Anthony J. Freeman

Expression of the chemokine IP‐10 (CXCL10) by hepatocytes in chronic hepatitis C virus infection correlates with histological severity and lobular inflammation

The factors influencing lymphocyte trafficking to the liver lobule during chronic hepaititis C virus (HCV) infection are currently not well defined. Interferon‐γ‐inducible protein 10 (IP‐10), a chemokine that recruits activated T lymphocytes, has recently been shown by in situ hybridization to be expressed in the liver during chronic HCV infection. This study sought to define the cellular source of IP‐10 in the liver by immunohistochemistry, to examine the expression of its receptor, CXCR3, on T lymphocytes isolated from blood and liver tissue, and to correlate IP‐10 expression with the histological markers of inflammation and fibrosis. IP‐10 was expressed by hepatocytes but not by other cell types within the liver, and the most intense immunoreactivity was evident in the areas of lobular inflammation. The IP‐10 receptor was expressed on a significantly higher proportion of T lymphocytes in the liver compared with blood. CD8 T lymphocytes, which predominate in the liver lobule, were almost uniformly CXCR3‐positive. The expression of IP‐10 mRNA correlated with lobular necroinflammatory activity but not with inflammation or fibrosis in the portal tracts. These findings suggest that IP‐10 may be induced by HCV within hepatocytes and may be important in the pathogenesis of chronic HCV infection, as recruitment of inflammatory cells into the lobule is an important predictor of disease progression.

Predicting progression to cirrhosis in chronic hepatitis C virus infection

Summary. A systematic evaluation of published studies was undertaken to identify factors associated with accelerated fibrosis progression in patients with chronic hepatitis C virus (HCV) infection. An ecologic analysis was used to estimate relative risk (RR) of cirrhosis across four study methodologies: liver clinic series, post‐transfusion cohorts, community‐based studies and blood donor series. In each study category, the following factors were independently associated with disease progression: male sex (RR = 1.08); heavy alcohol consumption (RR = 1.61); elevated serum ALT levels (RR = 1.23) and histology demonstrating high‐grade necro‐inflammatory activity. After adjusting for these cofactors, older age at HCV infection and acquisition of HCV through blood transfusion were not implicated in influencing disease outcome. Although not able to be examined in this study,co‐infection with HIV, and to a lesser extent HBV, is also likely to result in worse outcomes for patients with chronic HCV infection. Virological factors such as HCV genotype, viral load and quasispecies diversity are less likely to be important. A Weibull distribution was used to model disease progression at a population level. The influence of cofactors on individual prognosis was examined and an algorithm to predict the risk of subsequently developing cirrhosis is presented.

Clearance of Hepatitis C Viremia Associated with Cellular Immunity in the Absence of Seroconversion in the Hepatitis C Incidence and Transmission in Prisons Study Cohort

Understanding the earliest virological and immunological events in acute hepatitis C virus (HCV) infection may provide insight into the determinants of protective immunity. Four cases of HCV viremia with subsequent viral clearance, but without biochemical hepatitis or anti-HCV seroconversion, are reported from a prospective cohort study of prison inmates. Two of the subjects who developed sustained viremia were assessed for production of interferon (IFN)- gamma, by use of the enzyme-linked immunospot (ELISPOT) method and by assessment of HCV cytotoxic T lymphocyte (CTL) activity, CD4 lymphocyte proliferative responses, HCV load, and genotype. After 2-6 months of viremia, all 4 subjects cleared serum HCV RNA. Specific cellular responses were detected in both of the subjects who were assessed, and production of IFN- gamma was demonstrated in one subject. All subjects had weak, but consistent, serological reactivity against HCV nonstructural proteins on immunoblot testing, despite repeatedly nonreactive HCV ELISA tests. These cases highlight the potential for cellular immune responses against HCV to facilitate viral clearance, responses that may model those required for effective HCV vaccination.

Is severe liver disease a common outcome for people with chronic hepatitisC

Abstract  For people with chronic hepatitis C, an assessment of their riskof progression to advanced liver disease is a major priority. Earlystudies of the natural history of chronic hepatitis C suggestedthat development of cirrhosis was a relatively common outcome, evenin the first 20 years of infection. These studies wereeither cross‐sectional liver clinic series of people referred forassessment to specialist clinics, or longitudinal cohorts of peoplewith post‐transfusion hepatitis. More recent studies (particularlylongitudinal community‐based cohorts) indicate that liverdisease progression is generally slow, and that a minority of peoplewith chronic hepatitis C will develop advanced liver disease. Basedon an extensive review of studies reporting on chronic hepatitisC natural history, we have developed a Markov model of liver diseaseprogression. This model estimates that the risk of progression tocirrhosis is 7% and 20% after 20 and 40 yearsof infection, respectively. Corresponding estimates for hepatitisC‐related mortality are 1% and 4%. However, liverdisease progression is highly variable, and certain subgroups ofpeople with chronic hepatitis C are at increased risk of advancedliver disease. Those groups include people with a heavy alcoholintake, those who have coinfection with HIV or HBV, and those whohave already progressed to moderate to severe hepatic fibrosis.

Immunopathogenesis of hepatitis C virus infection.

