UL11 is required to activate the gE–UL16 interaction. Vero cells were transfected to express the indicated proteins alone (A), pairwise (B), or in combinations of three (C and D). At 16 to 18 h after transfection, the cells were fixed, stained with the appropriate antibodies, and examined by confocal microscopy. For triple transfections, the panels show the images of individual proteins being analyzed in the same cell.