Regulation of CC chemokine receptor 5 in hepatitis G virus infection

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.

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.

Molecular and Clinical Profiles of Human Pegivirus Type 1 Infection in Individuals Living with HIV-1 in the Extreme South of Brazil

Human pegivirus type 1 (HPgV-1) infection has been associated with a beneficial effect on the prognosis of human immunodeficiency virus type 1 (HIV-1)-coinfected individuals. However, the mechanisms involved in this protection are not yet fully elucidated. To date, circulating HPgV-1 genotypes in HIV-1-infected individuals have not yet been identified in the extreme south of Brazil. The present study aimed to determine the genotypic circulation of HPgV-1 and the influence of HPgV-1 status and persistence time on the evolution of HIV-1 infection. A retrospective cohort of 110 coinfected individuals was analyzed. Samples were subjected to viral RNA extraction, cDNA synthesis, nested PCR, and genotyping. Genotypes 1 (2.8%), 2 (47.9% of subtype 2a and 42.3% of subtype 2b), and 3 (7%) were identified. In antiretroviral treatment-naïve subjects HPgV-1 subtype 2b was associated with lower HIV-1 viral load (VL) rates (p = 0.04) and higher CD4+ T-cell counts (p = 0.03) than was subtype 2a, and the positivity for HPgV-1 was associated with higher CD4+ T-cell counts (p = 0.02). However, there was no significant difference in HIV-1 VL between HPgV-1-positive and HPgV-1-negative subjects (p = 0.08). There was no significant association between the different groups in HPgV-1 persistence and median HIV-1 VL (p = 0.66) or CD4+ T-cell counts (p = 0.15). HPgV-1 subtype 2b is associated with better prognosis of HIV-1 infection. Although HPgV-1 infection is persistent, our data suggest that the time of infection does not influence HIV-1 VL or CD4+ T-cell counts in coinfected subjects.

Baboon CD8 T cells suppress SIVmac infection in CD4 T cells through contact-dependent production of MIP-1α, MIP-1β, and RANTES

Simian immunodeficiency virus (SIV) infection in rhesus macaques is often characterized by high viremia and CD4 T cell depletion. By contrast, SIV infection in African nonhuman primate natural hosts is typically nonpathogenic despite active viral replication. Baboons are abundant in Africa and have a geographical distribution that overlaps with natural hosts, but they do not harbor SIVs. Previous work has demonstrated baboons are resistant to chronic SIV infection and/or disease in vivo but the underlying mechanisms remain unknown. Using in vitro SIVmac infections, we sought to identify SIV restriction factors in baboons by comparing observations to the pathogenic rhesus macaque model. SIVmac replicated in baboon PBMC but had delayed kinetics compared to rhesus PBMC. However, SIVmac replication in baboon and rhesus isolated CD4 cells were similar to the kinetics seen for rhesus PBMC, demonstrating intracellular restriction factors do not play a strong role in baboon inhibition of SIVmac replication. Here, we show CD8 T cells contribute to the innate SIV-suppressive activity seen in naïve baboon PBMC. As one mechanism of restriction, we identified higher production of MIP-1α, MIP-1β, and RANTES by baboon PBMC. Contact between CD4 and CD8 T cells resulted in maximum production of these chemokines and suppression of viral replication, whereas neutralization of CCR5-binding chemokines in baboon PBMC increased viral loads. Our studies indicate baboon natural restriction of SIVmac replication is largely dependent on CD4-extrinsinc mechanisms mediated, in part, by CD8 T cells.

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.

Cytokine/chemokine expression associated with Human Pegivirus (HPgV) infection in women with HIV

A beneficial impact of the Human Pegivirus (HPgV)-formerly called GB virus C (GBV-C)-on HIV disease progression has been reported previously. One possible mechanism by which HPgV inhibits HIV replication is an alteration of the cytokine/chemokine milieu. Their expression has not been specifically evaluated in women despite their influence on disease progression and the possibility of gender-based differences in expression. Moreover, the impact of HPgV genotype on cytokine/chemokine expression is unknown. Sera levels of IL-2, IL-4, IL-7, IL-8, IL-10, IL-12p70, IL-13, IFNγ, TNFα, IP-10, MIP-1α, MIP-1β, and TGF-β₁ were quantified in 150 HIV-positive women based on HPgV RNA status. Cytokines/chemokines with detection rates of at least 50% included IL-2, IL-4, IL-8, IL-10, IL-12p70, IFNγ, TNFα, IP-10, MIP-1α, MIP-1β, and TGF-β₁ . Absolute values were significantly higher for HPgV positive compared to HPgV negative women for IL-7, IL-13, IL-12p70, and IFNγ. Absolute values were significantly lower for HPgV positive women for IL-4, IL-8, TGF-β₁ , and IP-10. IFNγ values were higher for HPgV genotype 2 than for genotype 1 (P = 0.036). Further study of cytokine/chemokine regulation by HPgV may ultimately lead to the development of novel therapeutic agents to treat HIV infection and/or the design of vaccine strategies that mimic the "protective" effects of HPgV replication.

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.

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.

Downregulation of Cytokines and Chemokines by GB Virus C After Transmission Via Blood Transfusion in HIV-Positive Blood Recipients

BACKGROUND

An association between GB virus C (GBV-C) and improved outcomes of human immunodeficiency virus (HIV) infection has been reported in HIV-positive individuals with active GBV-C coinfection. This study provides insights into the immune mechanisms underlying the protective role of GBV-C in HIV-infected patients.

METHODS

The concentrations of 64 cytokines and chemokines were measured in plasma samples obtained from the Viral Activation Transfusion Study cohort before transfusion and longitudinally from 30 patients positive for both HIV and GBV-C (hereafter, "cases") and 30 patients positive for HIV and negative for GBV-C (hereafter, "controls").

