Detection of antigens related to hepatitis C virus RNA encoding the NS5 region in the livers of patients with chronic type C hepatitis

Hepatitis C virus receptor expression in normal and diseased liver tissue

The principal site of hepatitis C virus (HCV) replication is the liver. HCV pseudoparticles infect human liver derived cell lines and this suggests that liver-specific receptors contribute to defining HCV hepatotropism. At least three host cell molecules have been reported to be important for HCV entry: the tetraspanin CD81, scavenger receptor class B member I (SR-BI), and the tight junction (TJ) protein Claudin 1 (CLDN1). Hepatocytes in liver tissue coexpress CD81, SR-BI, and CLDN1, consistent with their ability to support HCV entry. CLDN1 localized at the apical-canalicular TJ region and at basolateral-sinusoidal hepatocyte surfaces in normal tissue and colocalized with CD81 at both sites. In contrast, CLDN1 appeared to colocalize with SR-BI at the basolateral-sinusoidal surface. CLDN1 expression was increased on basolateral hepatocyte membranes in HCV-infected and other chronically inflamed liver tissue compared with normal liver. In contrast, CLDN4 hepatocellular staining was comparable in normal and diseased liver tissue.

CONCLUSION

HCV infection of Huh-7.5 hepatoma cells in vitro significantly increased CLDN1 expression levels, consistent with a direct modulation of CLDN1 by virus infection. In HCV infected livers, immunohistochemical studies revealed focal patterns of CLDN1 staining, suggesting localized areas of increased CLDN1 expression in vivo which may potentiate local viral spread within the liver.

The role of core antigen detection in management of hepatitis C: a critical review

Several assays in research format and two commercial assays for the detection of hepatitis C virus (HCV) core protein or HCV core antigen have been developed in recent years. In order to elucidate the role and significance of HCV core antigen detection in the diagnosis and management of hepatitis C, we reviewed 56 studies published in peer-reviewed journals until September 2004. Evaluations in transfusion settings showed that the HCV core antigen assay detects HCV infection, similarly as nucleic acid techniques (NAT), between 40 and 50 days earlier than the current third generation HCV antibody screening assays. HCV core antigen levels closely track HCV RNA dynamics, and allow clinical monitoring of a patient's therapy, independently of HCV genotype, however, mainly in the samples with HCV RNA levels above 20,000 IU/ml. Considering the lower sensitivity of HCV core antigen detection in comparison to NAT, the HCV core antigen assay is not practical for the determination of the end of treatment response and sustained viral response, but could be useful for the determination of early viral response in the pegylated interferon-alpha and ribavirin treated patients infected with HCV genotype 1. The HCV core antigen detection is a viable tool for study of hepatitis C pathogenesis. The HCV core antigen can be used as a marker of HCV replication in anti-HCV positive individuals in the areas of the world that cannot afford NAT and/or in the settings that are not equipped or competent to perform HCV RNA testing. Because the manufacturer of HCV core antigen assays recently stopped an active marketing of these assays in several countries, it will, unfortunately and probably, never be possible to determine the actual potential and usefulness of HCV core antigen testing in the management of hepatitis C.

A novel antigen detection immunoassay for field diagnosis of hepatitis C virus infection

The limitations of dominant methods-based on the detection of anti-HCV antibodies or HCV viremia currently used for the diagnosis of HCV infection enhance efforts to have a rapid, simple, sensitive, and specific alternative diagnostic approach to detect viral antigens. A highly reactive IgG antibody was raised to HCV-NS4 recombinant antigen. The produced antibody showed no cross-reactivity with the other HCV structural and nonstructural recombinant antigens (C1 + 2, C3 + 4, E2/NS1, NS3, NS5). The well established ELISA technique was adapted to detect the new target HCV-NS4 antigen in serum samples. Extremely high agreement was found between the results of ELISA and qualitative detection of HCV-RNA, using a RT-PCR test as a gold standard for the diagnosis of HCV infection. Based on these encouraging results, a novel enzyme immunoassay; dot-ELISA was developed for rapid (approximately 5 min) and simple qualitative detection of the target HCV antigen in serum. The developed method detected the HCV target antigen in 95% of serum samples from HCV infected individuals, with a specificity of 97% using sera of noninfected individuals in comparison with PCR test. The antigen detection method showed high predictive values of positive (99%) and negative (90%). Moreover, the dot-ELISA could detect the HCV target antigen in sera negative for anti-HCV Abs, but positive for HCV-RNA, and in sera of HCV infected individuals with low viremia, as well as those with high viremia, using quantitative RT-PCR. Accordingly, the developed highly sensitive and specific HCV antigen detection method could be applied for mass screening of HCV infection.

