Lynn B. Dustin

Cell culture-produced hepatitis C virus does not infect peripheral blood mononuclear cells.

Hepatitis C virus (HCV) replicates primarily in the liver, but HCV RNA has been observed in association with other tissues and cells including B and T lymphocytes, monocytes, and dendritic cells. We have taken advantage of a recently described, robust system that fully recapitulates HCV entry, replication and virus production in vitro to re‐examine the issue of HCV infection of blood cell subsets. The HCV replicase inhibitor 2′C‐methyl adenosine was used to distinguish HCV RNA replication from RNA persistence. Whereas cell culture–grown HCV replicated in Huh‐7.5 hepatoma cells, no HCV replication was detected in B or T lymphocytes, monocytes, macrophages, or dendritic cells from healthy donors. No blood cell subset tested expressed significant levels of Claudin‐1, a tight junction protein needed for HCV infection of Huh‐7.5 cells. A B cell line expressing high levels of Claudin‐1, CD81, and scavenger receptor BI remained resistant to HCV pseudoparticle infection. We bypassed the block in HCV entry by transfecting HCV RNA into blood cell subsets. Transfected RNA was not detectably translated and induced high levels of interferon‐α. Supernatants from HCV RNA–transfected macrophages inhibited HCV replication in Huh‐7.5 cells. Conclusion: We conclude that multiple blocks prevent blood cells from supporting HCV infection. (HEPATOLOGY 2008;48:1843‐1850.)

Interferon (IFN)–γ–Inducible Protein–10: Association with Histological Results, Viral Kinetics, and Outcome during Treatment with Pegylated IFN-α2a and Ribavirin for Chronic Hepatitis C Virus Infection

BACKGROUND We investigated associations between interferon (IFN)-gamma-inducible protein (IP)-10 and liver histological results, viral kinetic response, and treatment outcome in patients infected with hepatitis C virus (HCV) genotypes 1-4. METHODS Plasma IP-10 was monitored before, during, and after treatment with pegylated IFN- alpha 2a and ribavirin in 265 HCV-infected patients. RESULTS In univariate analyses, a low baseline IP-10 level was significantly associated with low baseline viral load, rapid viral response (RVR), a sustained viral response (SVR), body mass index <25 kg/m2, and less-pronounced fibrosis, inflammation, and steatosis (for HCV genotypes other than 3). When the results of the univariate analyses were included in multivariate analyses, a low plasma IP-10 level, low baseline viral load, and genotype 2 or 3 infection were independent predictors of an RVR and SVR. IP-10 levels decreased 6 weeks into treatment and remained low in patients with an SVR. By contrast, plasma levels of IP-10 rebounded in patients who had detectable HCV RNA after the completion of treatment. Using cutoff IP-10 levels of 150 and 600 pg/mL for predicting an SVR in patients infected with HCV genotype 1 yielded a specificity and sensitivity of 81% and 95%, respectively. CONCLUSION Baseline IP-10 levels are predictive of the response to HCV treatment.

Diverse Hepatitis C Virus Glycoproteins Mediate Viral Infection in a CD81-Dependent Manner

ABSTRACT We recently reported that retroviral pseudotypes bearing the hepatitis C virus (HCV) strain H and Con1 glycoproteins, genotype 1a and 1b, respectively, require CD81 as a coreceptor for virus-cell entry and infection. Soluble truncated E2 cloned from a number of diverse HCV genotypes fail to interact with CD81, suggesting that viruses of diverse origin may utilize different receptors and display altered cell tropism. We have used the pseudotyping system to study the tropism of viruses bearing diverse HCV glycoproteins. Viruses bearing these glycoproteins showed a 150-fold range in infectivity for hepatoma cells and failed to infect lymphoid cells. The level of glycoprotein incorporation into particles varied considerably between strains, generally reflecting the E2 expression level within transfected cells. However, differences in glycoprotein incorporation were not associated with virus infectivity, suggesting that infectivity is not limited by the absolute level of glycoprotein. All HCV pseudotypes failed to infect HepG2 cells and yet infected the same cells after transduction to express human CD81, confirming the critical role of CD81 in HCV infection. Interestingly, these HCV pseudotypes differed in their ability to infect HepG2 cells expressing a panel of CD81 variants, suggesting subtle differences in the interaction of CD81 residues with diverse viral glycoproteins. Our current model of HCV infection suggests that CD81, together with additional unknown liver specific receptor(s), mediate the virus-cell entry process.

