Detection of intrahepatic replication of hepatitis C virus RNA by in situ hybridization and comparison with histopathology

Managing the sequence-specificity of antisense oligonucleotides in drug discovery

All drugs perturb the expression of many genes in the cells that are exposed to them. These gene expression changes can be divided into effects resulting from engaging the intended target and effects resulting from engaging unintended targets. For antisense oligonucleotides, developments in bioinformatics algorithms, and the quality of sequence databases, allow oligonucleotide sequences to be analyzed computationally, in terms of the predictability of their interactions with intended and unintended RNA targets. Applying these tools enables selection of sequence-specific oligonucleotides where no- or only few unintended RNA targets are expected. To evaluate oligonucleotide sequence-specificity experimentally, we recommend a transcriptomics protocol where two or more oligonucleotides targeting the same RNA molecule, but with entirely different sequences, are evaluated together. This helps to clarify which changes in cellular RNA levels result from downstream processes of engaging the intended target, and which are likely to be related to engaging unintended targets. As required for all classes of drugs, the toxic potential of oligonucleotides must be evaluated in cell- and animal models before clinical testing. Since potential adverse effects related to unintended targeting are sequence-dependent and therefore species-specific, in vitro toxicology assays in human cells are especially relevant in oligonucleotide drug discovery.

Imaging of hepatitis C virus infection in liver grafts after liver transplantation

BACKGROUND & AIMS

The detection of native hepatitis C virus (HCV) antigens in liver tissue may be relevant to diagnostic purposes and to better understand the pathogenesis of HCV infection. The aim of our study was to characterize HCV antigens in liver grafts.

METHODS

We selected 32 liver transplant (LT) recipients with recurrent hepatitis C. HCV core and NS5A antigens were detected in formalin-fixed, paraffin-embedded (FFPE) liver biopsies obtained immediately after graft reperfusion (negative controls), during the acute phase of HCV infection (1-6 months) and during follow-up (7-74 months) after LT. Viral antigens were assessed by immunohistochemistry and confocal microscopy.

RESULTS

All reperfusion biopsies were negative for both antigens. Core protein was detected in 75% and 33% of acute phase and follow-up biopsies, respectively. HCV antigens were not detected in any of the 10 samples from patients who cleared HCV after antiviral treatment. Immunostaining was hepatocellular, with a granular cytoplasmic pattern and a wide spectrum of intensity. We found a significant association between viral load and the presence of HCV core-positive hepatocytes (p=0.004). NS5A colocalized strongly with core (66%) and adipophilin (36%), supporting the localization of core and NS5A around lipid droplets. A detailed three-dimensional analysis showed that NS5A surrounded the core and adipophilin-positive areas.

CONCLUSIONS

HCV antigens can be detected in FFPE liver biopsies by immunohistochemistry. The in vivo colocalization of core and NS5A proteins around the lipid droplets supports that the latter may play a role in virus particle production, similar to what reported in vitro.

In situ hybridization for the detection of hepatitis C virus RNA in human liver tissue

In situ hybridization (ISH) enables visualization of specific nucleic acid in morphologically preserved cells and tissue sections. Detection of the HCV genomes in clinical specimens is useful for differential diagnosis, particularly between recurrent HCV infection and acute cellular rejection in transplant specimens. We optimized an ISH protocol that demonstrated sensitivity and specificity for detecting genomic and replicative form of HCV RNA in tissue biopsies. Digoxigenin (Dig)-labelled sense and anti-sense riboprobes were synthesized using a plasmid containing a fragment of the highly conserved HCV noncoding region as a template. The efficiency of the Dig-labelled riboprobes in detecting genomic and replicative-intermediate HCV RNA was analysed in 30 liver biopsies from patients infected or uninfected with HCV in a blinded study. A Huh7 cell line that stably replicates genome-length HCV RNA was developed to be used as a positive control. Negative control riboprobes were used in parallel to evaluate and control for background staining. The anti-sense probe detected HCV RNA in 20/21 specimens from HCV-infected liver tissues obtained from patients and in 0/9 samples from patients with non-HCV-related liver diseases, resulting in a sensitivity and specificity of 95% and 100%, respectively. HCV genomic RNA was variably distributed in tissue sections and was located primarily in the perinuclear regions in hepatocytes. Detection of HCV RNA by our optimized ISH protocol appears to be a sensitive and specific method when processing clinical specimens. It may also be revealing when exploring the pathophysiology of HCV infection by verifying the presence of viral genetic material within heptocytes and other cellular elements of diseased liver tissue. This methodology might also evaluate the response to antiviral therapies by demonstrating the absence or alteration of genetic material in clinical specimens from successfully treated patients.

Clinicopathological features of hepatitis C virus disease after living donor liver transplantation: relationship with in situ hybridisation data

AIMS

Recurrent hepatitis is a significant complication after liver transplantation for hepatitis C virus (HCV) disease. To evaluate responsiveness to treatment of HCV disease after liver transplantation, in situ hybridisation (ISH) was employed.

METHODS

Sense and anti-sense probes for HCV were synthesised, and ISH studies were performed on 19 liver biopsy specimens from 19 recipients who had undergone living donor liver transplantation for HCV disease. ISH positive cells and total hepatocytes were counted, and the percentage of positive cells was calculated. Other clinical findings were compared retrospectively with the ISH results.

RESULTS

The subjects were divided into three groups: recurrent HCV hepatitis (RHC, n = 11), acute cellular rejection (ACR, n = 5), and recurrent HCV hepatitis with ACR (MIX, n = 3). The percentage of ISH positive cells was almost the same degree (10-20%) in the three groups. The RHC group was subdivided into two sets of patients in whom serum HCV titres decreased (group D, n = 7) or did not decrease (group ND, n = 3) after 1 month of IFN therapy. The percentage of ISH positive cells in group D was significantly lower than that in group ND (p < 0.05)

CONCLUSIONS

ISH for the recipients with HCV may be useful for predicting the response to interferon therapy.