Ultrastructural observations in hepatitis C virus-infected lymphoid cells

It is currently unclear whether the hepatocellular damage in chronic hepatitis C virus (HCV) infection is produced through the intrahepatic action of the anti-HCV immune response or through a direct cytopathic effect. In order to investigate the features of HCV replication (morphogenesis and cytopathic effect), we studied the infection of a permissive lymphocytic B cell line, Daudi cells, which were infected with sera of HCV-positive patients, and were examined after various time points under electron microscope. Viral genomic RNA was detected by in situ hybridization, and apoptosis with the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) method. The amount of viral genomic RNA was observed to increase during infection. HCV replicated rapidly, since characteristics of viral morphogenesis resembling those of yellow fever virus in a hepatoma cell line could be found 2 days after infection. These included the following: a) several viral particles identical in size (about 42 nm) and structure (a spherical 30-nm-sized electron-dense nucleocapsid surrounded by a membrane) to yellow fever virus were present in the cytoplasm of cells displaying already typical signs of the early stage of apoptosis; b) numerous membrane-bound organelles and in particular the endoplasmic reticulum and vacuoles were observed; c) proliferation of membranes was apparent; and d) intracytoplasmic electron-dense inclusion bodies which have been demonstrated to correspond to nucleocapsids for other flaviviruses were detected. Several cells presented electron-dense areas in the endoplasmic reticulum displaying 30-nm circular structures lying among an amorphous material. Striking cytopathic features with ballooning, extremely enlarged vacuoles and signs of apoptosis were found in cells often containing sequestered aggregates of virus-like particles. By in situ hybridization we found that such enlarged cells contained HCV RNA. Our results thus indicate that the ultrastructural features of HCV viral particles and their morphogenesis resemble that of yellow fever virus and dengue virus. In Daudi cells, HCV infection seems to rapidly trigger apoptotic cell death, and efficient release of viral particles does not seem to take place.

Pathomorphological Characteristics and Pathogenesis of Viral Hepatitis

Viral hepatitis (VH) is an inflammatory reaction of the liver to hepatotropic viruses. Acute VH can be classified according to the virus and type of necrosis. Chronic hepatitis (CH) might be active, persistent or lobular based on previous classification. More recently the grade (necroinflammatory activity) and stage (fibrosis and architectural distorsion) of CH have been distinguished and scored. Apoptosis and necrosis probably coexist in VH and contribute to hepatocyte death. Several "death factors", such as transforming growth factor b, Apo1/Fas and tumor necrosis factor play a role in the execution of cell death. Injury of hepatocytes during viral infection can occur as a direct effect of the virus or as a result of the host immune response. Expression of different viral antigens can be detected during VH and might be visualized. Phenotyping of the portal inflammatory cell infiltrate in CH has shown a T-cell zone comprised of CD4+ helper T cells and CD8+ supressor/cytotoxic T cells at the periphery of the lobules. The pathogenetic mechanisms responsible for the final outcome of viral infection depend on viral factors (such as genotype, mutation etc.), virus-host interaction, expression of viral protein, several cytokines etc. which finally lead to the well known histological alterations of viral hepatitis.