Hepatitis C virus, a recently identified member of the family Flaviviridae, is an important cause of chronic viral hepatitis and cirrhosis. There are similarities in the nature of the immune response to this pathogen with immunity in other flavivirus and hepatotropic virus infections, such as hepatitis B. However, the high rate of viral persistence after primary hepatitis C infection, and the observation that neutralizing antibodies are not protective, would suggest that there are a number of important differences between hepatitis C, other flaviviruses, and hepatitis B. The phenomenon of quasispecies evolution and other viral factors have been proposed to contribute to immune evasion by hepatitis C virus. In the face of established persistent infection, virus‐specific cytotoxic T lymphocytes may exert some control over viral replication. However, these same effectors may also be responsible for the progressive liver damage characteristic of chronic hepatitis C infection. The nature of protective immunity, including the role of innate immune responses early after hepatitis C exposure, remains to be defined.

The presence of an intrahepatic cytotoxic T lymphocyte response is associated with low viral load in patients with chronic hepatitis C virus infection

BACKGROUND/AIMS The role of cytotoxic T lymphocytes (CTL) in limiting viral replication and producing hepatocellular injury in patients with chronic hepatitis C virus (HCV) infection is controversial. METHODS Intrahepatic and peripheral blood HCV-specific CTL activity against the entire HCV polyprotein was assessed in 26 patients. CTL responses were assessed after effector lymphocytes were re-stimulated for 6 days in vitro using HCV-vaccinia virus-infected autologous cells expressing HCV antigens. Serum and hepatic viral loads were measured and immunohistochemistry for CD3 and CD8 was performed to localise and enumerate effector cells in liver. RESULTS A positive CTL response was detected in 39/52 (75%) of assays conducted with intrahepatic mononuclear cells and 21/52 (40%) of peripheral blood assays (P<0.001). The presence of an intrahepatic CTL response was associated with low hepatic viral load (P=0.004). Hepatic lobular infiltration by CD8(+)T cells correlated weakly with serum alanine aminotransferase levels (r=0.42, P=0.04) and no relationship was demonstrated between CTL activity and histological evidence of liver damage. CONCLUSIONS HCV-specific CTL activity is found more commonly in liver than in blood. An inverse relationship between CTL responses and viral load supports the hypothesis that HCV-specific CTL limit viral replication in patients with chronic HCV infection.

Quantification of Hepatitis C Virus in Human Liver and Serum Samples by Using LightCycler Reverse Transcriptase PCR

ABSTRACT A highly sensitive, non-probe-based, real-time quantitative reverse transcriptase PCR was developed for viral load measurements in both serum and liver samples from patients with hepatitis C virus (HCV) infection. With synthetic RNA, the linearity of the approach was conserved over a wide range of HCV copy numbers. There was a strong correlation between hepatic and serum viral load measurements (r = 0.689, P = 0.004, n = 15), indicating that the level of viremia reflected the amount of virus present in the liver.

Prevalence of Production of Virus-Specific Interferon-γ among Seronegative Hepatitis C-Resistant Subjects Reporting Injection Drug Use

This report describes subjects who were highly likely to have been repeatedly exposed to hepatitis C virus (HCV) through injection drug use and who remained negative for anti-HCV antibody. Production of virus-specific interferon- gamma by peripheral blood mononuclear cells was seen in the majority of subjects (72%) and was associated with higher-risk behavior. For 92% of the subjects, results of recombinant immunoblot assays demonstrated faint bands against nonstructural proteins. The immune responses described are likely to have been primed and maintained by episodes of subclinical infection without classic seroconversion and may indicate a hepatitis C-resistant phenotype. Vaccine strategies to mimic this response may provide protection against persistent HCV infection.

Intrahepatic and peripheral blood virus-specific cytotoxic T lymphocyte activity is associated with a response to combination IFN-alpha and ribavirin treatment among patients with chronic hepatitis C virus infection.

Summary.  This report describes an association between intrahepatic and peripheral blood cytotoxic T lymphocytes (CTL) activity present prior to receiving treatment, and a response to combination interferon‐α (IFN‐α) and ribavirin therapy for chronic hepatitis C virus (HCV) infection. Recombinant vaccinia virus constructs were used to expand and detect cytotoxic effectors against the entire genotype 1a HCV polyprotein. Six patients with a sustained response to therapy were significantly more likely to display intrahepatic and peripheral blood HCV‐specific CTL activity than patients who relapsed or had no treatment response. Limited longitudinal data suggested that rather than combination therapy acting to enhance the CTL response to achieve viral clearance, detectable CTL prior to treatment increases the likehood of the host responding to the direct antiviral activity of IFN‐α and ribavirin.

Immunity against hepatitis C virus infection

between these factors and HCV incidence, and specific details of risk behaviour adjusted for in the proportional hazards regression model are not provided. Furthermore, younger age among injecting drug users has been strongly associated with higher HCV incidence, but age does not seem to have been included in the model. Thus, the contrasting characteristics of these two groups make confounding and residual confounding potential explanations for the partial immunity from infection in those previously infected. Although exposure to HCV infection is highly dependent on risk behaviour, persistence of viraemia seems more associated with host immunological characteristics. Factors such as HLA type and the magnitude and diversity of the cellular immune response have been linked to viral clearance. A lower rate of viral persistence in the previously infected group, who by definition had all previously cleared HCV viraemia, may show selection in favour of such host characteristics. Development of viral persistence in even a few people in this group argues against acquired protective immunity. The lower level of early HCV viraemia in the previously infected group could also be explained through host selection, since this characteristic is associated with HCV clearance. Assessment of immunovirological factors, including HLA type and cellular immune responses, may provide further insights into the contrasting early natural history of HCV infection between these two groups. Ideally, this approach would include longitudinal assessment of primary HCV infection, clearance, and re-exposure. Longerterm follow-up of cases of HCV reinfection is also required to assess the impact of previous infection on chronic disease pathogenesis. *Gregory J Dore, Anthony J Freeman, John M Kaldor