Functional characterization of capsid-specific T cells. (A) Intracellular IFN-γ staining on subject E's week-6 PBMCs; numbers indicate the percentage of CD4⁻CD8⁺ T cells that are IFN-γ⁺. Cells are gated on forward and side scatter, on singlets, and on CD4⁻CD8⁺ T cells. (B) Representation of 3 independent intracellular IFN-γ staining experiments (average ± SD of % CD4⁻CD8⁺IFN-γ⁺ T cells). (C) Perforin ELISpot on subject E's PBMCs. Medium indicates medium only control; irrelevant, human retinal pigment epithelium 65 protein; AAV-1, AAV-1 capsids; and positive, CEF peptide pool. Data are expressed in SFU per 10⁶ PBMCs. SFU per 10⁶ PBMCs were compared between AAV-1 and medium control (P = .008), AAV-1, and irrelevant control (P = .007), and AAV-1 and positive controls (P > .05, not significant).