Priming of hepatitis C virus-specific cytotoxic T lymphocytes in mice following portal vein injection of a liver-specific plasmid DNA

The immunology of hepatitis C virus (HCV) infection should be studied in the context of HCV antigen expression in the liver, because HCV primarily infects this organ. Indeed, the nature, function, and fate of T cells primed after antigen expression in the liver might differ from those primed when antigens are expressed systemically or in other organs, because the nature of the antigen-presenting cells (APCs) involved may be different. In addition, the normal liver contains a resident population of lymphocytes that differ from those present at other sites. Thus, we investigated whether HCV-specific CD8(+) cytotoxic T cells (CTLs) could be elicited following portal vein (PV) injection of plasmid DNA in mice whose hepatic veins were transiently occluded. We show that PV injection of mice with "naked" DNA expressing the HCV-NS5a protein, under the control of a liver-specific enhancer/promoter, resulted in NS5a expression in the liver and the priming of HCV-specific CTLs. These results suggested that such a model might be relevant to the study of HCV-specific immune responses primed during natural infection.

Intragraft localization of activated nuclear factor kappaB in recurrent hepatitis C virus disease following liver transplantation

Nuclear factor kappaB (NF-kappaB) is activated during viral infection and is central to the regulation of host immune responses. The NF-kappaB activation status and its morphological sources were assessed by immunohistochemistry in allograft biopsy specimens of orthotopic liver transplantation patients with recurrent hepatitis C virus (HCV). Hepatocellular NF-kappaB immunostaining was detected in HCV cases compared with controls (nontransplant: P <.001; transplant: P =.006), which correlated with the number of NF-kappaB positive hepatocytes (P =.007) and contrasted to the absent to weak staining of controls (nontransplant: P =.001; transplant: P =.009). Enhanced NF-kappaB staining of cytokeratin 19-positive bile ducts and proliferating ductules in the HCV group was in contrast to controls. Intense NF-kappaB immunoreactivity was detected in CD68-positive Kupffer cells and macrophages of all HCV specimens compared with a few controls (nontransplant: P <.001; transplant: P =.001) and contrasted to the weak staining of controls (nontransplant: P <.001; transplant: P =.001). NF-kappaB-positive immunoreactivity correlated with the number of T cell receptor (TCR) alpha/beta-positive lymphocytes (P <.001), which was not observed in controls. In those HCV cases showing evidence of necroinflammatory activity (grade) and individual features of portal inflammation, periportal inflammation/piecemeal necrosis, lobular inflammation, and fibrosis (stage), higher NF-kappaB staining intensity scores within bile ducts, proliferating ductules, hepatocytes (piecemeal necrosis: P =.016; stage: P =.030), and lymphocytes (stage: P =.044) and increased number of NF-kappaB-positive cells within bile ducts, proliferating ductules (grade, lobular inflammation, piecemeal necrosis, stage: P =.022), hepatocytes, and lymphocytes were observed. Increased staining intensity and frequency of NF-kappaB-positive cells were similarly observed in HCV-positive allografts obtained from patients under tacrolimus- compared with cyclosporine-based immunosuppression. These data implicate an immunoregulatory role of intragraft NF-kappaB activation in the pathogenesis and progression of posttransplantation HCV disease recurrence.

In situ distribution of hepatitis C virus replicative-intermediate RNA in hepatic tissue and its correlation with liver disease

Liver failure from chronic hepatitis C is the leading indication for liver transplantation in the United States. However, the pathogenesis of liver injury resulting from chronic hepatitis C virus (HCV) infection is not well understood. To examine the relationship between HCV replication in liver tissue and hepatocellular injury, a strand-specific in situ hybridization procedure was developed. The sensitivity and specificity of digoxigenin-labeled riboprobes were optimized by analyzing Northern blots and cell lines expressing HCV RNAs. For the current study, both genomic (sense) and replicative-intermediate (antisense) HCV RNAs were detected and quantified in 8 of 8 liver tissue specimens from infected patients versus 0 of 11 liver tissue specimens from noninfected controls. The distribution pattern for HCV replicative-intermediate RNA in liver was different from that for HCV genomic RNA. HCV genomic RNA was variably distributed throughout infected livers and was located primarily in the cytoplasm of hepatocytes, with some signal in fibroblasts and/or macrophages in the surrounding fibroconnective tissue. However, HCV replicative-intermediate RNA showed a more focal pattern of distribution and was exclusively localized in the cytoplasm of hepatocytes. There was no significant relationship between the distribution pattern for HCV genomic RNA and any indices of hepatocellular injury. However, a highly significant correlation was observed between the percentage of cells staining positive for replicative-intermediate RNA and the degree of hepatic inflammatory activity (P, < 0.0001). Furthermore, the ratio of cells staining positive for HCV replicative-intermediate versus genomic RNA correlated with the histological severity of liver injury (P, 0. 0065), supporting the hypothesis that active replication of HCV in liver tissue may be a significant determinant of hepatocellular injury.

