FIG. 4.

Mapping of minimal epitopes of HCV-specific CD4⁺ T-cell clones. Nine sets of synthesized N-terminal and C-terminal stepwise truncated peptide variants (up to 25 variants per epitope) were synthesized, and specific CD4⁺ T-cell clones were tested against the complete set of truncated variants. The four peptides neighboring the position where stimulatory capacity was lost were selected, and nine CD4⁺ T-cell clones (A to I) were stimulated with the peptides over a broad range of concentrations (x axis). The results are shown as counts per minute (y axis). Minimal stimulatory sequences were between 8 and 13 amino acids in length, but optimal T-cell stimulation was usually observed with 10- to 15-mers.