Visualization of double-stranded RNA in cells supporting hepatitis C virus RNA replication

The mechanisms involved in hepatitis C virus (HCV) RNA replication are unknown, and this aspect of the virus life cycle is not understood. It is thought that virus-encoded nonstructural proteins and RNA genomes interact on rearranged endoplasmic reticulum (ER) membranes to form replication complexes, which are believed to be sites of RNA synthesis. We report that, through the use of an antibody specific for double-stranded RNA (dsRNA), dsRNA is readily detectable in Huh-7 cells that contain replicating HCV JFH-1 genomes but is absent in control cells. Therefore, as that of other RNA virus genomes, the replication of the HCV genome may involve the generation of a dsRNA replicative intermediate. In Huh-7 cells supporting HCV RNA replication, dsRNA was observed as discrete foci, associated with virus-encoded NS5A and core proteins and identical in morphology and distribution to structures containing HCV RNA visualized by fluorescence-based hybridization methods. Three-dimensional reconstruction of deconvolved z-stack images of virus-infected cells provided detailed insight into the relationship among dsRNA foci, NS5A, the ER, and lipid droplets (LDs). This analysis revealed that dsRNA foci were located on the surface of the ER and often surrounded, partially or wholly, by a network of ER-bound NS5A protein. Additionally, virus-induced dsRNA foci were juxtaposed to LDs, attached to the ER. Thus, we report the visualization of HCV-induced dsRNA foci, the likely sites of virus RNA replication, and propose that HCV genome synthesis occurs at LD-associated sites attached to the ER in virus-infected cells.

Effect of early recurrence of hepatitis C on late biliary anastomotic stricture after liver transplantation

The aim of the current study was to clarify whether recurrence of hepatitis C (HCV) infection affects biliary complications after liver transplantation (OLT), with special reference to late biliary anastomotic strictures (LBAS). We reviewed 665 consecutive adult OLT recipients with a choledochocholedochostomy without T-tube placement between 1990 and 2005. Biliary anastomotic stricture was confirmed by ERCP. The LBAS was defined as stricture that occurred 30 days or more after OLT. Recurrence of HCV was diagnosed by histological examination using liver biopsy specimen and confirmed by the presence of HCV-RNA. Early HCV recurrence was defined as recurrence that occurred within 6 months after OLT; LBAS occurred in 54 patients (8% of total). Mean duration from OLT to occurrence of LBAS was 6.9 months (1-44 months). Patients with HCV infection had higher occurrence of LBAS than did non-HCV patients (11% vs 5%, P = .0093). Among HCV patients, those with early HCV recurrence had exclusively high rate of LBAS (16%). In multivariate analyses, early recurrence of HCV (P < .001, relative risk [RR] 6.4), as well as occurrence of HAT (P = .0018, RR 8.0), and prolonged CIT (P = .034, RR 3.3) were independent risk factors affecting LBAS. In conclusion, patients with HCV infection have increased occurrence of LBAS after OLT. Additionally, early recurrence of HCV contributes to a higher rate of LBAS.

Intrahepatic hepatitis C virus replication correlates with chronic hepatitis C disease severity in vivo

The role of viral factors in the pathogenesis of chronic hepatitis C is unknown. The objective of the present study was to characterize markers of hepatitis C virus (HCV) infection and replication in liver biopsy specimens obtained from 65 genotype 1-infected subjects, including 31 who were coinfected with human immunodeficiency virus (HIV), and to analyze associations between intrahepatic viral markers and hepatitis C disease severity. The percentages of liver cells harboring HCV genomes (%G) and replicative-intermediate RNAs (%RI) were evaluated using strand-specific in situ hybridization, while HCV core and NS3 antigens were assessed by immunocytochemistry. HIV-positive and HIV-negative subjects had similar mean grades and stages of liver disease and had similar indices of HCV infection and replication in liver, even though coinfected subjects had significantly shorter mean disease duration (P = 0.0003). Multivariate analysis showed that %G was not associated with grade or stage of liver disease (P = 0.5 and 0.4, respectively), while %RI was strongly associated with liver inflammation (P < 0.001), liver fibrosis (P < 0.001), and serum alanine aminotransferase levels (P = 0.01). NS3 antigen (but not core) was more frequently detected in HCV RI-positive versus RI-negative specimens (P = 0.028). These findings demonstrate a link between HCV proliferation and hepatitis C disease severity and suggest similar pathogenic mechanisms in HIV-positive and HIV-negative individuals.

Percentage of hepatitis C virus-infected hepatocytes is a better predictor of response than serum viremia levels

Pegylated alpha-interferon plus ribavirin is the current therapy for chronic hepatitis C virus (HCV) infection. Serum HCV-RNA concentration before treatment has been identified as an independent predictive factor of response. We have compared the percentage of HCV-infected hepatocytes with the concentration of serum HCV-RNA in baseline samples as predictors of response. We included 97 patients with chronic HCV infection (genotype 1), treated with pegylated-interferon-alpha2b plus ribavirin. Of these 97, 38 (39%) were sustained responders and 59 (61%) were not. Statistical differences between responders and nonresponders were found regarding the percentage of infected hepatocytes (6.83+/-4.50% versus 13.44+/-10.05%; P=0.00003) but not in serum HCV-RNA concentration [1.71+/-2.70 (x10(6) IU/L) versus 1.32+/-1.86 (x10(6) IU/L); P=0.40694]. Other factors associated with response were age, gamma-glutamyl transpeptidase level, and absence of previous therapy. Logistic regression demonstrated that percentage of infected hepatocytes (odds ratio, 1.160; 95% confidence interval, 1.065-1.264) and previous therapy (odds ratio, 0.294; 95% confidence interval, 0.109-0.795) were significant predictive factors for response. Therefore, the percentage of infected hepatocytes in liver biopsy before treatment is a better predictive factor of sustained response to 48 weeks of therapy with pegylated alpha-interferon plus ribavirin than serum HCV-RNA concentration in baseline serum sample.

