Hepatitis C epidemiology

Establishment of hepatitis C virus RNA-replicating cell lines possessing ribavirin-resistant phenotype

BACKGROUND

Ribavirin (RBV) is a potential partner of interferon-based therapy and recently approved therapy using direct acting antivirals for patients with chronic hepatitis C. However, the precise mechanisms underlying RBV action against hepatitis C virus (HCV) replication are not yet understood. To clarify this point, we attempted to develop RBV-resistant cells from RBV-sensitive HCV RNA-replicating cells.

METHODOLOGY/PRINCIPAL FINDINGS

By repetitive RBV (100 μM) treatment (10 weeks) of 3.5-year-cultured OL8 cells, in which genome-length HCV RNA (O strain of genotype 1b) efficiently replicates, dozens of colonies that survived RBV treatment were obtained. These colonies were mixed together and further treated with high doses of RBV (up to 200 μM). By such RBV treatment, we successfully established 12 RBV-survived genome-length HCV RNA-replicating cell lines. Among them, three representative cell lines were characterized. HCV RNA replication in these cells resisted RBV significantly more than that in the parental OL8 cells. Genetic analysis of HCV found several common and conserved amino acid substitutions in HCV proteins among the three RBV-resistant cell species. Furthermore, using cDNA microarray and quantitative RT-PCR analyses, we identified 5 host genes whose expression levels were commonly altered by more than four-fold among these RBV-resistant cells compared with the parental cells. Moreover, to determine whether viral or host factor contributes to RBV resistance, we developed newly HCV RNA-replicating cells by introducing total RNAs isolated from RBV-sensitive parental cells or RBV-resistant cells into the HCV RNA-cured-parental or -RBV-resistant cells using an electroporation method, and evaluated the degrees of RBV resistance of these developed cells. Consequently, we found that RBV-resistant phenotype was conferred mainly by host factor and partially by viral factor.

CONCLUSIONS/SIGNIFICANCE

These newly established HCV RNA-replicating cell lines should become useful tools for further understanding the anti-HCV mechanisms of RBV.

Genetic characterization of hepatitis C virus in long-term RNA replication using Li23 cell culture systems

BACKGROUND

The most distinguishing genetic feature of hepatitis C virus (HCV) is its remarkable diversity and variation. To understand this feature, we previously performed genetic analysis of HCV in the long-term culture of human hepatoma HuH-7-derived HCV RNA-replicating cell lines. On the other hand, we newly established HCV RNA-replicating cell lines using human hepatoma Li23 cells, which were distinct from HuH-7 cells.

METHODOLOGY/PRINCIPAL FINDINGS

Li23-derived HCV RNA-replicating cells were cultured for 4 years. We performed genetic analysis of HCVs recovered from these cells at 0, 2, and 4 years in culture. Most analysis was performed in two separate parts: one part covered from the 5'-terminus to NS2, which is mostly nonessential for RNA replication, and the other part covered from NS3 to NS5B, which is essential for RNA replication. Genetic mutations in both regions accumulated in a time-dependent manner, and the mutation rates in the 5'-terminus-NS2 and NS3-NS5B regions were 4.0-9.0×10(-3) and 2.7-4.0×10(-3) base substitutions/site/year, respectively. These results suggest that the variation in the NS3-NS5B regions is affected by the pressure of RNA replication. Several in-frame deletions (3-105 nucleotides) were detected in the structural regions of HCV RNAs obtained from 2-year or 4-year cultured cells. Phylogenetic tree analyses clearly showed that the genetic diversity of HCV was expanded in a time-dependent manner. The GC content of HCV RNA was significantly increased in a time-dependent manner, as previously observed in HuH-7-derived cell systems. This phenomenon was partially due to the alterations in codon usages for codon optimization in human cells. Furthermore, we demonstrated that these long-term cultured cells were useful as a source for the selection of HCV clones showing resistance to anti-HCV agents.

CONCLUSIONS/SIGNIFICANCE

Long-term cultured HCV RNA-replicating cells are useful for the analysis of evolutionary dynamics and variations of HCV and for drug-resistance analysis.