RESULTS

Cases had lower HIV viral loads and higher CD4 T-cell counts than controls after acquisition of GBV-C infection. Most of the modulated cytokines and chemokines were reduced after GBV-C detection, including many proinflammatory cytokines, suggesting an overall antiinflammatory effect of GBV-C in HIV-positive subjects. Most pathways and functions of the measured cytokines were downregulated in cases, except cell death pathways, which were upregulated in various cell subsets in the 3 months after GBV-C detection.

CONCLUSIONS

GBV-C has a protective effect, in part through a competition mechanism leading to decreased inflammation and improved HIV disease outcome in cases. Further studies are necessary to establish whether GBV-C may have deleterious effects on the host at the cellular level, including depleting the cells that are the targets of HIV.

Virus against virus (VIVI): a potential solution against HIV/AIDS

Most therapeutic regimens are aimed at the use of pharmacologic agents or the induction of immunological response against the pathological agent. However, these methods tend to be insufficient for the management of some of the most debilitating infectious diseases. Here we present a novel therapeutic approach. It involves voluntary super-infection of a subject having HIV/AIDS with a virus (GBV-C), which to date has not been shown to be responsible for any pathology. It has been shown to counter, suppress or eradicate the agent responsible for the severe disease. Several studies demonstrate the role of different micro-organisms in influencing the growth of other pathogens in the human body. This hypothesis requires meticulous testing before its implementation on humans. If the trials are successful, the implications for this hypothesis are promising considering the compliance issues and adverse effects associated with current standard of HIV care.

GB virus C infection and B-cell, natural killer cell, and monocyte activation markers in HIV-infected individuals

GB virus C (GBV-C), a pan-lymphotropic flavivirus capable of persistent infection, is associated with prolonged survival and reduced T-cell activation in HIV-infected patients. GBV-C was associated with reduced CD56brt/CD16- natural killer cell and monocyte activation, and a trend toward reduced B-cell activation by measuring cell surface activation markers or HIV entry coreceptors. The GBV-C association was independent of HIV viral load. Thus, GBV-C may influence non-T-cell immune activation in individuals with HIV infection.

HIV-1 fusion is blocked through binding of GB Virus C E2-derived peptides to the HIV-1 gp41 disulfide loop [corrected]

A strategy for antiviral drug discovery is the elucidation and imitation of viral interference mechanisms. HIV-1 patients benefit from a coinfection with GB Virus C (GBV-C), since HIV-positive individuals with long-term GBV-C viraemia show better survival rates than HIV-1 patients without persisting GBV-C. A direct influence of GBV-C on HIV-1 replication has been shown in coinfection experiments. GBV-C is a human non-pathogenic member of the flaviviridae family that can replicate in T and B cells. Therefore, GBV-C shares partly the same ecological niche with HIV-1. In earlier work we have demonstrated that recombinant glycoprotein E2 of GBV-C and peptides derived from the E2 N-terminus interfere with HIV entry. In this study we investigated the underlying mechanism. Performing a virus-cell fusion assay and temperature-arrested HIV-infection kinetics, we provide evidence that the HIV-inhibitory E2 peptides interfere with late HIV-1 entry steps after the engagement of gp120 with CD4 receptor and coreceptor. Binding and competition experiments revealed that the N-terminal E2 peptides bind to the disulfide loop region of HIV-1 transmembrane protein gp41. In conjunction with computational analyses, we identified sequence similarities between the N-termini of GBV-C E2 and the HIV-1 glycoprotein gp120. This similarity appears to enable the GBV-C E2 N-terminus to interact with the HIV-1 gp41 disulfide loop, a crucial domain involved in the gp120-gp41 interface. Furthermore, the results of the present study provide initial proof of concept that peptides targeted to the gp41 disulfide loop are able to inhibit HIV fusion and should inspire the development of this new class of HIV-1 entry inhibitors.

Chimpanzee GB virus C and GB virus A E2 envelope glycoproteins contain a peptide motif that inhibits human immunodeficiency virus type 1 replication in human CD4⁺ T-cells

GB virus type C (GBV-C) is a lymphotropic virus that can cause persistent infection in humans. GBV-C is not associated with any disease, but is associated with reduced mortality in human immunodeficiency virus type 1 (HIV-1)-infected individuals. Related viruses have been isolated from chimpanzees (GBV-Ccpz) and from New World primates (GB virus type A, GBV-A). These viruses are also capable of establishing persistent infection. We determined the nucleotide sequence encoding the envelope glycoprotein (E2) of two GBV-Ccpz isolates obtained from the sera of captive chimpanzees. The deduced GBV-Ccpz E2 protein differed from human GBV-C by 31 % at the amino acid level. Similar to human GBV-C E2, expression of GBV-Ccpz E2 in a tet-off human CD4(+) Jurkat T-cell line significantly inhibited the replication of diverse HIV-1 isolates. This anti-HIV-replication effect of GBV-Ccpz E2 protein was reversed by maintaining cells in doxycycline to reduce E2 expression. Previously, we found a 17 aa region within human GBV-C E2 that was sufficient to inhibit HIV-1. Although GBV-Ccpz E2 differed by 3 aa differences in this region, the chimpanzee GBV-C 17mer E2 peptide inhibited HIV-1 replication. Similarly, the GBV-A peptide that aligns with this GBV-C E2 region inhibited HIV-1 replication despite sharing only 5 aa with the human GBV-C E2 sequence. Thus, despite amino acid differences, the peptide region on both the GBV-Ccpz and the GBV-A E2 protein inhibit HIV-1 replication similar to human GBV-C. Consequently, GBV-Ccpz or GBV-A infection of non-human primates may provide an animal model to study GB virus-HIV interactions.

