FURIN and infection: To determine if the cleavage state of prM present on infectious virions impacts sensitivity to neutralization by anti-E antibodies, we compared the ability of mAbs to block infection of RVPs produced using either standard transfection conditions (Fig. 3; std-RVPs, blue circles) or cells that over-express human furin protease (Fig. 3; furin-RVPs, green circles).