FIG. 2.

Inhibition of KSHV infection by anti-integrin antibodies and soluble integrins. (A) Inhibition of GFP-KSHV infection by anti-integrin antibodies. Monolayers of HMVEC-d and HFF were incubated with 10 μg/ml of MAbs against integrins or integrin subunits for 1 h at 4°C, washed, and infected with GFP-KSHV at an MOI of 5 DNA copies/cell. After incubation for 2 h at 37°C, the cells were washed and incubated for 72 h, and the number of GFP-positive cells was estimated under a fluorescence microscope. Each experiment was done in duplicate, and each bar represents the average plus the standard deviation (SD) of three experiments. (B) Effects of anti-integrin antibodies on KSHV binding. HFF were incubated with anti-integrin antibodies (10 μg/ml) at 4°C for 90 min and incubated with a predetermined concentration of [³H]thymidine-labeled purified KSHV. The labeled KSHV was also mixed with 10 μg/ml of heparin or soluble integrins for 90 min at 4°C and then added to the cells. After incubation for 90 min at 4°C with the virus, the cells were washed, lysed, precipitated with trichloroacetic acid, and counted. The bound virus cpm in the absence of any treatment was considered to be 100% and was used to calculate the percentage inhibition of virus binding. Each reaction was done in triplicate, and each bar represents the average plus the SD of three independent experiments. The results with HFF are shown. (C) Inhibition of KSHV infection by soluble integrins. KSHV (5 DNA copies/cell) was mixed with 10 μg/ml of heparin or 10 μg/ml soluble integrins for 2 h at 37°C and added to the cells. After 2 h, the cells were washed to remove the unbound virus, treated with 0.25% trypsin-EDTA for 5 min at 37°C to remove the bound but noninternalized viruses, and washed, and total DNA was isolated. The number of KSHV ORF73 copies was estimated by real-time DNA PCR. The cycle threshold values were used to plot the standard graph and to calculate the relative copy numbers of viral DNA in the samples. The data are presented as percentages of inhibition of KSHV DNA internalization obtained when the cells were incubated with the virus alone. Each reaction was done in duplicate, and each bar represents the average ± SD of three experiments. (D) KSHV was mixed with 10 μg/ml soluble integrin combinations for 2 h at 37°C and added to HFF. After 2 h, the cells were washed to remove the unbound virus and treated with 0.25% trypsin-EDTA for 5 min at 37°C to remove the bound but noninternalized viruses, and the internalized viral DNA was estimated by real-time DNA PCR. Each reaction was done in duplicate, and each bar represents the average ± the SD of three experiments.