GB virus C infection is associated with altered lymphocyte subset distribution and reduced T cell activation and proliferation in HIV-infected individuals

GBV-C infection is associated with prolonged survival and with reduced T cell activation in HIV-infected subjects not receiving combination antiretroviral therapy (cART). The relationship between GBV-C and T cell activation in HIV-infected subjects was examined. HIV-infected subjects on cART with non-detectable HIV viral load (VL) or cART naïve subjects were studied. GBV-C VL and HIV VL were determined. Cell surface markers of activation (CD38(+)/HLA-DR(+)), proliferation (Ki-67+), and HIV entry co-receptor expression (CCR5+ and CXCR4+) on total CD4+ and CD8+ T cells, and on naïve, central memory (CM), effector memory (EM), and effector CD4+ and CD8+ subpopulations were measured by flow cytometry. In subjects with suppressed HIV VL, GBV-C was consistently associated with reduced activation in naïve, CM, EM, and effector CD4+ cells. GBV-C was associated with reduced CD4+ and CD8+ T cell surface expression of activation and proliferation markers, independent of HIV VL classification. GBV-C was also associated with higher proportions of naïve CD4+ and CD8+ T cells, and with lower proportions of EM CD4+ and CD8+ T cells. In conclusion, GBV-C infection was associated with reduced activation of CD4+ and CD8+ T cells in both HIV viremic and HIV RNA suppressed patients. Those with GBV-C infection demonstrated an increased proportion of naive T cells and a reduction in T cell activation and proliferation independent of HIV VL classification, including those with suppressed HIV VL on cART. Since HIV pathogenesis is thought to be accelerated by T cell activation, these results may contribute to prolonged survival among HIV infected individuals co-infected with GBV-C. Furthermore, since cART therapy does not reduce T cell activation to levels seen in HIV-uninfected people, GBV-C infection may be beneficial for HIV-related diseases in those effectively treated with anti-HIV therapy.

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.

Recombinant interferon-γ lentivirus co-infection inhibits adenovirus replication ex vivo

Recombinant interferon-γ (IFNγ) production in cultured lentivirus (LV) was explored for inhibition of target virus in cells co-infected with adenovirus type 5 (Ad5). The ability of three different promoters of CMV, EF1α and Ubiquitin initiating the enhanced green fluorescence protein (GFP) activities within lentiviruses was systematically assessed in various cell lines, which showed that certain cell lines selected the most favorable promoter driving a high level of transgenic expression. Recombinant IFNγ lentivirus carrying CMV promoter (LV-CMV-IFNγ) was generated to co-infect 293A cells with a viral surrogate of recombinant GFP Ad5 in parallel with LV-CMV-GFP control. The best morphologic conditions were observed from the two lentiviruses co-infected cells, while single adenovirus infected cells underwent clear pathologic changes. Viral load of adenoviruses from LV-CMV-IFNγ or LV-CMV-GFP co-infected cell cultures was significantly lower than that from adenovirus alone infected cells (P=0.005-0.041), and the reduction of adenoviral load in the co-infected cells was 86% and 61%, respectively. Ad5 viral load from LV-CMV-IFNγ co-infected cells was significantly lower than that from LV-CMV-GFP co-infection (P=0.032), which suggested that IFNγ rather than GFP could further enhance the inhibition of Ad5 replication in the recombinant lentivirus co-infected cells. The results suggest that LV-CMV-IFNγ co-infection could significantly inhibit the target virus replication and might be a potential approach for alternative therapy of severe viral diseases.

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.

Influence of GB virus C on IFN-γ and IL-2 production and CD38 expression in T lymphocytes from chronically HIV-infected and HIV-HCV-co-infected patients

This study was designed to assess the effect of GB virus (GBV)-C on the immune response to human immunodeficiency virus (HIV) in chronically HIV-infected and HIV- hepatitis C virus (HCV)-co-infected patients undergoing antiretroviral therapy. A cohort of 159 HIV-seropositive patients, of whom 52 were HCV-co-infected, was included. Epidemiological data were collected and virological and immunological markers, including the production of interferon gamma (IFN-γ) and interleukin (IL)-2 by CD4, CD8 and Tγδ cells and the expression of the activation marker, CD38, were assessed. A total of 65 patients (40.8%) presented markers of GBV-C infection. The presence of GBV-C did not influence HIV and HCV replication or TCD4 and TCD8 cell counts. Immune responses, defined by IFN-γ and IL-2 production and CD38 expression did not differ among the groups. Our results suggest that neither GBV-C viremia nor the presence of E2 antibodies influence HIV and HCV viral replication or CD4 T cell counts in chronically infected patients. Furthermore, GBV-C did not influence cytokine production or CD38-driven immune activation among these patients. Although our results do not exclude a protective effect of GBV-C in early HIV disease, they demonstrate that this effect may not be present in chronically infected patients, who represent the majority of patients in outpatient clinics.

Characterization of a peptide domain within the GB virus C envelope glycoprotein (E2) that inhibits HIV replication

GB virus C (GBV-C) infection is associated with prolonged survival in HIV-infected cohorts, and GBV-C E2 protein inhibits HIV entry when added to CD4+ T cells. To further characterize E2 effects on HIV replication, stably transfected Jurkat cell lines expressing GBV-C E2 or control sequences were infected with HIV and replication was measured. HIV replication (all 6 isolates studied) was inhibited in all cell lines expressing a region of 17 amino acids of GBV-C E2, but not in cell lines expressing E2 without this region. In contrast, mumps and yellow fever virus replication was not inhibited by E2 protein expression. Synthetic GBV-C E2 17mer peptides did not inhibit HIV replication unless they were fused to a tat-protein-transduction-domain (TAT) for cellular uptake. These data identify the region of GBV-C E2 protein involved in HIV inhibition, and suggest that this GBV-C E2 peptide must gain entry into the cell to inhibit HIV.

