Molecular biology of the hepatitis C viruses: implications for diagnosis, development and control of viral disease

Localization of hepatitis C virus in cutaneous vasculitic lesions in patients with type II cryoglobulinemia

OBJECTIVE

To investigate the role of hepatitis C virus (HCV) in the pathogenesis of the cutaneous vasculitis in patients with type II cryoglobulinemia.

METHODS

Using in situ hybridization detection of HCV, we studied 6 test patients and various control subjects. Serum HCV was quantitated, cryoglobulins were analyzed by column chromatography at 37 degrees C, and low-density lipoprotein (LDL) receptors on keratinocytes were detected using LDL labeled with fluorescent dye.

RESULTS

In the cutaneous vasculitic lesions from test patients, but not control subjects, the HCV virion was found in association with IgM and IgG. HCV alone was detected in some vessel walls, and in skin and ductal epithelium and vascular endothelium in inflamed, but not normal, skin. Cryoglobulins showed HCV, monomeric IgM, and monomeric IgG, with little or no immune complexes. The extent of the lesions correlated with levels of viremia. Up-regulation of LDL receptors on keratinocytes was detected in inflamed, but not normal, skin.

CONCLUSION

HCV was present in the cutaneous vasculitic lesions, most likely in complexes with IgM and IgG formed in situ. These findings and the correlation of the severity of the rash with the level of viremia suggest that HCV plays a major role in the pathogenesis of cutaneous vasculitis in these patients and strengthens the rationale for antiviral drug therapy. The presence of HCV in keratinocytes and ductal epithelial and vascular endothelial cells may be the in vivo manifestation of endocytosis of HCV by the LDL receptors that has recently been demonstrated in vitro. The up-regulation of LDL receptors on keratinocytes in inflamed skin is consistent with this postulation.

Hepatitis C infection in transplantation

This review emphasizes the role of HCV in the transplant setting. Prolonged HCV infection results in end-stage liver disease and as such represents a common indication for liver transplantation. Recurrence of infection is almost universal after transplantation in those with viremia before transplantation. Acquired disease is uncommon but nevertheless important, particularly in organ populations in whom screening for infection is not routine. The natural history of post-transplantation disease suggests that the effect on graft or patient survival is minor, at least during short-term follow-up. Long-term follow-up is needed, as well as more detailed study of the factors contributing to severity of post-transplantation disease. Kidney transplant recipients are commonly infected with HCV prior to transplantation. HCV infection after transplantation is associated with an increased risk of liver disease and infectious complications, but its effect on survival is still controversial. Similarly, observations in recipients of other solid organ transplants, such as heart and lung, and bone marrow patients suggest that HCV infection usually is not a major cause of mortality in the first 5 to 10 years of follow-up. Many issues still need to be addressed. The most important is the identification of factors that contribute to disease progression. Finally, effective therapies to eradicate infection and prevent disease progression are awaited.

In vitro study of the NS2-3 protease of hepatitis C virus

Processing at the C terminus of the NS2 protein of hepatitis C virus (HCV) is mediated by a virus-encoded protease which spans most of the NS2 protein and part of the NS3 polypeptide. In vitro cotranslational cleavage at the 2-3 junction is stimulated by the presence of microsomal membranes and ultimately results in the membrane insertion of the NS2 polypeptide. To characterize the biochemical properties of this viral protease, we have established an in vitro assay whereby the NS2-3 protease of HCV BK can be activated posttranslationally by the addition of detergents. The cleavage proficiency of several deletion and single point mutants was the same as that observed with microsomal membranes, indicating that the overall sequence requirements for proper cleavage at this site are maintained even under these artificial conditions. The processing efficiency of the NS2-3 protease varied according to the type of detergent used and its concentration. Also, the incubation temperature affected the cleavage at the 2-3 junction. The autoproteolytic activity of the NS2-3 protease could be inhibited by alkylating agents such as iodoacetamide and N-ethylmaleimide. Metal chelators such as EDTA and phenanthroline also inhibited the viral enzyme. The EDTA inhibition of NS2-3 cleavage could be reversed, at least in part, by the addition of ZnCl2 and CdCl2. Among the common protease inhibitors tested, tosyl phenylalanyl chloromethyl ketone and soybean trypsin inhibitor inactivated the NS2-3 protease. By means of gel filtration analysis, it was observed that the redox state of the reaction mixture greatly influenced the processing efficiency at the 2-3 site and that factors present in the rabbit reticulocyte lysate, wheat germ extract, and HeLa cell extract were required for efficient processing at this site. Thus, the in vitro assay should allow further characterization of the biochemical properties of the NS2-3 protease of HCV and the identification of host components that contribute to the efficient processing at the 2-3 junction.

Analysis of the cell tropism of HCV by using in vitro HCV-infected human lymphocytes and hepatocytes

BACKGROUND/METHODS

We recently established two hepatitis C virus (HCV) replication systems, using MT-2, a human T-cell leukemia virus type I-infected human T-cell line, and PH5CH, a non-neoplastic human hepatocyte line immortalized with simian virus 40 large T antigen. These HCV replication systems were used to assess the infective potencies of seven sera containing more than 10(6) HCV genomes per ml obtained from HCV-positive blood donors.

RESULTS

The results showed that these sera had different infectivities for MT-2 and PH5CH cells. One of the seven sera, 1B-1, was more infective for MT-2 cells than PH5CH cells, whereas all the sera except serum 1B-1 were more infective for PH5CH cells than for MT-2 cells. Intracellular HCV RNA could be detected at least 30 days after inoculation with three of the sera. These findings suggested that the infective potency of each serum depends on the type of target cells. To further investigate HCV replication in these cells, we examined the hypervariable region 1 (HVR1) populations of HCV recovered from both MT-2 and PH5CH cells at 8 days postinoculation. The results revealed that the shift to limited HVR1 populations from the quasi-species of HVR1 populations in both cells usually occurred within 8 days after virus inoculation. Furthermore, in two of four sera, the predominant HVR1 populations in MT-2 and PH5CH cells appeared to be different.

CONCLUSION

These results suggest that HCV exhibits cell tropism.

Subcellular localization of hepatitis C virus structural proteins in the liver of transgenic mice

Hepatitis C virus (HCV) core and envelope proteins are suggested to be responsible for the pathogenesis of hepatic and extrahepatic manifestations in chronic hepatitis C. Moreover, the core protein is implicated in the regulation of the transcription of cellular genes including c-myc, RB and p53. Determining the subcellular localization of the core and envelope proteins is therefore necessary to elucidate their behaviors, particularly in vivo ones, regarding the interaction with transcriptional regulatory proteins or gene elements. We defined the subcellular localization of HCV envelope and core proteins which were expressed in substantial levels in the liver of transgenic mice. Subcellular fractionation by ultra-centrifugation revealed that the envelope proteins were present principally in the microsomes of the liver, while a small amount of the protein was detected also in the nuclei. Immunohistochemistry confirmed the localization of envelope proteins in the nuclei. In contrast, the core protein was detected principally in the cytoplasmic fraction, where it was closely associated with lipids. A low level of the core protein was detected also in the nuclei and microsomal fraction. These results suggest possible interaction of the HCV structural proteins with some factors in hepatocytes thereby perturbing intracellular circumstances.