Hepatitis C virus induces interferon-λ and interferon-stimulated genes in primary liver cultures

Hepatitis C virus (HCV) replication in primary liver cells is less robust than that in hepatoma cell lines, suggesting that innate antiviral mechanisms in primary cells may limit HCV replication or spread. Here we analyzed the expression of 47 genes associated with interferon (IFN) induction and signaling following HCV infection of primary human fetal liver cell (HFLC) cultures from 18 different donors. We report that cell culture‐produced HCV (HCVcc) induced expression of Type III (λ) IFNs and of IFN‐stimulated genes (ISGs). Little expression of Type I IFNs was detected. Levels of IFNλ and ISG induction varied among donors and, often, between adapted and nonadapted HCV chimeric constructs. Higher levels of viral replication were associated with greater induction of ISGs and of λ IFNs. Gene induction was dependent on HCV replication, as ultraviolet light‐inactivated virus was not stimulatory and an antiviral drug, 2′‐C‐methyladenosine, reduced induction of λ IFNs and ISGs. The level of IFNλ protein induced was sufficient to inhibit HCVcc infection of naïve cultures. Conclusion: Together, these results indicate that despite its reported abilities to blunt the induction of an IFN response, HCV infection is capable of inducing antiviral cytokines and pathways in primary liver cell cultures. Induction of ISGs and λ IFNs may limit the growth and spread of HCV in primary cell cultures and in the infected liver. HCV infection of HFLC may provide a useful model for the study of gene induction by HCV in vivo. (HEPATOLOGY 2011;)

Hepatitis C virus–induced cryoglobulinemia

In this review we discuss the clinical manifestations, pathogenesis, and treatment of hepatitis C virus (HCV)-related cryoglobulinemia. HCV is a major cause of liver-related morbidity and is increasingly recognized as an instigator of B-cell lymphoproliferative disorders such as mixed cryoglobulinemia and non-Hodgkin lymphoma. Cryoglobulinemia is characterized by the clonal expansion of rheumatoid factor-expressing B cells in the liver, lymph nodes, and peripheral blood, resulting in the presence of cryoglobulins in the circulation. Cryoglobulins are cold-insoluble immune complexes containing rheumatoid factor, polyclonal IgG, and HCV RNA that precipitate and deposit on vascular endothelium, causing vasculitis in organs such as the skin, kidneys, and peripheral nerves. A subset of patients develops a low-grade lymphoma composed of B cells that are immunophenotypically similar to the expanded B cells seen in cryoglobulinemia. HCV-related B-cell lymphoproliferative disorders likely comprise a spectrum of disease, ranging from asymptomatic clonal B-cell expansions to pathogenic cryoglobulinemia and lymphoma. It is unclear how B cells become dysregulated during the course of chronic HCV infection, and continued patient-centered research is necessary to elucidate the pathogenesis of HCV-related B-cell dysregulation.

Immunotherapy of chronic hepatitis C virus infection with antibodies against programmed cell death-1 (PD-1)

Hepatitis C virus (HCV) persistence is facilitated by exhaustion of CD8+ T cells that express the inhibitory receptor programmed cell death 1 (PD-1). Blockade of PD-1 signaling improves in vitro proliferation of HCV-specific T lymphocytes, but whether antiviral function can be restored in infected individuals is unknown. To address this question, chimpanzees with persistent HCV infection were treated with anti–PD-1 antibodies. A significant reduction in HCV viremia was observed in one of three treated animals without apparent hepatocellular injury. Viremia rebounded in the responder animal when antibody treatment was discontinued. Control of HCV replication was associated with restoration of intrahepatic CD4+ and CD8+ T-cell immunity against multiple HCV proteins. The responder animal had a history of broader T-cell immunity to multiple HCV proteins than the two chimpanzees that did not respond to PD-1 therapy. The results suggest that successful PD-1 blockade likely requires a critical threshold of preexisting virus-specific T cells in liver and warrants consideration of therapeutic vaccination strategies in combination with PD-1 blockade to broaden narrow responses. Anti–PD-1 immunotherapy may also facilitate control of other persistent viruses, notably the hepatitis B virus where options for long-term control of virus replication are limited.

MAIT cells are activated during human viral infections.

Mucosal-associated invariant T (MAIT) cells are abundant in humans and recognize bacterial ligands. Here, we demonstrate that MAIT cells are also activated during human viral infections in vivo. MAIT cells activation was observed during infection with dengue virus, hepatitis C virus and influenza virus. This activation—driving cytokine release and Granzyme B upregulation—is TCR-independent but dependent on IL-18 in synergy with IL-12, IL-15 and/or interferon-α/β. IL-18 levels and MAIT cell activation correlate with disease severity in acute dengue infection. Furthermore, HCV treatment with interferon-α leads to specific MAIT cell activation in vivo in parallel with an enhanced therapeutic response. Moreover, TCR-independent activation of MAIT cells leads to a reduction of HCV replication in vitro mediated by IFN-γ. Together these data demonstrate MAIT cells are activated following viral infections, and suggest a potential role in both host defence and immunopathology.

