Effect of SDF-1 on HHV-7 infection. (A) SDF-1–dependent CXCR4 downmodulation (left panel) and inhibition of HHV-7 infection (right panel). SupT1 cells were preincubated with SDF-1 (2.5 μg/mL) for 30 minutes at room temperature and then either remained uninfected or inoculated with HHV-7. Before HHV-7–infection, surface CXCR4 was analyzed by flow cytometry (left panel). Horizontal axis, surface CXCR4 expression detected by PE fluorescence intensity; vertical axis, relative cell number. Negative control (Cont) is represented by cells stained with irrelevant isotype-matched control MoAb. The right panel shows HHV-7 expression determined by specific RT-PCR in SupT1 cells preincubated with nothing (lane 1), 2.5 μg/mL of SDF-1 (lane 2), 25 μg/mL of control mouse IgG2a (lane 3), and 25 μg/mL of 12G5 anti-CXCR4 MoAb (lane 4). Equivalent amounts of RNA, extracted at 40 hours PI, were used as template for RT-PCR using either HHV-7–specific primers (U10 ORF) or β-actin primers. Control reaction, performed by amplifying the same RNA samples before RT (−RT) is also shown; lane BL, blank. The data are representative of three separate experiments. (B) CD4⁺ SupT1 or CD4⁻ BC7 cells were inoculated with HHV-7 and monitored for HHV-7 expression and replication by specific viral RT-PCR at 40 hours PI (left panels) and by indirect immunofluorescence at 8 days PI (microphotographs). For RT-PCR, equivalent amounts of RNA samples, before (−) and after (+) RT, were used as template for the amplification reactions. PCR products for HHV-7/U10 ORF and β-actin are shown; lane BL, blank. Immunofluorescence microscopy was performed as described by using the 5E1 HHV-7–specific MoAb; negative reactions are counterstained with Evans blue. The data are representative of three experiments from separate infections.