Association of hepatitis C virus infection with mortality and graft survival in kidney-pancreas transplant recipients

BACKGROUND

Although most studies have not demonstrated decreased patient or graft survival in kidney-alone allograft recipients infected with hepatitis C virus (HCV), the impact of HCV infection on patient and graft survival in HCV-infected kidney-pancreas recipients has not been studied.

METHODS

We undertook a retrospective cohort analysis of 137 kidney-pancreas transplant recipients who were transplanted between January 1989 and May 1996. HCV infection was determined by a positive polymerase chain reaction. Relative risk of death and graft failure was calculated using the Cox proportional hazards model with time-dependent covariates. Relative risks were adjusted (aRR) to control for the number of OKT3-treated rejections and cytomegalovirus status of the recipient at the time of transplantation.

RESULTS

Mean length of follow-up was 30.4 months in the HCV-infected patients compared with 31.7 months in noninfected patients. Seven (5.1%) patients were infected with HCV before transplant, one (1%) relapsed after transplantation, and four (2.9%) acquired the infection after transplantation. The HCV-infected group had a 3.7-fold (95% confidence interval [CI], 1.0-13.5) increased risk of death after transplant compared with the HCV-negative group, with an aRR of 5.5 (95% CI, 1.5-20.0). Death in the HCV-infected group (n=3) was generally the result of liver failure and sepsis, whereas death for those in the uninfected group (n=11) was primarily of cardiovascular origin. Patients infected with HCV were 3.4-fold (95% CI, 1.1-10.1) more likely to develop kidney graft failure than HCV-negative patients with an aRR of 5.1 (95% CI, 1.7-15.4). The risk of pancreatic allograft failure was not significantly increased.

CONCLUSIONS

We conclude that HCV infection in kidney-pancreas transplant patients results in a significantly increased risk of kidney allograft failure and death.

Impaired induction of cytotoxic T lymphocytes by antagonism of a weak agonist borne by a variant hepatitis C virus epitope

An epitope that acted as a weak agonist in the cytotoxicity assay was identified as part of the capsid protein of a hepatitis C virus (HCV) variant. In a low concentration, the variant epitope also had a weak antagonistic effect. When a minute amount of this variant epitope was added to the culture for induction, it selectively attenuated the expansion of major cytotoxic T cell populations and drastically reduced the cytotoxic responses against the wild-type epitope. Thus, antagonism to induction suppressed immune responses against both the wild type and the variant, thereby helping the persistence of not only variant itself but also the wild-type HCV. Because this variant was a weak agonist, most cytotoxic T cells induced with the wild-type epitope were cross-reactive with the variant and susceptible to the antagonism to induction. Only the T cells which were not cross-reactive with the variant and not susceptible to the antagonism survived the antagonism in induction. This implied that the specificity of the remaining immune response, if any, was directed exclusively to the wild-type epitope after the emergence of the variant. For viruses like HCV, being heterogeneous itself may contribute significantly toward persistent infection through antagonism to induction.

The possible role of zinc and metallothionein in the liver on the therapeutic effect of IFN-alpha to hepatitis C patients

We have studies zinc deficiency in hepatitis C patients (complete responder [CR] 22, nonresponder [NR] 25) with relation to the therapeutic effect of interferon-alpha (IFN-alpha). Circadian variations in serum zinc levels were high in the morning (basal level) and then gradually decreased during the day in both chronic hepatitis C patients and healthy controls. Basal zinc levels in serum were significantly lower in chronic hepatitis C patients (73 +/- 3 micrograms/dL, n = 12) than in controls (93 +/- 5 micrograms/dL). An injection of 10 MU of IFN-alpha to hepatitis C patients augmented the serum zinc reductions, up to 40% in 8 h. Serum cortisol levels were significantly elevated 8 h (25.6 +/- 2.3 micrograms/dL) after IFN-alpha dose. Forty-seven chronic hepatitis C patients were treated with IFN-alpha for 24 wk, and serum zinc and copper levels were determined 12 and 24 wk during and after the completion of IFN-alpha therapy. Serum zinc levels and zinc/copper ratio were higher in CRs than in NRs to IFN therapy at each time-point. Hepatic metallothionein staining became prominent after IFN therapy in most of CRs, whereas it diminished NRs. These data suggest that nutritional status of zinc influences the effect of IFN on hepatitis C patients.

Evaluation of hepatitis C virus envelope proteins expressed in E. coli and insect cells for use as tools for antibody screening

BACKGROUND/METHODS

The two envelope proteins of hepatitis C virus, E1 and E2, were expressed in E. coli and, as secretory proteins, in Sf9 insect cells using recombinant baculoviruses. Co-infection of insect cells with E1 and E2-recombinant baculoviruses was performed, which has been shown to result in formation of E1-E2 dimers. All envelope proteins were purified by Ni2+-NTA chromatography and used for screening of serum samples in a HCV EIA assay. Serum samples of normal blood donors, chronically HCV-infected patients, a mixed titer panel and several seroconversion panels were screened and compared to test results with Cobas Core Anti-HCV EIA.

RESULTS

Screening of the sera of chronically HCV-infected patients (100% positive in Cobas Core Anti-HCV EIA) revealed 10-40% anti-E1 positive sera using different Sf9-expressed, glycosylated proteins and 93% using E. coli-expressed, non-glycosylated E1 protein. When the same sera were tested with different E2 proteins expressed in Sf9 cells and in E. coli, about 70-73% showed anti-E2 reactivity. When the proteins from Sf9 cells co-infected with E1- and E2-recombinant baculoviruses were tested, 70-80% of the same sera showed anti-envelope reactivity.

CONCLUSIONS

Testing of these patient antisera, and those from the well-characterized mixed titer panel BBI-PHV203, showed that recombinant E1 expressed in E. coli and co-expressed E1 and E2 proteins from Sf9 cells could be used as additional tools for anti-HCV antibody screening.

Barriers to hepatitis C transmission within breathing systems: efficacy of a pleated hydrophobic filter

It has been suggested that breathing circuits contaminated with body fluids may provide a route of nosocomial patient-to-patient transmission of the hepatitis C virus. Thus, a number of authorities have recommended the use of breathing circuit filters to minimize such risks. The present study sought to simulate a humidified breathing circuit and evaluate two different designs of breathing circuit filters to determine their efficacy in preventing passage of the hepatitis C virus. A hydrophobic pleated-membrane filter consistently prevented the passage of hepatitis C virus while a large-pore "electret" filter design was ineffective. We conclude that not all filter types are equally suited to preventing the passage of viruses and we therefore consider it essential that, if filters are intended to prevent the passage of named pathogens in a humidified breathing circuit, they should be evaluated in a similar experimental system to that described in order to prove their efficacy.

