Fluorescent virus neutralizing antibody plaque titers. A) Scatter plots of virus neutralization (VN) titers obtained by automatically counted plaques of fluorescence E7-rRSV versus manually coloured and counted plaque reduction of the parental rRSV. B) Serum antibody neutralization titers of cotton rat, mouse and human serum samples obtained with the fluorescent virus neutralizing antibody assay. Serum neutralizing titers from different experiments are depicted. Animals were immunized with RSV vaccine candidates . Pre-immune serum was obtained at day 0 (black bars) and were at the lower limit of detection. Mice were immunized at day 0 and day 28 with 10^6 RSV- ΔG and serum was obtained at day 28 (light gray) and at day 51 (gray) (n=6 per group). Cotton rats were immunized at day 0, day 14 and day 28 with 10^5 RSV-ΔG and serum was obtained at day 28 (light gray) and at day 51 (gray) (n=5 per group). As reference, serum from animals immunized with formalin-inactivated RSV (white) are included (n=5 per group). The human reference human sera: high (green), medium (blue) and low (orange) were included as standards . Error bars indicate standard deviation.