Expression of CD80 (B7.1) in HSVB7.1 amplicon-infected EL4 cells. EL4 cells (A), EL4 cells transduced with HSVlac (B), or HSVB7.1 (C) at an estimated MOI of 1 pfu/cell were stained with PE-conjugated anti-CD80 antibody and analyzed by flow cytometry as described in Materials and Methods.