54G10 neutralization of respiratory syncytial virus (RSV). A, 54G10 binds to RSV, as revealed by immunofluorescent assay. B, 54G10 neutralizes RSV in vitro. Brackets represent the standard error of the mean. Palivizumab neutralizes RSV, but DS7 does not. C, Prophylactic 54G10 decreases virus titer in the lungs, compared with control (***P < .001). D, Therapeutic 54G10 decreases lung virus titer, compared with control (***P < .001). Virus titer was log10 transformed and analyzed by analysis of variance with the post-hoc Dunnett multiple comparisons test. Abbreviations: mAb, monoclonal antibody; PFU, plaque-forming unit.