Hepatitis C Virus-Specific T-Cell Reactivity During Interferon and

Ribavirin Treatment in Chronic Hepatitis C

 

CTL responses to HCV antigen appears important in one's ability to respond to treatment. Response occurs 4-8 weeks following initiation of therapy and may be key to phase 2 viral decay response.

  MATTHEW E. CRAMP,* SIEGBERT ROSSOL, SHILPA CHOKSHI,*, PATRIZIA CARUCCI,*ROGER WILLIAMS,*, and NIKOLAI V. NAOUMOV*,

* Institute of Liver Studies, King's College Hospital, London, England; Institute of Hepatology, University College London, London, England; and  Department of Gastroenterology, Mannheim, Germany
GASTROENTEROLOGY 2000;118:346-355
Abstract

Background & Aims: The role of virus-specific T-helper lymphocyte reactivity in determining the therapeutic response in chronic hepatitis C virus (HCV) infection is not fully understood.

Methods: We studied CD4+ T lymphocyte proliferation together with interferon (IFN)- and interleukin (IL)-10 production from peripheral blood mononuclear cells in response to 4 HCV antigens (core, NS3, NS4, and NS5) in 25 patients with chronic hepatitis C undergoing antiviral therapy with IFN alone or in combination with ribavirin, prospectively, before, during, and after treatment.

Results: HCV-specific T-cell reactivity was uncommon at baseline but increased markedly during antiviral therapy, peaking around treatment weeks 4-8. Resolution of hepatitis C viremia was significantly more likely in patients who developed HCV-specific T-cell proliferation with increased IFN- production. The main difference in T-cell reactivity of patients treated with IFN plus ribavirin was a significantly lower production of IL-10, whereas lymphocyte proliferation was similar to that in patients receiving IFN monotherapy.

Conclusions: Treatment-induced control of hepatitis C viremia is associated with the development of HCV-specific T-cell responses with enhanced IFN- and low IL-10 production. The greater efficacy of combination therapy with IFN- plus ribavirin may be related to its ability to suppress HCV-specific IL-10 production.

The results show that virological response to treatment is associated with activation of HCV-specific Th cell reactivity, particularly in the early phase between weeks 4 and 8 of treatment. Patients with sustained HCV clearance show much stronger and long-lasting enhancement of virus-specific T-cell reactivity, which correlates with increased IFN- production at week 4 of treatment. In contrast, treatment nonresponders show only weak or absent lymphoproliferation with production of IL-10 rather than IFN- at week 4.

Introduction

Chronic infection with hepatitis C virus (HCV) is a major cause of liver disease and liver cancer worldwide. Effective treatment is needed not only to stop viral replication and progression of liver damage in individual patients, but in addition it would have an important role in the overall control of HCV infection. Until recently, the sole therapeutic option available has been treatment with interferon (IFN)-, which results in sustained remission only in a minority of cases. Three patterns of therapeutic response to IFN- have been recognized. Approximately 50% of patients are nonresponders with failure to normalize serum aminotransferase levels and to lose detectable HCV RNA in the serum. Among the other 50% who do have an initial response to treatment with normalization of aminotransferases, at least half will relapse shortly after treatment is discontinued (relapse patients), thus leaving only 25% of IFN-treated patients with normal aminotransferase levels in the long term (sustained biochemical responders). When the virological endpoint is considered, the sustained response rate is even poorer, with HCV RNA remaining undetectable in the serum at 6 months after stopping treatment in 15% or less of those treated. Recently, 2 major multicenter clinical trials have established that the combination of IFN- with ribavirin (IFN+R) markedly increases the sustained biochemical and virological response rates in previously untreated patients with chronic hepatitis C to about 40% overall and as high as 64% in cases infected with HCV genotype 2 or 3.

