Transient immunological control during acute hepatitis C virus infection: ex vivo analysis of helper T-cell responses

Hepatitis C virus (HCV) readily sets up persistence after acute infection. Cellular immune responses are thought to play a major role in control of the virus. Failure of CD4+ T-cell responses in acute disease is associated with viral persistence but the dynamics of this are poorly understood. We aimed to assess such responses using a novel set of Class II tetrameric complexes (tetramers) to study helper T-cells ex vivo in acute disease. We analysed the HCV-specific CD4+ T-cell response in a patient with acute hepatitis c infection. We were able to track the virus-specific CD4+ T-cells directly ex vivo with HLA DR4 tetramers. Proliferative responses were absent initially, recovered as viral load dropped and were lost again during relapse. Longitudinal tetramer analyses showed expanded populations of antiviral CD4+ T-cells throughout acute infection despite lack of proliferation. A pattern of transient CD4+ T-cell proliferative responses as HCV is partially controlled is observed. Failure to control virus is associated with emergence of 'dysfunctional' CD4+ T-cell populations. Failure to control HCV in acute disease may relate to the capacity to sustain efficient immune responses as virus attempts to 'bounce back' after partial control.

Different levels of T-cell receptor triggering induce distinct functions in hepatitis B and hepatitis C virus-specific human CD4(+) T-cell clones

CD4(+) T cells play a major role in the host defense against viruses and intracellular microbes. During the natural course of such an infection, specific CD4(+) T cells are exposed to a wide range of antigen concentrations depending on the body compartment and the stage of disease. While epitope variants trigger only subsets of T-cell effector functions, the response of virus-specific CD4(+) T cells to various concentrations of the wild-type antigen has not been systematically studied. We stimulated hepatitis B virus core- and hepatitis C virus NS3-specific CD4(+) T-cell clones which had been isolated from patients with acute hepatitis during viral clearance with a wide range of specific antigen concentrations and determined the phenotypic changes and the induction of T-cell effector functions in relation to T-cell receptor internalization. A low antigen concentration induced the expression of T-cell activation markers and adhesion molecules in CD4(+) T-cell clones in the absence of cytokine secretion and proliferation. The expression of CD25, HLA-DR, CD69, and intercellular cell adhesion molecule 1 increased as soon as T-cell receptor internalization became detectable. A 30- to 100-fold-higher antigen concentration, corresponding to the internalization of 20 to 30% of T-cell receptor molecules, however, was required for the induction of proliferation as well as for gamma interferon and interleukin-4 secretion. These data indicate that virus-specific CD4(+) T cells can respond to specific antigen in a graded manner depending on the antigen concentration, which may have implications for a coordinate regulation of specific CD4(+) T-cell responses.

Sustained dysfunction of antiviral CD8+ T lymphocytes after infection with hepatitis C virus

Hepatitis C virus (HCV) sets up persistent infection in the majority of those exposed. It is likely that, as with other persistent viral infections, the efficacy of T-lymphocyte responses influences long-term outcome. However, little is known about the functional capacity of HCV-specific T-lymphocyte responses induced after acute infection. We investigated this by using major histocompatibility complex class I-peptide tetrameric complexes (tetramers), which allow direct detection of specific CD8+ T lymphocytes ex vivo, independently of function. Here we show that, early after infection, virus-specific CD8+ T lymphocytes detected with a panel of four such tetramers are abnormal in terms of their synthesis of antiviral cytokines and lytic activity. Furthermore, this phenotype is commonly maintained long term, since large sustained populations of HCV-specific CD8+ T lymphocytes were identified, which consistently had very poor antiviral cytokine responses as measured in vitro. Overall, HCV-specific CD8+ T lymphocytes show reduced synthesis of tumor necrosis factor alpha (TNF-alpha) and gamma interferon (IFN-gamma) after stimulation with either mitogens or peptides, compared to responses to Epstein-Barr virus and/or cytomegalovirus. This behavior of antiviral CD8+ T lymphocytes induced after HCV infection may contribute to viral persistence through failure to effectively suppress viral replication.

