FIG. 4.

Evidence of peptide contamination within two pools of overlapping peptide sets obtained from manufacturer B. Cryopreserved PBMC from four HIV-1-seronegative subjects were tested for their ability to respond to three different HIV-1-derived peptide pools (Gag, Pol, and Env) in a CFC assay for IFN-γ production. Note that only the subjects possessing the HLA-A0201 allele respond to the Env and Pol peptide sets, and the response is observed within the CD3⁺ CD8⁺ T-cell population (A) but not the CD3⁺ CD4⁺ T-cell population (B). (C) IFN-γ ELISPOT response from an HIV-1-seronegative subject to all individual peptides (326 peptides) from the Env (179 peptides) and Pol (147 peptides) peptide sets. Three peptides, Env 97, Env 137, and Pol 31 (indicated with circles), were identified clearly as positive stimulators of IFN-γ production in the HLA-A0201-positive subject (subject BC238). Pos, positive; Neg, negative.