Purified EBVgp350/220-F VLPs bind CD21 and CD35. (A) Raji (positive control), Nalm6 (negative control) and CD21 or CD35 transfected sublines of (A) Nalm6 and (B) K562 were characterized and prepared as described . First, the respective complement receptors were stained with primary mAbs followed by AF594-coupled goat Fab’2 anti-mouse IgG (red). Attachment of EBVgp350/220-F VLPs was next detected directly with AF488-coupled anti-gp350/220 (mAb-2 L10)(green) that recognizes an epitope distal to the attachment site. Cell content was documented by nuclear staining with DAPI. Sequential confocal images showed that the chimeric VLP binds to CD21 or CD35 bearing cells whereas no binding to receptor negative Nalm6 cells was seen. Visualization of 3D merged images confirmed extensive co-localization (yellow) of the chimeric VLPs with both CD21 and CD35.