FIG. 2.

Apoptosis and detection of caspase-8 activity in lyssavirus-infected neuroblastoma cells. Cells were either mock infected (A, E, and I) or infected with THA (B, F, and J), MOK (C, G, and K), or LAG (D, H, and L) (MOI, 1). (A through D) After 72 h at 37°C, cells were processed for TUNEL staining (red) and viral NC antigen staining (green) and were analyzed with a laser scanning confocal microscope (magnification, ×600). (E through H) Active caspase-8 was detected 48 h p.i. by using the carboxyfluorescein-labeled caspase inhibitor FAM-LETD-fmk (green). (I through L) Cells were counterstained with Hoechst 33342 (blue) and analyzed by fluorescence microscopy (magnification, ×1,000). (M) Matrix protein fused to His₆ was visualized by use of an anti-His₆ antibody conjugated with FITC (green). (N) Cells were transfected with the matrix-His₆ fusion protein (M) and treated for the TUNEL assay (red). (O) Cells were counterstained with TOPRO-3 (blue) and analyzed by confocal microscopy (magnification, ×600).