Construction and expression of EBVgp350/220-F chimeric protein. (A) Diagram of full length EBVgp350/220-WT (top), full length wild type NDV-F (middle), and chimeric EBVgp350/220-F (bottom) (not to scale). C-terminal amino acid sequences comprising the gp350/220 ectodomain (ED) and N-terminal sequences from NDV-F HR2 at the point of fusion are indicated. The bolded black line represents amino acid sequences deleted in frame in the gp220 isoform. Both isoforms contain the N-terminal B-cell attachment epitope. (B) Expression of EBVgp350/220-WT and EBVgp350/220-F on the surface of four cell lines (CHO, ELL-0, Vero and 293A). 106 cells from each line were transfected with 1 μg of pCAGGS-EBVgp350/220 WT, pCAGGS-EBVgp350/220-F or pCAGGS alone (vector control). At 72 h post-transfection, cells were stained with anti-gp350/220 mAb-72A1 followed by AF488-coupled goat anti-mouse IgG (H + L) and analyzed by flow cytometry.