Chemotactic response to CCL5 and CXCL12 in THP-1 cells expressing mock, UL33 or UL78. THP-1 cells coexpressing HA-CCR5 (A-B) or not (C-D) and mock (closed circles), Flag-UL33-YFP (closed squares) or Flag-UL78-YFP (closed triangles) were pretreated or not as indicated with pertussis toxin (PTX, 100 ng/mL, overnight) or YM254890 (0.1μM, 15 minutes) and then stimulated with 10nM (B-D) or increasing (A-C) doses of CCL5 (A-B) or CXCL12 (C-D) in a 24-well chemotaxis chamber. The assay was done in triplicates, and the number of migrated cells was counted per well. Each point represents the mean percentage of migrated cells ± SEM in 3 separate experiments. Mock = pcDNA3 expression vector. Statistical differences in the percentage of migrated cells compared with mock nucleofected cells were assessed using the Student t test (**P < .01; ***P < .001).