Mutations in the putative HCV-E2 CD81 binding regions and correlation with cell surface CD81 expression

Mir-194 is a hepatocyte gate keeper hindering HCV entry through targeting CD81 receptor

OBJECTIVE

The tetraspanin CD81 is one of the main receptors involved in hepatitis C virus entry. Herein, we aimed to explore the role of microRNAs in regulating CD81 receptor expression and function.

PATIENTS AND METHODS

Bioinformatics analysis was carried out to select potential mircroRNAs that binds CD81 3'untranslated region. Liver biopsies taken from 28 HCV genotype- 4 patients and 10 healthy donors were screened. Naïve, JFH1 and ED43/JFH1- infected- Huh7 cells were transfected with mimics and inhibitors followed by analyzing CD81 protein and mRNA expression. This was done using flow cytometry and Q-RT PCR, respectively. HCV entry into Huh7 cells was investigated post-transfection. Binding confirmation was done using luciferase reporter vector harboring wild/mutant target sites of microRNA. The impact of Epigallocatechin-gallate on modulating microRNA/CD81 expression was assessed.

RESULTS

Bioinformatics revealed that CD81 is a potential down-stream target for miR-194. A significant inverse correlation was found between miR-194 and CD81 expression in liver biopsies of HCV patients. Forcing the expression of miR-194 showed a down-regulation of CD81 protein, mRNA expression and significantly abrogated the HCV infectivity of Huh7 cells. Stimulation with EGCG enhanced mir-194 expression and down-regulated CD81 expression.

CONCLUSION

This study showed that mir-194 hinders HCV entry through targeting CD81 receptors.

CD81 sequence and susceptibility to hepatitis C infection

Several cell surface molecules have hepatitis C virus (HCV) binding properties and may serve as receptors facilitating viral entry into cells. The large extracellular loop (LEL) of CD81 has been shown to bind the HCV envelope protein E2 with several critical residues for the CD81-HCV-E2 interaction. It was hypothesised that variation in the CD81 LEL sequence may modify susceptibility to HCV infection. HCV RNA negative patients with spontaneous viral clearance (RNA -ve); HCV RNA positive cases, who are affected chronically (RNA +ve); and patients at high risk of HCV infection, exposed but uninfected patients (EU) were studied. Genomic DNA was extracted from whole blood samples and four exons of the CD81 LEL gene were amplified by PCR and sequenced. The cDNA derived from CD81 (≈700 bp) was sequenced following RNA extraction from peripheral blood mononuclear cells. Patients, who are RNA positive, RNA negative, and exposed uninfected were sequenced for four DNA sections (A, B, C, and D). Sixty-two (43M:19F) patients, from all the patient cohorts, were sequenced and compared for the C section alone (which encompasses the important binding region of the molecule for envelope protein) including 21 (14M:7F) HCV RNA negative, 15 (10M:5F) HCV RNA positive and 26 (20M:6F) exposed uninfected and no sequence differences were observed. The entire CD81 sequence from cDNA was obtained in 23 cases-11 RNA -ve, 5 RNA +ve and 7 EU. In 7 of the 23 cases, the nucleotides were confirmed with the genomic sequence (4 RNA -ve and 3 EU cases). No sequence variation was found in any of the patients studied by either method, including gene sections encoding the residues most important for CD81-HCV E2 binding. The LEL of CD81 is a molecule that is highly conserved. No differences in nucleotide sequence influencing susceptibility to, or outcome of HCV infection or evidence of methylation of the gene were found.

Hepatitis C virus infection and mixed cryoglobulinemia

Hepatitis C virus (HCV) chronic infection is recognized as the major cause of mixed cryoglobulinemia (MC). Its persistence represents a continuous stimulus for host immune system with production of circulating immune complexes (ICs), one-third of them with cryoprecipitate property. Several factors contribute to the biological activities of ICs, many of which are not completely known. Among them, complement factors play a crucial role in the cold-insoluble ICs-mediated vasculitis, involving primarily small blood vessels in different tissues including skin, kidney, peripheral, and central nervous system. Liver represents the major target of HCV infection with inflammatory infiltrates, resembling secondary lymphoid follicles. Cytokine like CXCL13 contribute to B-cell homing in intraportal lymphoid aggregates, in which B-cell clonal selection may arise. B-cell clonal expansion starts as an antigen-driven event and expands towards indolent and malignant B-cell proliferation. Occurrence of intrahepatic B-cell clonalities correlates with extrahepatic clinical manifestations of HCV infection. In this context, cryoglobulinemic patients should be considered a peculiar HCV-infected population that needs a clinical multidisciplinary approach and more articulated therapeutic measures.