Necessity for reassessment of patients with serogroup 2 hepatitis C virus (HCV) and undetectable serum HCV RNA

We encountered a patient positive for anti-hepatitis C virus (HCV) whose serum HCV RNA was undetectable with the Roche AmpliPrep/Cobas TaqMan HCV assay (CAP/CTM) version 1 but showed a high viral load with the Abbott RealTime HCV assay (ART). Discrepancies in the detectability of serum HCV RNA were investigated among 891 consecutive patients who were positive for anti-HCV. Specific nucleotide variations causing the undetectability of HCV RNA were determined and confirmed by synthesizing RNA coding those variations. Serum samples with the discrepancies were also reassessed by CAP/CTM version 2. Among the 891 anti-HCV-positive patients, 4 patients had serum HCV RNA levels that were undetectable by CAP/CTM version 1 despite having levels of >5 log IU/ml that were detected by ART. All four patients had HCV genotype 2a and high titers of anti-HCV. Sequencing of the HCV 5' noncoding regions revealed 2 common variations, A at nucleotide (nt) 145 and T at nt 151. Synthesized RNAs of the HCV 5' noncoding region with standard (NCR145G151C) and variant nucleotides at nt 145 and nt 151 were quantified with CAP/CTM. RNAs of NCR145G151C and NCR145G151T were quantifiable with CAP/CTM version 1, while those of NCR145A151T and NCR145A151C went undetected. The substitution from G to A at nt 145 specifically conferred this undetectability, while this undetectability was reverted in synthesized HCV RNA with correction of this variation. Reassessment of these samples by CAP/CTM version 2 resulted in similar levels of HCV RNA being detected by ART. We conclude that HCV patients with undetectable HCV RNA by CAP/CTM version 1 should be reassessed for viral quantification.

Tandem Repeats of Lactoferrin-Derived Anti-Hepatitis C Virus Peptide Enhance Antiviral Activity in Cultured Human Hepatocytes

Previously, we found that bovine and human lactoferrin (LF) specifically inhibited hepatitis C virus (HCV) infection in cultured non-neoplastic human hepatocyte-derived PH5CH8 cells, and we identified 33 amino acid residues (termed C-s3-33; amino acid 600-632) from human LF that were primarily responsible for the binding activity to the HCV E2 envelope protein and for the inhibiting activity against HCV infection. Since the anti-HCV activity of C-s3-33 was weaker than that of human LF, we speculated that an increase of E2 protein-binding activity might contribute to the enhancement of anti-HCV activity. To test this possibility, we made two repeats [(C-s3-33)(2)] and three repeats [(C-s3-33)(3)] of C-s3-33 and characterized them. Far-Western blot analysis revealed that the E2 protein-binding activities of (C-s3-33)(2) and (C-s3-33)(3) became stronger than that of the C-s3-33, and that the binding activity of (C-s3-33)(3) was stronger than that of (C-s3-33)(2). Using an HCV infection system in PH5CH8 cells, we demonstrated that the anti-HCV activities of (C-s3-33)(2) and (C-s3-33)(3) became stronger than that of the C-s3-33. Furthermore, using a recently developed infection system with a VSV pseudotype harboring the green fluorescent protein gene and the native E1 and E2 genes, we demonstrated that the antiviral activities of (C-s3-33)(2) and (C-s3-33)(3) were stronger than that of C-s3-33. These results suggest that tandem repeats of LF-derived anti-HCV peptide are useful as anti-HCV reagents.

Effects of IL-28B gene polymorphism on response to peginterferon plus ribavirin combination therapy for genotype 2 chronic hepatitis C

AIM

Interleukin (IL)-28B gene polymorphism is closely linked with treatment response to peginterferon plus ribavirin combination therapy for hepatitis C virus genotype 1. However, few studies have reported its effects on therapy for genotype 2. We aimed to examine the effects of IL-28B gene polymorphism on treatment response in hepatitis C virus genotype 2 patients.

