A) Anti-ebola neutralizing antibody (serum). Sera collected from immunized mice were inactivated at 56uC for 45 minutes. Serial dilutions of each sample (1:10, 1:20, 1:40, etc, in 50 ml of DMEM) were mixed with equal volumes of recombinant Ebola Zaire expressing the enhanced green fluorescent protein (EGFP) reporter gene (ZEBOV-EGFP, 100 transducing units/well, according to EGFP expression) and incubated at 37uC for 90 minutes [41] . The mixture was then added to subconfluent VeroE6 cells in 96-well flat-bottomed plates and incubated for 5-10 minutes at room temperature. Control wells were infected with equal amounts of either ZEBO-EGFP with media without serum or that containing non-immune serum. 100 ml of DMEM supplemented with 20% FBS was then added to each well and plates were incubated at 37uC in 5% CO 2 for 48 hr. Cells were subsequently fixed with 10% buffered formalin for 24 h and examined under a fluorescent microscope. Sample dilutions which showed .50% reduction in the number of green cells compared to controls scored positive for neutralizing antibody.