Hepatitis C virus-specific CD4+ T cell response after liver transplantation occurs early, is multispecific, compartmentalizes to the liver, and does not correlate with recurrent disease

The role of hepatitis C virus (HCV)-specific CD4+ T cells in recurrent HCV infection after orthotopic liver transplantation (OLTx) is unclear. In parallel, 73 intrahepatic and 73 blood-derived T cell lines were established from 34 patients. At a single cell level, virus-specific interferon (IFN)-gamma production to various HCV proteins was determined by ELISPOT assay: 45 (62%) of 73 liver- or blood-derived T cell lines produced IFN-gamma in response to one of the HCV antigens. HCV specificity was detected mainly in the liver (47% vs. 23% in the blood; P<.05, chi(2) test) and was detectable earlier (< or =6 months) significantly more often than later (>6 months) after OLTx (78% vs 49%; P<.05, chi(2) test). Histology, histologic activity index, liver enzymes, and virus load did not correlate with the occurrence of HCV-specific CD4+ T cells. Despite strong immunosuppressive treatment, OLTx recipients can develop an early, multispecific, preferentially intrahepatic CD4+ T cell response that decreases over time, making it a potential candidate target for novel therapeutic approaches in the transplant setting.

CD8+ T lymphocyte responses are induced during acute hepatitis C virus infection but are not sustained

Cellular immune responses are likely to play a key role in determining the clinical outcome in acute infection with hepatitis C virus (HCV), but the dynamics of such responses and their relationship to viral clearance are poorly understood. In a previous study we have shown highly activated, multispecific cytotoxic T lymphocyte responses arising early and persisting in an individual who subsequently cleared the virus. In this study the HCV-specific CD8+ lymphocytes response has been similarly analyzed, using peptide-HLA class I tetramers, in a further nine individuals with documented acute HCV infection, six of whom failed to clear the virus. Significant populations of virus-specific CD8+ lymphocytes were detected at the peak of acute hepatic illness (maximally 3.5% of CD8+ lymphocytes). Frequencies were commonly lower than those seen previously and were generally not sustained. Early HCV-specific CD8+ lymphocytes showed an activated phenotype in all patients (CD38+ and HLA class II+), but this activation was short-lived. Failure to sustain sufficient numbers of activated virus-specific CD8+ lymphocytes may contribute to persistence of HCV.

CD8+ T lymphocyte responses are induced during acute hepatitis C virus infection but are not sustained

Cellular immune responses are likely to play a key role in determining the clinical outcome in acute infection with hepatitis C virus (HCV), but the dynamics of such responses and their relationship to viral clearance are poorly understood. In a previous study we have shown highly activated, multispecific cytotoxic T lymphocyte responses arising early and persisting in an individual who subsequently cleared the virus. In this study the HCV-specific CD8+ lymphocytes response has been similarly analyzed, using peptide-HLA class I tetramers, in a further nine individuals with documented acute HCV infection, six of whom failed to clear the virus. Significant populations of virus-specific CD8+ lymphocytes were detected at the peak of acute hepatic illness (maximally 3.5% of CD8+ lymphocytes). Frequencies were commonly lower than those seen previously and were generally not sustained. Early HCV-specific CD8+ lymphocytes showed an activated phenotype in all patients (CD38+ and HLA class II+), but this activation was short-lived. Failure to sustain sufficient numbers of activated virus-specific CD8+ lymphocytes may contribute to persistence of HCV.

CD8+ T lymphocyte responses are induced during acute hepatitis C virus infection but are not sustained

Cellular immune responses are likely to play a key role in determining the clinical outcome in acute infection with hepatitis C virus (HCV), but the dynamics of such responses and their relationship to viral clearance are poorly understood. In a previous study we have shown highly activated, multispecific cytotoxic T lymphocyte responses arising early and persisting in an individual who subsequently cleared the virus. In this study the HCV-specific CD8+ lymphocytes response has been similarly analyzed, using peptide-HLA class I tetramers, in a further nine individuals with documented acute HCV infection, six of whom failed to clear the virus. Significant populations of virus-specific CD8+ lymphocytes were detected at the peak of acute hepatic illness (maximally 3.5% of CD8+ lymphocytes). Frequencies were commonly lower than those seen previously and were generally not sustained. Early HCV-specific CD8+ lymphocytes showed an activated phenotype in all patients (CD38+ and HLA class II+), but this activation was short-lived. Failure to sustain sufficient numbers of activated virus-specific CD8+ lymphocytes may contribute to persistence of HCV.

Cytokine profile of liver- and blood-derived nonspecific T cells after liver transplantation: T helper cells type 1/0 lymphokines dominate in recurrent hepatitis C virus infection and rejection

