Antigen mapping assays. (A) CD4⁺ T-cell clone P2c2 specific for the EBNA2_276-295 PRS epitope and (B) LCL-reactive clones P1 c1, N1 c7, and N3 c1 were cocultured overnight with HLA class II–matched B95.8 LCL cells and HLA class II–matched CD40L-activated B lymphoblasts either uninfected (B blasts) or infected with a panel of recombinant MVA vectors each expressing an invariant chain (Ii)–targeted form of one of the EBV latent proteins EBNA-1 (glycine-alanine repeat-deleted, Ii E1dGA), EBNA-2 (Ii E2), EBNA-3A (Ii E3A), EBNA-3B (Ii E3B), EBNA-3C (Ii E3C), or LMP-2 (Ii LMP2); parallel assays on EBNA-LP and LMP-1 peptide panels gave uniformly negative results (data not shown). (C) B cells isolated from autologous PBMCs (Auto) and from HLA mismatched PBMCs (Allo) were infected with B95.8 EBV. At day 5 and 12 after infection, 5 × 10⁴ target B cells/well were cocultured with CD4⁺ T-cell clones N1c9 and N1c3 in an IFNγ ELISA. In each case, the autologous B95.8 LCL was used as a positive control target. All results shown are the mean ± 1 SD of triplicate wells in which IFNγ release into the supernatant medium was determined by ELISA (in ng/mL). Results are representative of those seen on 3 occasions of testing.