METHODS

In a retrospective study of 101 patients infected with either genotype 2a (n = 65) or 2b (n = 36) and treated with peginterferon plus ribavirin, we investigated predictive factors for a sustained virological response (SVR), including genetic variations near the IL-28B gene (rs8099917, rs11881222 and rs8103142) and clinical variables such as age, sex, body mass index, stage of fibrosis and drug adherence.

RESULTS

Ultra-rapid virological response, rapid virological response (RVR), end-of-treatment response, SVR and relapse rates were 22.2%, 61.4%, 95.0%, 87.1% and 7.9%, respectively. In univariate analysis, RVR and IL-28B single nucleotide polymorphisms (SNP) (rs8099917, rs11881222 and rs8103142) were significantly associated with SVR. In subgroup analysis, IL-28B SNP were significantly associated with SVR in genotype 2a patients but not in genotype 2b patients. In multiple logistic regression analysis, RVR and IL-28B SNP (rs8099917) were independently associated with SVR. Furthermore, IL-28B SNP was significantly associated with relapse but RVR was not.

CONCLUSION

In genotype 2 patients treated with peginterferon plus ribavirin combination therapy, IL-28B gene polymorphism was a significant independent predictor of SVR as well as RVR. IL-28B major allele may favor reduced relapse rates in patients with genotype 2 chronic hepatitis C.

New preclinical antimalarial drugs potently inhibit hepatitis C virus genotype 1b RNA replication

BACKGROUND

Persistent hepatitis C virus (HCV) infection causes chronic liver diseases and is a global health problem. Although new triple therapy (pegylated-interferon, ribavirin, and telaprevir/boceprevir) has recently been started and is expected to achieve a sustained virologic response of more than 70% in HCV genotype 1 patients, there are several problems to be resolved, including skin rash/ageusia and advanced anemia. Thus a new type of anti-HCV drug is still needed.

METHODOLOGY/PRINCIPAL FINDINGS

Recently developed HCV drug assay systems using HCV-RNA-replicating cells (e.g., HuH-7-derived OR6 and Li23-derived ORL8) were used to evaluate the anti-HCV activity of drug candidates. During the course of the evaluation of anti-HCV candidates, we unexpectedly found that two preclinical antimalarial drugs (N-89 and its derivative N-251) showed potent anti-HCV activities at tens of nanomolar concentrations irrespective of the cell lines and HCV strains of genotype 1b. We confirmed that replication of authentic HCV-RNA was inhibited by these drugs. Interestingly, however, this anti-HCV activity did not work for JFH-1 strain of genotype 2a. We demonstrated that HCV-RNA-replicating cells were cured by treatment with only N-89. A comparative time course assay using N-89 and interferon-α demonstrated that N-89-treated ORL8 cells had more rapid anti-HCV kinetics than did interferon-α-treated cells. This anti-HCV activity was largely canceled by vitamin E. In combination with interferon-α and/or ribavirin, N-89 or N-251 exhibited a synergistic inhibitory effect.

CONCLUSIONS/SIGNIFICANCE

We found that the preclinical antimalarial drugs N-89 and N-251 exhibited very fast and potent anti-HCV activities using cell-based HCV-RNA-replication assay systems. N-89 and N-251 may be useful as a new type of anti-HCV reagents when used singly or in combination with interferon and/or ribavirin.

Response of hepatitis C virus to long-term passage in the presence of alpha interferon: multiple mutations and a common phenotype

