AgAb can accommodate and efficiently elicit presentation of large viral antigens. (A) We fused fragments of EBNA3C with the C terminus of the Ig heavy chain that recognizes human CD21 and assessed their ability to induce specific T-cell recognition. Three AgAbs were thus generated with a 102-, 300-, or 963-bp fragment from the EBNA3C open reading frame, each of which include the 5H11 epitope. (B) The AgAbs were expressed in 293 cells and submitted to a western blot analysis using antibodies specific for mouse IgG proteins. Nontransfected 293 cells provided negative controls and anti-human CD20 antibody was used as a control for transfection. (C) The results of a T-cell assay performed in triplicate with 1 of the ex vivo–expanded 5H11-specific T-cell clones and LCLs loaded with the larger AgAbs. All assays were performed in triplicate and means and standard deviations are shown.