Comparison of the breath of the HCV-specific CD4⁺ T-cell response in patients with chronic GT1 or non-GT1 infection or spontaneously resolved HCV. (A) PBMCs from 44 patients with chronic HCV infection were CD8⁺ depleted and stimulated with recombinant HCV proteins (or overlapping peptides) covering the entire polyprotein in the presence of recombinant IL-2. Expanded cell lines were tested for IFN-γ production upon stimulation with pools of 10 to 20 overlapping peptides by ELISPOT. All peptide pools eliciting a positive response by IFN-γ production were further deconvoluted to identify specific 20mer peptides targeted by the CD4⁺ T-cell response. Each single response detected in the ELISPOT assay was confirmed by ICS for IFN-γ production as well. Horizontal bars indicate the mean numbers of targeted HCV CD4⁺ T-cell responses against single peptides for each patient as tested by ICS. The number of responses is significantly higher (P = .017) in chronically infected patients with non-GT1 virus than in patients infected with GT1 virus when comparing the number of CD4⁺ T-cell responses detected with GT1-specific peptides in short-term lines across the entire polyprotein. (B) Genotype-specific subanalysis of previously published data¹⁰  reveals that within the group of patients with spontaneously resolved HCV, more responses are detected with GT1 peptide set in patients who are serologically GT1 than patients who are tested non-GT1 (P < .05). Serotyping was performed with the Murex HCV serotyping 1-6 assay (Abbott; “Patients, materials, and methods”).