CD81 expression for discrimination between sustained virologic response and relapse in patients with chronic hepatitis C

BACKGROUND AND AIM

The hepatitis C virus (HCV) receptor CD81 is overexpressed on peripheral blood mononuclear cells (PBMC) in patients chronically infected with HCV compared with healthy controls, and expression declines during antiviral therapy. The aim of this study was to prospectively investigate CD81 expression on PBMC for early discrimination between sustained virologic response (SVR) and relapse (REL) to pegylated interferon alfa-2b and ribavirin treatment.

METHODS

Sixty-one patients with chronic HCV infection (genotype, GT, 1 and low baseline viremia <600,000 IU/ml, n = 30; GT 2 or 3, n = 31) were investigated. CD81 expression on CD4(+), CD8(+), CD19(+), and CD56(+) cells was measured at baseline, therapy week (TW) 4 and 12 during antiviral therapy by fluorescence-activated cell sorting (FACS) analysis.

RESULTS

Baseline levels of CD81 on CD4(+), CD8(+), and CD56(+) cells were similar between patients who achieved a SVR (n = 42) and those who relapsed (n = 19). On CD19(+) cells, baseline CD81 expression was higher in patients with SVR than in patients with virologic relapse (REL) (p < 0.006). A cutoff value of 720 relative fluorescence units (RFU) discriminated correctly between SVR and REL with a sensitivity and specificity of 73.7% and 66.7%, respectively. SVR patients showed a significant decline of CD81 expression on CD4(+), CD8(+), CD19(+), and CD56(+) cells (p < 0.01 for all) while in REL patients a significant decline of CD81 expression was observed on CD8(+) and CD56(+) cells, only (p = 0.050 and p = 0.038, respectively).

CONCLUSIONS

The current study confirms significant down-regulation of CD81 expression on different lymphocyte subpopulations during pegylated interferon alfa-based antiviral therapy in patients with chronic hepatitis C. Baseline CD81 expression on CD19(+) cells was found to discriminate between SVR and REL.

Comparison of envelope 2 CD81 binding regions in PBMC-derived versus serum-derived hepatitis C virus isolates: higher conservation of CD81 region 2 in PBMC isolates

The aim of the present study was to investigate the variability of hepatitis C virus (HCV) CD81 binding regions (CD81-1/2) in peripheral blood mononuclear cells (PBMC)-derived and serum-derived HCV-RNA samples. HCV-RNA was isolated from PBMC (10⁴ cells) and serum samples from 37 patients chronically infected with HCV genotype 1a/1b (n=21/16). The hypervariable regions 1/2 (amino acid 384-410, amino acid 474-482) and regions CD81-1/2 (amino acid 474-494, amino acid 522-551) were analysed. Mutational frequency of amino acid sequences was compared between PBMC-derived and serum-derived HCV variants as well as local accumulation of mutations. Furthermore, CD81 was quantified on PBMC. Mutational frequency was not different between PBMC-derived and serum-derived HCV variants. A trend to lower mutational frequency in genotype 1a PBMC variants compared with serum-derived variants was observed in region CD81-2 (5%vs 10%). Smoothed mutational frequency analysis showed a significantly lower variability within genotype 1a CD81-2 in PBMC-derived compared to serum-derived HCV-RNA (P=0.026). CD81 expression on PBMC was not correlated with the number of mutations within the CD81 binding regions.

CONCLUSION

A higher conservation was observed in region CD81-2 in PBMC-derived versus serum-derived HCV-RNA indicating selection of HCV variants on PBMC. The variability in the CD81 binding regions appeared to be independent from CD81 expression.