Cell culture-produced hepatitis C virus (HCV) has been subjected to up to 100 serial passages in human hepatoma cells in the absence or presence of different doses of alpha interferon (IFN-α). Virus survival, genetic changes, fitness levels, and phenotypic traits have been examined. While high initial IFN-α doses (increasing from 1 to 4 IU/ml) did not allow HCV survival beyond passage 40, a gradual exposure (from 0.25 to 10 IU/ml) allowed the virus to survive for at least 100 passages. The virus passaged in the presence of IFN-α acquired IFN-α resistance as evidenced by enhanced progeny production and viral protein expression in an IFN-α environment. A partial IFN-α resistance was also noted in populations passaged in the absence of IFN-α. All lineages acquired adaptative mutations, and multiple, nonsynonymous mutations scattered throughout the genome were present in IFN-α-selected populations. Comparison of consensus sequences indicates a dominance of synonymous versus nonsynonymous substitutions. IFN-α-resistant populations displayed decreased sensitivity to a combination of IFN-α and ribavirin. A phenotypic trait common to all assayed viral populations is the ability to increase shutoff host cell protein synthesis, accentuated in infections with IFN-α-selected populations carried out in the presence of IFN-α. The trait was associated with enhanced phosphorylation of protein kinase R (PKR) and eIF2α, although other contributing factors are likely. The results suggest that multiple, independent mutational pathways can confer IFN-α resistance to HCV and might explain why no unified picture has been obtained regarding IFN-α resistance in vivo.

Development of NS3/4A protease-based reporter assay suitable for efficiently assessing hepatitis C virus infection

A cell culture system for the production of hepatitis C virus (HCV) whole virions has greatly accelerated studies of the virus life cycle and the discovery of anti-HCV agents. However, the quantification of the HCV titers in a whole-virus infection/replication system currently relies mostly on reverse transcription-PCR or immunofluorescence assay, which would be cumbersome for high-throughput drug screening. To overcome this problem, this study has generated a novel cell line, Huh7.5-EG(Delta4B5A)SEAP, that carries a dual reporter, EG(Delta4B5A)SEAP. The EG(Delta4B5A)SEAP reporter is a viral protease-cleavable fusion protein in which the enhanced green fluorescence protein is linked to secreted alkaline phosphatase (SEAP) in frame via Delta4B5A, a short peptide cleavage substrate for NS3/4A viral protease. This study demonstrates that virus replication/infection in the Huh7.5-EG(Delta4B5A)SEAP cells can be quantitatively indicated by measuring the SEAP activity in cell culture medium. The levels of SEAP released from HCV-infected Huh7.5-EG(Delta4B5A)SEAP cells correlated closely with the amounts of HCV in the inocula. The Huh7.5-EG(Delta4B5A)SEAP cells were also shown to be a suitable host for the discovery of anti-HCV inhibitors by using known compounds that target multiple stages of the HCV life cycle. The Z'-factor of this assay ranged from 0.64 to 0.74 in 96-well plates, indicating that this reporter system is suitable for high-throughput screening of prospective anti-HCV agents.

Ultra-structural localisation of hepatocellular PKR protein using immuno-gold labelling in chronic hepatitis C virus disease

The greater resistance of HCV genotype 1 infection to IFN therapy has been partially attributed to functional inhibition of the type 1 interferon induced anti-viral protein PKR in vitro. Whether PKR has antiviral activity against HCV in vivo is unknown. Whilst the ultra-structural localisation of PKR is known in vitro, it is not defined in chronic hepatitis C disease. Using a novel immuno-gold technique we characterised the expression of intrahepatic PKR protein at the ultra-structural level in four patients with chronic HCV disease compared to normal human PBMCs, HepG2 cells and a normal human liver biopsy. All four HCV patients labelled for PKR protein, localising to the nucleus, nucleolus and cytoplasm. Nuclear labelling was confined mainly to the nucleolus and euchromatin. Cytoplasmic labelling was evident within smooth vesicles. Strong immunogold labelling was also evident within the cisternae of the rough endoplasmic reticulum. A similar pattern of ultra-structural nuclear and cytoplasmic PKR protein labelling was seen in PBMCs from healthy donors, HepG2 cells and a normal liver biopsy. The mean nuclear and cytoplasmic count for PKR protein in the HCV group was 21 +/- 4 and 18 +/- 3 gold particles/microm(2), respectively. This represented an increase, though not statistically significant, in nuclear and cytoplasmic labelling for PKR protein in HCV biopsies relative to normal liver tissue.