Adaptive immune responses in acute and chronic hepatitis C virus infection

The hepatitis C virus (HCV) persists in the majority of infected individuals and is a significant cause of human illness and death globally. Recent studies have yielded important insights into immunity to HCV, in particular revealing the central role of T cells in viral control and clearance. Other key features of adaptive immune responses remain obscure, including mechanisms by which T cells control HCV replication, the role of antibodies in conferring protection and how cellular and humoral immunity are subverted in persistent infection.

Replicative homeostasis II: influence of polymerase fidelity on RNA virus quasispecies biology: implications for immune recognition, viral autoimmunity and other "virus receptor" diseases

Much of the worlds' population is in active or imminent danger from established infectious pathogens, while sporadic and pandemic infections by these and emerging agents threaten everyone. RNA polymerases (RNA_pol) generate enormous genetic and consequent antigenic heterogeneity permitting both viruses and cellular pathogens to evade host defences. Thus, RNA_pol causes more morbidity and premature mortality than any other molecule. The extraordinary genetic heterogeneity defining viral quasispecies results from RNA_pol infidelity causing rapid cumulative genomic RNA mutation a process that, if uncontrolled, would cause catastrophic loss of sequence integrity and inexorable quasispecies extinction. Selective replication and replicative homeostasis, an epicyclical regulatory mechanism dynamically linking RNApol fidelity and processivity with quasispecies phenotypic diversity, modulating polymerase fidelity and, hence, controlling quasispecies behaviour, prevents this happening and also mediates immune escape. Perhaps more importantly, ineluctable generation of broad phenotypic diversity after viral RNA is translated to protein quasispecies suggests a mechanism of disease that specifically targets, and functionally disrupts, the host cell surface molecules – including hormone, lipid, cell signalling or neurotransmitter receptors – that viruses co-opt for cell entry. This mechanism – "Viral Receptor Disease (VRD)" – may explain so-called "viral autoimmunity", some classical autoimmune disorders and other diseases, including type II diabetes mellitus, and some forms of obesity. Viral receptor disease is a unifying hypothesis that may also explain some diseases with well-established, but multi-factorial and apparently unrelated aetiologies – like coronary artery and other vascular diseases – in addition to diseases like schizophrenia that are poorly understood and lack plausible, coherent, pathogenic explanations.

Associations among clinical, immunological, and viral quasispecies measurements in advanced chronic hepatitis C

The relationships among host immune and viral factors and the severity of liver disease due to hepatitis C virus (HCV) are poorly understood. Previous studies have focused on individual components of the immune response to HCV, often in relatively small numbers of patients. We measured HCV-specific lymphoproliferation (LP), intrahepatic cytotoxic T lymphocyte (CTL), and neutralizing antibody (NA) responses and HCV quasispecies (QS) diversity and complexity in a large cohort of subjects with advanced liver fibrosis (Ishak stages 3-6) on entry into the HALT-C (Hepatitis C Antiviral Long-term Treatment against Cirrhosis) trial. We correlated LP, CTL, NA, and QS results with clinical characteristics, including serum alanine aminotransferase (ALT), HCV RNA level, HCV genotype, and hepatic histopathology. LP, CTL, and NA responses were detected in 37%, 22%, and 22% of subjects tested, respectively. The only association that was statistically significant was higher mean serum ALT values in patients with detectable HCV-specific CTL responses (P = .03). In conclusion, immune responses to HCV and viral diversity showed little relationship to clinical or histological features at a single time point in this selected population of patients with advanced chronic hepatitis C for whom prior interferon treatment had failed.

Cell-Mediated Immunity and the Outcome of Hepatitis C Virus Infection

The hepatitis C virus (HCV) infects approximately three percent of the world's population. Some individuals resolve the infection spontaneously, but the majority develop persistent viremia that often causes progressive liver disease. There is an emerging consensus that cellular immune responses are essential for spontaneous resolution of acute hepatitis C and long-term protection from persistent infection. This review focuses on the recent advances in understanding mechanisms of protective immunity and why they fail in most infected individuals. The distinct yet complementary role of CD4+ and CD8+ T lymphocytes in this process is highlighted.

Detection of hepatitis C virus RNA in formalin-fixed paraffin-embedded sections with digoxigenin-labeled cRNA probes

Although recent studies have analyzed Hepatitis C (HCV) infections in liver tissue by in situ hybridization (ISH), many of these studies have been of limited diagnostic utility because of the low copy numbers of HCV in formalin-fixed paraffin-embedded (FFPE) tissue and failure to correlate the ISH analysis with other methods of detecting HCV. Thirty six cases of liver biopsies from patients with known HCV antibody status including 20 cases of serum HCV positive and 16 cases of serum HCV negative were analyzed. All cases showed histologic features suggestion of HCV infection. Analyses of all 36 cases were done by RT-PCR combined with Southern hybridization (RT-PCR-SH) and in situ hybridization (ISH). A prolactin riboprobe was used as a negative control. Immunohistochemistry (IHC) with an antibody against HCV (Rb 246) was also used to analyze HCV viral protein in the tissues. Of the 20 serum antibody-positive cases, RT-PCR-SH detected 18 positive cases, while ISH and IHC detected 19 and 16 positive cases, respectively. Of the 16 serum antibody-negative cases, RT-PCR-SH detected 8 positive cases while ISH and IHC detected 8 and 11 positive cases, respectively. A positive ISH signal for HCV was also detected in some lymphocytes and bile ducts in the liver. These results show that ISH with a highly specific riboprobe is comparable to RT-PCR-SH for detection of HCV infection in liver tissue.

Hepatitis C virus-associated tubulointerstitial injury

BACKGROUND

Tubulointerstitial damage is recognized as a determinant of the prognosis of kidney disease. Various types of viral infection have been reported to induce tubulointerstitial lesions; however, that caused by hepatitis C virus (HCV) remains unclear, although glomerular lesions caused by this viral infection have been well documented.

