Tat-BR peptide enhances receptor-dependent KSHV transmission. (A) Western blot analysis of GFP, KSHV vIL-6, and α-actin (loading control) expression in BCBL-1–GFP (positive control), HEK293, and murine angiosarcoma ISOS-1 cells. HEK293 cells were also treated with Tat-BR after removal of rKSHV-GFP from the supernatant (KSHV → Tat; lane 5). Representative experiment. (B) Stable KSHV infection in ISOS-1 cells after direct coculture of BCBL-1 cells producing rKSHV-GFP with ISOS-1 cells. Original magnification, × 100. (C) Flow cytometry profile of GFP fluorescence in HEK293 and ISOS-1 cells exposed to rKSHV-GFP in the presence of 100 μM Tat-BR and Tat-CR peptides.