Orthotopic liver transplantation (OLT) is a successful treatment in patients with hepatitis C virus (HCV)-associated end-stage liver disease worldwide. T lymphocytes and their cytokines are believed to have a pivotal role in the defense against HCV and in allograft rejection. An immunosuppressive drug regimen may cause a cytokine imbalance toward a T helper (TH) cell type 2 profile that is associated with the persistence of infection and acceptance of the graft. The aim of this study is to assess whether cytokine imbalances toward a TH1- or TH2-type response may have a role in recurrent HCV infection and rejection after OLT. Twenty-one intrahepatic T-cell lines of 15 patients with recurrent HCV infection after OLT (group A) and 15 lines of 11 patients with rejection (group B) were studied. Both patient groups had received liver allografts because of HCV-associated end-stage liver disease. Patients with HCV-induced liver disease who did not undergo OLT served as controls: 17 patients with chronic hepatitis C (CH-C) and 8 patients with cirrhosis. At the time of liver biopsy, 14 blood-derived T-cell lines of 12 patients with recurrent HCV infection, 7 of 10 patients with rejection, and 18 of 18 control patients were also investigated. Regardless of the underlying disease (recurrent HCV infection, rejection, HCV-induced hepatitis, and cirrhosis), all liver tissue-derived T-cell lines produced interferon-gamma; some additionally produced interleukin-4 (IL-4), but none produced IL-10, indicating that the TH0/1 cytokine profile dominates. T-cell lines showing a TH1 cytokine profile derived from intrahepatic T cells could be established significantly more often in recurrent HCV infection and rejection than in controls with CH-C (Fisher's exact test, P <.05). The cytokine profile of intrahepatic T cells did not differ from that obtained in peripheral blood. TH0/1 cytokine profile dominates the intrahepatic and blood-derived immune response in recurrent HCV infection and rejection after OLT regardless of the mode of immunosuppression. The lymphokine profile of immunocompromised patients with recurrent HCV infection or rejection does not differ principally from that of patients with HCV-induced hepatitis and cirrhosis, but seems to show a TH1 profile significantly more often.

Recurrence of hepatitis C virus after loss of virus-specific CD4(+) T-cell response in acute hepatitis C

BACKGROUND & AIMS

The prospective comparison of patients with acute hepatitis C virus (HCV) who spontaneously clear the virus with those who cannot achieve viral elimination and progress to chronic hepatitis offers the unique opportunity to analyze natural mechanisms of viral elimination.

METHODS

We studied the HCV-specific CD4(+) T-cell response in 38 patients with acute HCV and correlated the clinical course with the antiviral immune response. The individual HCV-specific T-cell response was assessed in a proliferation assay ((3)H-thymidine uptake) and an enzyme-linked immunospot assay.

RESULTS

Patients were classified according to their clinical course and pattern of CD4(+) T-cell responses in 3 categories: first, patients mounting a strong and sustained antiviral CD4(+)/Th1(+) T-cell response who cleared the virus (HCV RNA-negative; n = 20); second, patients who were unable to mount an HCV-specific CD4(+) T-cell response and developed chronic disease (n = 12); and third, patients who initially displayed a strong CD4(+) T-cell response and eliminated the virus (HCV PCR-negative) but subsequently lost this specific T-cell response (n = 6). The loss of the HCV-specific CD4(+) T-cell response was promptly followed by HCV recurrence.

CONCLUSIONS

The results indicate that a virus-specific CD4(+)/Th1(+) T-cell response that eliminates the virus during the acute phase of disease has to be maintained permanently to achieve long-term control of the virus. The induction and/or maintenance of virus-specific CD4(+) T cells could represent a promising therapeutic approach in HCV infection.

Identification of HLA-A3 and -B7-restricted CTL response to hepatitis C virus in patients with acute and chronic hepatitis C

The inverse relationship between peripheral blood CTL responsiveness to multiple hepatitis C virus (HCV) epitopes and viral titer in patients with persistent HCV infection suggests that enhancement of the CTL response might result in viral clearance. Since several HLA-A2-restricted HCV CTL epitopes are already known, we aimed to identify CTL epitopes restricted by other HLA types in an effort to expand the epitope repertoire available for T cell-mediated therapeutic vaccine development. Scanning of 14 different HCV genome sequences for the presence of conserved peptides containing the HLA-A3 and -B7 motifs revealed 9- to 10-mer peptides that were synthesized and assayed for binding to HLA-A3, -B7 supertype molecules. Peptides with good HLA-binding affinities and cross-reactivities with at least three of five most common molecules of each supertype were tested for the ability to stimulate a memory CTL response in the peripheral blood from selected HCV-infected patients and normal seronegative donors in vitro. We identified eight HLA-A3 supertype-restricted CTL epitopes and one HLA-B7 supertype-restricted CTL epitope that were recognized by infected patients but not by healthy seronegative donors. HLA class I serotyping of 158 chronically infected patients revealed that 80% expressed one or more of HLA molecules belong to either the A2, A3, or B7 supertypes. In conclusion, the epitopes, herein identified combined with previously defined HLA-A2-restricted CTL epitopes, should be useful for the design of an ethnically unbiased, therapeutic CTL vaccine for the treatment of patients with chronic HCV infection.