METHODS

To identify any association, we retrospectively investigated 320 patients who underwent renal biopsy and did not have extrarenal diseases causing tubulointerstitial nephritis.

RESULTS

Of these patients, 13 patients had HCV infection and 307 patients did not. In a case-control study, HCV infection showed a significant association with the prevalence of tubulointerstitial injury. To offset the secondary tubulointerstitial change caused by advanced glomerulopathy, we performed a glomerular stage-matched comparison of patients with membranous nephropathy (MN). Nine patients with MN among the 13 HCV-infected patients and 18 HCV-negative patients with electron microscopic glomerular stage-matched MN were randomly selected from the overall pool of patients. Comparing areas of interstitial fibrosis and inflammatory cell infiltration, both were greater in HCV-infected than HCV-negative patients. In biopsy tissues from HCV-infected patients, positive signal for HCV was observed in the perinuclear area of tubular epithelial cells and infiltrating cells on immunohistochemistry and in situ hybridization. By a strand-specific reverse-transcription polymerase chain reaction for HCV, both genomic- and replicative-strand RNA were detected in renal tissues.

CONCLUSION

These results suggest that HCV infection is a potent pathogenic factor of tubulointerstitial injury.

A study of susceptibility of primary human Kupffer cells to hepatitis C virus

BACKGROUND/AIMS

Histological examination of a liver-biopsy from a patient with chronic hepatitis C shows activated Kupffer cells. In vitro infection of human Kupffer cells (KC) was performed to study their interaction with hepatitis C virus (HCV).

METHODS

KC, isolated by collagenase perfusion and centrifugal elutriation, were infected with various HCV positive sera. The presence of the viral genome was followed, at different times, quantitatively by a branched-DNA assay and qualitatively by reverse transcriptase-nested polymerase chain reaction. A strand-specific assay performed with the thermostable enzyme rTth was used to detect the synthesis of a negative replicative intermediate. Cytopathic effect was examined by electron microscopy. Production of cytokines and inducible nitric oxide synthase was evaluated in the supernatants.

RESULTS

Quantification of HCV-RNA showed that the level of viral RNA associated with KC after adsorption decreased rapidly. Genomic viral RNA disappeared within 5 days of infection. Negative-strand RNA was never detected in any of these experiments. No cytopathic effects could be detected at any time. KC did not produce inflammatory nor antiviral cytokines.

CONCLUSIONS

Our results strongly suggest that primary cultures of KC are not permissive for HCV in vitro.

Lack of in vivo blockade of Fas- and TNFR1-mediated hepatocyte apoptosis by the hepatitis C virus

In vitro data have shown that the hepatitis C virus (HCV) core protein binds to protein members of the tumour necrosis factor receptor (TNFR) superfamily. Since this interaction could be relevant to HCV persistence and oncogenesis, this study assessed whether HCV may interfere with the apoptotic cascade in vivo. Apoptosis (by TUNEL) and Fas and TNFR1 expression (by immunohistochemistry) were scored in the liver of 60 chronic hepatitis C patients. Results were compared with the liver disease grading and staging scores and the HCV replication level in serum and liver. Apoptotic hepatocytes were stained in 29 cases. Fas was expressed in 35 cases and TNFR1 in 21, 15 patients (25%) being negative for both receptors. Overall, the numbers of TUNEL-, Fas- and TNFR-positive hepatocytes did not correlate with the extent of intrahepatic CD8+ T-lymphocyte infiltration, the grading and staging of liver disease, or the serum or liver HCV RNA levels. Furthermore, when patients expressing either Fas or TNFR1 were stratified according to serum HCV RNA levels, cases with detectable hepatocyte apoptosis had higher HCV viraemias. In conclusion, an HCV-mediated, in vivo blockade of hepatocyte apoptosis via the Fas- or TNFR1-dependent pathways seems unlikely.

Correlation of histology, viral load, and in situ viral detection in hepatic biopsies from patients with liver transplants secondary to hepatitis C infection

The diagnosis of hepatitis C infection in the setting of liver transplantation in based on several variables, including histopathologic changes and the presence of viral RNA in the serum. It may be difficult to differentiate acute rejection from recurrent viral hepatitis in liver biopsies from patients who received liver transplants for end-stage hepatitis C infection. The purpose of this study was to analyzed the histologic features, viral load, and in situ viral detection in 37 biopsies taken from 25 people who underwent liver transplant for end-stage hepatitis C infection. Hepatitis C antigen was detected in 9 of 37 (24%) biopsies using immunohistochemistry; the detection rate increased to 19 of 37 (51%) using reverse transcriptase in situ polymerase chain reaction for viral cDNA. Hepatitis E cDNA was detected in 4 of 37 (11%) cases, hepatitis G cDNA in 3 of 37 (8%) cases and in 1 case cytomegalovirus was noted; with several cases of dual infection, 22 of 37 (59%) of tissues were positive for at least 1 virus. Histologic parameters that significantly correlated with in situ viral detection included single-cell hepatocyte necrosis (P = 0.02), bile duct damage (P = 0.03), lymphoid aggregates (P = 0.02), and cholestasis (P = 0.01). Further, a serum viral load exceeding 1,250,000 viral equivalents/ml was strongly correlated with in situ viral detection in the liver (P = 0.01). We conclude that certain histologic features and an increased viral load are highly correlated with the in situ detection of viral RNA in the liver, which is consistent with recurrent viral infection.

