=2.39; P=0.007), and >2.5 log10 HCV-RNA drop within 8 weeks (OR=2.48; P=0.016) were independently associated with spontaneous clearance. ALT normalization and undetectable HCV-RNA predicted SVR. Exposed apparently uninfected participants had a higher frequency of IL-28B-CC than patients with unresolved acute HCV (P<0.001). IL-28B-CC was associated with multispecific T-cell response (r(2)=0.0.835; P<0.001). CONCLUSIONS: IL-28B-CC genotype, multispecific HCV T-cell responses, rapid decline in ALT, and viral load predict spontaneous clearance and response to acute HCV-G 4 therapy. IL-28B-CC genotype correlates with developing early multispecific T-cell responses. These findings have important implications for predicting the outcome of HCV exposure and acute infection and identifying patients likely to benefit from therapy.

Impact of GB virus C viraemia on clinical outcome in HIV-1-infected patients: a 20-year follow-up study.

OBJECTIVES: The impact of coexisting GB virus C (GBV-C) infection on the clinical course of HIV infection remains controversial. Early data from HIV-1 infected patients attending the Hannover Medical School in 2001 suggested prognostic benefit in GBV-C viraemic patients. The aim of this study was to evaluate patterns in long-term mortality and morbidity outcomes in this cohort. The impact of the introduction of antiretroviral therapy (ART) on the perceived benefits of GBV-C viraemia was subsequently investigated. METHODS: A retrospective follow-up analysis of data in this cohort was performed. GBV-C status (GBV-C RNA positive, antibodies against GBV-C envelope protein E2 or no evidence of GBV-C exposure) had been determined at enrolment, with several markers of HIV disease progression (such as viral load and CD4 cell count) being collated from 1993/1994, 2000 and 2012. These eras were chosen to reflect variations in treatment strategies within the cohort. In addition, mortality and HIV-related morbidity data were collated for all patients. RESULTS: Complete data were available for 156 of 197 patients (79%). In highly active antiretroviral therapy (HAART)-naïve patients, GBV-C RNA positivity conferred significant improvements in the course of HIV infection and mortality as well as lower rates of HIV-related diseases. E2 positivity alone conferred no significant advantage. With the advent of HAART, however, the benefits GBV-C RNA positivity disappeared. CONCLUSIONS: Although GBV-C coinfection appears to inherently improve morbidity and mortality in HIV-infected patients, modern HAART has eradicated these advantages. Evidence of synergy between GBV-C status and HAART response exists, with further studies examining the role of GBV-C in existing treatment de-escalation strategies being required.

Epidemiology of GB virus type C among patients infected with HIV in Singapore.

Several studies have shown that individuals co-infected with GB virus type C (GBV-C), and human immunodeficiency virus (HIV) have slower progression to acquired immunodeficiency syndrome (AIDS) and a prolonged lifespan, compared to those infected with only HIV. In Singapore, despite the steadily increasing number of HIV infections in recent years, there are no studies documenting the extent of GBV-C/HIV co-infection in this group of patients. To fill this dearth of information, two GBV-C screening assays was performed on 80 archived HIV-1-positive samples from the National University Hospital. The overall prevalence of GBV-C co-infection among patients infected with HIV in this study was 10% (8/80). Phylogenetic analysis of the eight dual-infection cases revealed that genotypes 3 (4/8, 50%) and 2a (2/8, 25%) were the main genotypes circulating among these Singaporean HIV patients. One case each of genotypes 2b (1/8, 12.5%) and 4 (1/8, 12.5%), which have not been described previously in Singapore, were identified. These findings hint at the complex epidemiology of GBV-C in different patient groups and a larger study would be needed to characterize, and understand the potential clinical impact of GBV-C co-infection on the patients.

GB virus C envelope protein E2 inhibits TCR-induced IL-2 production and alters IL-2-signaling pathways.

GB virus type C (GBV-C) viremia is associated with reduced CD4+ T cell expansion following IL-2 therapy and with a reduction in T cell activation in HIV-infected individuals. The mechanism(s) by which GBV-C might alter T cell activation or IL-2 signaling have not been studied. In this study, we assess IL-2 release, IL-2R expression, IL-2 signaling, and cell proliferation in tet-off Jurkat cells expressing the GBV-C envelope glycoprotein (E2) following activation through the TCR. TCR activation was induced by incubation in anti-CD3/CD28 Abs. IL-2 release was measured by ELISA, STAT5 phosphorylation was assessed by immunoblot, and IL-2Rα (CD25) expression and cell proliferation were determined by flow cytometry. IL-2 and IL-2Rα steady-state mRNA levels were measured by real-time PCR. GBV-C E2 expression significantly inhibited IL-2 release, CD25 expression, STAT5 phosphorylation, and cellular proliferation in Jurkat cells following activation through the TCR compared with control cell lines. Reducing E2 expression by doxycycline reversed the inhibitory effects observed in the E2-expressing cells. The N-terminal 219 aa of E2 was sufficient to inhibit IL-2 signaling. Addition of purified recombinant GBV-C E2 protein to primary human CD4+ and CD8+ T cells inhibited TCR activation-induced IL-2 release and upregulation of IL-2Rα expression. These data provide evidence that the GBV-C E2 protein may contribute to the block in CD4+ T cell expansion following IL-2 therapy in HIV-infected individuals. Furthermore, the effects of GBV-C on IL-2 and IL-2-signaling pathways may contribute to the reduction in chronic immune activation observed in GBV-C/HIV-coinfected individuals.

GB virus type C E2 protein inhibits human immunodeficiency virus type 1 assembly through interference with HIV-1 gag plasma membrane targeting.

GB virus type C (GBV-C) is a single-stranded positive-sense RNA virus classified in the Flaviviridae family. Persistent coinfection with GBV-C is associated with lower human immunodeficiency virus type 1 (HIV-1) load, higher CD4(+) T-cell count, and prolonged survival in HIV-1 coinfected patients. The GBV-C envelope glycoprotein E2 has been reported to interfere with HIV-1 entry. In this study, we showed that the expression of GBV-C E2 inhibited HIV-1 Gag assembly and release. Expression of glycosylated GBV-C E2 inhibited HIV-1 Gag precursor processing, resulting in lower production of CAp24 and MAp17, while the overall expression level of the Gag precursor Pr55 remained unchanged. Membrane floatation gradient and indirect immunofluorescence confocal microscopy analysis showed that glycosylated E2 disrupted HIV-1 Gag trafficking to the plasma membrane, resulting in Gag accumulation in subcellular compartments. This interference in HIV-1 Gag trafficking led to diminished HIV-1 particle production, which is a critical step for HIV-1 to infect new host cells. These findings shed light on a novel mechanism used by GBV-C E2 to inhibit HIV-1 replication and may provide insight into new approaches for suppressing HIV-1 replication.