Hepatitis C virus antigen in hepatocytes: immunomorphologic detection and identification

Virology of hepatitis C virus

Advances in molecular biology techniques have allowed the cloning of HCV and the characterization of this virus. This article provides a short summary of our current knowledge on the genomic organization of HCV, the implications of its genetic heterogeneous nature, and the probable replication strategy of this virus.

Histopathology of HCV infection

The basic morphologic features of acute and chronic viral hepatitis C are similar to those of other hepatitides; however, hepatitis C is characterized by the histologic triad of lymphoid aggregates in portal tracts, epithelial damage of small bile ducts and microvesicular and macrovesicular steatosis of hepatocytes. Significant progress has been made in the demonstration of HCV in infected liver tissues by immunohistochemical and in situ hybridization techniques. The new classification of chronic hepatitis, based on etiology, grading (extent of necroinflammatory activity) and staging (extent of fibrosis) has been widely accepted and will lead to a better understanding of the variable course and response to therapy of this enigmatic disease.

Histopathology and pathobiology of hepatotropic virus-induced liver injury

The present report concerns current knowledge regarding immunopathogenesis that can be applied in the interpretation of histopathological changes in acute and chronic viral hepatitis. The histopathological features of viral hepatitis have not been changed and light microscopic examination remains essential for making a diagnosis and classification of chronic hepatitis and for the provision of objective parameters on grading and staging. However, new understanding and knowledge of viral pathogenesis, host immune responses, the biological behaviour of the causative viral agents and, in particular, viral interference in multiple hepatotropic viral infections must be taken into consideration in the interpretation of histopathological and immunopathological findings of liver tissues. This report also presents some histopathological analyses on multiple hepatotropic viral infections. It can be concluded that the diagnostic histological criteria for acute hepatitis remain applicable in such settings. However, the cause of acute flare up in chronic hepatitis could not be determined without clinical, virological and serological information. Routine histopathology cannot distinguish a new infection from an acute exacerbation due to a high level of viral replication or mutant virus. A repertoire of immunocytochemical stainings for viral antigens is helpful, but caution must be exercised in suggesting a specific viral aetiology due to the fact that suppression of pre-existing viral antigens can be pronounced when the new or concurrent infection is hepatitis C virus related.

Clinical implications of GBV-C/HGV infection in patients with "HCV-related" chronic hepatitis

BACKGROUND/AIMS

To evaluate the clinical, biochemical and histological implications of a concomitant HGV infection in "HCV-related" chronic liver disease.

METHODS

Eighty-three HCV-RNA positive patients with chronic liver disease were tested for GBV-C/HGV coinfection by heminested PCR.

RESULTS

Twenty-two (26.5%) patients were found to be positive for GBV-C/HGV RNA. GBV-C/HGV+ patients differed significantly from GBV-C/HGV- ones for younger age, higher frequency of history of drug addiction, which in turn might favor coinfection with interferon-sensitive HCV genotypes (3a), and increased probability of long-term response to interferon. GBV-C/HGV infection appears to have no responsibility for specific aspects of HCV infection such as biochemical or histological cholestatic features, lymphoid follicles, symptomatic cryoglobulinemia or presence of serum autoantibodies, including LKM1. It does not worsen the HCV-related disease (ALT levels and histological activity) and does not significantly interfere with HCV infection, as explored by the number of hepatocytes positive for HCV antigens. The amount of steatosis (mean score) was shown to be higher in GBV-C/HGV+ patients. A virological follow up was performed in 17 interferon-treated GBV-C/HGV+ patients On the whole, GBV-C/HGV seems to be as sensitive to IFN treatment as HCV, but recurrence after withdrawal is more frequent. In spite of this, ALT levels often remain normal after treatment withdrawal.

CONCLUSIONS

The present data suggest that GBV-C/HGV infection, apart from more marked liver steatosis, does not modify the overall picture of chronic hepatitis due to HCV infection.

Nonstructural protein 3 of hepatitis C virus blocks the distribution of the free catalytic subunit of cyclic AMP-dependent protein kinase

Chronic hepatitis resulting from hepatitis C virus (HCV) infection develops into cirrhosis in at least half of infected patients and increases the risk of hepatocellular carcinoma. The pathogenic effects of a number of viruses result from the disturbance of intracellular signal cascades caused by viral antigens. Therefore, we investigated the interaction of nonstructural protein 3 (NS3) of HCV with the cyclic AMP-dependent signal pathway. We found a similarity between the HCV sequence Arg-Arg-Gly-Arg-Thr-Gly-Arg-Gly-Arg-Arg-Gly-Ile-Tyr-Arg localized in NS3 and the general consensus sequence of protein kinase A (PKA). Consequently, the catalytic (C) subunit of PKA bound to a bacterially expressed fragment of HCV polyprotein containing amino acid residues 1189 to 1525. When this fragment was introduced into cells, it inhibited the translocation of the C subunit into the nucleus after stimulation with forskolin. The result of this inhibition was significantly reduced histone phosphorylation. Therefore, the presence of NS3 in the cytoplasm of infected cells may affect a wide range of PKA functions and contribute to the pathogenesis of the diseases caused by HCV.

Quantitative liver parameters of HCV infection: relation to HCV genotypes, viremia and response to interferon treatment

BACKGROUND/AIMS

This study aimed to evaluate the relation between the number of hepatocytes positive for HCV antigens and the amount of HCV RNA in the liver and to evaluate the relationship between the above parameters and viremia levels, HCV genotype and response to interferon treatment.

METHODS

This was a retrospective study on 31 consecutive patients with chronic HCV-related liver disease, selected on the basis of the availability of frozen liver tissue for both liver HCV antigens detection and liver HCV RNA quantitation. HCV antigens (immunohistochemistry), liver and plasma HCV RNA (competitive RT-PCR), and HCV genotype (commercial kit) were studied.

RESULTS

A significant correlation (p=0.0005) was found between the amount of liver HCV RNA (log 10 copy/microg of extracted RNA) and the number of HCV-infected hepatocytes (scored from 0 to 3). These parameters were not significantly correlated with viremia levels. The highest liver HCV RNA levels and HCV antigen scores were found in patients infected with genotype 1b. Liver HCV RNA (median 541 x 10(3) vs 118 x 10(3) copy number/microg, p=0.031) and liver HCV antigens (mean score 2.3 vs 1.3, p=0.018) but not plasma HCV RNA (median 14956 x 10(3) vs 2885 [correction of 2.885] x 10(3) copy number/ml, ns) were significantly higher in patients not responding to interferon treatment compared to responders.