An enzyme-linked immunosorbent assay for detecting proteolytic activity of hepatitis C virus proteinase

An ELISA method for the quantitation in vitro of HCV serine proteinase activity was developed. A peptide substrate, Ac-Gly-Glu-Ala-Gly-Asp-Asp-Ile-Val-Pro-Cys-Ser-Met-Ser-Tyr-Thr-Trp-Thr-L ys (biotin) -OH (Sub-1), was hydrolyzed by a recombinant NS3 proteinase fused with maltose binding protein (MBP-NS3) into a product with a free amino moiety at the N-terminus. The product was immobilized, and the amino moiety was analyzed by digoxigenin labeling followed by immunological reaction with anti-digoxigenin-alkaline phosphatase conjugate and then the colorimeteric reaction. This method is suited for the high throughput screening of inhibitors, and the screening can be accelerated by automatic operation.

Quantitative detection of hepatitis C virus RNA in the serum of patients with chronic hepatitis C treated with interferon: a pilot study

BACKGROUND

It is not known whether the measurement of serum hepatitis C virus (HCV) RNA by reverse transcription polymerase chain reaction (RT-PCR) could improve the management of patients with chronic hepatitis C being treated with interferon.

OBJECTIVES

We analysed, in a pilot study, the relations between the variations of HCV-RNA and alanine aminotransferase (ALT) serum levels in 18 anti-HCV positive patients treated with interferon.

STUDY DESIGN

Serum HCV-RNA was measured, using a non competitive coamplification assay (Amplicor HCV Monitor), before (at 3, 2 and 1 months and baseline), during (first, third and sixth month) and after treatment for at least 8 months (range 8-17 months). HCV-RNA levels fluctuations were correlated with those of ALT and treatment outcome. According to the ALT pattern, four patients were non responders, seven partial responders, four relapsers and two long term responders.

RESULTS

The median and mean baseline HCV-RNA levels were significantly different in patients infected by HCV type 1, 2 and 3, being 248,449, 235,506; 4170, 17,866 and 22,315, 79,273 molecules per ml, respectively (P < 0.0001). We did not find any significant difference between median and mean baseline viremia of responders and non responders. After 1 month of treatment viremia was below the sensitivity levels of the assay in 77.7% (14/18) of the patients who normalized ALT, at least temporarily. On the contrary, HCV-RNA remained detectable in non responders.

CONCLUSIONS

Our data suggest that HCV-RNA detection using Amplicor Monitor at the first month of treatment can be useful to identify non responders, avoiding three additional months of treatment as would be required by ALT monitoring alone. During the post-treatment follow-up, persistence of undetectable HCV-RNA and normal ALT levels helps to identify long term responders from patients with the risk of relapse in spite of biochemical remission.

Effect of immunosuppression on composition of quasispecies population of hepatitis C virus in patients with chronic hepatitis C coinfected with human immunodeficiency virus

BACKGROUND/AIMS

To study the effects of the immunosuppression caused by the reduction of CD4 activity on the composition of hepatitis C virus (HCV) populations, we analyzed the number of HCV quasispecies clones and the nucleotide diversity of the hypervariable region 1 (HVR1) of HCV in 37 patients with hemophilia with persistent HCV infection, with or without human immunodeficiency virus (HIV).

METHODS

The numbers of HCV quasispecies clones were measured by fluorescence single-strand conformation polymorphism analysis. Direct sequencing was used to analyze the degree of diversity of HVR1. We compared these values according to coinfection with HIV, and CD4 counts of patients.

RESULTS

There were no differences in either the number of HCV clones or the diversity between patients with and without HIV coinfection. In HIV coinfected patients the diversity decreased in association with the decrease in CD4 count while the number of HCV clones did not. The diversity of HVR1 was 3.64 +/- 5.03% in patients with a CD4 count < 50/microliters and 14.92 +/- 6.03% in patients with a CD4 count > or = 50/microliters; it was significantly lower in the former (p = 0.0002).

CONCLUSIONS

A severe reduction in the CD4 count, which is considered to cause a decline in the activity of helper T-lymphocytes, induced changes in the composition of HCV populations; one or a few quasispecies clones are predominant in the HCV population in the serum of individual patients.

Delineation of regions important for heteromeric association of hepatitis C virus E1 and E2

Hepatitis C virus (HCV) is the major causative agent of blood-borne non-A non-B hepatitis. The persistence of HCV infection is believed to reflect escape from the host immunosurveillance system by mutations in hypervariable region 1 (HVR1) of the envelope protein 2 (E2). Two envelope proteins of HCV, E1 and E2, have been reported to form a heteromeric complex but the exact organization of the viral envelope proteins remains uncertain. We examined the interaction of E1 and E2 by far- Western blotting using the bacterial recombinant proteins and also by pull-down assay using mammalian expressed proteins. The major E1-interacting site of E2 was mapped within the N-terminal part of E2 (NCD1) (aa 415 to 500 of the polyprotein). Both HVR1 and HVR2, located at the N-terminal part of E2, were dispensable for the interaction. Although several discontinuous regions within NCD1 seemed to contribute to the strong binding to E1, the highly conserved amino acid sequences flanking HVR2 had the most significant effect. The amino acid residues "WHY" from 489 to 491 of E2 played an especially crucial role since the constructs with the internal deletion or substitution of the residues showed severely impaired E1-binding. The N-terminal part of E1 is important for the E2-binding as determined by far-Western blotting using the mammalian- and bacterial-expressed E2 proteins as probes. The mammalian-expressed, glycosylated forms of the E1 and E2 proteins exhibited E1-E2 binding activities similar to those of the bacterial-expressed, nonglycosylated forms in pull-down assays, suggesting that glycosylation is not prerequisite for the heteromeric complex formation of E1 and E2.

Identification of hepatitis B virus integration in hepatitis C virus-infected hepatocellular carcinoma tissues

BACKGROUND/AIMS

The integration of HBV DNA is thought to be involved in the initial stage of hepatocarcinogenesis, and it has been reported that transactivating factors encoded by the X and preS2/S genes stimulate transcription of multiple viral and cellular genes. We assessed the possible contributions of hepatitis B virus integration to the occurrence of hepatocellular carcinoma in hepatitis C virus-infected as well as in hepatitis B virus-infected patients by identifying the integrated HBV DNA sequence, and the X and preS2/S regions were further investigated in HBV DNA-integrated cases.

METHODS

Southern blot hybridization for detecting HBV DNA in tumor tissues from 28 hepatocellular carcinoma patients was carried out with full-length HBV DNA, and then with X and preS2/S regions as probes. We also carried out reverse transcription-polymerase chain reaction for detecting HCV RNA to confirm hepatitis C virus-infection in liver tissues.

RESULTS

Clonally integrated HBV DNA sequences were demonstrated in 16 of 28 patients (57.1%), including five HBsAg seropositive and 11 HBsAg seronegative patients. Of these 11 HBsAg seronegative patients, 10 were also positive for anti-HCV in their sera, and all nine examined cases had HCV RNA in liver. Furthermore, the X region was identified in 14 of 16 HBV DNA integrated cases (87.5%), and the preS2/S region in 6/16 (37.5%).

