GFP expression reflects KSHV infectivity. (A) Flow cytometry analysis of HEK293 cell viability 24 hours after infection with rKSHV-GFP. Most GFP-positive cells are PI-negative. Numbers in quadrants represent percentages of total cells in each cell fraction. Representative experiment. (B) GFP and LANA expression in HUVECs 24 hours after infection with rKSHV-GFP. Fluorescence-positive (GFP and LANA/Alexa 594) populations were counted under fluorescence microscopy after LANA staining. Mean ± SD (triplicate samples) in a representative experiment. (C) KSHV vIL-6 and GFP expression in HEK293 cells 24 hours after infection with rKSHV-GFP. Western blots show expression of GFP, KSHV vIL-6, and α-actin (loading control) in BCBL-1–GFP (positive control) and HEK293 cells. Representative experiment. (D) Latent KSHV infection in HUVECs. Two months after infection with rKSHV-GFP, expression of KSHV LANA was visualized with Alexa 594 (red) staining localized to the blue nucleus (DAPI). Original magnification, × 320.