GB virus type C infection polarizes T-cell cytokine gene expression toward a Th1 cytokine profile via NS5A protein expression

Human immunodeficiency virus (HIV) disease progression is associated with a helper T cell 1 (Th1) to helper T cell 2 (Th2) cytokine profile switch. Persistent GB virus type C (GBV-C) infection is associated with survival and a serum Th1 cytokine profile in HIV-infected individuals. We found that GBV-C infection increased gene expression of Th1 cytokines and decreased Th2 cytokine expression in peripheral blood mononuclear cells. Furthermore, expression of GBV-C NS5A protein in a CD4(+) cell line resulted in upregulation of Th1 cytokines (tumor necrosis factor α) and downregulation of Th2 cytokines (interleukin 4, interleukin 5, interleukin 10, interleukin 13). GBV-C-induced modulation in T-cell cytokines may contribute to the beneficial effect of GBV-C in HIV-infected individuals.

Transmission of GB virus type C via transfusion in a cohort of HIV-infected patients

BACKGROUND

GB virus C (GBV-C) infection is transmitted by blood exposure and associated with lower human immunodeficiency virus (HIV) load and slower HIV disease progression. Few studies describe predictors of acute GBV-C infection following transfusion in HIV-infected patients.

METHODS

We used a limited-access database from the National Heart Lung and Blood Institute's Viral Activation Transfusion Study, a randomized controlled trial of leukoreduced versus nonleukoreduced transfusions received by HIV-infected, transfusion-naive patients. Blood samples from 489 subjects were tested for GBV-C markers in pretransfusion and posttransfusion samples. We estimated the risk of acquiring GBV-C RNA and predictors of GBV-C acquisition, using pooled logistic regression.

RESULTS

GBV-C RNA was detected ≤120 days following the first transfusion in 22 (7.5%) of 294 subjects who were GBV-C negative before transfusion. The risk of GBV-C RNA acquisition increased with each unit transfused (odds ratio, 1.09; 95% confidence interval, 1.06-1.11). Lower baseline HIV load and use of antiretroviral therapy were associated with subsequent GBV-C RNA acquisition, after control for units of blood transfused. Leukoreduced status of transfused units was not associated with GBV-C transmission.

CONCLUSIONS

Blood transfusion is associated with a significant risk of GBV-C acquisition among HIV-infected patients. Transmission of GBV-C by blood transfusion was inversely related to HIV load.

GB virus C: the good boy virus?

GB virus C (GBV-C) is a lymphotropic human virus discovered in 1995 that is related to hepatitis C virus (HCV). GBV-C infection has not been convincingly associated with any disease; however, several studies found an association between persistent GBV-C infection and improved survival in HIV-positive individuals. GBV-C infection modestly alters T cell homeostasis in vivo through various mechanisms, including modulation of chemokine and cytokine release and receptor expression, and by diminution of T cell activation, proliferation and apoptosis, all of which may contribute to improved HIV clinical outcomes. In vitro studies confirm these clinical observations and demonstrate an anti-HIV replication effect of GBV-C. This review summarizes existing data on potential mechanisms by which GBV-C interferes with HIV, and the research needed to capitalize on this epidemiological observation.

Down-regulation of intra-hepatic T-cell signaling associated with GB virus C in a HCV/HIV co-infected group with reduced liver disease

BACKGROUND & AIMS

Studies have shown that GB virus C (GBV-C) infection leads to reduced liver disease in hepatitis C virus (HCV)/human immunodeficiency virus (HIV) co-infection. Considering that the underlying mechanism(s) are unknown, we aim to identify differential gene and protein expression associated with GBV-C in HCV/HIV co-infection that may be responsible for reduced liver disease.

METHODS

Liver, peripheral blood mononuclear cells (PBMCs), and plasma samples were collected from 43 HCV/HIV patients. Plasma was tested for GBV-C RNA by RT-PCR with NS5B gene primers. A microarray was performed on the liver and RT-qPCRs on the liver/PBMC samples. Hepatic protein expression was measured by immunohistochemistry.

RESULTS

Sixteen out of 43 patients had GBV-C RNA. GBV-C was associated with reduced hepatic fibrosis (p=0.005) and inflammation (p=0.007). The microarray analysis of the liver samples (n=10) showed down-regulation of genes critical to intra-hepatic T-cell signaling associated with GBV-C. Quantitative RT-PCR of the liver samples (n=13) confirmed the down-regulation of lymphocyte-specific protein tyrosine kinase (LCK) (p=0.02) and docking protein 2 (DOK2) (p=0.04). No differences in the expression levels of these genes were observed in PBMCs (n=22) according to the GBV-C status. The hepatic expression of the LCK protein, measured by immunohistochemistry (n=36), was decreased in CD3-positive T-cells within portal tracts associated with GBV-C (p=0.003). This remained significant in multivariate analysis controlling for hepatic fibrosis and inflammation (p=0.027). No differences were observed in plasma cytokine concentrations (n=25) or ex-vivo peripheral T-cell responses (n=13) versus GBV-C status.

CONCLUSIONS

GBV-C infection is associated with down-regulation of critical genes involved in intra-hepatic T-cell signaling in HCV/HIV co-infection. This may be relevant to the pathogenesis of reduced HCV-related liver disease in HIV co-infection.