CONCLUSIONS

The present Southern blot analysis demonstrates that clonally integrated HBV DNA sequences were identified even in hepatitis C virus-infected hepatocellular carcinoma patients at a high rate (10/18, 55.6%), and suggests that integrated hepatitis B virus, whose major component is the X gene, may play an important role in hepatocarcinogenesis in hepatitis B virus-integrated cases with and without hepatitis C virus infection.

The La antigen binds 5' noncoding region of the hepatitis C virus RNA in the context of the initiator AUG codon and stimulates internal ribosome entry site-mediated translation

Translation initiation of the hepatitis C virus (HCV) RNA genome occurs through an internal ribosome entry site in a cap-independent manner. Here, we have examined the interaction between La antigen and the HCV 5' noncoding region (5'NCR). In this analysis, competitor RNAs derived from HCV 5'NCR carrying deletions and a point mutation were used to identify the site(s) of La antigen binding during UV cross-linking assay. These studies suggest that La antigen recognizes the intact HCV 5'NCR structure. Further, these interactions occurred in the context of the initiator AUG. The latter view is supported by an analysis in which mutants of the HCV 5'NCR RNA with deletion or substitution in the initiator AUG codon failed to compete for La antigen binding to the wild-type 5'NCR. The evidence for the interaction between liver cell-derived La antigen and the HCV 5'NCR is provided by immunoprecipitation of a UV cross-linked species from the S100 fraction of Huh7 cell lysates. The functional relevance of this interaction was demonstrated by the stimulation of the HCV internal ribosome entry site-mediated translation in the presence of La protein. These results suggest an important functional role of La protein in the regulation of internal initiation of translation of the HCV RNA genome.

Distribution of hepatitis C virus genotypes in German patients with chronic hepatitis C: correlation with clinical and virological parameters

BACKGROUND/AIMS

The hepatitis C virus genotypes have been shown to be differently distributed between distinct geographical areas and to be associated with different clinical presentations. In the present study we investigated the distribution of HCV genotypes in 379 German patients with chronic hepatitis C in relation to age, sex, route of infection, liver histology and viremia.

METHODS

Typing of HCV was done using restriction fragment length polymorphism analysis as well as a DNA enzyme immunoassay. HCV RNA concentrations were determined by quantitative polymerase chain reaction. Liver biopsies were performed in 187 patients and the histological activity was graded by the Knodell score.

RESULTS

Seventy percent were infected with genotype 1 (20% subtype 1a, 80% subtype 1b), 4% with genotype 2 and 26% with genotype 3 (all subtype 3a). Genotype 3a and 1a infection was significantly associated with intravenous drug abuse. In contrast, genotype 1 predominated in patients with post-transfusion hepatitis and infection of unknown origin. A changing relative prevalence of HCV genotypes in relation to age was also observed. Patients with genotype 3 infection showed significantly lower HCV RNA levels and a lower mean histological activity score as compared to patients with genotype 1 and genotype 2. However, using multivariate analysis, only age and mode of transmission but not histological activitiy score were shown to be independent variables.

CONCLUSIONS

Our study confirms previous reports from other countries that HCV variants can be classified into a relatively small number of discrete genotypes, and that the subtype 1b clearly predominates. However, we found evidence that there is a changing relative prevalence of HCV genotypes in relation to age, and that the mode of transmission is reflected in the predominance of certain genotypes.

Human monoclonal recombinant Fabs specific for HCV antigens obtained by repertoire cloning in phage display combinatorial vectors

Molecular cloning of the antibody repertoire in phage display combinatorial vectors is a powerful method enabling the dissection of the immunoresponse against a given pathogen. In this paper we describe the construction of a combinatorial library displayed on phage surface, containing the antibody repertoire of a patient with high serological response against hepatitis C virus (HCV) antigens. Following selection of the library against solid-phase-bound antigen, sixteen human antibody Fab fragments able to bind to HCV-specific antigens were generated and studied for binding characteristics. The majority of them appeared to have specificity for the HCV c33 peptide. All the clones reacting with the c33 peptide shared the same heavy-chain CDR3 sequence. This is the first report of molecular cloning in a combinatorial phage display vector of the antibody repertoire of an anti-HCV-positive patient.

Improved reactivity of hepatitis C virus core protein epitopes in a conformational antigen-presenting system

Recent studies have identified several epitopes in the N-terminal portion of the nucleocapsid protein which are predominantly recognized by sera of patients infected with hepatitis C virus (HCV). The characterization of the sequences recognized by theses antibodies and the evaluation of their reactivities have been performed mainly with synthetic peptides. However, synthetic peptides are notoriously unreliable as antigens when the immune response is directed against conformational epitopes. In order to improve the detection of antibody responses in HCV-infected patients, we have evaluated the reactivities of three immunodominant regions of the HCV core protein (residues 1 to 20, 21 to 40, and 32 to 46) displayed in a conformation-specific manner on the surface of the Flock House virus (FHV) capsid protein. The results obtained with these proteins in the analysis of 94 serum samples positive by anti-HCV enzyme-linked immunosorbent assay where then compared with those obtained with the corresponding synthetic peptides. The sequence most reactive both with the peptide and with the FHV protein was the region from residues 1 to 20, confirming the low conformational requirements for the display of these residues. On the other hand, the already reported conformational nature of residues 32 to 46 is in keeping with its observed high reactivity when displayed by the FHV recombinant protein and with the low reactivity displayed by its corresponding synthetic peptide. Finally, the high reactivity observed for the chimeric protein displaying the region from residues 21 to 40, as opposed to the results obtained with the synthetic peptide, also suggests that this sequence contains one or more conformational epitopes whose structures cannot be mimicked correctly with synthetic peptides.

Analysis of T-cell receptor Vbeta repertoire in liver-infiltrating lymphocytes in chronic hepatitis C

BACKGROUND/AIMS

To examine the T-cell repertoire which is involved in the immunopathogenesis of chronic hepatitis, we analyzed the T-cell receptor Vbeta gene usage in liver-infiltrating lymphocytes by reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemical technique.

METHODS

Complementary DNA was synthesized from RNA which was extracted from 26 liver biopsy specimens and from peripheral blood lymphocytes from eight subjects, and amplified by RT-PCR. Radioactivity of each amplified product using 32P-labeled primers was measured and the percentage of each Vbeta expression was calculated.

RESULTS

The mean frequency of Vbeta5.1 (11.1%) in liver-infiltrating lymphocytes of chronic hepatitis C was highest among those of all Vbeta regions, and was significantly higher than that in both peripheral blood lymphocytes of chronic hepatitis C and liver-infiltrating lymphocytes of chronic hepatitis B. In the immunohistochemical analysis, Vbeta5.1-positive cells were mostly observed in portal areas where inflammatory reactions occurred. The sequences of the complementarity determining region (CDR)3 on T-cell receptor expressing Vbeta5.1 were examined in six patients with chronic hepatitis C. The sequences were similar to each other and all had one common amino acid (valine) irrespective of different HLA haplotype.