CONCLUSIONS

The tissue parameters tested in this study were significantly correlated, shared the same clinical implications and predicted short-term response to interferon treatment better than viremia levels. We suggest that these tests should be included in the study protocol of patients under evaluation for interferon treatment, basing the choice on local facilities.

Acute non-A-E hepatitis in the United States and the role of hepatitis G virus infection. Sentinel Counties Viral Hepatitis Study Team

BACKGROUND

Little is known about the relation of the newly discovered hepatitis G virus (HGV) to the cause and clinical course of acute and chronic viral hepatitis.

METHODS

We selected patients from a surveillance study of acute viral hepatitis in four U.S. counties who had acute disease during 1985 to 1986 or 1991 to 1995. Serum samples were tested for HGV RNA by the polymerase chain reaction.

RESULTS

HGV RNA was detected in 4 of 45 patients with a diagnosis of non-A-E hepatitis (9 percent), 23 of 116 patients with hepatitis C (20 percent), 25 of 100 patients with hepatitis A (25 percent), and 32 of 100 patients with hepatitis B (32 percent) (P<0.05 for the comparison of hepatitis B with hepatitis non-A-E or C). The clinical characteristics of the acute illness were similar for patients with HGV alone and those with hepatitis A, B, or C with or without HGV infection. During a follow-up period of one to nine years, chronic hepatitis did not develop in any of the patients with HGV alone, but 75 percent were persistently positive for HGV RNA, as were 87 percent of those with both hepatitis C and HGV infection. The rates of chronic hepatitis were similar in patients with hepatitis C alone (60 percent) and those with both hepatitis C and HGV infection (61 percent).

CONCLUSIONS

The evidence from this surveillance study does not implicate HGV as an etiologic agent of non-A-E hepatitis. Persistent infection with HGV was common, but it did not lead to chronic disease and did not affect the clinical course in patients with hepatitis A, B, or C.

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.

Comparative features of hepatitis C virus infection in humans and chimpanzees

Several features of human HCV infection are recapitulated in the chimpanzee model. Most importantly, the frequency of persistent infection is high in both species, and virus replication occurs despite evidence of cellular and humoral immune responses. A key difference is that necroinflammatory lesions in chronically infected chimpanzees are almost always mild, whereas in humans the disease spectrum is very wide, ranging from mild to severe hepatitis and end-stage cirrhosis requiring transplantation. Understanding the basis for both the similarities and differences in persistent hepatitis C in the two species will probably be important for the development of effective prevention and therapy of HCV infection.

A histopathological study of the effects of 6-month versus 12-month interferon alpha-2b therapy in chronic hepatitis C

BACKGROUND/AIMS

Interferon therapy has been shown to have beneficial effects in chronic hepatitis C, but the optimal duration of treatment has not been clearly defined. The aims of this study were: (a) to perform a detailed histological comparison of the effects of a 6-month and a 12-month treatment using the Knodell score as well as a recently proposed grid of analysis, (b) to determine possible histological predictive factors of response to therapy, and (c) to attempt to relate histological and biochemical modifications.

METHODS

Liver biopsies obtained before and 18 months after beginning of treatment were therefore compared in 26 patients treated for 6 months, and in 34 patients treated for 12 months.

RESULTS

Six months of treatment induced a significant decrease in periportal (p = 0.02) and intralobular (p = 0.004) hepatocyte necrosis. The same items were improved in the 12-month-treated patients but, in addition, portal inflammation (p = 0.01), bile duct lesions (p = 0.03), lymphoid aggregates (p = 0.002) and fibrosis (p = 0.008) were also improved, according to the Knodell score. Low scores for fibrosis, steatosis and cholangiolar proliferation on the pretreatment liver biopsy could be considered predictive factors for alanine aminotransferase normalization at 6 months. There was no relationship between biochemical response and modification of fibrosis.

CONCLUSION

Our results suggest that: (a) a decrease in fibrosis might be detected only after a 12-month interferon treatment, and (b) initial fibrosis, cholangiolar proliferation and steatosis are predictive of a lack of biochemical response. The absence of a relation between biochemical response and evolution of fibrosis implies that the evaluation of treatments in chronic hepatitis C should always include a detailed histopathological study.

Hepatitis C virus RNA quantification in right and left lobes of the liver in patients with chronic hepatitis C

Quantification of hepatitis C virus RNA in liver tissue is likely to be useful in the study of the natural history, pathogenesis, progression and treatment of hepatitis C virus-associated liver disease. Quantitative measurements of hepatitis C virus RNA in liver biopsy samples using the branched DNA (bDNA) signal amplification assay were carried out. The aims of this study were threefold: first, to assess the level of hepatitis C virus RNA in biopsy samples from the right and left lobes of the liver; second, to evaluate the correlation between hepatitis C virus RNA levels in serum and liver; and third, to investigate the relationship between serum and liver hepatitis C virus RNA levels and the severity of hepatic histology in non-cirrhotic patients with chronic hepatitis C. There was a strong correlation (r = 0.92, P < 0.01) between hepatitis C virus RNA levels in the right and left lobes of the liver as well as a strong correlation between hepatitis C virus RNA levels in liver and serum (r = 0.82, P < 0.01). However, there was no significant correlation between the severity of hepatic histology and levels of hepatitis C virus RNA in serum and liver among patients with chronic active hepatitis classified according to Knodell's hepatic activity index (KI). Our results indicate that hepatitis C virus RNA quantification from a single liver biopsy is representative of both lobes in patients with chronic hepatitis, and suggest that serum hepatitis C virus RNA levels are a meaningful reflection of hepatitis C virus RNA levels in the liver.

