FIG. 4.

Absence of gp48 expression after disruption of ORF27. (A) BHK-21 cells were infected (18 h, 2 PFU/cell) as indicated and assayed for cell surface gp48 expression by flow cytometric staining with the MAbs T8A11 and T6E11. The gp150-specific MAb T4G2 was used as a positive control. (B) BHK-21 cells were infected as described for panel A, fixed in methanol, permeabilized with 0.1% Tween 20, and stained as indicated. The gB-specific MAb T7H9 and the gp150-specific MAb T4G2 were used as positive controls. (C) Wild-type (WT) and mutant (27⁻ FRT and 27⁻ STOP) virus stocks were lysed in Laemmli's buffer and immunoblotted for gp48 with the T8H3 MAb or for gp150 with the T4G2 MAb. The 65-kDa band corresponds to bovine albumin (virus stocks were resuspended in medium with 10% fetal calf serum) and was absent from density gradient-purified virions (WT VIR), which were resuspended in PBS.