CEACAM1-Ig specifically binds to CMV-infected fibroblasts. (a) Binding of CEACAM1-Ig to .221/CEACAM1 cells (bold line) but not to parental .221 (thin line). The figure shows a representative experiment out of three performed. (b) Day-by-day staining of uninfected and CMV-infected HFF cells in the presence or absence of 300 μg/ml of the antiviral agent PFA. Cells were stained with CEACAM1-Ig and with the control CD99-Ig fusion protein as described in Methods. Data are presented as fold increase above the staining of uninfected cells. The average of two independent experiments is shown.