Liver-infiltrating and circulating CD4+ T cells in chronic hepatitis C: immunodominant epitopes, HLA-restriction and functional significance

The aim was to assess the specificity and functional significance of liver-infiltrating and peripheral blood T cells in chronic hepatitis C. Peripheral blood mononuclear cells hepatitis C virus from 50 of 58 (86.2%) patients with chronic hepatitis C virus infection and 6 of 28 (21.4%) controls showed a proliferative T cell response to at least one of 16 synthetic peptides covering highly conserved regions of the core, envelope (El) and non-structural regions (NS4) of hepatitis C virus. However, six immunodominant peptides were exclusively recognized by the proliferating blood mononuclear cells from 46 patients with chronic hepatitis C virus infection (79.3%). Fine specificity and HLA-restriction were studied with 15 peptide-specific CD4+ T cell lines and 23 T cell clones isolated from liver tissue and peripheral blood of 12 patients with chronic hepatitis C. It was demonstrated that the peptide-specific response of CD4+ T cells was restricted to the presence of autologous accessory cells and HLA-DR and -DP molecules. Eight peptide-specific T cell lines and five T cell clones derived from liver tissue and peripheral blood, released interferon-gamma (200-6600 pg/ml) and tumor necrosis factor-alpha (100-400 pg/ml) and no or little interleukin-4 (< 140 pg/ml) after peptide-specific or mitogeneic stimulation, thus resembling a Th1-like cytokine profile. Patients with active liver disease showed significantly higher proliferative responses to hepatitis C virus core peptides than asymptomatic hepatitis C virus carriers or complete responders to interferon therapy. In conclusion, class II-restricted CD4+ T cell responses to some immunodominant epitopes within the hepatitis core region correlated with disease activity in chronic hepatitis C virus infection. Functionally, liver-infiltrating and peripheral blood T cells released Th1-like cytokines in response to the specific stimulus. Thus, it can be suggested that CD4+ T cells can mediate the pathogenesis of chronic hepatitis C virus induced liver disease.

Non-structural protein 3 of hepatitis C virus inhibits phosphorylation mediated by cAMP-dependent protein kinase

Inspection of the amino acid sequence of the non-structural region of the hepatitis C virus (HCV) gene product reveals a sequence of 14 amino acids, Arg1487-Arg-Gly-Arg-Thr-Gly-Arg-Gly-Arg-Arg-Gly-Ile-Tyr-Arg1500 , located in the non-structural protein, NS3. This sequence is highly similar to the inhibitory site of the heat-stable inhibitor of cAMP-dependent protein kinase (PKA) and to the autophosphorylation site in the hinge region of the PKA type II regulatory domain. A synthetic peptide that corresponds to the HCV sequence above and a set of shorter analogues act as competitive inhibitors of PKA. A 43.5-kDa fragment of NS3 that consists of residues 1189-1525 of the HCV polyprotein inhibits PKA in a similar range to the investigated synthetic peptides. In contrast to the short peptides, which show competitive inhibition, HCV-polyprotein-(1189-1525) influences PKA in a mixed-inhibition-type manner. A possible mechanism explaining these differences is the formation of complexes that consist of the protein substrate, the enzyme and the HCV-polyprotein-(1189-1525). Binding studies with PKA and the non-hydrolysable ATP analogue [14C]fluorosulfonylbenzoyladenosine and [3H]cAMP do not reveal any influence of the short HCV-derived peptides or HCV-polyprotein-(1189-1525) upon the affinity of PKA for these nucleotides. The complex interactions of the NS3 fragments could influence one of the most important signal pathways of the cell and, therefore, could possibly provide new pathological mechanisms for HCV infections of liver.

Characterization of three novel monoclonal antibodies against hepatitis C virus core protein

Three novel monoclonal antibodies (MAbs) were established against a recombinant hepatitis C virus (HCV) core protein derived from cloned genotype 1b HCV cDNA. MAbs C7-50 and C8-59 recognize a conserved linear epitope represented by amino acid residues 21 to 40 of the nucleocapsid protein. MAb C8-48 is directed against a strain-specific conformational epitope located within the first 82 amino acids. A sensitive two-site MAb-based immunoradiometric assay was established using antibodies directed against distinct epitopes on the nucleocapsid protein. Processed 21 kDa core protein was detected by immunoblotting in human hepatocellular carcinoma cell lines and primary adult rat hepatocytes transfected with a cytomegalovirus promoter-driven expression construct. Immunofluorescence microscopy studies revealed a granular and vesicular cytoplasmic staining pattern. MAb C7-50 was used successfully to detect HCV core antigen in chronically infected chimpanzee liver tissue. These MAbs represent important reagents for the study of HCV biology and for the development of immunodiagnostic assays.

Detection of hepatitis C virus (HCV) proteins by immunofluorescence and HCV RNA genomic sequences by non-isotopic in situ hybridization in bone marrow and peripheral blood mononuclear cells of chronically HCV-infected patients

Immunofluorescence (IF) to detect HCV antigens and non-isotopic in situ hybridization (NISH) to detect HCV RNA genome were carried out on bone marrow (BM) and peripheral blood (PB) mononuclear cells (MC) of 11 chronically HCV-infected patients. In four patients (36.4%) HCV antigens were detected in monocytes/macrophages as well as in B lymphocytes in both BMMC and PBMC. Positive T lymphocytes in BMMC were found in three of them, but only one patient showed positive T cells in PBMC. NISH invariably demonstrated minus and plus HCV RNA genomic strands either in monocytes/macrophages or B and T lymphocytes in BMMC and PBMC in the four HCV antigen-positive patients and in two further patients not expressing viral proteins in blood MC. IF signals appeared diffusely distributed within the cytoplasm, or as brilliant granules in distinct submembrane areas or else in cytoplasm membrane. Nuclei never stained. Similarly, NISH displayed HCV RNA accumulation restricted to MC cytoplasm only, nuclei being persistently negative. NISH, however, was unable to detect cell membrane signal. Infection of blood MC is a common event in naturally acquired HCV infection, since none of these patients was conditioned by immunomodulating or immunosuppressive therapies. No difference was found in terms of age, length of disease, anti-HCV immune response, type and severity of chronic liver damage between patients with HCV-infected MC and patients without cell infection. These results demonstrate that HCV can infect BMMC and PBMC that represent important extrahepatic sites of virus replication, and may help to explain the immunological abnormalities observed in chronic HCV carriers.

