liver-infiltrating lymphocytes 4 of patients with chronic hepa-A cytotoxic T lymphocyte (CTL) response to the hepatitis C, the role of CTL responses in HCV infection is untitis C virus (HCV) nucleoprotein residues 88-96 that are known. HCV infection frequently persists and is implicated the minimal and optimal epitope for human leukocyte in the development of chronic hepatitis, cirrhosis, and hepatoantigen (HLA) B44-restricted CTLs was assessed in 27 cellular carcinoma. 5 Posttransfusion HCV infection has de-HLA B44-positive patients with chronic HCV infection.
creased substantially after introduction of an anti-HCV assay Serum HCV RNA concentration and the amino acid sefor blood screening, but community-acquired HCV infection quence of the residues 81-100 were also determined.
still occurs. Interferon therapy is effective in less than 50% Three patients were infected with HCV with uncommon of patients with chronic hepatitis C. 6 Understanding the role amino acid substitutions within the epitope. One was of CTL responses in HCV infection may contribute to the infected with HCV with an amino acid substitution in development of strategies for the prevention of HCV infection the flanking residues of the epitope. To stimulate CTLs and the elimination of HCV from infected individuals. in the peripheral blood, 9-mer peptides that corre-Recently, we showed the presence of CTLs that recognize sponded to the residues 88-96 of the individual patients endogenously synthesized HCV antigen in the peripheral were synthesized and used. Seven of the 27 patients demblood of some patients with HCV infection by stimulation onstrated a CTL response to the residues 88-96 with of peripheral blood lymphocytes (PBLs) with HCV synthetic specific cytotoxic activities higher than 20%. The CTL peptides. 3 activities were significantly higher in patients with a
The CTLs recognized an epitope in the HCV nucleoprotein low titer of serum HCV RNA than in those with a high residues 81-100 in association with human leukocyte antigen titer of serum HCV RNA (P Γ
.0006). Some of the patients (HLA) B44. The minimal and optimal epitope was further dethat demonstrated a CTL response to the residues 88fined to be the residues 88-96. 7 The 9-mer peptide of the resi-96 also demonstrated a CTL response to a newly identidues 88-96 was recognized by and stimulated the CTLs more fied HLA B44-restricted CTL epitope or a known HLA efficiently than the 20-mer peptide of the residues 81-100.
A11-restricted CTL epitope or both. No apparent associa-
In a characteristic antiviral CTL response in vivo, immunotion was observed between the CTL response and the dominant CTLs recognize only one or a few multiple immunostage of disease, or between the CTL response and the genic CTL epitopes in the antigen, 8,9 but as many as five grade of necroinflammatory activity. The results suggest different epitopes for HCV-specific CTLs were detected in a that the HLA B44-restricted CTLs together with other single individual. 10 CTL activities to HCV could not be dem-HCV-specific CTLs may inhibit the outgrowth of HCV onstrated in fresh PBLs of patients with chronic HCV infecand that high-titer infection with HCV may suppress the tion. In vitro secondary stimulation with antigen was neces-CTL responses. (HEPATOLOGY 1997;25:705-712.) sary to detect HCV-specific CTLs. Because no appropriate cells synthesizing the HCV antigen endogenously are avail-Cytotoxic T lymphocytes (CTLs) are thought to be one of able, we used synthetic HCV peptides to stimulate CTLs; the the major host defense arms against viral infection 1 and are method could induce CTLs that are not necessarily immunoalso implicated in the immunopathogenesis of viral infecdominant in vivo. The HLA B44-restricted CTL epitope may tion. 2 Although hepatitis C virus (HCV)-specific CTLs have represent the immunodominant CTL epitope or one of the been demonstrated in both the peripheral blood 3 and among multiple immunogenic CTL epitopes in the HCV antigen in HLA B44-positive patients infected with HCV.
In the present study, we studied the relationship of HLA Abbreviations: CTL, cytotoxic T lymphocyte; HCV, hepatitis C virus; PBL, peripheral B44-restricted CTL responses and viral load in 27 HLA B44blood lymphocyte; HLA, human leukocyte antigen; EBV, Epstein-Barr virus; VAC-HCVc, positive patients infected with HCV. We also studied CTL recombinant vaccinia virus that expresses the nucleoprotein of HCV; BCL, Epstein-Barr responses to multiple peptides synthesized based on the virus-transformed B cell line; Eu, europium; PCR, reverse-transcription polymerase chain HLA-binding motifs within the HCV proteins, known HCVreaction.