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.