Efficient Replication of Genotype 3a and 4a Hepatitis C Virus Replicons in Human Hepatoma Cells

ABSTRACT Despite recent advances in the treatment of hepatitis C, the quest for pan-genotype, effective, and well-tolerated inhibitors continues. To facilitate these efforts, it is desirable to have in vitro replication systems for all major HCV genotypes. However, cell culture replication systems exist for only genotypes 1a, 1b, and 2a. In this study, we generated G418-selectable subgenomic replicons for prototype strains of genotypes 3a (S52) and 4a (ED43). Production of G418-resistant colonies by S52 and ED43 in Huh-7.5 cells required the amino acid substitutions S2210I and R2882G, respectively, cell culture adaptive mutations originally reported for genotype 1b replicons. RNA replication was confirmed by quantitative reverse transcription-PCR and detection of viral protein. Sequencing of multiple independent replicon clones revealed the presence of additional nonsynonymous mutations. Interestingly, all potentially adaptive mutations mapped to the NS3 protein. These mutations, when introduced back into original constructs, substantially increased colony formation efficiency. To make these replicons useful for high-throughput screening and evaluation of antiviral compounds, they were modified to express a chimeric fusion protein of firefly luciferase and neomycin phosphotransferase to yield stable replicon-expressing cells. Using these constructs, the inhibitory effects of beta interferon (IFN-β), an NS3 protease inhibitor, and an NS5B nucleoside polymerase inhibitor were readily detected by monitoring luciferase activity. In conclusion, we have established functional replicons for HCV genotypes 3a and 4a, important new additions to the armamentarium required to develop inhibitors with a pan-genotype activity.

Quasispecies Heterogeneity within the E1/E2 Region as a Pretreatment Variable during Pegylated Interferon Therapy of Chronic Hepatitis C Virus Infection

ABSTRACT A series of 29 patients undergoing treatment for chronic hepatitis C virus (HCV) genotype 1 infection with pegylated alpha-2a interferon plus ribavirin were studied for patterns of response to antiviral therapy and viral quasispecies evolution. All patients were treatment naive and had chronic inflammation and fibrosis on biopsy. As part of an analysis of pretreatment variables that might affect the outcome of treatment, genetic heterogeneity within the viral E1-E2 glycoprotein region (nucleotides 851 to 2280) was assessed by sequencing 10 to 15 quasispecies clones per patient from serum-derived PCR products. Genetic parameters were examined with respect to response to therapy based on serum viral RNA loads at 12 weeks (early viral response) and at 24 weeks posttreatment (sustained viral response). Nucleotide and amino acid quasispecies complexities of the hypervariable region 1 (HVR-1) were less in the responder group in comparison to the nonresponder group at 12 weeks, and genetic diversity was also less both within and outside of the HVR-1, with the difference being most pronounced for the non-HVR-1 region of E2. However, these genetic parameters did not distinguish responders from nonresponders for sustained viral responses. Follow-up studies of genetic heterogeneity based on the HVR-1 in selected responders and nonresponders while on therapy revealed greater evolutionary drift in the responder subgroup. The pretreatment population sequences for the NS5A interferon sensitivity determinant region were also analyzed for all patients, but no correlations were found between treatment response and any distinct genetic markers. These findings support previous studies indicating a high level of genetic heterogeneity among chronically infected HCV patients. One interpretation of these data is that early viral responses are governed to some extent by viral factors, whereas sustained responses may be more influenced by host factors, in addition to effects of viral complexity and diversity.

Expression of Paramyxovirus V Proteins Promotes Replication and Spread of Hepatitis C Virus in Cultures of Primary Human Fetal Liver Cells

Here we demonstrate that primary cultures of human fetal liver cells (HFLC) reliably support infection with laboratory strains of hepatitis C virus (HCV), although levels of virus replication vary significantly between different donor cell preparations and frequently decline in a manner suggestive of active viral clearance. To investigate possible contributions of the interferon (IFN) system to control HCV infection in HFLC, we exploited the well‐characterized ability of paramyxovirus (PMV) V proteins to counteract both IFN induction and antiviral signaling. The V proteins of measles virus (MV) and parainfluenza virus 5 (PIV5) were introduced into HFLC using lentiviral vectors encoding a fluorescent reporter for visualization of HCV‐infected cells. V protein‐transduced HFLC supported enhanced (10 to 100‐fold) levels of HCV infection relative to untransduced or control vector‐transduced HFLC. Infection was assessed by measurement of virus‐driven luciferase, by assays for infectious HCV and viral RNA, and by direct visualization of HCV‐infected hepatocytes. Live cell imaging between 48 and 119 hours postinfection demonstrated little or no spread of infection in the absence of PMV V protein expression. In contrast, V protein‐transduced HFLC showed numerous HCV infection events. V protein expression efficiently antagonized the HCV‐inhibitory effects of added IFNs in HFLC. In addition, induction of the type III IFN, IL29, following acute HCV infection was inhibited in V protein‐transduced cultures. Conclusion: These studies suggest that the cellular IFN response plays a significant role in limiting the spread of HCV infection in primary hepatocyte cultures. Strategies aimed at dampening this response may be key to further development of robust HCV culture systems, enabling studies of virus pathogenicity and the mechanisms by which HCV spreads in its natural host cell population. (HEPATOLOGY 2011;)