The inhibitory effects of caspase inhibitors on 11kDa/NS1 transfection– and B19V infection–induced apoptosis. (A-B) Inhibitory effects of caspase inhibitors on apoptosis induced by 11kDa and NS1 transfection. (A) UT7/Epo-S1 cells were transfected with pGFP-11kDa or pGFP-NS1. (B) CD36⁺EPCs were transfected with pGFP-11kDa and pGFP-NS1, respectively, as shown. Individual caspase inhibitors (at 20μM), caspase-1, -2, -3&7, -4, -6, -8, -9, -10, and -13 inhibitors, as indicated by 1, 2, 3&7, 4, 6, 8, 9, 10, and 13, respectively, and pan-caspase inhibitors, Z-VAD (20μM) and Q-VD (10μM), were applied at the time of transfection. Dimethyl sulfoxide (DMSO) served as a control at 0.5% vol/vol. Apoptosis was measured by annexin V/PI staining at different times after transfection as indicated. The annexin V⁺/PI⁺ population is shown as a relative percentage (%) to the DMSO control that is arbitrarily set as 100%. (C) Inhibitory effects of caspase inhibitors on apoptosis induced by B19V infection. CD36⁺ EPCs were infected with B19V. Caspase inhibitors were applied upon infection at the concentrations described in panel B. TUNEL assay was used to measure apoptosis induced in capsid⁺ cell population at 48 hours after infection by flow cytometer. The TUNEL⁺ population is shown as a relative percentage to the DMSO control, arbitrarily set as 100%. All the numbers shown as percentage (%) are averages from at least 2 individual experiments.