TAP-independent antigen presentation requires endogenous protein synthesis. (A) T2.B35 cells were infected with AdUL138 with or without UV inactivation and then assessed for endogenous presentation of pUL138 CD8⁺ T-cell epitope at 16 hours after infection. (B) T2 cells (HLA-B35⁻) were electroporated with an expression plasmid encoding pUL138 and then cocultured with mock electroporated T2.B35 (HLA-B35⁺) cells for 18 hours. These cells were then used as antigen-presenting cells in a standard intracellular cytokine secretion assay. The absolute (mean) percentages of T-cell response to reference cells were 20.2% and 35.9% in panels A and B, respectively. Data shown are from 2 independent experiments, each performed in triplicate samples (mean ± SEM).