Double-stranded RNA-induced interferon-beta and inflammatory cytokine production modulated by hepatitis C virus serine proteases derived from patients with hepatic diseases

We previously demonstrated that hepatitis C virus (HCV) serine protease NS3-4A was unable to cleave TRIF (adaptor protein of Toll-like receptor 3), resulting in a lack of suppression of the TRIF-mediated pathway, whereas NS3-4A cleaved Cardif (adaptor protein of retinoic acid-inducible gene I or melanoma differentiation-associated gene-5), resulting in an interruption of the Cardif-mediated pathway in non-neoplastic human hepatocyte PH5CH8 cells. To elucidate these observations, we examined the cleavage potential of NS3-4A for TRIF in PH5CH8 cells, genome-length HCV RNA-replicating O cells, and HCV-infected cells, and we demonstrated that NS3-4A lacked the ability to cleave endogenous TRIF, regardless of HCV strains derived from patients with different stages of hepatic disease. Furthermore, we demonstrated that inflammatory cytokine production by NF-kappaB activation via the TRIF-mediated pathway also remained unsuppressed by NS3-4A. These results suggest that the inhibitory effects of NS3-4A on antiviral signaling pathways are limited to the Cardif-mediated pathway in human hepatocytes.

The DNA damage sensors ataxia-telangiectasia mutated kinase and checkpoint kinase 2 are required for hepatitis C virus RNA replication

Cellular responses to DNA damage are crucial for maintaining genome integrity, virus infection, and preventing the development of cancer. Hepatitis C virus (HCV) infection and the expression of the HCV nonstructural protein NS3 and core protein have been proposed as factors involved in the induction of double-stranded DNA breaks and enhancement of the mutation frequency of cellular genes. Since DNA damage sensors, such as the ataxia-telangiectasia mutated kinase (ATM), ATM- and Rad3-related kinase (ATR), poly(ADP-ribose) polymerase 1 (PARP-1), and checkpoint kinase 2 (Chk2), play central roles in the response to genotoxic stress, we hypothesized that these sensors might affect HCV replication. To test this hypothesis, we examined the level of HCV RNA in HuH-7-derived cells stably expressing short hairpin RNA targeted to ATM, ATR, PARP-1, or Chk2. Consequently, we found that replication of both genome-length HCV RNA (HCV-O, genotype 1b) and the subgenomic replicon RNA were notably suppressed in ATM- or Chk2-knockdown cells. In addition, the RNA replication of HCV-JFH1 (genotype 2a) and the release of core protein into the culture supernatants were suppressed in these knockdown cells after inoculation of the cell culture-generated HCV. Consistent with these observations, ATM kinase inhibitor could suppress the HCV RNA replication. Furthermore, we observed that HCV NS3-NS4A interacted with ATM and that HCV NS5B interacted with both ATM and Chk2. Taken together, these results suggest that the ATM signaling pathway is critical for HCV RNA replication and may represent a novel target for the clinical treatment of patients with chronic hepatitis C.

Limited suppression of the interferon-beta production by hepatitis C virus serine protease in cultured human hepatocytes

Toll-like receptors and RNA helicase family members [retinoic acid-inducible gene I (RIG-I) and melanoma differentiation associated gene-5 (MDA5)] play important roles in the induction of interferon-beta as a major event in innate immune responses after virus infection. TRIF (adaptor protein of Toll-like receptor 3)-mediated and Cardif (adaptor protein of RIG-I or MDA5)-mediated signaling pathways contribute rapid induction of interferon-beta through the activation of interferon regulatory factor-3 (IRF-3). Previously, it has been reported that the hepatitis C virus NS3-4A serine protease blocks virus-induced activation of IRF-3 in the human hepatoma cell line HuH-7, and that NS3-4A cleaves TRIF and Cardif molecules, resulting in the interruption of antiviral signaling pathways. On the other hand, it has recently been reported that non-neoplastic human hepatocyte PH5CH8 cells retain robust TRIF- and Cardif-mediated pathways, unlike HuH-7 cells, which lack a TRIF-mediated pathway. In the present study, we further investigated the effect of NS3-4A on antiviral signaling pathways. Although we confirmed that PH5CH8 cells were much more effective than HuH-7 cells for the induction of interferon-beta, we obtained the unexpected result that NS3-4A could not suppress the interferon-beta production induced by the TRIF-mediated pathway, although it suppressed the Cardif-mediated pathway by cleaving Cardif at the Cys508 residue. Using PH5CH8, HeLa, and HuH-7-derived cells, we further showed that NS3-4A could not cleave TRIF, in disagreement with a previous report describing the cleavage of TRIF by NS3-4A. Taken together, our findings suggest that the blocking of the interferon production by NS3-4A is not sufficient in HCV-infected hepatocyte cells.