A comparison between previous and present histologic assessments of chronic hepatitis C viral infections in humans

AIM To compare the previously employed classification of liver histology (minimal, chronic persistent hepatitis, chronic active hepatitis and cirrhosis) with a new classification recently described by Sheuer et al (activity grade and fibrosis stage) in percutaneous liver biopsies from patients with chronic hepatitis C viral infections.

METHODS Liver biopsies from 79 untreated patients were reviewed. Anti-HCV testing had been performed by ELISA and confirmed by a recombinant immunoblot assay. With respect to the new classification, all the specimens were evaluated using the Knodell score for activity.

RESULTS A good correlation was revealed between the previous and more recent histologic classifications in patients with abnormal liver enzyme tests. However, in 13/15 (87%) of patients with normal aminotransferase values, changes were consistent with chronic persistent hepatitis whereas normal activity and no fibrosis were demonstrated by the Sheuer classification.

CONCLUSION The old classification is more often misleading but correlates well with the new classification and thereby permits comparisons between historically clinical studies.

Detection and localization by in situ molecular biology techniques and immunohistochemistry of hepatitis C virus in livers of chronically infected patients

Hepatitis C virus (HCV) detection in the livers of chronically infected patients remains a debatable issue. We used immunohistochemistry, in situ hybridization (ISH) alone or after microwave heating with FITC-labeled probes, RT-PCR with unlabeled primers followed by ISH (RT-PCR-ISH), and in situ RT-PCR with FITC-labeled primers (in situ RT-PCRd) to localize the virus in 38 liver biopsy specimens from 21 chronically infected HCV patients treated with interferon-alpha (IFN-alpha). Biopsies were taken at the beginning and end of IFN-alpha treatment and 1 year later. Results were compared with that of HCV-PCR in serum. RT-PCR-ISH and in situ RT-PCRd showed HCV signal in all liver biopsies even in responders with seronegative HCV PCR. This signal was intranuclear, diffuse, or peripheral, in hepatocytes, bile ductule cells, and lymphocytes. Cytoplasmic signals were occasionally observed. Whereas the percentage of labeled hepatocytes remained constant, the number of labeled lymphoid follicles decreased after INF-alpha therapy. Immunohistochemistry resulted in the same pattern of positivity but it was weaker and inconstant. This study indicates the persistency of HCV latency in IFN-alpha responders 1 year after IFN-alpha treatment cessation, a finding that certainly deserves confirmation.

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.

Preparation and application of monoclonal antibodies against hepatitis C virus nonstructural proteins

AIM: To prepare hybridoma cell lines that secrete monoclonal antibodies against hepatitis C virus (HCV) recombinant proteins NS3 and NS5 and to evaluate their use in the study of HCV NS3 and NS5 antigen distribution in human liver tissue.

METHODS: Hybridoma cell lines were generated using spleen cells from BALB/C mice immunized with recombinant NS3 and NS5 proteins, following conventional protocols. Antibody-secreting cells were screened by solid phase ELISA and cloned by limited dilution. The specificity of the monoclonal antibodies was determined by testing hybridoma culture supernatants by Western blots of E. coli expressing the recombinant HCV proteins and ELISA with HCV core and hepatitis B virus (HBV) antigens. The monoclonal antibodies were employed in immunohistochemistry studies to determine the distribution of HCV NS5 and NS3 antigens in 51 paraffin embedded human liver tissue samples.