Development of a novel nested in situ PCR-ISH method for detection of hepatitis C virus RNA in liver tissue

Hepatitis C virus (HCV) is a major cause of chronic hepatitis with liver-related death occurring in 20-25% of patients who develop cirrhosis. Detection of the virus RNA in liver is difficult since viral expression is very low. In situ polymerase chain reaction (PCR) in situ hybridisation (ISH) was developed for detection and localisation of viral RNA in formalin-fixed, paraffin-embedded liver tissue. Nested PCR technology was adapted for in situ use employing primers derived from the 5' end of the HCV genome. Seventeen liver blocks from known HCV-infected patients were examined. Viral RNA was detected in liver from eleven patients using solution phase reverse transcriptase-PCR. Of these positive samples, ten were positive by the in situ method. Positive signal was detected in the cytoplasm of hepatocytes and mononuclear cells. No Kupffer cell or bile duct epithelial positivity was observed. No positive signal was evident in any of the negative controls. A reliable method is described to demonstrate the presence and localisation of HCV RNA in liver tissue using an in situ PCR-ISH assay and it is believed that this will be a valuable tool for the understanding of HCV replication and pathogenesis.

Detection of the negative-strand hepatitis C virus RNA in tissues: implications for pathogenesis

The replication of hepatitis C virus (HCV) RNA is believed to occur via its transcription into a complementary, genomic-length RNA, the so-called negative-strand HCV RNA. This is based on the comparison with the replication of other members of the Flaviviridae family. Detection of the negative-strand HCV RNA in human tissues by semi-quantitative, strand-specific RT-PCR has contributed to the understanding of the HCV cell tropism and of the pathogenesis of HCV-associated disease manifestations. In particular, it was shown that the levels of intrahepatic HCV RNA are not correlated to the extent of the necroinflammation, but that a significant correlation was found with the liver steatosis. These results suggest that most liver disease associated with HCV infection is mediated by the host immune response. However, in some patients, most notably those infected with HCV genotype 3, HCV may cause a cytopathic effect, consisting in the lipid accumulation within hepatocytes.

Hepatitis C. Epidemiologic quandaries

Although many aspects of the transmission of HCV have been clarified, some important issues remain controversial, and the conventional wisdom may be based more on opinion than data (Table 2). HCV is transmitted by percutaneous exposure to contaminated blood, uncommonly from a mother to her infant and between sexual partners, and rarely during the provision of medical care in developed nations. Improved behavioral research instruments are needed to further the understanding of the practices that actually transmit infection. In addition, large, prospective studies are necessary to characterize the frequency [table: see text] of transmission between sexual partners and the potential role of cesarian section in reducing HCV transmission to infants.

Generation of infectious and transmissible virions from a GB virus B full-length consensus clone in tamarins

The strong similarity between GB virus B (GBV-B) and hepatitis C virus (HCV) makes tamarins infected by GBV-B an acceptable surrogate animal model for HCV infection. Even more attractive, for drug discovery purposes, is the idea of constructing chimeric viruses by inserting HCV genes of interest into a GBV-B genome frame. To accomplish this, infectious cDNA clones of both viruses must be available. The characterization of several HCV molecular clones capable of infecting chimpanzees has been published, whereas only one infectious GBV-B clone inducing hepatitis in tamarins has been reported so far. Here we describe the infection of tamarins by intrahepatic injection of RNA transcribed from a genomic GBV-B clone (FL-3) and transmission of the disease from infected to naive tamarins via serum inoculation. The disease resulting from both direct and secondary infection was characterized for viral RNA titre and hepatitis parameters as well as for viral RNA distribution in the hepatic tissue. Host humoral immune response to GBV-B antigens was also monitored. The progression of the disease was compared to that induced by intravenous injection of different amounts of the non-recombinant virus.

Direct in situ reverse transcriptase-polymerase chain reaction

In situ hybridization has been used for localization of specific nucleic acid sequences at the cellular level despite providing relatively low-detection sensitivity. In situ reverse transcriptase-polymerase chain reactions (RT-PCR) enhance sensitivity and thus enable localization of low-abundance mRNA in a cell. However, the available methods are fraught with problems of nonspecific amplifications as a result of mispriming and/or amplification from partially digested residual genomic DNA in tissue. Herein, we demonstrate that nonspecific background amplification can be eliminated by pretreatment of samples with restriction enzymes before DNase I digestion. Primers tagged with a far-red shifted fluorescent dye such as Cy5 in PCR reactions allow identification of target mRNA by fluorescence microscopy. These novel modifications lead to increased specificity and rapid in situ detection of cellular mRNA and thus may be used for pathological diagnosis.

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.

Fas-mediated apoptosis of peripheral blood mononuclear cells in patients with hepatitis C

In the present study, we demonstrated that a close relationship exists between hepatitis C virus (HCV) infection of peripheral blood mononuclear cells (PBMCs) and cell-surface Fas expression in patients with hepatitis C, and showed the possibility of PBMCs apoptosis via a Fas-mediated system. The expression of Fas on PBMCs was found by flowcytometric analysis to be significantly increased in these patients. In addition, the treatment of patients' PBMCs with anti-Fas antibody induced cell death, with nuclear condensation and fragmentation and cellular DNA fragmentation. These data indicate that the patients' PBMCs expressed a large amount of functional Fas on the cell surface and were susceptible to stimulation against Fas, causing apoptotic cell death. We then quantified the serum-soluble Fas ligand (sFasL), which was known to bind to Fas and induce the apoptotic signals into the sensitized cells. The patients' serum sFasL levels were significantly higher than those of normal subjects and showed a good negative correlation with their PBMC number. To demonstrate the correlation between Fas expression and HCV infection, nested reverse transcriptase polymerase chain reaction (RT-PCR) was performed to detect HCV RNA. Interestingly, HCV RNA was preferentially detected from Fas-positive cells but not from Fas-negative cells, which had been isolated from PBMCs by magnetic beads. These results suggest that HCV infection of PBMCs might induce Fas expression and additional stimulation such as sFasL might induce apoptosis in these Fas-expressing cells. These mechanisms, in addition to hypersplenism, may explain the decrease in the number of PBMCs observed in patients with chronic hepatitis C.

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.