Development of a heterologous, multigenotype vaccine against hepatitis C virus infection

BACKGROUND

Unquestionably viral diversity and genetic heterogeneity in hepatitis C virus (HCV) infection and other viral diseases play an essential role in viral immune escape and the development of chronicity. Despite this knowledge most vaccine approaches against HCV have excluded this important issue. Moreover the feasibility of developing an effective HCV vaccine has been questioned, mainly because prophylactic immunity against HCV cannot be achieved in chimpanzees by either vaccination or previous HCV infection, and reinfection in men has been reported, most likely due to genetic shift and immune escape. To analyse and characterize a new technique of a 'multigenotype'- and/or 'library'-vaccine, we established an envelope 1 (E1) plasmid vaccine against HCV and characterized humoral and cellular immune responses after vaccination in a mouse model.

MATERIAL AND METHODS

Normally genetic information of one or two target proteins is cloned into a DNA-vaccine. In our approach we cloned a defined number of different genotypes and subtypes (defined vaccine, DV) or the genetic information from 20 patients (undefined) into a plasmid (library vaccine, LV).

RESULTS

As expected, immunized animals showed both stronger humoral (ELISA) and cellular (T-cell proliferation, ELISPOT) immune responses against genotype 1, since the stimulating antigen was genotype 1 derived. However, not all genotype 1 immunized animals recognized this viral antigen leading to the assumption that some epitopes lost their immunogenicity through a change in the amino acid sequence. Interestingly, some of the genotype 4 and 5 immunized mice sera were able to react against E1 protein.

CONCLUSION

Most of the assays showed immune reactivity against the DV or LV vaccine demonstrating the cross-reactive potential of such a vaccination approach. This cloning and immunization strategy based on the viral heterogeneity of the virus has in our view major implications for HCV, a virus with a broad viral genetic diversity, and may become in the future in the context of DNA- or viral-based vaccination strategies a possibility to overcome viral immune escape both in the prophylactic or therapeutic setting.

Trends in testing behaviours for hepatitis C virus infection and associated determinants: results from population-based laboratory surveillance in Alberta, Canada (1998-2001)

Little is currently known about hepatitis C virus (HCV) test seeking behaviours at the population level. Given the centralized nature of testing for HCV infection in the province of Alberta, Canada, we had an opportunity to examine HCV testing behaviour at the population level on all newly diagnosed HCV-positive cases using laboratory data to validate the time and number of prior tests for each case. Record linkage identified 3323, 2937, 2660 and 2703 newly diagnosed cases of HCV infections in Alberta during 1998, 1999, 2000 and 2001, respectively, corresponding to age-adjusted rates of 149.8, 129, 114.3 and 113.7 per 100,000 population during these years, respectively. Results from secondary analyses of laboratory data suggest that the majority of HCV cases (95.3%) who were newly diagnosed between 1998 and 2001 were first-time testers for HCV infection. Among repeat testers, analysis of a negative test result within 1 year prior to a first of a positive test report suggests that 211 (38.4%) may be seroconvertors. These findings suggest that 339 or 61.7% of repeat testers may not have discovered their serostatus within 1 year of infection. Among this group, HCV testing was sought infrequently, with a median interval of 2.3 years between the last negative and first positive test. This finding is of concern given the risks for HCV transmission, particularly if risk-taking behaviours are not reduced because of unknown serostatus. These findings also reinforce the need to make the most of each test-seeking event with proper counselling and other appropriate support services.