Distribution of hepatitis C virus RNA in the liver and its relation to histopathological changes

To investigate a cellular mode of HCV-infection in the liver and its pathological implications in relation to histopathological changes or clinical data, we studied the distribution of HCV-RNA in the livers of 21 patients with HCV-related chronic liver disease (chronic active hepatitis, 14 cases; cirrhosis, 7 cases) using the in situ hybridization technique. In situ hybridization was performed on 4% paraformaldehyde-fixed frozen sections with digoxigenin-labeled DNA probe deduced from the core region of HC-J4. In situ hybridization showed positive signals in the liver specimens of 20/21 cases. The signals were localized in the cytoplasm of hepatocytes. The distribution pattern of positive cells was individually different, whereas the pattern was identical in the right and left lobes. There were no correlations of the HCV-positive cell number with serum aminotransferase levels at biopsy or with genotypes of HCV. The positive hepatocytes were occasionally associated with infiltrating mononuclear cells, and they were sparsely distributed in the area of piecemeal necrosis. These findings suggest that factors such as host immunoreaction to the virus may be more important than its direct cytopathy in the pathogenesis of chronic hepatitis C virus infection.

Sequence-based identification of microbial pathogens: a reconsideration of Koch's postulates

Over 100 years ago, Robert Koch introduced his ideas about how to prove a causal relationship between a microorganism and a disease. Koch's postulates created a scientific standard for causal evidence that established the credibility of microbes as pathogens and led to the development of modern microbiology. In more recent times, Koch's postulates have evolved to accommodate a broader understanding of the host-parasite relationship as well as experimental advances. Techniques such as in situ hybridization, PCR, and representational difference analysis reveal previously uncharacterized, fastidious or uncultivated, microbial pathogens that resist the application of Koch's original postulates, but they also provide new approaches for proving disease causation. In particular, the increasing reliance on sequence-based methods for microbial identification requires a reassessment of the original postulates and the rationale that guided Koch and later revisionists. Recent investigations of Whipple's disease, human ehrlichiosis, hepatitis C, hantavirus pulmonary syndrome, and Kaposi's sarcoma illustrate some of these issues. A set of molecular guidelines for establishing disease causation with sequence-based technology is proposed, and the importance of the scientific concordance of evidence in supporting causal associations is emphasized.

Significance of hepatic expression of hepatitis C viral antigens in chronic hepatitis C

To determine the significance of hepatic expression of hepatitis C viral (HCV) antigens, HCV core and NS4 antigens were detected by immunohistochemistry in 46 patients with chronic HCV infection. Serum HCV RNA was quantitated by branched DNA assay in 41 and HCV genotype determined in 30 patients. HCV core and NS4 antigens were detected exclusively in the cytoplasm of hepatocytes in 83% and 61% of patients, respectively. There was no correlation between the expression of HCV antigens and clinical, biochemical, histological parameters and HCV genotype. Hepatic expression of HCV antigens was positively associated with serum HCV-RNA levels (P < 0.02). At the end of interferon-alpha (IFN) therapy, expression of HCV antigens remained either unchanged or decreased in 11/12 patients studied (undetectable in all four patients who had complete and sustained response). We conclude that hepatic expression of HCV core and NS4 antigens parallels serum HCV-RNA levels and IFN therapy reduces hepatic expression of these viral antigens.

Detection by in situ hybridization of hepatitis C virus positive and negative RNA strands using digoxigenin-labeled cRNA probes in human liver cells

In situ hybridization was performed using cRNA probes on human liver biopsies to localize both positive and negative RNA strands of hepatitis C virus. From the 5' non-coding region of the viral genome, 210 bp, were amplified by reverse transcriptase-polymerase chain reaction and cloned in a plasmid. Probes were produced by in vitro transcription, and labeled using digoxigenin-11-UTP. Positive HCV-RNA strands were detected in all 20 of the patients analyzed, whereas negative strands were detected in only nine patients, as confirmed using computerized image analysis. Both probes labeled the cytoplasm of hepatocytes with a perinuclear intensification. Few of the mononuclear cells infiltrating the portal connective space contained positive HCV-RNA strands only. Stacks of dilated endoplasmic reticulum cisternae were observed by electron microscopy and their relationship with the infection was discussed. This study confirmed that non-radioactive in situ hybridization represents a useful tool to analyze the localization and replication of hepatitis C virus in liver tissue.

Plasma glutathione concentration in patients with chronic hepatitis C virus infection

It has recently been proposed that a depletion of glutathione (GSH) may be a contributing factor to viral persistence and resistance to interferon-alpha (IFN-alpha) therapy in chronic hepatitis C virus (HC) infection. The aim of this study was: (1) to compare plasma GSH levels in patients with chronic HCV infection and normal healthy controls; and (2) to correlate GSH levels with liver histology and serum HCV RNA levels. Twenty-four patients with compensated chronic hepatitis C and 27 healthy subjects were studied. Serum and heparinized plasma were prospectively prepared and frozen within 1 h of collection. Plasma glutathione and glutathione peroxidase (GP) levels were measured spectrophotometrically. The serum HCV RNA level was quantitated by the branched chain DNA signal-amplification assay. Plasma GSH levels were not decreased in patients with chronic HCV infection but were actually greater than in controls (control 1.27 +/- 0.12 micrograms ml-1, HCV 1.62 +/- 0.11 micrograms ml-1, P < 0.05). There was also no difference in plasma GP activity between these two groups (control 0.233 +/- 0.007 U ml-1, HCV 0.230 +/- 0.007 U ml-1). Among the patients with chronic HCV infection, there was no correlation between either plasma GSH or GP levels and the serum alanine aminotransferase (ALT) or aspartate aminotransferase (AST), serum HCV RNA level, or liver histology. This study demonstrates that chronic HCV infection does not decrease the plasma GSH and GP levels.

