Michio Imawari

A minimal and optimal cytotoxic T cell epitope within hepatitis C virus nucleoprotein

Amino acid residues 81-100 of the hepatitis C virus (HCV) nucleoprotein contain a cytotoxic T cell epitope that is recognized by cytotoxic T lymphocytes (CTLs) in association with human leukocyte antigen B44. With panels of truncated and overlapping peptides, the minimal and optimal epitope recognized by CTLs was shown to be a 9-mer peptide (residues 88-96). The peptide can stimulate effectively CTLs that are able to recognize endogenously synthesized and processed HCV nucleoprotein.

Three new cytotoxic T cell epitopes identified within the hepatitis C virus nucleoprotein.

Cytotoxic T lymphocytes (CTLs) may play a role in host defence against hepatitis C virus (HCV) infection, and HCV-specific CTL epitopes may be included in vaccines to induce protective CTLs. We identified three new epitopes within the HCV nucleoprotein recognized by CTLs. HCV nucleoprotein residues 28-37 are the minimal epitope recognized by CTLs in association with the class I human leukocyte antigen B60, and epitopes in HCV nucleoprotein residues 111-130 and 161-180 are both recognized by CTLs in association with the class II human leukocyte antigen DRBI*08032.

HLA B44-restricted cytotoxic T lymphocyte responses to the peptides of HCV nucleoprotein residues 81-100 in patients with chronic hepatitis C.

Human leukocyte antigen B44-restricted cytotoxic T lymphocytes (CTLs) recognize an epitope in hepatitis C virus (HCV) nucleoprotein residues 81–100. CTLs that recognize two wild-type peptides 81–100 of HCV genotypes 1b/II and 2a/III were generated from peripheral blood lymphocytes of each of three patients studied. Although CTLs that recognize a wild-type peptide 81–100 of HCV genotypes 1a/I and 2b/IV were not generated from any patient, CTLs that recognize peptide 81–100 of a rate HCV isolate of type 1a/I were generated from two patients. The results suggest that HLA B44-restricted CTLs recognize most, if not all, HCV isolates of types 1b/II and 2a/III and rare variants of type 1a/I and that the wild-type HCV isolates of genotypes 1a/I and 2b/IV may be less immunogenic for HLA B44-restricted CTLs.

Immune response to hepatitis C virus core protein in mice.

To analyse the immune response to the hepatitis C virus (HCV) core protein, we immunized mice with the protein. BALB/c (H‐2d) and C3H/He (H‐2k) mice were high responders, while C57BL/6 (H‐2b) mice were low responders in terms of Th cell proliferative responses. All the strains showed comparable levels of antibody responses to the HCV core protein. The Th cell lines recognized residues 61–90 of the HCV core protein in the context of I‐Ad (BALB/c) and residues 11–30 in the context of I‐Ek (C3H/He), respectively. The Th cell lines were restricted by I‐Ab in C57BL/6 mice but recognized no synthetic peptide that spanned the region, although derivative clones from the line recognized residues 1–20 and 91–110 of the HCV core protein, respectively. The Th cell lines were Thl subset in all three strains based on the profile of lymphokine secretion. The major B cell epitope of the protein was found to be within residues 21–40 of the HCV core protein in all three strains. These observations should be useful for better understanding of the immune response to the HCV core protein in vivo.

Recognition of Hepatitis C Virus Nucleocapsid Protein-derived Peptides by Cytotoxic T Lymphocytes

Cytotoxic T lymphocytes (CTL) are thought to be involved in the immune clearance of virus-infected cells as well as in the pathogenesis in viral infection. We studied the CTL response to the putative nucleocapsid protein (NP) of hepatitis C virus (HCV) in patients with chronic hepatitis C. Peripheral blood lymphocytes (PBL) were stimulated repeatedly with synthetic HCV-NP peptides. HCV-NP peptide-specific CTL could be induced from PBL in seven of ten HCV-positive patients with chronic hepatitis while they could not be induced from PBL of HCV-negative individuals. The results suggests the existence of HCV-specific CTL in the peripheral blood of patients with chronic hepatitis C, and provide a strategy to study the role of CTL in the viral clearance and the pathogenesis in HCV infection.