Epigenetic silencing of interferon-inducible genes is implicated in interferon resistance of hepatitis C virus replicon-harboring cells

BACKGROUND/AIMS

We previously established hepatitis C virus (HCV) replicon-harboring cell lines possessing two interferon (IFN)-resistant phenotypes: a partially resistant phenotype (alphaR series) and a severely resistant phenotype (betaR series). We recently found that the severe IFN resistance of the betaR-series cells is caused by the functional disruption of type I IFN receptors. Here, we aimed to clarify the mechanism(s) underlying the partial IFN resistance of the alphaR-series cells.

METHODS

alphaR-series cells were pre-treated with 5-azacytidine to evaluate the effects of DNA demethylation on IFN resistance. cDNA microarray analysis was carried out in order to compare 1alphaR cells, which belong to the alphaR series, treated with both 5-azacytidine and IFN-alpha with cells treated with 5-azacytidine or IFN-alpha alone.

RESULTS

We found that the IFN-resistant phenotype of alphaR-series cells was impaired by treatment with 5-azacytidine. cDNA microarray analysis identified seven IFN-stimulated genes, which were up-regulated by 5-azacytidine treatment. We demonstrated here that the ectopic expression of each of these seven genes in 1alphaR cells frequently weakened the IFN resistance of these cells.

CONCLUSIONS

The present results suggest that the epigenetic silencing of IFN-stimulated genes is implicated in the acquisition of a partially IFN-resistant phenotype of HCV replicon-harboring cells.

Prophylactic and therapeutic vaccination with dendritic cells against hepatitis C virus infection

Antigen uptake and presentation capacities enable DC to prime and activate T cells. Recently, several studies demonstrated a diminished DC function in hepatitis C virus (HCV) infected patients showing impaired abilities to stimulate allogenic T cells and to produce IFN-gamma in HCV infected patients. Moreover, DC of patients who have resolved HCV infection behave like DC from healthy donors responding to maturation stimuli, decrease antigen uptake, up-regulate expression of appropriate surface marker, and are potent stimulators of allogenic T cells. A number of studies have demonstrated in tumour models and models of infectious diseases strong induction of immune responses after DC vaccination. Because DC are essential for T-cell activation and since viral clearance in HCV infected patients is associated with a vigorous T-cell response, we propose a new type of HCV vaccine based on ex vivo stimulated and matured DC loaded with HCV specific antigens. This vaccine circumvents the impaired DC maturation and the down regulated DC function of HCV infected patients in vivo by giving the necessary maturation stimuli and the HCV antigens in a different setting and location ex vivo. Strong humoral and cellular immune responses were detected after HCV core DC vaccination. Furthermore, DC vaccination shows partial protection in a therapeutic and prophylactic model of HCV infection. In conclusion, mice immunized with HCV core pulsed DC generated a specific antiviral response in a mouse HCV challenge model. Our results indicate that HCV core pulsed DC may serve as a new modality for immunotherapy of HCV especially in chronically infected patients.

Impaired renal allograft, but not patient survival, in patients with antibodies to hepatitis C virus

BACKGROUND

The impact of hepatitis C virus (HCV) infection in renal transplant patients is controversial and there are no data on the outcome of renal transplantation in this sub-group of Irish patients.

AIM

To examine the outcome of renal transplantation in patients with hepatitis C.

METHODS

We examined the outcome of first grafts from renal transplant patients with hepatitis C antibody positive and compared them to a control group. During this period, 24 HCV positive patients received 33 grafts. All were treated with standard immunosuppression.

RESULTS

Graft survival rate was less in the HCV positive cases (p=0.0087). Graft survival at 1 year was 75% in the HCV positive group versus 85% in the HCV negative group, 40% versus 62% at 5 years and 14% compared with 40% at 10 years. Patient survival was similar in both groups (p=0.78). Patient survival at 1 year was 96% versus 94%, 87% versus 80% at 5 years and 70% in both groups at 10 years.

