a, Infection assays showing that addition of increasing concentrations of ADI-15946 (left), but not KZ52 (right), to fixed concentrations of FVM09 (5, 20 or 80 nM) promotes rVSV-EBOV GP neutralization. The reciprocal fold change in neutralization half-maximal inhibitory concentration (IC50) is shown (inset). b, Infection assays showing that addition of increasing concentrations of FVM09 to a fixed, subneutralizing concentration of ADI-15946 enhances rVSV-EBOV GP neutralization. The same experiment against KZ52 shows inhibition of neutralization as the concentration of FVM09 is increased. c–f, Infection assays as in a,b, with authentic EBOV (c,d) showing similar trends; this trend is present but less pronounced with rVSV-SUDV GP (e,f). Data in a–f are mean ± s.d., n = 6 biologically independent samples. g, A cartoon showing the proposed relationship between FVM09 binding and subsequent exposure of the ADI-15946 binding site.