Peptides derived from a distinct region of GB virus C glycoprotein E2 mediate strain-specific HIV-1 entry inhibition

The nonpathogenic human GB virus C (GBV-C), a member of the Flaviviridae, is highly prevalent in individuals with HIV-1 infections or with parenteral and sexual risk factors. Long-term GBV-C viremia has been associated with better survival or improved diagnosis in several epidemiological studies. In a previous study we reported that the E2 glycoprotein of GBV-C interferes with HIV-1 entry in vitro. To address the question what region of the E2 protein is involved in suppression of HIV-1 replication, we performed an E2-derived peptide scanning and determined the HIV-inhibitory activity of each peptide in HIV replication assays. We demonstrate here that peptides representing the N-terminal part of the E2 protein from amino acids (aa) 29 to 72 are able to inhibit efficiently HIV-1 replication in vitro. In particular, the peptides P6-2 (representing the E2-region from aa 45 to 64) and P4762 (aa 37 to 64) showed the highest potency in HIV replication assays performed on TZM-bl cells with 50% inhibitory concentrations between 0.1 and 2 μM. However, primary HIV-1 isolates representing clades A to H showed a high variability in their sensitivity to E2 peptides. Pseudovirus inhibition assays revealed that the sensitivity is determined by the gp120/gp41 envelope proteins. Using HIV-1 BlaM-Vpr-based fusion assays, we demonstrate that the E2-derived peptides prevent HIV-1 binding or fusion, presumably via interaction with the HIV-1 particle. Together, these findings reveal a new mechanism of viral interference, suggesting that the envelope protein E2 of GBV-C target directly HIV-1 particles to avoid entry of these virions.

GB virus C coinfection in advanced HIV type-1 disease is associated with low CCR5 and CXCR4 surface expression on CD4(+) T-cells

BACKGROUND

Coinfection with the flavivirus GB virus C (GBV-C) is frequent in patients suffering from HIV type-1 (HIV-1) infection because of shared routes of transmission. GBV-C coinfection has been proposed to exert a beneficial influence on HIV-1 infection. In vitro studies demonstrated down-regulation of C-C chemokine receptor type 5 (CCR5) as a potential mechanism by which GBV-C modulates HIV-1 disease progression. We therefore studied surface expression of the two major HIV-1 coreceptors, CCR5 and CXC chemokine receptor type 4 (CXCR4), on CD4(+) and CD8(+) T-cells in 128 HIV-1-positive patients stratified with respect to their GBV-C status, immune function and highly active antiretroviral therapy (HAART) status in vivo.

METHODS

GBV-C infection was studied in 128 HIV-1-infected patients by nested reverse transcriptase PCR. Fluorescence-activated cell sorting analysis was used to measure CCR5 and CXCR4 surface expression on CD4(+) and CD8(+) T-cells.

RESULTS

GBV-C RNA replication was detected in 30% (38/128) of patients. In HIV-1-positive patients with advanced immunodeficiency, we found up-regulation of CCR5 surface expression on CD4(+) T-cells; however, in patients with GBV-C coinfection, no up-regulation of CCR5 CD4(+) T-cells was detected. Furthermore, CXCR4 surface expression was reduced in GBV-C-coinfected patients. These findings were independent of HAART status and HIV-1 viral load. HIV-1 coreceptor expression on CD8(+) T-cells was not altered in patients with GBV-C coinfection.

CONCLUSIONS

GBV-C coinfection in HIV-1 disease leads to reduced expression of the two major HIV-1 coreceptors, CCR5 and CXCR4, on CD4(+) T-cells in patients at an advanced stage of immunodeficiency, providing a possible molecular explanation for the clinical benefit of GBV-C coinfection in late-stage HIV-1 disease.

Prevalence and distribution of the GBV-C/HGV among HIV-1-infected patients under anti-retroviral therapy

Infection with GB virus C (GBV-C) or hepatitis G virus (HGV) is highly prevalent among HIV/AIDS patients. GBV-C/HGV viremia has not been associated with liver disease and seems to slow HIV disease progression. To study the GBV-C/HGV genotypes prevalence among HIV/AIDS patients and its association with HIV viral load (VL) and CD4+ lymphocyte counts. From February 2003 to February 2004, we analyzed 210 HIV-1-infected subjects who were on anti-retroviral therapy (ART). For 63 of them a PCR-nested to the non-coding 5' (5'NCR) region of the GBV-C/HGV was done, and for 49 a DNA direct sequencing was done. A phylogenetic analysis was performed by PHYLIP program. 63 (30%) of the HIV-1-infected patients were co-infected with GBV-C/HGV. The phylogenetic analysis revealed the following genotypes (and respective relative frequencies): 1 (10%), 2a (41%), 2b (43%), and 3 (6%). Co-infected patients presented lower HIV-1 VL and higher T CD4+ lymphocyte cells counts as compared with patients negative for GBV-C/HGV sequences (log=4.52 vs. 4.71, p=0.036), and T CD4+ lymphocyte counts (cells/mm(3)=322.6 vs. 273.5, p=0.081, respectively). T CD4+ cells counts equal to, or higher than, 200/mm(3) were significantly more common among co-infected patients than among HIV-infected-only patients (p=0.042). The lowest T CD4+ cells counts were associated with genotype 1 and the highest with genotype 2b (p=0.05). The GBV-C/HGV infection prevalence was 30% among HIV-1-infected subjects, and was associated with lower VL and higher CD4+ lymphocyte counts. GBV-C/HGV genotype 2b may be associated with better immunological response.

