Natural cytotoxicity and antibody-dependent cellular cytotoxicity (ADCC) is not impaired in patients suffering from chronic hepatitis C.

BACKGROUND/AIMS: Recent observations suggest that natural killer (NK) cell activity might be impaired in chronic hepatitis C. However, to date antibody-dependent cellular cytotoxicity (ADCC) has not been studied in chronic hepatitis C in detail. METHODS: Therefore, we investigated spontaneous and cytokine-induced (interleukin-2 and interferon-gamma) natural cytotoxicity and ADCC in 29 patients suffering from chronic hepatitis C and 19 healthy controls. Cytotoxicity was determined with a flow-cytometric assay, which can also assess monocyte cytotoxicity. As target cells we used the colorectal tumor cell line HT29 and the lymphoma cell line Raji. RESULTS: We found no significant differences with respect to spontaneous cytotoxicity (HCV versus healthy controls (32 vs. 46%) and 17-1A specific ADCC (59 vs. 48%), even if isolated monocytes or NK cells were studied. Preincubation and stimulation of effector cells with cytokines increased both natural cytotoxicity and ADCC by 20-30%. However, natural cytotoxicity and ADCC after stimulation did not differ between the two groups. CONCLUSIONS: Our data obtained with a long-term cytotoxicity assay do not reveal impaired cytolytic capacity of the innate immune system in chronic hepatitis C, even when isolated monocytes and NK cells were studied as effector cells.

Transient loss of T-cell reactivity in a patient with hepatitis C virus reinfection.

BACKGROUND/AIMS: Self-limited acute hepatitis C virus (HCV) infection with spontaneous recovery is only rarely observed in clinical practice. All existing studies correlate strong cellular immune responses to the recovery from HCV infection. CASE REPORT: Here, we present a 49-year-old haemophiliac, who had successfully recovered from an acute hepatitis, which was classified retrospectively as HCV infection based on his antibody profiles. This patient was reinfected with HCV 18 years later from an exogenous source, and successfully recovered from this reinfection within 2 months. After his first hepatitis the patient displayed strong cellular responses against recombinant HCV proteins. During reinfection, T-cell proliferation was markedly reduced, while HCV antibody titres increased. However, E2 antibodies were consistently not detectable. T-cell proliferation returned to the pre-reinfection level only several months after loss of viraemia. DISCUSSION: Our observations resulted in the unexpected finding that our patient cleared HCV reinfection despite an apparent loss of his pre-existing T-cell reactivity in the peripheral blood.

Intrahepatic MxA expression is correlated with interferon-alpha expression in chronic and fulminant hepatitis.

Interferon-alpha (IFN-alpha) has potent pro-inflammatory and anti-viral functions. It exerts its effects by inducing intracellular proteins such as MxA. To analyse the role of intrahepatic interferon activation, IFN-alpha and MxA expression was studied by immunohistochemistry in explant livers of 20 patients with fulminant hepatic failure (FHF), 41 patients with chronic liver disease (CLD), and ten normal controls (NCs). In NCs only small numbers of Kupffer cells, but no hepatocytes, showed IFN-alpha and MxA expression. In contrast, significantly enhanced numbers of IFN-alpha- and MxA-positive Kupffer cells, along with small numbers of MxA-positive and larger numbers of IFN-alpha-positive lymphocytes, were found in CLD and in FHF. MxA protein was also expressed on hepatocytes and bile ducts in the vicinity of IFN-alpha-positive inflammatory infiltrates (hepatocytes: NCs: 0%, CLD: 8%, FHF: 68%; bile ducts: NCs: 19%, CLD: 46%, FHF: 83%). A significant correlation was found between the numbers of IFN-alpha- and MxA-positive cells (r=0.67, p<0.001). Thus, large amounts of IFN-alpha are released in the livers of patients with FHF, which is likely to contribute to immune-mediated liver cell damage. Intrahepatic MxA expression corresponds to IFN-alpha produced particularly by infiltrating inflammatory cells, rather than by hepatocytes themselves.

Flow cytometric analysis of peptide binding to major histocampatibility complex class I for hepatitis C virus core T-cell epitopes.

BACKGROUND/METHODS: To characterize the repertoire of T-cell epitopes on the hepatitis C virus (HCV) core protein, we studied major histocompatibility complex (MHC) class I binding of 75 decapeptides on 20 human B-cell lines and murine spleen cells using a flow cytometric assay. The results were compared with MHC class I stabilization on T2 cells, the SYFPEITHI algorithm, and known T-cell epitopes from the literature. RESULTS: Binding of peptides proved to be specific for MHC class I molecules. We observed peak fluorescence signals at positions amino acids (aa) 35-44, aa 87-96, aa 131-140, and aa 167-176 in virtually all HLA-A2-positive cell lines. These sites corresponded to T-cell epitopes predicted by SYFPEITHI and the positions of known T-cell epitopes, whereas T2 stabilization was at variance for two peptides. The assay was applied to HLA-A2-negative cells and murine spleen cells without further modification, and identified additional peptides, corresponding to known T-cell epitopes. CONCLUSIONS: Peptide binding to different MHC class I alleles can be mapped rapidly by a flow cytometric assay and enables a first orientation on the sites of possible T-cell epitopes. Application of this assay to HCV core suggests a rather limited repertoire of epitopes in the Caucasoid population.