CONCLUSION

In the Irish renal transplant population, the presence of hepatitis C antibodies, before or after transplantation is associated with worse long-term graft, but not patient survival.

[Sporadic transmission of hepatitis C in dental practice]

Percutaneous contact with contaminated blood is the principal mode of transmission of the hepatitis C virus (HCV). However, the diagnosis of infection in patients in whom no parenteral risk factor can be identified allows speculation on the existence of other routes of transmission. In the field of dentistry, the role of saliva has still not been defined as a potential vehicle for infection nor the role of dental treatment as a possible occult factor in the sporadic transmission of hepatitis C. HVC-RNA is detectable in the saliva of over 50% of patients with chronic hepatitis C. The infectivity of the HVC particles detected in the saliva has not been determined, though it may be deduced from epidemiological studies that their potential for transmission, if it exists, is extremely limited. There has been no documented case of HVC transmission in a dental clinic. Studies which propose a history of dental treatment as a risk factor for HVC infection have not achieved conclusive results. The age distribution of the prevalence of HVC could indicate that a risk of iatrogenic transmission existed in the past, before the systematic application of universal barriers. The transmission of HVC in dental clinics may be considered a very infrequent occurrence as long as the norms for the control of cross-infection are respected.

Does sequencing the PKRBD of hepatitis C virus NS5A predict therapeutic response to combination therapy in an Australian population?

Abstract Background and Aim: The presence of four or more amino acid substitutions within the interferon sensitivity determining region (ISDR) of the hepatitis C virus (HCV) genotype 1b NS5A gene determines sensitivity to interferon (IFN) monotherapy in Japanese patients. Resistance of HCV genotype 1 to IFN-alpha has been attributed to the functional inhibition of a RNA dependent protein kinase (PKR) by the HCV NS5A PKR binding domain (PKRBD), which includes the ISDR. The ability of the ISDR and PKRBD sequence to predict a response to IFN-alpha and ribavirin combination therapy was investigated in an Australian population.

METHODS

The sequence of the PKRBD of NS5A, including the ISDR, for the dominant quasi-species of HCV was determined in 37 genotype 1 (genotype 1a: n = 26, genotype 1b: n = 11) and 13 genotype 3a infected patients.

RESULTS

The number of PKRBD amino acid substitutions in HCV genotype 1 infected patients with a sustained virological response was significantly higher than that in patients with a non-response to treatment (P = 0.047). It was found that only 2/37 HCV genotype 1 infected patients had four or more amino acid substitutions relative to the prototype ISDR sequence (HCV-J). Importantly, a sustained virological response was not found in any of the HCV infected patients who had a prototype ISDR genotype 1 sequence (n = 5).

CONCLUSIONS

There are relatively few amino acid mutations within the ISDR of this Western Australian patient population. Patients infected with a HCV genotype 1 prototype sequence should be counseled before receiving combination IFN-alpha and ribavirin therapy as they have a poor response to treatment.

Recent advances in prevention and treatment of hepatitis C virus infections

Hepatitis C virus (HCV) is the leading cause of chronic hepatitis in humans. As members of the flavivirus family, HCVs are a group of small single-stranded, positive-sense RNA viruses. Upon translation of the genome, a polyprotein precursor is synthesized and further processed by both cellular and viral proteases to generate functional viral proteins. Treatment options are currently limited to the administration of alpha-interferon alone or in combination with ribavirin. Unfortunately, these approaches are characterized by relatively poor efficacy and an unfavorable side-effect profile. Therefore, intensive effort is directed at the discovery of novel molecules to treat this disease. These new approaches include the development of prophylactic and therapeutic vaccines, the identification of interferons with improved pharmacokinetic characteristics, and the discovery of novel drugs designed to inhibit the function of three major viral proteins: protease, helicase and polymerase. Finally, the HCV RNA genome itself, particularly the IRES element, is being actively exploited as an antiviral target using antisense molecules and catalytic ribozymes. This review summarizes the most recent findings in each of these areas. Although not intended to be comprehensive, it should serve as a first resource for those individuals who desire updated information in this rapidly changing field.