CONCLUSIONS

These data suggest that Vbeta5.1-positive cells are preferentially accumulated in the liver of chronic hepatitis C and are involved in the immunopathogenesis of the disease. Sequence analysis showed that Vbeta5.1-positive cells recognize a common conventional antigen and valine recognized at the same position of the CDR3 may be a key residue in determining an antigen/major histocompatibility complex contact point.

Hepatitis C virus core protein shows a cytoplasmic localization and associates to cellular lipid storage droplets

There is now abundant evidence to substantiate an important role of hepatitis C virus (HCV) core protein in cellular gene expression as well as in the viral cycle. Thus the subcellular localization of this protein has important implications. However, several studies have shown controversial results: the HCV core has been, indeed, described as cytoplasmic or nuclear depending on the size of the protein or on the genotype analyzed. We have studied the localization of the HCV core protein in two different cell lines, one nonhepatic (CHO) and the other hepatic (HepG2). Double immunofluorescence staining using a nuclear membrane marker and confocal analysis showed the core protein pattern to be cytoplasmic and globular. This pattern is not cell cycle-regulated. Electron microscopy analysis revealed the nature of the globular staining observed in immunofluorescence. The HCV core protein accumulated at the surface of lipid droplets that were also the unique morphological feature of nonhepatic core transfected cells. The lipid droplets were isolated by sequential ultracentrifugation on the basis of their density; biochemical analysis revealed a prevalence of triglycerides. In addition the core protein colocalized with apolipoprotein AII at the surface of the lipid droplets as revealed by confocal microscopy. Moreover analysis of liver biopsies from chronically HCV-infected chimpanzees revealed that HCV core is cytoplasmic and localized on the endoplasmic reticulum and on lipid droplets. These results clearly define the subcellular localization of the HCV core protein and suggest a relationship between the expression of the HCV core protein and cellular lipid metabolism.

Mutations in a hydrophilic part of the core gene of hepatitis C virus in patients with hepatocellular carcinoma in China

We investigated the association between hepatocellular carcinoma (HCC) and the genomic characteristics of the hepatitis C virus (HCV) isolated from residents of the inshore region of the Yangtze River, an area that has one of the highest incidence of HCC in China. We determined the genomic heterogeneity of HCV, and the sequence divergence of the HCV core gene in individuals with chronic hepatitis and HCC. HCV genotype II was predominant among these isolates, which were homologous to other Chinese and Japanese HCV isolates. The rate of nucleotide substitutions in the core gene was significantly greater for isolates from HCC patients than for those from individuals with chronic hepatitis. The nucleotide substitutions were unevenly scattered along the core gene; a cluster of missense mutations was apparent in the region encoding the second hydrophilic domain of the core protein. The rate of occurrence of missense mutations per nucleotide substitution was significantly greater in this clustering variable region (CVR) of the core gene than in the remaining core gene sequence. These observations suggest that mutations in the CVR may be involved in the pathogenesis of chronic HCV infection during hepatocellular carcinogenesis.

Sialadenitis histologically resembling Sjogren syndrome in mice transgenic for hepatitis C virus envelope genes

Hepatitis C virus (HCV), a major causative agent of non-A, non-B chronic hepatitis, is also suggested to be associated with extrahepatic manifestations such as mixed cryoglobulinemia and glomerulonephritis. Two independent lines of transgenic mice carrying the HCV envelope genes have been shown previously to express the HCV envelope proteins in organs, including the liver and salivary glands, which results in no pathological changes in the liver. Further analysis of these animals now has revealed that they develop an exocrinopathy involving the salivary and lachrymal glands. This pathology resembles Sjogren syndrome, which also is suggested to have a possible association with chronic hepatitis C. These observations suggest that HCV might be involved in the pathogenesis of sialadenitis in humans and that this transgenic mouse system would be a good animal model for the study of HCV infection.

Regulated processing of hepatitis C virus core protein is linked to subcellular localization

Posttranslational processing and subcellular localization of the HCV core protein are critical steps involved in the assembly of hepatitis C virus (HCV). In this study, both of these events were investigated by in vitro translation and transient COS-1 cell transfection of core protein expression constructs. Mutations at amino acid residues 173 to 174 and 191 to 192 disrupted processing events at the two putative cleavage sites in the C-terminal hydrophobic region of the core protein, indicating that these residues are implicated in the pathway of core protein maturation. As a result, two forms of core protein, C173 and C191, were detected by immunoblotting. Indirect immunofluorescence experiments showed that core proteins C173 and C191, when produced from HCV full-length protein or various polyprotein precursors, displayed a cytoplasmic localization. The C173 species, however, was translocated to the nucleus when expressed in the absence of C191. These findings indicate that preferential cleavage may occur during core protein maturation and that the association of the C191 with the C173 species may contribute to the distinct subcellular distribution of core protein. This may provide a possible mechanism for the control of the diverse biological functions of core protein during HCV replication and assembly.

Characteristics of the intrahepatic cytotoxic T lymphocyte response in chronic hepatitis C virus infection

Based on our CTL studies of over 44 persons with chronic HCV infection, we are able to arrive at a number of conclusions. Clearly this cellular immune response is heterogeneous among infected persons. We have not identified any specific HCV protein which appears to be immunodominant for CTL responses, but rather we have detected diverse responses to both structural and non-structural proteins. Using an identical stimulation strategy for all persons studied, we have been able to detect responses in only approximately one third of persons with chronic infection. Among these persons, the responses among liver-infiltrating lymphocytes are greater than those detected in fresh peripheral blood, suggesting that the CTL are homing to the site of maximal viral burden in these persons. Some viral proteins contain overlapping epitopes presented by more than one HLA class I molecule, and we have also found cases where peptides in the same HLA superfamily, such as the HLA A3 superfamily which contains A11, for which the same peptide can be presented by both alleles (manuscript in preparation). Although sequence variation between the infecting strain and the vaccinia constructs used to test for responses may lead to non-recognition of some variants, even the highly conserved core protein appears to be an inconsistent and actually infrequent target for detectable CTL responses. The magnitude of the CTL response appears to vary greatly, from being undetectable to being so vigorous that it an be detected in stimulated peripheral blood. The breadth of the response also varies widely, ranging from the detection of a response to a single epitope in some persons, to the simultaneous recognition of up to five different epitopes in others. Even in persons of the same HLA type, we have not seen consistent targeting of the same epitopes except in rare cases. Despite the detection of over 20 epitopes and their restricting class I alleles using CTR derived from liver-infiltrating lymphocytes, we have identified only one epitope that has been shown to be targeted by more than one person of the same HLA type. These findings lead us to speculate that the CTL response may be submaximal in the majority of infected persons. The reasons for this are presently obscure, but could relate to a number of factors. The epitopes targeted are found within variable regions of the virus, such that immune escape from established CTL responses has to be considered a real possibility. Sequence variation may also lead to antagonism of CTL responses, as has been demonstrated for both HIV and HBV infections. Furthermore, sequence variation either within or adjacent to regions containing CTL epitopes can lead to altered antigen processing, either due to alteration of proteolytic processing of the viral peptides in the cytoplasm or to altered transport and altered association with class I molecules. A number of issues regarding the CTL response in HCV infection still require substantial attention. The apparent inability of CTL to clear this virus needs to be addressed, as does the potential role for viral immunomodulatory molecules in HCV persistence. Although we and others have shown CTL responses to be present in persons with chronic infection, the role of CTL in acute HCV infection needs to be determined. The best studied chronic human viral infection is HIV infection, in which expanding data indicate that the early events following primary infection predict the subsequent course of illness. Viral load in the first 1-2 years after infection is highly predictive of the subsequent disease course in HIV infection, and recent experimental data in humans suggest that early immune responses may be predictive of subsequent disease course. Such studies in HCV infection have been difficult to achieve, since primary HCV infection is often asymptomatic, and transfusion-related cases are now rare. (ABSTRACT TRUNCATED)