Viruses within the Flaviviridae decrease CD4 expression and inhibit HIV replication in human CD4+ cells

Viral infections alter host cell homeostasis and this may lead to immune evasion and/or interfere with the replication of other microbes in coinfected hosts. Two flaviviruses are associated with a reduction in HIV replication or improved survival in HIV-infected people (dengue virus (DV) and GB virus type C (GBV-C)). GBV-C infection and expression of the GBV-C nonstructural protein 5A (NS5A) and the DV NS5 protein in CD4(+) T cells inhibit HIV replication in vitro. To determine whether the inhibitory effect on HIV replication is conserved among other flaviviruses and to characterize mechanism(s) of HIV inhibition, the NS5 proteins of GBV-C, DV, hepatitis C virus, West Nile virus, and yellow fever virus (YFV; vaccine strain 17D) were expressed in CD4(+) T cells. All NS5 proteins inhibited HIV replication. This correlated with decreased steady-state CD4 mRNA levels and reduced cell surface CD4 protein expression. Infection of CD4(+) T cells and macrophages with YFV (17D vaccine strain) also inhibited HIV replication and decreased CD4 gene expression. In contrast, mumps virus was not inhibited by the expression of flavivirus NS5 protein or by YFV infection, and mumps infection did not alter CD4 mRNA or protein levels. In summary, CD4 gene expression is decreased by all human flavivirus NS5 proteins studied. CD4 regulation by flaviviruses may interfere with innate and adaptive immunity and contribute to in vitro HIV replication inhibition. Characterization of the mechanisms by which flaviviruses regulate CD4 expression may lead to novel therapeutic strategies for HIV and immunological diseases.

GB virus type C infection modulates T-cell activation independently of HIV-1 viral load

BACKGROUND

Many clinical studies have suggested a beneficial effect of GB virus type C (GBV-C) on the course of HIV-1 infection, but the mechanisms involved in such amelioration are not clear. As recent evidence has implicated cellular activation in HIV-1 pathogenesis, we investigated the effect of GBV-C viremia on T-cell activation in early HIV-1 infection.

METHODS

Forty-eight recently infected HIV-1 patients (23 GBV-C viremic) were evaluated for T-cell counts, expanded immunophenotyping GBV-C RNA detection, and HIV-1 viral load. Nonparametric univariate and multivariate analyses were carried out to identify variables associated with cellular activation, including GBV-C status, HIV-1 viral load, T lymphocyte counts, and CD38 and chemokine (C-C motif) receptor 5 (CCR5) surface expression.

FINDING

We not only confirmed the positive correlation between HIV-1 viral load and the percentage of T cells positive for CD38(+)CD8(+) but also observed that GBV-C viremic patients had a lower percentage of T cells positive for CD38(+)CD4(+), CD38(+)CD8(+), CCR5(+)CD4(+), and CCR5(+)CD8(+) compared with HIV-1-infected patients who were not GBV-C viremic. In regression models, GBV-C RNA(+) status was associated with a reduction in the CD38 on CD4(+) or CD8(+) T cells and CCR5(+) on CD8(+) T cells, independent of the HIV-1 viral load or CD4(+) and CD8(+) T-cell counts. These results were also supported by the lower expression of CD69 and CD25 in GBV-C viremic patients.

INTERPRETATION

The association between GBV-C replication and lower T-cell activation may be a key mechanism involved in the protection conferred by this virus against HIV-1 disease progression to immunodeficiency in HIV-1-infected patients.

GB virus type C interactions with HIV: the role of envelope glycoproteins

GB virus C/hepatitis G virus (GBV-C/HGV) is the most closely related human virus to hepatitis C virus (HCV). GBV-C is lymphotropic and not associated with any known disease, although it is associated with improved survival in HIV-infected individuals. In peripheral blood mononuclear cells, GBV-C induces the release of soluble ligands for HIV entry receptors (RANTES, MIP-1a, MIP-1b and SDF-1), suggesting that GBV-C may interact with lymphocytes to induce a chemokine and/or cytokine milieu that is inhibitory to HIV infection. Expression of GBV-C envelope glycoprotein E2 in CD4+ T cells or addition of recombinant E2 to CD4 cells recapitulates the HIV inhibition seen with GBV-C infection. Like HCV E2, GBV-C E2 is predicted to be post-translationally processed in the endoplasmic reticulum and is involved with cell binding. The C-termini of GBV-C E1 and E2 proteins contain predicted transmembrane domains sharing features with HCV TM domains. To date, cellular receptor(s) for GBV-C E2 have not been identified. GBV-C E2-mediated HIV inhibition is dose-dependent and HIV replication is blocked at the binding and/or entry step. In addition, a putative GBV-C E2 fusion peptide interferes with HIV gp41 peptide oligomerization required for HIV-1 fusion, further suggesting that GBV-C E2 may inhibit HIV entry. Additional work is needed to identify the GBV-C E2 cellular receptor, characterize GBV-C E2 domains responsible for HIV inhibition, and to examine GBV-C E2-mediated fusion in the context of the entire envelope protein or viral-particles. Understanding the mechanisms of action may identify novel approaches to HIV therapy.

RNA interference effectively degrades mRNA and inhibits protein expression of GBV-C E2 gene in Huh7 cells

The GB virus C/hepatitis G virus (GBV-C/HGV) is a Flaviviridae member that despite its nonpathogenicity, has become of great interest given that it could inhibit the replication of the human immunodeficiency virus (HIV). Therefore, a better knowledge of the viral protein E2 has become our aim. In this study, a GBV-C model cell system (HuhEG) which expressing a fusion protein of the GBV-C E2 protein and enhanced green fluorescent protein (EGFP) stably was established. And the expression of these proteins was silenced effectively by the two E2 gene-specific siRNAs and an EGFP gene-specific siRNA. This inhibition is sequence-specific and extensive (90%). This HuhEG/specific siRNAs system can provide an approach for investigating the association between GBV-C E2 and HIV replication, which may be of potential value in the development of novel prophylactic or therapeutic agents for HIV infection.