Primary hepatic diffuse large B-cell lymphoma in a patient with chronic hepatitis C

Epidemiological and experimental data suggest that the hepatitis C virus infection might be associated with the development of distinct types of non-Hodgkin's lymphomas. Here, we report a case of a patient with chronic hepatitis C and type II mixed cryoglobulinemia, who developed a primary hepatic non-Hodgkin's B-cell lymphoma. A diffuse, large B-cell lymphoma was diagnosed based on morphological, immunophenotypical and molecular genetic findings. Hepatitis C virus replication, as evaluated by strand-specific reverse transcriptase-polymerase chain reaction, was detected in the nonneoplastic liver, but not in the lymphomatous tissue. High grade non-Hodgkin's lymphomas, although rare complications, have to be considered as part of the spectrum of hepatitis C virus-related hepatic lesions.

Shift of hepatitis E virus RNA from hepatocytes to biliary epithelial cells during acute infection of rhesus monkey

Hepatitis E virus (HEV) has been considered to be the major cause of enterically transmitted non-A, non-B hepatitis in developing countries. However, little is known about viral replication and localization in the liver. The aim of this study was to examine the distribution of HEV-infected cells in experimentally infected animals. Seven captured wild rhesus monkeys were inoculated intravenously with faecal extract derived from a Myanmar strain of HEV. Animals were killed at different time-points of clinical illness: during early infection, during prehepatitis with viral-like particles in bile, during acute hepatitis and during convalescence. Intrahepatic localization of HEV was analysed using non-isotopic thymine dimer in situ hybridization (NITDISH). Both plus and minus strands of HEV RNA were found in hepatocytes during the early infection period. Staining in the submembranous cytoplasmic region of hepatocytes was observed. In the prehepatitis period, both plus and minus strand HEV RNAs appeared in the canalicular side of isolated bile epithelial cells. Subsequently, HEV RNA became universally distributed in the cytoplasm of medium-size bile epithelial cells. After recovery, HEV RNA disappeared.

Functional B-cell response in intrahepatic lymphoid follicles in chronic hepatitis C

Intrahepatic lymphoid follicle (ILF) formation is one of the most characteristic and commonly observed histological features in patients with chronic hepatitis C. However, little is known regarding whether follicles in the liver belong to functional lymphoid tissues, where B cells are activated, differentiated, and proliferated, or if the lymphocytes are merely infiltrated after recruitment from the secondary lymphoid organs. To ascertain this possibility, we examined the expression of markers for B-cell activation, differentiation, and proliferation in ILFs in patients with chronic hepatitis C using surgically resected specimens, and compared them with specimens of perihepatic lymph nodes by an immunohistochemical technique. Germinal center (GC) formation in the ILFs was frequently found in HCV-positive cases. The distribution of immunoglobulin M (IgM)-, IgD-, and IgG-positive cells and the expression patterns of Ki-67, CD23, or bcl-2 and bcl-6 gene products in the follicles with GC formation in the liver of patients with chronic hepatitis C were similar to those of lymph nodes, indicating that B cells are activated, proliferated, and differentiated in the ILFs with GC formation in patients with chronic hepatitis C. Oligoclonal expansion of B cells in the livers with ILFs was confirmed by an analysis of immunoglobulin heavy chain (IgH) gene rearrangement determined by polymerase chain reaction (PCR). These data strongly suggest that ILFs with GC formation, which are frequently found in patients with chronic hepatitis C, may functionally be the same as those found in lymph nodes with respect to B-cell expansion and maturation.

Direct in situ reverse transcriptase-linked polymerase chain reaction with biotinylated primers for the detection of hepatitis C virus RNA in liver biopsies

To assess the presence and the cellular distribution of hepatitis C virus (HCV) RNA in the liver of 11 patients with confirmed HCV infection, a direct in situ reverse transcriptase-linked polymerase chain reaction (RT-PCR) method was performed on formalin-fixed and paraffin-embedded biopsies. The oligonucleotide primers used were specific to the 5' non coding region. An unlabelled downstream oligonucleotide served as a primer for reverse transcription as well as PCR. The upstream oligonucleotide serving as a primer for PCR was biotinylated, allowing a direct enzymatic detection of PCR products. HCV infected cells revealed cytoplasmic staining mainly concentrated towards the interface of the nucleus and cytoplasm. Most of the stained cells were hepatocytes and sometimes Kupffer cells. The results were compared with those obtained by RT-PCR of RNA extracted from the corresponding tissue block. Extracted HCV RNA could be detected in liver tissues of nine out of 11 (82%) infected patients. The detection rate using in situ RT-PCR was 7/11 (63%). The use of labelled primers improved specificity of direct in situ methods, by preventing non-specific incorporation of labelled dNTPs into fragmented DNA. Further studies are however required in order to increase detection sensitivity of HCV infection by in situ molecular methods.

Cell-based and animal models for hepatitis B and C viruses

Reliable cell-based assays and animal models have been developed for evaluating agents against hepatitis B virus. Although much progress has been made, in vitro and in vivo assays for hepatitis C virus are still on the horizon. Advances towards establishing inexpensive and reliable experimental models have accelerated the development of therapeutic modalities for these life-threatening viral infections. The characterization of well-defined viral targets coupled with improved molecular diagnostic technologies have illuminated this field.

Hepatitis G virus infection among liver graft recipients: anatomoclinical correlations

Hepatitis G virus (HGV) causes persistent infection in man, but its disease association is controversial. We studied the HGV disease association in 25 liver transplantation (LT) recipients without evidence of hepatitis B and C infection. HGV RNA was tested by semiquantitative RT-PCR in serial serum samples and its presence was correlated with the biochemical and histological evidence of liver damage. The overall prevalence of HGV infection in this population was 9/25 (36%), one patient being HGV RNA positive since before LT, while the other eight apparently acquired de novo infections after LT. In five cases, appearance of HGV was followed by biochemical and histological evidence of liver damage: the liver biopsy showed acute rejection in two cases, acute cholangitis in two, and acute hepatitis in one. At the end of follow-up, histological evidence of chronic hepatitis was found in one HGV-positive patient but also in three HGV-negative patients, whereas the only patient with acute hepatitis at the time HGV RNA was first detected in serum developed an intralobular gigantocellular granuloma. In conclusion, HGV infection after LT may be seldom associated with acute and chronic liver damage, but comparable histological features can be observed also among HGV-negative controls.