Hepatitis C virus (HCV) genotype, tissue HCV antigens, hepatocellular expression of HLA-A,B,C, and intercellular adhesion-1 molecules. Clues to pathogenesis of hepatocellular damage and response to interferon treatment in patients with chronic hepatitis C

To obtain information on the mechanisms of hepatocellular damage and the determinants of response to interferon, hepatitis C virus (HCV) genotype, tissue HCV antigens, hepatocellular expression of HLA-A,B,C and intercellular adhesion-1 molecules, and the number of lobular T lymphocytes were studied in 38 anti-HCV-positive patients. 14 patients did not show a primary response to interferon treatment. HCV genotype 1b was detected in 11 of them. They displayed higher scores of HCV-positive hepatocytes, HLA-A,B,C, and ICAM-1 molecules expression than with the responders. HCV-infected hepatocytes maintained the capacity to express HLA-A,B,C and ICAM-1 molecules. CD8-positive T cells in contact with infected hepatocytes and Councilman-like bodies were observed. A significant correlation was found between the number of lobular CD8-positive T cells and alanine amino transferase levels. No differences were observed in clinical, biochemical, and histological features between patients with high and low number of hepatocytes containing HCV antigens. These data suggest a prominent role of T cell-mediated cytotoxicity in the genesis of hepatocellular damage. The high expression of interferon-inducible antigens like HLA-A,B,C molecules suggests the presence of strong activation of the interferon system possibly related to high HCV replication in nonresponder patients infected with genotype 1b.

Pathology of hepatitis C virus infection

This paper reviews our current knowledge of hepatitis C virus, its structure, epidemiology and pathological effects in man. The histopathological features of acute and chronic hepatitis due to hepatitis C virus are detailed and illustrated. The possible pathogenetic mechanisms involved in the liver injury are outlined and the significance of genotypic subtypes of the virus and of host genetic predisposition in relation to the liver injury and the response to therapy are summarized.

Hepatocellular codistribution of c100, c33, c22, and NS5 hepatitis C virus antigens detected by using immunopurified polyclonal spontaneous human antibodies

Hepatitis C virus (HCV) antigens in liver biopsy have been detected by immunohistochemistry using both spontaneous human IgG and murine monoclonal or rabbit polyclonal monospecific reagents. Conflicting results have been obtained in different studies. This was probably because of the incapacity of single experimental antibodies, raised against synthetic or recombinant peptides, to recognize native tissue antigens. To overcome this possibility, we immunopurified monospecific spontaneous polyclonal human Ig, therefore induced by native antigens, from the single antigen-containing bands of RIBA 3 strips. Antibodies to c100, c33, c22, and NS5 antigens were obtained from the serum of a patient affected by chronic hepatitis C. The IgG fraction of this serum had proved to stain tissue HCV antigens. Eight biopsies were selected on the basis of strong hepatocellular reactivity with the whole IgG fraction in a variable number (from 5% to 75%) of cells. The four antigens were detected in all biopsies; a clear cellular codistribution was observed on serial sections. These data demonstrate that the possibility to identify HCV antigens in liver biopsies is higher when using human antibodies induced by native antigens rather than experimental antibodies. The approach of immunopurification of human antibodies can be extended to other HCV-related epitopes to obtain reagents useful for the selection and optimization of monoclonal or polyclonal antibodies.

Intrahepatic expression of hepatitis C virus antigens in chronic liver disease

Localization of hepatitis C virus (HCV) antigens was studied in fresh frozen and formalin-fixed, paraffin-embedded liver tissue by immunoperoxidase using monoclonal antibodies to nucleocapsid protein and polyclonal human immunoglobulin G purified from plasma containing antibodies to structural and non-structural antigens of hepatitis C virus. The results observed using monoclonal antibody to HCV core were similar to those of polyclonal IgG against HCV antigens in the majority of cases and both correlated well with HCV status as defined by 'nested' polymerase chain reaction. HCV antigens were detected in both hepatocytes and mononuclear cells. Using polyclonal human IgG, a small proportion of biliary epithelial cells were also positive in 6/29 patients. In most of the specimens examined, relatively few cells (1-5 per cent) were found to be positive for HCV antigens. The cryostat sections, using polyclonal IgG against HCV antigens, exhibited greater immunohistochemical staining, suggesting that the fixation and processing of the tissue may be a major factor in the conservation and the outcome of HCV antigen(s) findings. However, the results using monoclonal antibodies may reflect the specificity of antigen expression.

Detection of hepatitis C virus RNA by in situ hybridization: a critical appraisal

Despite the several papers that have appeared in the literature or have been communicated at scientific meetings, the detection of hepatitis C virus RNA by in situ hybridization seems a difficult goal to achieve. There have been conflicting reports on the type and proportion of hepatitis C virus-infected cells, the intracellular distribution of viral RNA and the topographical association with cell damage. As a consequence, some of the findings should probably be considered as non-specific and all protocols and data critically reviewed before a firm conclusion be made.

Hepatitis C virus appears to replicate not only in hepatocytes but also in hepatocellular carcinoma cells as demonstrated by immunostaining

Persistent infection with hepatitis C virus is a major risk factor for the development of hepatocellular carcinoma (HCC). It has been unclear whether hepatitis C virus replicates in HCC. A total of 39 hepatitis B surface-antigen-negative HCC were resected surgically at Nihon University Itabashi Hospital between January 1990 and December 1992. Of them, serum anti-hepatitis C was positive in 28 cases, negative in three and not examined in eight. The indirect immunoperoxidase technique was used for detection of the hepatitis C core antigen on formalin-fixed, paraffin-embedded sections. Positive staining was found within non-tumor hepatocytes in 22 (78.6%), one and four cases, respectively. Fourteen (58.3%) of these 24 cases, which were positively immunostained in non-tumor hepatocytes (three were excluded because of complete necrosis of HCC), were also stained for the core antigen in HCC cells. Core antigen was stained in both hepatocytes and HCC cells within the cytoplasm, diffusely or focally with varying intensity in a local or patchy distribution. Hepatitis C virus appears to replicate in HCC cells and the significance of such viral replication in hepatocarcinogenesis remains to be clarified.

Expression of cytokine-dependent immune adhesion molecules by hepatocytes and bile duct cells in chronic hepatitis C

BACKGROUND/AIMS

The pathogenesis of liver cell injury in chronic hepatitis C is poorly understood. To test whether immune-mediated mechanisms might be involved in the pathogenesis of liver cell injury during infection by hepatitis C virus, the expression of cytokine-dependent immune molecules by hepatocytes and bile duct cells during chronic hepatitis C was studied.

METHODS

In 35 patients, expression of class I and II HLA antigens, intercellular adhesion molecule (ICAM) 1, and lymphocyte function antigen (LFA) 3 was studied by immunohistochemistry and scored by a semiquantitative grading system. Statistical analysis was performed using Spearman's test and t test.