Simultaneous detection of hepatitis C virus and human immunodeficiency virus RNA in serum using amplicor PCR tests

Several tests are currently available to assist in the diagnosis of the hepatitis C virus (HCV) and human immunodeficiency virus (HIV). Tests that actually detect or quantify these viruses are based on the polymerase chain reaction (PCR) technique. However, the application of PCR is limited by the cost, labor, time-consumption, and potential for contamination. In this article we describe some procedures developed to reduce these limitations. We have developed and validated simultaneous detection methods for HIV RNA and HCV RNA in single serum samples using Amplicor PCR tests. The sensitivity and specificity of this method are comparable with the results obtained with commercial reverse transcription polymerase chain reaction (RT-PCR) techniques for HIV and HCV RNA detection. In addition we have modified the HIV Amplicor test for the RT-PCR procedure and the Chomczynski's method of RNA isolation. We hope that our method can find same applications in HIV and HCV coinfection research, blood screening, and medical diagnosis.

Laboratory diagnosis of hepatitis C

In 1989 the hepatitis C virus was cloned, some 20 years after the first suggestion that hepatitis C virus(es) (HCV) existed. Since that time there has been rapid development of serological tests for detection of antibody to HCV and molecular tests for detection, quantitation, and characterization of HCV RNA. The development and performance characteristics of these test methods are reviewed and their implications for diagnosis, prognosis, and monitoring patients on therapy are discussed.

Characterization of the nuclear localization signal and subcellular distribution of hepatitis C virus nonstructural protein NS5A

Hepatitis C virus (HCV) has a positive strand RNA genome that codes for a polyprotein that is processed co-translationally and post-translationally into three structural and at least seven nonstructural (NS) proteins. To investigate the function of NS5A, a recombinant vaccinia virus was constructed in which the NS5A gene was cloned under the control of T7 promoter and encephalomyocarditis virus 5'-untranslated region (EMCV-UTR) for cap-independent translation in mammalian cells. In addition, the NS5A gene was also cloned under the control of cytomegalovirus (CMV) early promoter. The NS5A expressed in monkey kidney (CV-1) cells was located predominantly in the cytoplasm. Using immunohistochemical analysis, the subcellular distribution of NS5A in liver biopsy samples from chronic HCV-infected patients was also found to be in the cytoplasm. However, the NS5A protein has a stretch of positively charged domain in the vicinity of proline and valine residues, (PPRKKRTVV), characteristic of a nuclear localization signal (NLS), in the COOH-terminal half of the protein. To investigate whether the putative NLS of NS5A is functional, chimeric expression plasmids were constructed in which regions containing the NLS were fused to the N-terminus of the E. coli beta-galactosidase (E. coli beta-Gal). The expression of the fusion proteins in CV-1 cells resulted in their nuclear localization, indicating that the putative NLS is functional in targeting the heterologous protein, E. coli beta-Gal, to the nucleus, although the native NS5A is retained in the cytoplasm.

Differential prevalence of hepatitis C virus subtypes in healthy blood donors, patients on maintenance hemodialysis, and patients with hepatocellular carcinoma in Surabaya, Indonesia

Determination of the prevalence of liver disease caused by hepatitis C virus (HCV) of various genotypes helps provide an understanding of the virulences of these genotypes. Differences in the prevalences of these genotypes are known to exist in the various geographical regions of the world. Hence, we performed seroepidemiological and molecular epidemiological analyses of HCV in Surabaya, Indonesia. The prevalences of anti-HCV antibodies were 2.3, 76.3 and 64.7% in healthy blood donors, patients on maintenance hemodialysis, and patients with hepatocellular carcinoma (HCC), respectively. HCV-2a was the most common (52%) among the HCV clones obtained from blood donors; this was followed by HCV-1b (15%), HCV-1a (7%), and HCV-1d (7%), a unique Indonesian subtype. The high prevalence of HCV-2a in blood donors was further supported by serotyping analysis that could discriminate HCV type 2 (HCV-2a and -2b) from HCV type 1 (HCV-1a, -1b, and -1d). HCV-1a, -1b, and -1d were strongly associated with elevated serum alanine aminotransferase (ALT) levels in blood donors, suggesting a possibly more pathogenic feature of those subtypes than HCV-2a. In patients on maintenance hemodialysis, HCV-1a and -1b (each 31%) were among the most common subtypes, and in contrast to the case with blood donors, HCV-1a, -1b, and -1d were found in those with normal ALT as well as those with elevated ALT levels. Impaired immune responses of hemodialyzed patients might be responsible for the apparently decreased hepatocytic injury caused by infection with HCV type 1. In patients with HCC, HCV-1b (57%) was the most common; this was followed by HCV-1d (19%) and HCV-2a (5%). Subtype prevalence was not different between HCC patients with advanced liver cirrhosis and those without advanced cirrhosis.

Superinfection by homotypic virus in hepatitis C virus carriers: studies on patients with post-transfusion hepatitis

Although heterotypic superinfection and mixed infections of hepatitis C virus (HCV) may be possible for hepatitis flares in chronic hepatitis C, the possibility of homotypic HCV superinfection in HCV carriers with post-transfusion hepatitis has not been explored. Six HCV carriers with post-transfusion non-A, non-B hepatitis found in a prospective study of post-transfusion hepatitis were included. Serum samples before transfusion and during hepatitis were selected to determine genotypes of HCV and nucleotide sequences of the hypervariable region (HVR). The genotypes identified before and after transfusion were concordant in all. There were four with type 1b and one each with type 2a and type 2b. Amplified nucleotide sequences of the HVR before transfusion and during hepatitis were compared in four patients, and a > 95% homology was observed in three, suggesting persistence of original viruses. In contrast, only a 51% homogeneity was seen in a given patient, suggesting a homotypic HCV superinfection. Phylogenetic tree analysis validated further these findings. This study implies that HCV carriers can be reinfected by homotypic HCV, and this may contribute to hepatitis flares in chronic hepatitis C. These findings also confirm a weak or inadequate protective immunity in HCV infection and justify protection from reinfection of HCV of patients with chronic hepatitis C.