Role of chemokines and their receptors in viral persistence and liver damage during chronic hepatitis C virus infection

Chemokines produced in the liver during hepatitis C virus (HCV) infection induce migration of activated T cells from the periphery to infected parenchyma. The milieu of chemokines secreted by infected hepatocytes is predominantly associated with the T-helper cell/Tc1 T cell (Th1/Tc1) response. These chemokines consist of CCL3 (macrophage inflammatory protein-1 alpha; MIP-1 alpha), CCL4 (MIP-1 beta), CCL5 (regulated on activation normal T cell expressed and secreted; RANTES), CXCL10 (interferon-gamma-inducible protein-10; IP-10), CXCL11 (interferon-inducible T-cell alpha chemoattractant; I-TAC), and CXCL9 (monokine induced by interferon gamma; Mig) and they recruit T cells expressing either CCR5 or CXCR3 chemokine receptors. Intrahepatic and peripheral blood levels of these chemokines are increased during chronic hepatitis C. The interaction between chemokines and their receptors is essential in recruiting HCV-specific T cells to control the infection. When the adaptive immune response fails in this task, non-specific T cells without the capacity to control the infection are also recruited to the liver, and these are ultimately responsible for the persistent hepatic damage. The modulation of chemokine receptor expression and chemokine secretion could be a viral escape mechanism to avoid specific T cell migration to the liver during the early phase of infection, and to maintain liver viability during the chronic phase, by impairing non-specific T cell migration. Some chemokines and their receptors correlate with liver damage, and CXCL10 (IP-10) and CXCR3 levels have shown a clinical utility as predictors of treatment response outcome. The regulation of chemokines and their receptors could be a future potential therapeutic target to decrease liver inflammation and to increase specific T cell migration to the infected liver.

GBV-C viremia is associated with reduced CD4 expansion in HIV-infected people receiving HAART and interleukin-2 therapy

OBJECTIVE

Interleukin-2 (IL-2) is a cytokine with multiple effects on lymphocytes including induction of CD4 T-cell proliferation. IL-2 administration has been shown to increase CD4 cell counts in HIV-infected people receiving antiretroviral therapy. GB virus C (GBV-C) is an apparently nonpathogenic flavivirus that replicates in CD4 T cells and inhibits HIV replication in vitro by mechanisms including downregulation of HIV entry coreceptors (CCR5 and CXCR4) and induction of chemokines (RANTES, MIP-1alpha, MIP-1 beta, and SDF-1). GBV-C replication is significantly inhibited in vitro by activation of primary CD4 cell cultures with IL-2 and phytohemagglutinin. We sought to determine if there is an interaction between GBV-C and IL-2 in vivo.

METHODS

GBV-C viremia status was characterized in 92 HIV-infected individuals participating in a randomized trial of IL-2 and antiretroviral therapy [AIDS Clinical Trials Group Study (ACTG) 328]. Changes in CD4 cell counts and HIV RNA levels in individuals assigned IL-2 were compared with those in individuals assigned antiretroviral therapy alone.

RESULTS

Individuals lacking GBV-C viremia had a significantly greater rise in CD4 cell count with IL-2, compared with GBV-C viremic individuals (by 511 cells/microl at week 84; interaction P = 0.02): GBV-C viremic individuals assigned IL-2 did not demonstrate a significant increase in CD4 cell count compared with individuals not assigned to receive IL-2 (95% CI for difference -255 to 397 cells/microl).

CONCLUSION

GBV-C viremia was associated with a block in CD4 cell expansion following IL-2 therapy in the ACTG 328 study, and GBV-C status may be an important factor in IL-2 treatment response.

Role of chemokines and their receptors in viral persistence and liver damage during chronic hepatitis C virus infection

Chemokines produced in the liver during hepatitis C virus (HCV) infection induce migration of activated T cells from the periphery to infected parenchyma. The milieu of chemokines secreted by infected hepatocytes is predominantly associated with the T-helper/T-cytotoxic type-1 cell (Th1/Tc1) response. These chemokines consist of CCL3 (macrophage inflammatory protein-1α; MIP-1α), CCL4 (MIP-1β), CCL5 (regulated on activation normal T cell expressed and secreted; RANTES), CXCL10 (interferon-γ−inducible protein-10; IP-10), CXCL11 (interferon-inducible T-cell α chemoattractant; I-TAC), and CXCL9 (monokine induced by interferon γ; Mig) and they recruit T cells expressing either CCR5 or CXCR3 chemokine receptors. Intrahepatic and peripheral blood levels of these chemokines are increased during chronic hepatitis C. The interaction between chemokines and their receptors is essential in recruiting HCV-specific T cells to control the infection. When the adaptive immune response fails in this task, non-specific T cells without the capacity to control the infection are also recruited to the liver, and these are ultimately responsible for the persistent hepatic damage. The modulation of chemokine receptor expression and chemokine secretion could be a viral escape mechanism to avoid specific T cell migration to the liver during the early phase of infection, and to maintain liver viability during the chronic phase, by impairing non-specific T cell migration. Some chemokines and their receptors correlate with liver damage, and CXCL10 (IP-10) and CXCR3 levels have shown a clinical utility as predictors of treatment response outcome. The regulation of chemokines and their receptors could be a future potential therapeutic target to decrease liver inflammation and to increase specific T cell migration to the infected liver.

A Bayesian analysis of doubly censored data using a hierarchical Cox model

Two common statistical problems in pooling survival data from several studies are addressed. The first problem is that the data are doubly censored in that the origin is interval censored and the endpoint event may be right censored. Two approaches to incorporate the uncertainty of interval-censored origins are developed, and then compared with more usual analyses using imputation of a single fixed value for each origin. The second problem is that the data are collected from multiple studies and it is likely that heterogeneity exists among the study populations. A random-effects hierarchical Cox proportional hazards model is therefore used. The scientific problem motivating this work is a pooled survival analysis of data sets from three studies to examine the effect of GB virus type C (GBV-C) coinfection on survival of HIV-infected individuals. The time of HIV infection is the origin and for each subject this time is unknown, but is known to lie later than the last time at which the subject was known to be HIV negative, and earlier than the first time the subject was known to be HIV positive. The use of an approximate Bayesian approach using the partial likelihood as the likelihood is recommended because it more appropriately incorporates the uncertainty of interval-censored HIV infection times.

