Interferon-gamma (IFN-γ) enzyme-linked immunospot (ELISpot) assay for the 4 children. The 4 cases analyzed did not have detectable human immunodeficiency virus type 1 (HIV-1) Gag or Nef protein-specific T cells in their peripheral blood mononuclear cells (PBMCs). A, HIV-1 Gag and Nef responses were screened using an IFN-γ ELISpot assay. Spot-forming units per million PBMCs are reported after stimulation with each corresponding antigen's peptide pool tested at 1 µg/mL/peptide. ∧ Represents responses characterized by a >2.5-fold increase over the no-treatment (DMSO) condition. B, Representative ELISpot wells for case 1 are shown. Each experiment was performed in duplicate. Abbreviations: CMV, cytomegalovirus; DMSO, dimethyl sulfoxide; HIV-1, human immunodeficiency virus type 1; NT, no treatment; PBMCs, peripheral blood mononuclear cells; SEB, staphylococcal enterotoxin B; SFU, spot-forming units.