Single-step PCR in molecular diagnosis of hepatitis C virus infection

The diagnostic utility of two PCR systems and three PCR detection methods for hepatitis C virus (HCV) RNA was evaluated in serum samples. A nested PCR was considered the reference assay and was compared with two single-step PCR methods: the first is based on the detection of PCR products by liquid hybridization with a 32P-end-labeled probe, and the second is the Roche Amplicor colorimetric assay using microwell plate hybridization with a specific nucleic acid probe. Using the Pelicheck HCV RNA Eurohep genotype 1 proficiency panel, our laboratory achieved medium-high levels of performance with all three methods. The highest sensitivity was, however, observed with the isotopic single-step PCR (ss-PCR) method. The analytical sensitivity of ss-PCR with isotopic detection and ss-PCR with colorimetric detection was identical to that of nested PCR, with a 100% result concordance. Comparison of ss-PCR with enzyme-linked immunosorbent and RIBA assays in the analysis of clinical samples showed a high concordance. ss-PCR methods appear more suitable for diagnostic application. Nevertheless, HCV RNA PCR cannot be considered a screening assay; it should be requested in the presence of reactive serology or specific clinical symptomatology with altered liver parameters, and it is a potential tool for the follow-up of patients with HCV infection.

Serum hepatitis C virus titers in the progression of type C chronic liver disease. With special emphasis on patients with type 1b infection

The correlation of serum hepatitis C virus (HCV) titers to the progression of type C chronic liver disease remains controversial. We have investigated the relationship between serum HCV titers and different histological stages of chronic liver disease, including chronic persistent hepatitis (CPH), chronic active hepatitis and/or liver cirrhosis (CAH/LC), and hepatocellular carcinoma (HCC) in 94 well-characterized Taiwanese patients. The mean age of patients in the HCC group was significantly older than those in the CPH and CAH/LC groups, whereas those in the CAH/LC group had the highest mean serum alanine aminotransferase level among the three groups. The prevalence of HCV type 1b increased with the progression of histological severity, and the mean serum titer of the HCC group was significantly higher than that of CPH group. The difference of virus titers between the HCC group and those of the other two groups became more significant when only type 1b virus-infected patients were analyzed. In conclusion, elevated serum HCV titers are more frequently observed among Taiwanese patients with advanced type C chronic liver disease, an association not related to the high prevalence of HCV type 1b infection in such patients.

Rapid reverse transcription-PCR detection of hepatitis C virus RNA in serum by using the TaqMan fluorogenic detection system

We describe the application of a new fluorogenic probe-based PCR assay (TaqMan; Perkin Elmer Corp./Applied Biosystems, Foster City, Calif.) for the detection of hepatitis C virus RNA in serum and plasma. This assay allows for the direct direction of specific PCR products within minutes of completion of the PCR by monitoring the increase in fluorescence of a dye-labeled oligonucleotide probe. We evaluated this assay by comparing the results obtained by nested PCR with those obtained by TaqMan PCR. Test samples included two separate dilutions series of plasma samples from experimentally infected chimpanzees and a panel of 48 serum specimens from patients with community-acquired hepatitis C virus. The quantity of HCV RNA in each chimpanzee plasma sample was determined by using branched DNA (bDNA) signal amplification assay (Quantiplex HCV RNA assay; Chiron Corp., Emeryville, Calif.). Both PCR assays demonstrated similar levels of detection and could reliably detect 13 bDNA genome equivalents per sample. We found an overall concordance of 88% between results of two PCR assays with the community-acquired panel, which resolved to 100% when discrepant samples were retested by nested PCR. TaqMan compared favorably with nested PCR with key advantages of speed, increased throughput, and decreased opportunity for false-positive results because of elimination of second-round amplification.

Hepatitis C virus: a historical perspective

Identification and diagnosis of the infecting agent responsible for hepatitis C have only recently occurred. Recognition of an infecting agent distinct from that resulting in hepatitis A or B was made approximately 50 years ago. However, the ability to screen and detect this agent was possible only after molecular biology studies which led to the cloning of parts of the hepatitis C virus (HCV) and the development of a diagnostic antibody test reported by Michael Houghton and colleagues in 1989. The discovery and cloning of HCV has led to a greater understanding of its relationship to acute and chronic hepatitis, cirrhosis, primary liver cancer, and extrahepatic conditions including essential cryoglobulinemia, glomerulonephritis, and serum autoantibody positivity. New antibody tests and quantitation of HCV-RNA have allowed better diagnosis of infectivity and monitoring of treatment effects. HCV genotypes are being related to the natural history of the disease and the effects of treatment. Research continues on HCV hepatitis and other newly identified viral hepatitis agents.

Hepatitis C virus: molecular biology and genetic variability

The pathogenetic mechanisms of hepatitis C virus (HCV) infection are poorly known. An understanding of HCV biology and the potential clinical impact of HCV genetic variability is essential to managing, treating, and preventing HCV infections. HCV is a member of the Flaviviridae viral family. Its genome is a positive, single-strand RNA molecule. The structure of the HCV particles is poorly known due to the lack of an efficient cell culture system as well as a striking heterogeneity in density. The core protein may have a regulatory role on both viral and cellular gene expression. The mechanisms of HCV-RNA replication may include synthesis of negative strand intermediates, which drive synthesis of new positive RNA genomes. New procedures have been developed to better identify and characterize the HCV-RNA genome. The mechanisms of HCV persistence are currently unknown, although it is known that HCV chronicity develops despite humoral and cellular responses to HCV proteins. HCV-RNA shows significant genetic variability with an estimated rate of nucleotide change of approximately 10(-3) substitutions/site/year. Currently, three major HCV genotypes and three to seven minor subtypes can be distinguished. The geographical distribution of these genotypes and subtypes varies significantly. It appears that poor clinical response to interferon (IFN) is more common with HCV genotype 1. In addition, some studies have shown an association between chronic infection, severe chronic hepatitis, and cirrhosis with subtype 1b. Further, there is evidence for a potential direct effect of HCV in liver carcinogenesis, with subtype 1b possibly being an independent risk factor for hepatic carcinoma development. HCV-RNA circulates as a population of RNA molecules, which creates a heterogeneity referred to as "quasispecies." It is possible that some HCV strains might have direct clinical implications. It may be that highly heterogeneous populations observed prior to treatment might correlate with a lower rate of response to IFN therapy.

Infection with GB virus C (GBV-C) in patients with fulminant hepatitis

BACKGROUND/METHODS

There appear to be hepatitis viruses other than hepatitis A, B, C, D and E. One of these has been proposed with a designation of GB virus C. Sera from 44 patients with fulminant hepatitis were tested for RNA of GB virus C by reverse-transcription polymerase chain reaction with nested primers deduced from the putative non-structural 3 (helicase) region.

RESULTS

RNA of GB virus C was detected in three (20%) of 15 patients with hepatitis B virus infection and three (12%) of 25 patients without markers of hepatitis A-E virus infection. Overall, GB virus C RNA was detected in six (14%) of the 44 patients with fulminant hepatitis, at a frequency significantly higher (p < 0.001) than that in three (0.9%) of 326 blood donors matched for age with the patients.

CONCLUSIONS

These results indicate a role of GB virus C in inducing fulminant hepatitis either by itself or in concert with the other hepatitis viruses.

