Suppression of MDCK cell infection by pseudovirus 1194 with mAb A (top left), C (top right), 3C4 (lower left), and 6B8 (lower right). Y-axis indicates transfected firefly luciferase activity, expressed as fluorescence unit (FU). Pseudoviruses were premixed with mAb for 4 hours prior to infection on MDCK cells. All mAb showed substantial but weak suppression of infection by pseudovirus 1194. A concurrent series of virus dilutions were performed in parallel in the absence of mAb as the control.