RESULTS

Class I HLA antigens were induced on hepatocytes in 20 cases. In all cases, HLA-DR, ICAM-1, and/or LFA-3 were detected on hepatocytes in piecemeal necrosis and intralobular clusters. Bile duct cells expressed HLA-DR in 32 cases and ICAM-1 and LFA-3 in 14 cases. Expression levels of immune molecules on hepatocytes correlated with aminotransferase activity (P < 0.035), histological activity (P < 0.001), and score of necrosis (P < 0.01). ICAM-1 expression on hepatocytes was higher in patients with intraportal lymphoid nodules (P = 0.005). Expression levels of ICAM-1 and LFA-3 on bile ducts correlated with the severity of bile duct damage (P < 0.015).

CONCLUSIONS

These results suggest the involvement of immune-mediated mechanisms in the pathogenesis of liver cell injury in chronic hepatitis C.

Relationship between serum HCV markers and response to interferon therapy in chronic hepatitis C. Evaluation of HCV genotypes during and after long-term follow-up

Hepatitis C virus is the most frequent cause of chronic non-A, non-B hepatitis, and the antibodies to structural and nonstructural proteins encoded by viral genome have been suggested to be markers of ongoing HCV infection. We studied the behavior of these antibodies during interferon therapy in 18 patients with chronic hepatitis C and also during a follow-up period of at least four years. A significant decrease of anti-HCV titer was found only in patients who had shown positive response to therapy and all of them were anti-HCV negative at the end of follow-up. Analysis by recombinant immunoblotting assay showed that only anti-c100 were affected by interferon therapy, whereas anti-c22 and anti-c33 were not modified. Using polymerase chain reaction to detect small amounts of HCV genome in serum, we could confirm that the behavior of HCV-RNA during and after interferon therapy is similar to that of anti-HCV and the loss of anti-c100 seems to be closely related to HCV-RNA disappearance from serum. Our patients with chronic hepatitis C were found to be of type 1b and 2, according to the recent score of Simmonds, and the clearance of serum HCV-RNA during treatment and its sustained negative status are closely related to genotype 2 and to long-term positive response to interferon.

Hepatitis C: progress and problems

The hepatitis C virus (HCV), a single-stranded RNA virus, is the major cause of posttransfusion hepatitis. HCV isolates differ in nucleotide and amino acid sequences. Nucleotide changes are concentrated in hypervariable regions and may be related to immune selection. In most immunocompetent persons, HCV infection is diagnosed serologically, using antigens from conserved regions. Amplification of RNA may be necessary to detect infection in immunosuppressed patients. Transmission by known parenteral routes is frequent; other means of spread are less common and may represent inapparent, percutaneous dissemination. Infection can lead to classical acute hepatitis, but most infected persons have no history of acute disease. Once infected, most individuals apparently remain carriers of the virus, with varying degrees of hepatocyte damage and fibrosis ensuing. Chronic hepatitis may lead to cirrhosis and hepatocellular carcinoma. However, disease progression varies widely, from less than 2 years to cirrhosis in some patients to more than 30 years with only chronic hepatitis in others. Determinants important in deciding outcome are unknown. Alpha interferon, which results in sustained remission in selected patients, is the only available therapy. Long-term benefits from such therapy have not been demonstrated. Prevention of HCV infection by vaccination is likely to be challenging if ongoing viral mutation results in escape from neutralization and clearance.

Viral specificity of hepatitis E virus antigens identified by fluorescent antibody assay using recombinant HEV proteins

A fluorescent antibody (FA) assay for hepatitis E virus antigen (HEVAg) in infected liver tissue was used to confirm the presence of virus-specific antigens in hepatocytes during the course of infection. With the cloning of the HEV genome it is now possible to determine which viral antigens are recognized by this FA assay. Recombinant HEV proteins covering the carboxyl half of HEV open reading frame 2 (ORF2) were used in this study to demonstrate that some of the most immunoreactive virus-specific antigens detected by FA are contained within this region of ORF2 (nucleotides 6169-7126).

Immune response to a hepatitis C virus nonstructural protein in chronic hepatitis C virus infection

The immune responses to a hepatitis C virus nonstructural protein (T3Ag) overlapping with the C100-3 antigen were examined in three groups of patients with chronic non-A, non-B hepatitis. Group I included 20 cases positive for both anti-C100-3 and the second-generation anti-HCV test (anti-HCV-II): Group II, five cases with anti-C100-3(-)/anti-HCV-II(+); and Group III, seven cases negative for both tests. HCV RNA was detectable in 20 (100%), 4 (80%) and 0 (0%) patients in each group, respectively. Proliferative responses of peripheral blood mononuclear cells to T3Ag were present in 16 (80%), 3 (60%) and 0 (0%) cases in each group, respectively (p < 0.05). Removal of CD8+ T cells from peripheral blood mononuclear cells resulted in a conversion of unresponsiveness to significant proliferation to T3Ag in the remaining cases in groups I and II, but not in group III. This change paralleled the antigen-induced production of interferon-gamma and interleukin-2, but not interleukin-4. The removal also enhanced the T3Ag-stimulated anti-C100-3 antibody production from cultured peripheral blood mononuclear cells in group II patients. These results indicate that the T3Ag-specific type 1 T helper cells play an important role in regulating anti-C100-3 antibody secretion in hepatitis C patients.

Pathology of hepatitis C

The basic morphological patterns of acute or chronic viral hepatitides are very similar, irrespective of the causative hepatitis viruses A, B, C, D or E. In addition, however, acute and chronic hepatitis C shows characteristic, although not pathognomonic histological changes. These consist of lymphoid aggregates in portal tracts, sometimes with germinal centers, damage of bile duct epithelium, and micro- or macrovesicular steatosis of hepatocytes. A combination of two of these three characteristic alterations is seen in over half of the patients with chronic hepatitis C and is helpful in the histological diagnosis of the disease.