RESULTS: Eight hybridoma cell lines secreting monoclonal antibodies against HCV NS3 and NS5 proteins were generated and named 2B6, 2F3, 3D8, 3D9, 8B2, 6F11, 4C6 and 7D9. Only one of them, 2B6 (secreting antibodies against NS3 protein), cross-reacted with the C7 polypeptide, a different recombinant NS3 polypeptide. The rest of the cell lines showed no cross-reactivity with HCV core or HBV antigens. In addition, monoclonal antibodies against NS3 antigens did not cross-react with NS5 antigens, and vice versa. In immunohistochemistry studies, these monoclonal antibodies did not detect HCV antigens in specimens from patients infected only with HBV (n = 20). In HCV-infected specimens (n = 31), the rates of positive detection of NS3 and NS5 antigens were 51.6% (16/31) and 54.9% (17/31), respectively. Six of these 31 specimens were from patients infected only with HCV and half of them were positive for HCV NS3 and NS5 antigens. In specimens from patients co-infected with HBV and HCV (n = 25), the rates of NS3 and NS5 antigen positive detection were 52% (13/25) and 56% (14/25), respectively, which are similar to those obtained in samples from patients infected only with HCV. In specimens from chronic active cirrhosis patients, the rates of HCV NS3 and NS5 antigen detection were 70.6% (12/17) and 76.5% (13/17), respectively.

CONCLUSION: We successfully prepared monoclonal antibodies that are specific against recombinant HCV NS3 and NS5 proteins and could be useful for clinical immunohistochemistry diagnosis.

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.

Relation between viremia level and liver disease in patients with chronic HCV infection

AIM: To explore the relation between level of hepatitis C virus (HCV) viremia and HCV-related chronic liver disease.

METHODS: Serum HCV RNA was measured by competitive reverse transcription polymerase chain reaction (CRT-PCR) in 27 patients with chronic HCV infection.

RESULTS: Levels of serum HCV RNA were low (10²-10⁶ copies/50 μL serum) in patients with chronic HCV infection. Patients with chronic active hepatitis (10^{5.739 ± 0.25} copies/50 μL serum) and with cirrhosis (10^{5.803 ± 0.76} copies/50 μL serum) had higher levels of serum HCV RNA than patients with chronic persistent hepatitis (10^{5.068 ± 1.04} copies/50 μL serum) (P < 0.05). There was a positive relation between levels of serum HCV RNA and alanine aminotransferase.

CONCLUSION: All of these results suggest that viremia level is low in chronic HCV infection. HCV itself plays an important role in progress of chronic liver disease, and HCV replication is related to liver damage.

In situ detection of hepatitis C virus RNA in liver tissue using a digoxigenin-labeled probe created during a polymerase chain reaction

The cellular localization of hepatitis C virus (HCV) RNA in liver tissue was studied by nonisotopic in situ hybridization using a digoxigenin-labeled cDNA probe created during a polymerase chain reaction on samples from 16 patients with chronic HCV infection. Hybridization signals were recognized in the cytoplasm of the hepatocytes, and a few hepatocytes had hybridization signals in the nucleus as well. HCV RNA positive hepatocytes were found in 1 of 9 patients with chronic persistent hepatitis, 2 of 5 patients with chronic active hepatitis, and in each of 2 patients with chronic active hepatitis and cirrhosis. Positive signals were found in many hepatocytes within the lobule in liver sections of patients with advanced chronic active hepatitis. A number of HCV RNA positive hepatocytes were found in nodules, but not in the area of fibrosis. On the other hand, positive signals were found in a few hepatocytes scattered in the lobule in a patient with chronic persistent hepatitis. The mean ALT levels in the patients with positive signal (175.6 +/- 44.2 U/L) were significantly higher than in those without a signal (70.27 +/- 16.1 U/L) (P < 0.05). The findings suggest that a larger amount of HCV may be present during the advanced than during the early stages of type C hepatitis and nonisotopic in situ hybridization using a digoxigenin-labeled HCV cDNA probe created during a polymerase chain reaction deserves wider application for the detection of HCV replication in specimens.

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.

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.