FIG 1.

Syncytial variants display unique properties. (A) Diagram of proteins required for cell-to-cell spread that are relevant to this study. The fusion machinery consists of gB, gH/gL, and gD. Basic residues in gD that are needed for cell-to-cell spread are indicated (+++). Eight substitutions in gB, gK, UL20, and UL24 that dysregulate the fusion machinery are represented with red dots, and the specific changes are listed below the diagram. The accessory proteins investigated are gE, gI, and UL16, which are highlighted in yellow. (B) Vero cells were infected with each Syn variant, cell lysates were harvested at 18 h postinfection (hpi), and immunoblots were probed for VP5, gE, gI, and UL16 expression. (C) Vero cells were infected with each Syn variant at a low MOI and overlaid with 0.5% agarose in DMEM. At 36 hpi, 30 individual syncytia were imaged for each variant: the average areas are shown. (D) Vero cells were infected at a low MOI, incubated for 36 h, fixed, and stained with DAPI and an antibody against the major capsid protein, VP5. Corresponding bright-field and fluorescent images were taken for each variant. The scale bar is set at 50 μm.