Interferon therapy for hepatitis C

Initial trials indicated that around 50% of patients respond to recombinant alpha interferon by normalizing alanine aminotransferase (ALT) at the end of therapy and that half of these relapsed within 6 months following cessation of treatment. Both dose and duration of treatment are critical in the response to therapy. Higher doses and longer duration have been suggested to be more effective than the current recommendations of 3 MUI thrice weekly for 6 months based on results of these initial studies which used ALT and histological scores to evaluate the efficacy of interferon therapy. Following studies using virological markers have shown that improvements in clinical features of disease are associated with decrease or loss of hepatitis C virus (HCV) from serum and liver. The heterogeneity of the response rates between clinical centers using identical protocol emphasizes that the selection of the patients treated was as important for the outcome that the therapy regimen itself with better responses in cases without cirrhosis and with low levels of HCV RNA. Furthermore, the genotype of HCV seems to be also critical for the response rate. Virological evaluations appears therefore crucial to assess not only HCV infection but also for the indication and monitoring of therapy.

Serial quantitative analysis of serum hepatitis C virus RNA level in patients with acute and chronic hepatitis C

To examine changes in the serum level of hepatitis C virus RNA in acute and chronic phases of hepatitis C virus infection, we tested serial serum samples of six patients with acute hepatitis C (posttransfusion: three; sporadic: three) and 11 patients with chronic hepatitis C using a competitive reverse transcription and polymerase chain reaction assay. The internal standard consisted of known amounts of synthetic mutated RNA. No patient with acute hepatitis showed resolution during the follow-up period (24-57 weeks). In posttransfusion cases, titers of hepatitis C virus RNA (log10[hepatitis C virus RNA copies/ml serum]) rose to a high level (7.5-9.5) in the early phase of infection (4-12 weeks after the transfusions) in association with the first serum alanine aminotransferase peaks. Titers of hepatitis C virus RNA then decreased, while serum alanine aminotransferase levels fluctuated with multiple peaks. In sporadic cases, titers of hepatitis C virus RNA had already reached a high level (7.0-7.5) at the first alanine aminotransferase peaks 2-3 weeks after the clinical onset. In chronic hepatitis C virus infection, titers of hepatitis C virus RNA remained high for follow-up periods of 6-12 years in patients with chronic active hepatitis. These results indicate that the replication of hepatitis C virus rose to a high level in the early phase of infection and that a high replicative level of hepatitis C virus might be related with progression of liver disease in the chronic phase of infection.

Serum hepatitis C virus RNA quantity and histological features of hepatitis C virus carriers with persistently normal ALT levels

We studied hepatitis C virus carriers with normal liver function to evaluate the histological features of their livers and the replicative levels of hepatitis C virus. Liver biopsies were performed in 22 hepatitis C virus carriers with persistently normal ALT levels. Hepatitis C virus RNA in serum was quantified with a competitive assay that combined reverse transcription and the polymerase chain reaction, which is based on co-amplification of the target RNA with known amounts of synthetic mutated RNA. Three patients had normal livers on histological study, whereas the other 19 had chronic persistent hepatitis, with lymphoid infiltrates or aggregates in portal tracts commonly observed but intralobular inflammatory changes absent or minimal. The titer of hepatitis C virus RNA (logarithmic transformed copy number per milliliter of serum) varied from 4.0 to 8.0 (mean +/- S.D.: 6.3 +/- 1.1); it was significantly lower in the three patients with normal livers (4.3 +/- 0.2) than in those with chronic persistent hepatitis with mild (6.4 +/- 0.8, n = 11) or moderate (7.1 +/- 0.5, n = 8) portal inflammation. The titer of hepatitis C virus RNA was correlated with the total score (r = 0.68) and the score for portal inflammation (r = 0.68) in the histological activity index. These results indicated that there seem to be "healthy carriers" of hepatitis C virus with extremely low levels of viral replication. However, in most hepatitis C virus carriers with persistently normal ALT levels, there are inflammatory changes in the portal tracts, with severity depending on the replicative levels of hepatitis C virus.

Rolling review--the pathogenesis, diagnosis and management of viral hepatitis

Five major hepatotrophic viruses have been identified. The pathogenesis, diagnosis and treatment of chronic viral hepatitis continues to be intensely researched. Experimental evidence suggests that HLA restricted virus-specific T cells play a role in hepatocellular injury in type A hepatitis. The absence of chronic infection indicates the effectiveness of the host immune response to hepatitis A virus (HAV). It is postulated that HAV may rarely trigger an autoimmune chronic hepatitis. Active prophylaxis of hepatitis A is possible. The elimination of hepatitis B is dependent on the recognition of viral determinants in association with HLA proteins on infected hepatocytes by cytotoxic T cells. The specific epitopes recognized by B and T cells are being mapped. Polymerase chain reaction (PCR) amplification and sequencing of genomic DNA in patients with chronic hepatitis B has indicated that nucleotide substitutions in the genome are not uncommon. Their pathogenicity is being explored. Antiviral therapy for hepatitis B remains difficult. Interferon is effective in a proportion of patients. Thymosin may prove to be more effective immunomodulatory therapy. New nucleoside analogues suppress HBV replication, but the safety of these drugs has been questioned after the appearance of severe liver toxicity with fialuridine. The data that hepatitis D virus is pathogenic has recently been challenged with the observation that HDV re-occurs in transplanted liver after engrafting, but without signs of HBV recurrence or evidence of liver damage. Treatment of hepatitis D virus remains difficult. Several isolates of hepatitis C virus have been cloned, and the sequence divergence of these isolates indicates that there are several major genotypes and component subtypes of this polymorphic virus.(ABSTRACT TRUNCATED AT 250 WORDS)

Detection of hepatitis C virus antigen by immuno-histochemical staining: a histological marker of hepatitis C virus infection

Hepatitis C virus has been recognized as a major cause of non-A, non-B viral hepatitis. Although serologic tests have been commercialized, no specific histological or immuno-histochemical markers for hepatitis C virus infection are available for routine use. In an effort to detect hepatitis C virus antigen in liver tissue we investigated the immuno-reactivity to monoclonal antibodies on frozen liver tissue from a chimpanzee and patients with chronic non A, non B hepatitis. Monoclonal antibodies were developed in mice immunized with a synthetic peptide derived from hepatitis C virus core antigen. One monoclonal antibody was reactive and showed typical cytoplasmic granules in chimpanzee hepatocytes. Using this monoclonal antibody a similar staining pattern was found in the liver biopsies of 21 out of 28 chronic non-A, non-B hepatitis patients, positive for hepatitis C virus-RNA and anti-HCV. The granular immuno-reactivity was abolished after pre-incubation of this monoclonal antibody with infected chimpanzee liver or with hepatitis C virus synthetic peptide but not with normal chimpanzee or human liver tissue. There was no reactivity in four patients with hepatitis C virus-RNA-negative, anti-HCV-positive chronic non-A, non-B hepatitis, in 11 patients with chronic type B hepatitis or in 12 hepatitis C virus-RNA-negative, anti-HCV-negative patients with various liver diseases. However, staining was found in three out of four additional chronic type B hepatitis patients suspected of co-infection with non-A, non-B agents.(ABSTRACT TRUNCATED AT 250 WORDS)