[Tropism of hepatitis C virus for leukocytes-- importance of the analysis of viral E1 and E2 envelope glycoprotein genes by sequencing]

The ability of hepatitis C virus (HCV) to infect leukocytes could favour HCV pathogenesis. Although viral infection of these immunocompetent cells is poorly (or not) productive, the impact on their immunomodulatory functions could be important. Viral envelope glycoproteins E1 and E2, because of their crucial role in the recognition of viral receptors on permissive cells, could contribute to viral leukocytic tropism and, as a consequence, to the pathophysiology of HCV chronic infection.

Hepatitis C Virus entry: the early steps in the viral replication cycle

Approximately 170 million are infected with the hepatitis C virus (HCV) world wide and an estimated 2.7 million are HCV RNA positive in the United States alone. The acute phase of the HCV infection, in majority of individuals, is asymptomatic. A large percentage of those infected with HCV are unable to clear the virus and become chronically infected. The study of the HCV replication cycle was hampered due to difficulties in growing and propagating the virus in an in vitro setting. The advent of the HCV pseudo particle (HCVpp) and HCV cell culture (HCVcc) systems have made possible the study of the HCV replication cycle, in vitro. Studies utilizing the HCVpp and HCVcc systems have increased our insight into the early steps of the viral replication cycle of HCV, such as the identification of cellular co-receptors for binding and entry. The aim of this article is to provide a review of the outstanding literature on HCV entry, specifically looking at cellular co-receptors involved and putting the data in the context of the systems used (purified viral envelope proteins, HCVpp system, HCVcc system and/or patient sera) and to also give a brief description of the cellular co-receptors themselves.

Microwave-Assisted Syntheses of Amino Acid Ester Substituted Benzoic Acid Amides: Potential Inhibitors of Human CD81-Receptor HCV-E2 Interaction

Results from our group showed benzyl salicylate to be a moderate inhibitor of the CD81-LEL-HCV-E2 interaction. To increase the biological activity, heterocyclic substituted benzoic acids were coupled to amino acid esters via microwave assisted DCC-reaction. The prepared compounds were tested for their inhibitory potency by means of a fluorescence labeled antibody assay system using HUH7.5 cells.

Hepatitis C virus productive infection in mononuclear cells from patients with cryoglobulinaemia

The relationship between the occurrence of cryoglobulins and hepatitis C virus (HCV) productive infection in peripheral blood and bone marrow-derived lymphocytes was explored. HCV minus strand RNA, the viral replicative intermediate, was searched for by a polyA(+) tract strand-specific Tth-based reverse transcriptase-polymerase chain reaction (RT-PCR) in lymphoid cells of 46 patients with acute and chronic infection. The HCV minus strand was demonstrated in RNA extracted from six (13%) and five (11%) peripheral blood and bone marrow-derived lymphocytes, respectively. The HCV replicating form in lymphoid cells was associated strictly with mixed cryoglobulinaemia (MCG), in that it was found in six of 13 (46%) MCG patients, including two with B cell non-Hodgkin's lymphoma (NHL). No traces of HCV-negative strand RNA were found in four patients with acute hepatitis C, in 15 with chronic active hepatitis without extrahepatic disorders, in seven with monoclonal gammopathy of undetermined significance, and in seven with B-NHL without MCG. These results emphasize the direct role of the virus in the pathogenesis of MCG and support the contention that HCV is not specifically lymphotropic, its entry and replication in lymphoid cells being determined largely by selective interactions.

Virological analysis and phenotypic characterization of peripheral blood lymphocytes of hepatitis C virus-infected patients with and without mixed cryoglobulinaemia

In clinical and pathological terms hepatitis C virus (HCV)-infected patients can be subdivided into two main groups with and without mixed cryoglobulinaemia (MC). Involvement of blood mononuclear cells by HCV has potentially important implications. To this end, HCV-RNA levels in peripheral blood lymphocytes (PBL) preparations of 20 chronically HCV-infected patients with MC were measured and compared with those found in a group of 20 patients without MC matched for age, serum HCV-RNA, infectious genotype, source and presumable duration of infection. Phenotypic abnormalities of PBL subsets in each group of patients were determined by cell surface marker expression and compared. Results showed a significant enrichment of HCV-RNA in PBL of MC patients compared with a non-MC group (P = 0.01). Different distribution of HCV-RNA was accompanied by evidence of an increased frequency of circulating B cells. These data indicate that MC patients are characterized distinctly by a higher quota of cell-associated viral load.