The mechanisms by which either IFN monotherapy or IFN+R bring about resolution of infection remain poorly understood. IFN- has direct antiviral effects and a number of immunomodulatory activities that can enhance antiviral immune responses.5 Ribavirin is a nucleoside analogue that inhibits the replication of DNA and RNA viruses, although when used alone in patients with chronic hepatitis C it has no significant effect on HCV replication, despite reducing the levels of liver enzymes.  6-9 HCV-specific T-helper (Th) cell responses have been shown to be important in the resolution of acute HCV infection with strong T-cell reactivity found in patients who clear HCV spontaneously and weak responses in those progressing to chronic infection.10,11 Furthermore, strong and multispecific Th responses have been found in HCV antibody-positive patients without detectable viremia, but not in those with chronic HCV infection and persistent viremia, thus indicating the role of virus-specific T-cell reactivity in the long-term control of viremia.12 Several studies on virus-specific T-cell reactivity in association with IFN treatment have found increased numbers of patients with chronic hepatitis C with demonstrable HCV-specific Th responses either during treatment or after a sustained therapeutic response.13-16 These findings raise

the possibility that enhancement of HCV-specific T-cell reactivity may be one mechanism for successful antiviral treatment. So far, no study has prospectively evaluated the evolution of Th responses during antiviral treatment in standard protocol samples. In this study, we investigated whether the variable therapeutic responses in patients with chronic hepatitis C are associated with different patterns of virus-specific T-cell reactivity. In addition, we looked for differences in the effects of IFN alone compared with combination treatment of IFN+R. We have followed up serially HCV-specific Th cell responses before, during, and after treatment in a group of HCV-infected patients receiving either IFN- alone or IFN+R.

Patients who demonstrated HCV-specific Th reactivity on treatment were more likely to have a virological response to treatment (i.e., undetectable HCV RNA) than those who did not. Of the 18 patients with an end of treatment response, 11 had HCV-specific Th cell reactivity at the time of completion of treatment compared with 1 of the 7 treatment nonresponders (2 = 4.43, P = 0.035; Figure 2). Over the entire study period, the 18 patients with a virological response to treatment showed significant HCV-specific Th cell reactivity on 108 occasions of a total of 508 (21.3%) test points, compared with 15 of 192 (7.8%) test points in the 7 treatment nonresponders (2 = 17.4, P = 0.00003).

The induction of persistent HCV-specific Th cell reactivity (defined as significant T-cell reactivity detected on a minimum of 3 time points during treatment) was found to be associated with treatment response. Of the 10 patients in whom persistent Th cell reactivity was shown, 7 went on to have a sustained treatment response and 3 a

transient treatment response, whereas none were treatment nonresponders (P = 0.01 for sustained vs. nonresponders; P = NS for transient vs. nonresponders, Fisher exact test). Both patients showing significant Th reactivity before treatment had a sustained response to treatment with HCV-specific Th reactivity maintained throughout the study and an increase in the SI on treatment.

The present study shows in a prospective manner that antiviral therapy of patients with chronic hepatitis C is associated with enhancement of HCV-specific CD4+ T-cell

reactivity. In some cases, this immune reactivity is maintained for at least 24 weeks after stopping treatment. These findings are in keeping with previous studies showing that most patients with a sustained virological response after IFN treatment have a significant T-cell proliferative reactivity to HCV antigens, unlike nonresponders to treatment. Serial testing of T-cell proliferation to HCV core protein before and during IFN treatment in 2 groups of patients infected with HCV genotypes 1b and 2 has also shown IFN-induced enhancement of T-cell responses, which was greater in patients with genotype 2 than in patients infected with genotype 1b.

An interesting observation in the present study is the change of T-cell reactivity in patients with posttreatment relapse. Among these transient responders, 5 of 7 cases had HCV-specific CD4+ T-cell reactivity detectable during but not before treatment; in 4 of them, this was maintained during posttreatment follow-up. This differs from the pattern observed in treatment nonresponders, who showed no HCV-specific Th reactivity either before or after treatment, and may indicate one factor contributing to the success of a second course of IFN+R in transient responders, although there is very little benefit in nonresponders.