Isolation and epitope characterization of human monoclonal antibodies to hepatitis C virus core antigen

In this study we describe the establishment of two hybridoma cell lines secreting human monoclonal antibodies to the 22-kD nucleocapsid protein (core, p22) of the hepatitis C virus (HCV). For this purpose we isolated B lymphocytes from an anti-HCV positive blood donor and infected them with Epstein-Barr (EBV). We obtained several lymphoblastoid cell clones secreting antibodies to the recombinant HCV core protein. The B-cell cultures were oligoclonally expanded and two of them were fused with the (mouse:human) heteromyeloma cell line K6H6/B5. The resulting stable hybridomas produce antibodies of the IgG1/kappa (U1/F10) and the IgM/kappa (Ul/F11) isotype reacting specifically with the recombinant core protein p22. To identify the epitopes recognized by these antibodies we synthesized overlapping peptides (13-mer and 6-mer) from the amino terminus of the core amino acid sequence. Antibody reactivity to these peptides was analyzed in an immunoblot assay. Finally, we were able to define a linear epitope recognized by the Ul/F10 antibody on the nucleocapsid protein. The antibody shows specificity to the sequence N-VYLLPR-C, which corresponds to the amino acids 34-39 of the core sequence.

Optimization for the detection of hepatitis C virus antigens in the liver

To optimize the detection of hepatitis C viral antigens in liver tissue, cryostat and formalin-fixed, paraffin-embedded liver sections from 21 patients with chronic hepatic C viral infection were studied. For cryostat sections, six different fixatives were compared. Sixteen primary antibodies were tested: nine different mouse monoclonal anti-hepatitis C virus-core antibodies, a human monoclonal anti-hepatitis C virus-non-structural 4, and six rabbit polyclonals directed against synthetic peptides of the hepatitis C virus core, envelope, and non-structural 3, non-structural 4, non-structural 5. Three detection systems, 3- and 5-step peroxidase-antiperoxidase and avidin-biotin complex, were examined. In cryostat sections, acetone/chloroform formation consistently produced the best signal-to-background ratio. Five anti-hepatitis C virus-core monoclonals which recognize amino acid sequence 26-45 of the hepatitis C virus-core region consistently detected the viral antigen, but not the monoclonals directed against 39-74 of the hepatitis C virus-core region. The human anti-hepatitis C virus-non-structural 4, which reacts to amino acid sequence 1700-1705, also regularly detected viral antigen. The rabbit polyclonals produced either negative or nonspecific staining. The 5-step peroxidase-antiperoxidase provided the strongest signal and the avidin-biotin system produced high background consistently. Overall, hepatitis C virus core and non-structural 4 antigens were detected in 71% and 57% of the patients studied. Of the 16 patients seropositive for hepatitis C virus RNA, 75% and 69% had detectable hepatitis C virus core and non-structural 4, in contrast to 60% and 20% of the five hepatitis C virus RNA seronegative patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in hepatitis C virus antigen in liver with antiviral therapy

BACKGROUND

Although it has recently become possible to detect hepatitis C viral antigens in liver biopsy specimens, the frequency and clinical significance of this finding remains uncertain. Therefore, 49 liver biopsy specimens from 35 patients with hepatitis C were studied to make these assessments.

METHODS

Hepatitis C virus antigen was detected by immunofluorescence staining of snap-frozen liver biopsy sections.

RESULTS

Hepatitis C virus antigen was present in 86% of patients; the amount and pattern of hepatitis C virus antigen staining did not correlate with the degree of hepatic injury as assessed by serum aminotransferase levels or liver histology or with the level of viral replication assessed by the titer of HCV RNA in serum. Patients who had a beneficial response to antiviral therapy had significantly less hepatitis C virus antigen staining in pretreatment liver biopsy specimens than those who did not respond. The degree of hepatitis C virus antigen staining decreased significantly following interferon alfa therapy but not after ribavirin therapy. Hepatic hepatitis C virus antigen became undetectable after therapy in those patients who had a long-term beneficial response to therapy.

CONCLUSIONS

Hepatic hepatitis C virus staining may be useful in predicting and monitoring the response to antiviral therapy.

Significance of serum hepatitis C virus RNA levels in chronic hepatitis C

Hepatitis C virus (HCV) is the main cause of parenteral non-A, non-B hepatitis and serum can be tested for the virus itself by reverse-transcription polymerase chain amplification. What of the level of this viraemia? To find out if quantitative study of HCV RNA might be useful clinically we took advantage of participation in trials of interferon-alpha in patients with chronic HCV infection and applied a new assay, branched DNA (bDNA) signal amplification. Paired serum and liver biopsy specimens from 47 patients with confirmed chronic HCV infection and evidence of HCV RNA in their serum were studied. The quantitative bDNA assay (detection limit 350,000 equivalents/mL [eq/mL]) was positive in 34 sera (sensitivity 72%). Patients who acquired HCV infection by blood transfusion had a higher viraemia (median 2,701,000 eq/mL, n = 29) than health workers and intravenous drug users (635,000 eq/mL, n = 13; p < 0.01). Patients with a sustained complete response to interferon-alpha therapy had lower pre-treatment viraemia levels (median at bDNA cut-off, n = 11) than complete responders who relapsed after the drug was stopped (1,613,000 eq/mL, n = 15; p < 0.01) and non-responders (3,066,000 eq/mL, n = 20; p < 0.01). High viraemia levels were not related to the histological diagnosis but were associated with lobular inflammation, lymphoid aggregates, and bile-duct lesions. These findings indicate that mode of acquisition is an important determinant of HCV viraemia and that patients with low HCV viraemia levels are more likely to respond to interferon in a sustained fashion.