Purification and in vitro-phospholabeling of secretory envelope proteins E1 and E2 of hepatitis C virus expressed in insect cells

The putative envelope glycoproteins of hepatitis C virus (HCV), E1 and E2, were expressed as recombinant, secretory proteins in Sf9 insect cells through infection with recombinant baculoviruses. The influenza virus hemagglutinin signal sequence (HASS) was inserted upstream of the HCV-cDNAs in order to effect secretion. Furthermore, a hexa-histidine tag for purification on a Ni(2+)-nitrilotriacetic acid (Ni(2+)-NTA) column and a protein kinase A (PKA) recognition sequence for in vitro-phospholabeling were fused upstream of the HCV-cDNA. E1- and E2 proteins lacking their carboxy-terminal, hydrophobic sequence were produced by baculovirus-infected insect cells in bioreactors of 23 1. The medium was concentrated and proteins were purified under native conditions on Ni(2+)-NTA columns. Purified proteins could be phospholabeled in vitro using the catalytic subunit of protein kinase. A isolated from bovine heart and gamma-[32P]ATP. Labeled E1 and E2 proteins expressed in insect cells could be immunoprecipitated with sera from HCV-infected patients. Co-expression of these E1 and E2 proteins led to the formation of E1-E2 complexes within the insect cell and to secretion of these complexes into the medium.

Presentation of the hydrophilic domains of hepatitis C viral E2 envelope glycoprotein on hepatitis B surface antigen particles

Subviral particles of hepatitis B virus have been used to present foreign epitopes. We attempted to present the hydrophilic domains of E2 envelope protein of hepatitis C virus (HCV) as a fusion protein with hepatitis B virus surface antigen (HBsAg). The five hydrophilic domains of HCV E2 antigen were inserted into HBsAg such that the inserted hydrophilic domains were presented on the outer surface of HBV subviral particles. In addition, a fusion encoding the hypervariable region (HVR) of E2 antigen was also made. Cell lysate and culture medium were analyzed for the synthesis and secretion of the fusion proteins by immunoprecipitation with polyclonal anti-HBsAg antibody using recombinant vaccinia virus system. The results showed that the fusion proteins containing these six E2 domains were made in the cell, but only two out of six fusion proteins were secreted into culture medium. Further, cesium chloride density gradient analysis and electron microscopy revealed that these fusions were secreted into culture media as particles. It will be of interest to test immunogenicity of the HBsAg fusion particles containing the HCV E2 domains in animal model.

Hepatitis vaccines

The past two decades have seen a series of breakthroughs in the understanding, prevention, and treatment of viral hepatitis. Developed countries have an increasing number of adults who are susceptible to hepatitis A virus (HAV) infection. The licensing of an effective hepatitis A vaccine presents new opportunities for prevention in persons at risk for HAV infection. Hepatitis B virus infection is an important cause of chronic liver disease throughout the world. Although a hepatitis B vaccine has been available in the United States for 15 years, recommendations for its use have undergone changes. Report of the discovery of hepatitis C virus (HCV) in 1989 has led to marked decrease in the risk of transfusion-transmitted viral hepatitis. HCV infection, however, remains a common cause of chronic liver disease, and a hepatitis C vaccine is needed to prevent the consequences of the disease. Basic research into the hepatitis C viral genome has elucidated some of the obstacles in the way of hepatitis C vaccine development.

Pseudouridine for monitoring interferon treatment of patients with chronic hepatitis C

Pseudouridine is a modified nucleoside derived from RNA catabolism; the concentration of this nucleoside is elevated in body fluids of both tumour-bearing and human immunodeficiency virus (HIV) infected patients. We used an HPLC procedure to evaluate the serum pseudouridine concentration in patients with chronic hepatitis C in an attempt to determine whether the nucleoside serum concentration was related to the response to alpha-interferon treatment. We found that: a) pseudouridine serum concentration was increased significantly in 76% (29/39) of patients with chronic hepatitis C at the time of diagnosis and before any therapeutic treatment; b) pseudouridine excretion was higher in patients affected by chronic hepatitis C with cirrhosis; c) there was a positive correlation between response to therapy and pseudouridine serum concentration in patients undergoing treatment with alpha-interferon; d) during one year of alpha-interferon treatment, the pseudouridine serum concentration remained within the normal range in responder patients. These results indicate that serum pseudouridine might be useful as a valuable biochemical marker with which to monitor chronic hepatitis C patients treated with alpha-interferon.

The quantitative humoral immune response to the hepatitis C virus is correlated with disease activity and response to interferon-alpha

BACKGROUND/AIM

Virus-host interactions may have pathogenetic significance in chronic hepatitis. Thus the humoral immune response was evaluated during the clinical course of HCV-infected patients.

METHODS

Eighteen selected chronic HCV patients received three doses of 3 or 6 MU interferon-alpha 2a weekly for 6 to 12 months and were followed up for 6 to 60 months. Anti-HCV antibody levels were serially measured either in end-point diluted sera with the Matrix-Assay or with quantitative anti-HC34-IgG and -IgM ELISA. Circulating immune complexes were assessed by flow cytometry and the results were correlated with histology, quantitative HCV-RNA levels and genotypes.

RESULTS

Nine complete responders (CR; genotypes 1a n = 4; 1b n = 1; 2a n = 1; 3a n = 3) showing sustained virus elimination and ALT normalisation had low HCV-RNA pretreatment levels (mean 14 x 10(3) copies/ml) compared to six nonresponders and three partial responders (NR/PR; genotypes 1a n = 2; 1b n = 7) who had significantly higher HCV-RNA pretreatment levels (mean 254 x 10(3) copies/ml; p < 0.01). In untreated NR/PR the HC34 core-antigen was most immunogenic, in CR the NS3-derived HC29-antigen. Pre-treatment levels of anti-HC 34-IgG and -IgM antibody levels in NR/PR were higher than in CR (IgM/IgG p = 0.05, n.s.) and these differences became significant during or after therapy (3 months therapy: IgM p < 0.02/IgG p < 0.07; end of therapy: IgM 0.006/IgG p < 0.04; 6 months post-therapy: IgM p < 0.002/IgG p < 0.004). The PR patients showed recurrent anti-HC34 antibody levels that preceded disease reactivation and detectable HCV-RNA in serum. Immune complex formation increased in some patients during treatment but did not correlate with disease activity, quantitative viraemia, antibody levels or therapy outcome.

CONCLUSION

Anti-HC34 antibodies, i.e. of the IgM-subtype, correlated quantitatively with viraemia and disease activity. Monitoring the antibody levels may predict the long-term therapy outcome during interferon-alpha treatment.

Serologic diagnosis of viral hepatitis

Viral hepatitis has become a difficult field in which clinical and laboratory skills are needed to establish the correct diagnosis and plan for the appropriate therapy. For example, it is no longer enough to diagnose chronic hepatitis B or C. Now, the viral titer or viral genotype must be known. The laboratory test then must be understood in the context of the clinical presentation. This article helps the clinician to acquire such working knowledge. It summarizes available data for hepatitis A, B, C, D, and E. It also includes the recently discovered viral agents, hepatitis G and the hepatitis GB agents.