Hepatitis C virus infection, mixed cryoglobulinemia, and non-Hodgkin's lymphoma: an emerging picture

Hepatitis C virus (HCV) is a single-stranded RNA agent which expresses its genetic informations in the form of a single, large polyprotein encoded by an open reading frame (ORF) that extends through most of its genomic RNA. Proteolytic cleavage of the ORF product is essential for the virogenesis and the production of viral progeny. HCV is responsible for chronic liver disease, cirrhosis and possibly hepatocellular carcinoma. Viral persistence is considered the greatest problem in the management of HCV infection. It may result from several mechanisms, two of which are established. In the first, the high rate of genetic variations during viral replication results in the production of mutants capable of escaping the immune attack. In the second, the virus infects cells of the immune system itself, which represent a privileged site that cannot be reached by virus-specific T cell response. Involvement of lymphoid cells in the early stages of HCV infection may provide insight into the pathobiologic patterns of extrahepatic dissemination (lymph nodes, major salivary glands, kidneys, blood vessels). Dissemination of HCV-infected lymphoid cells throughout the organism is likely to maintain a mobile and extensive reservoir of the virus. In this respect, extrahepatic sites may act as a source of continuous reinfection of hepatocytes. Studies of intrahepatic B lymphocytes indicate that they are infected with HCV, clonally expanded and activated to secrete IgM molecules with rheumatoid factor activity. This strongly suggests that HCV directly stimulates B cell expansion, which may result in an indolent stage of lymphoproliferation (i.e., mixed cryoglobulinemia) or in frank B cell non-Hodgkin's lymphoma (NHL). The frequency of NHL, however, is much lower than that of HCV infection, suggesting that HCV alone is not able to induce tumors and that cellular events, in addition to the presence of virus and virus-encoded products, are necessary in order to obtain a malignant B cell phenotype. The demonstration of HCV productive infection in bone marrow-recruited and circulating pluripotent hematopoietic CD34+ stem cells indicates that HCV replication occurs in the early differentiation stages of hematopoietic progenitors. These are stable cell populations and are likely to represent the initial site of infection and a continuous source of virus production.

Histologic distribution of hepatitis A, B, C, D, E, and G with concomitant cytokine response in liver tissue

The purpose of this study was to determine the frequency of infection by hepatitis A, B, C, D, E, and G in liver biopsy specimens from symptomatic patients and to correlate viral localization with the expression of interferon tau, interleukin 4, and tumor necrosis factor messenger RNA. Tissue biopsy specimens were taken from 78 patients as follows: 14 patients with transplants, 23 patients with cirrhotic livers, and 41 patients with chronic hepatitis. At least one of the hepatitis viruses was detected in 60 of 78 (77%) specimens; multiple infection was evident in 18 of 78 (23%) specimens. The overall incidence of the different viruses was as follows: 8% hepatitis A, 3% hepatitis B, 52% hepatitis C, 1% hepatitis D, 24% hepatitis E, 18% hepatitis G. Throughout each category, hepatitis C was the most common virus detected. No histologic variable correlated with either the percentage of infected hepatocytes per lobule or nodule or with the specific viral type. The cytokines localized to monocytes or lymphocytes adjacent to infected hepatocytes. These results demonstrate that viral infection is present in most biopsy specimens of patients with chronic hepatitis and liver transplants and that hepatitis C, E, and G account for most of the infections. The results also suggest that direct viral infection in conjunction with expression of different cytokines is important in the pathophysiology of viral-induced liver disease.

The use of non-human primates as animal models for the study of hepatitis viruses

Hepatitis viruses belong to different families and have in common a striking hepatotropism and restrictions for propagation in cell culture. The transmissibility of hepatitis is in great part limited to non-human primates. Enterically transmitted hepatitis viruses (hepatitis A virus and hepatitis E virus) can induce hepatitis in a number of Old World and New World monkey species, while the host range of non-human primates susceptible to hepatitis viruses transmitted by the parenteral route (hepatitis B virus, hepatitis C virus and hepatitis delta virus) is restricted to few species of Old World monkeys, especially the chimpanzee. Experimental studies on non-human primates have provided an invaluable source of information regarding the biology and pathogenesis of these viruses, and represent a still indispensable tool for vaccine and drug testing.

Detection of widespread hepatocyte infection in chronic hepatitis C

The controversial question of the extent of hepatocyte infection in chronic hepatitis C was re-examined in both chimpanzees and humans using a newly modified in situ hybridization (ISH) method for detecting hepatitis C virus (HCV) RNA. The specificity of the methodology for distinguishing positive- and negative-strand synthetic HCV RNA was at least six magnitudes greater than the reverse-transcription polymerase chain reaction (RT-PCR) assay for HCV. The sensitivity of the methodology as determined by cell culture assay was 14 +/- 2 genomic equivalents (gE) of HCV positive strand per cell, which was three magnitudes less sensitive than RT-PCR quantitation of HCV. In contrast to previous studies in both humans and chimpanzees with chronic hepatitis C, a high percentage of hepatocytes positive for both positive- and negative-strand HCV RNA was found in most specimens studied. In humans, the extent of hepatocyte infection varied with histological activity index (HAI). In the two chimpanzees studied, the liver biopsies showed minimal histological disease activity, but high percentages of hepatocytes were HCV-positive by ISH that correlated with hepatocyte ultrastructural changes associated with HCV infection. Hepatocyte infection was confirmed by RNA extraction and RT-PCR techniques for detecting HCV RNA that minimize the false detection of negative strands. In both human and chimpanzee liver biopsies showing minimal HAI, the hepatocyte concentration of HCV was estimated to be very low. These findings suggested the hypothesis that persistent infection in the liver may be caused in part by low-level HCV replication. The theoretical and clinical implications of these findings are discussed.