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.

Expression of GB virus C NS5A protein from genotypes 1, 2, 3 and 5 and a 30 aa NS5A fragment inhibit human immunodeficiency virus type 1 replication in a CD4+ T-lymphocyte cell line

GB virus type C (GBV-C) is a common human flavivirus that has been associated with prolonged survival in HIV-positive individuals in several, though not all, epidemiological studies. There are five distinct GBV-C genotypes that are geographically localized, and it has been speculated that GBV-C genotypic differences may explain variable outcomes observed in different clinical studies. Expression of an 85 aa fragment of the GBV-C NS5A phosphoprotein (genotype 2) in a CD4+ T cell line (Jurkat) resulted in inhibition of HIV replication, mediated in part by decreased surface expression of the HIV coreceptor CXCR4 and upregulation of SDF-1. We expressed the NS5A protein from genotypes 1, 2, 3 and 5 in Jurkat cells, and demonstrated that all genotypes inhibited HIV replication. Further deletion mapping demonstrated that expression of a 30 aa fragment resulted in decreased CXCR4 surface expression, upregulation of SDF-1 and inhibition of HIV replication.

The role of CCR5/CXCR3 expressing CD8+ cells in liver damage and viral control during persistent hepatitis C virus infection

BACKGROUND/AIMS

CXCR3 and CCR5 play a major role in recruiting cytotoxic T cells (Tc) and secreting secondary type 1 cytokines (Tc1) in the liver. HCV could impair their expression as a survival mechanism. The role of these chemokine receptors on CD8+ cells in chronic hepatitis C is analysed.

METHODS

Serum, chemokines, peripheral blood and intrahepatic lymphocytes from chronic hepatitis C patients were studied. CXCR3/CCR5 expressing CD8+ cells were quantified by flow-cytometry. Serum chemokines concentration (CXCL10/CCL3) was measured by ELISA. Basal data were correlated with liver inflammation. Longitudinal data were obtained during treatment and correlated with virologic response.

RESULTS

CCR5/CXCR3 expressing CD8+ cells were enriched in the liver and correlated with inflammation. Chronic HCV patients presented the same frequency of CCR5(high)/CXCR3(high) expressing CD8+ cells in peripheral blood as in healthy controls but higher serum concentration of CXCL10/CCL3. Treatment with PEG-interferon alpha-2b plus ribavirin increased CCR5(high)/CXCR3(high) expressing CD8+ cells frequency in peripheral blood and decreased CXCL10/CCL3 serum concentration. Increase in CXCR3(high) expressing CD8+ cells after 24 weeks of treatment was correlated with SVR.

CONCLUSIONS

In chronic hepatitis C, anti-viral treatment induces an increase in CD8+ cells expressing chemokine receptors associated with Tc1 response and a reduction in their ligands. Achievement of viral control is associated with an increase in CXCR3(high) expressing CD8+ cells during treatment.

The GBV-C envelope glycoprotein E2 does not interact specifically with CD81

The addition of GB virus C (GBV-C) E2 protein to cells inhibits HIV replication in vitro, presumably triggered by interactions with a specific cellular receptor. Indirect evidence suggests that CD81 is the GBV-C E2 cellular receptor. We found that E2 binding to cells was not dependent upon human CD81, and that soluble CD81 did not compete with GBV-C E2 for cell binding. GBV-C E2 protein thus does not appear to interact with CD81.

CCR5 and CCR3 expression on T CD3+ lymphocytes from HIV/Leishmania co-infected subjects

CC chemokine receptor 5 (CCR5) and CC chemokine receptor 3 (CCR3) are membrane-bound proteins involved in HIV-1 entry into susceptible cells. All T lymphocyte subsets display CCR5 and CCR3 on their membrane surface. T helper 1 cells are known to express CCR5 but not CCR3, and most of T cells expressing CCR3 are T helper 2. This study aimed to assess the expression of CCR5 and CCR3 on peripheral blood CD3+ T lymphocytes of HIV-Leishmania co-infected individuals. A total of 36 subjects were enrolled; nine had HIV-Leishmania co-infection; nine were HIV-infected without Leishmania, nine had visceral leishmaniasis without HIV co-infection and nine were healthy blood donors. HIV-Leishmania co-infected subjects showed a significantly higher rate of CCR5+CD3+ T lymphocytes in comparison with the other studied groups. The higher rate of CD3+ T-cells expressing CCR5 found in HIV-Leishmania co-infected subjects may be related to the role of Leishmania as an enhancer of the progression to AIDS.

Dichotomous effects of C-C chemokines in HIV-1 pathogenesis

Chemokines play a critical role in shaping innate and adaptive immunity. These molecules also participate in maintaining the immune balance in the body. Apart from their regulatory role, these mediators are involved in several inflammatory and autoimmune diseases including viral infection such as HIV-1/AIDS. Chemokine co-receptor CCR5 and CXCR4 and their ligands significantly contribute to HIV-1 disease progression. C-C chemokines such CCL3, CCL4 and CCL5 have been shown to possess antiviral effects by binding to HIV-1 co-receptors. CCL2, a member of the C-C chemokine family, displays a different feature instead. It is a potential enhancer rather than inhibitor of viral replication, a property exhibited by most of the C-C chemokine members. In addition, the role of CCL2 is well established in forming a Th2 type of response by directing differentiation of Th0 cells towards Th2 type, a unique feature of HIV-1 disease. We propose a hypothesis in which the chemotactic nature of CCL2 drives recruitment of target cells to the site of infection as one of the mechanisms operating in vivo that favours viral replication and eventually a high viral load in infected individuals.