Increased peroxide production by polymorphonuclear cells of chronic hepatitis C virus-infected patients

To evaluate the oxidative burst in hepatitis C virus (HCV) infection, intracellular hydrogen peroxide (H2O2) production of polymorphonuclear (PMN) cells isolated from 15 chronic HCV-infected patients and 11 controls was assessed by flow cytometry in a time kinetic. Under nonstimulated and phorbol myristate acetate (PMA)-stimulated conditions, H2O2 production was higher in HCV-infected patients than in controls (P <0.05) at the time points of 20, 30, and 40 min. A positive correlation between H2O2 production by PMA-stimulated cells and serum levels of alanine aminotransferase and aspartate aminotransferase was found in the HCV-infected patients (r = 0.877, P <0.01 and r = 0.9351, P <0.001, respectively). RT-PCR analysis of purified mononuclear (MN) and PMN cells from HCV-infected patients revealed the presence of HCV RNA in 60% of MN and 27% of PMN cell samples. These results suggest that a functional alteration of PMN cells is manifested in this chronic viral infection which may represent an additional factor in the development of liver lesions.

Detection of intrahepatic hepatitis C virus replication by strand-specific semi-quantitative RT-PCR: preliminary application to the liver transplantation model

BACKGROUND/AIMS

Although the hepatitis C virus infection recurs in virtually all patients after liver transplantation, up to 50% of patients may not have histological recurrent hepatitis 1 year after liver transplantation. To study the relationship between hepatitis C virus infection and liver disease after liver transplantation, we compared the intrahepatic hepatitis C virus replication levels with the liver histopathology among liver transplant recipients.

METHODS

The intrahepatic negative-strand HCV RNA (i.e. the putative hepatitis C virus replication intermediate RNA) was evaluated by a semi-quantitative, strand-specific reverse transcriptase-polymerase chain reaction in 44 liver specimens from 23 patients with hepatitis C virus reinfection after liver transplantation. Results were compared with the time from liver transplantation, presence, grading and staging of the recurrent hepatitis, amount of hepatitis C virus antigens in the liver and serum HCV RNA levels.

RESULTS

Negative-strand HCV RNA was detected in 42 liver specimens as early as 7 days after liver transplantation. Its titers correlated with the amount of intrahepatic hepatitis C virus antigens, but not with HCV RNA levels in serum. Levels of negative-strand HCV RNA in 19 specimens without hepatitis were comparable to those seen in 25 specimens with hepatitis (p=0.492), and were unrelated to the liver disease grading and staging scores. The intrahepatic hepatitis C virus replication could occasionally precede the recurrence of the hepatitis by several months.

CONCLUSIONS

Molecular evidence has been obtained for intrahepatic hepatitis C virus replication occurring early after liver transplantation. The level of replication is not correlated with the development of recurrent hepatitis, suggesting that hepatitis C virus may replicate without inducing morphological evidence of liver damage.

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.

Relative quantification and mapping of hepatitis C virus by in situ hybridization and digital image analysis

Although several reports concerning the detection of hepatitis C virus (HCV) by in situ hybridization have been published, there are no data concerning the relative viral load in infected hepatocytes or about its relation with serum viremia levels. To address these issues, liver biopsies from 10 patients with chronic hepatitis C were analyzed by in situ hybridization and digital image analysis of hybridization signals. Serum HCV RNA levels were measured using the Amplicor Monitor test. HCV RNA was detected by in situ hybridization in the hepatocytes of the ten liver samples. The hybridization signals were mainly found in the cytoplasm. The relative viral load per infected cell fit the second order polynomial curves in all cases. The minimum and maximum relative viral load per infected hepatocyte differed in the ten cases; however, large differences were not observed in the mean relative viral load among the samples, especially when compared with the increasing values detected for copy number per milliliter in serum. The percentage of infected cells ranged from 4.8% to 87.6% in the ten cases. The percentage of positive cells correlated with the serum viremia levels. Our data suggest that HCV viremia does not depend on the relative viral load per infected cell but on the number of infected hepatocytes.

Clonality of B-cells in portal lymphoid infiltrates of HCV-infected livers

Evidence has been accumulating in favour of a role for hepatitis C virus (HCV) in the pathogenesis of human lymphoproliferative disorders. HCV infection has been documented in the majority of patients with essential mixed cryoglobulinaemia type II (MC-II); in patients with HCV infection, B-cell clonal expansion have been detected in peripheral blood and bone marrow, and a high prevalence of B-cell non-Hodgkin's lymphomas has been documented. Liver biopsies in chronic hepatitis C frequently show portal lymphoid infiltrates with features of B follicles, whose clonality has not yet been investigated. This study has analysed the B-cell clonality of portal lymphoid infiltrates from 16 patients with chronic HCV hepatitis. Portal tracts showing obvious lymphoid infiltrates were microdissected from the paraffin-embedded liver tissue sections and the clonality of lymphoid B-cells was tested using a polymerase chain reaction (PCR) approach designed to identify immunoglobulin heavy chain gene (IgH) rearrangements. A successful IgH-PCR analysis was achieved in 35 lymphoid infiltrates from 11 patients (seven with the four without MC-II) and yielded a single band in 21 cases, two bands in ten cases, and three bands in four cases. Comparison of the IgH-PCR amplification bands obtained from the different lymphoid aggregates of the same biopsy revealed that they differed in size. This finding indicates that each aggregate derives from the proliferation of one or a few founder B-cells, which are not related to each other. The results obtained in patients with and without MC-II were similar, suggesting that the presence of B-cell clonal proliferations in liver biopsies is independent of the occurrence of B-cells producing monoclonal IgMk cryoglobulins.