High-protein-binding 96-well ELISA plates (Corning) were coated with purified human mAbs (40 ng per well, ‘first mAb’) at 37°C and blocked with 3% (w/v) bovine serum albumin (BSA; Thermo Fisher) in PBS. The membranes of rVSV-PUUV-Gn/Gc particles were labelled with a short-chain phospholipid probe, functional-component spacer diacyl lipid conjugated to biotin (FSL-biotin, Sigma-Aldrich), as described (30 (link)). Subsequently, pre-titrated amounts of biotin-labeled rVSVs were incubated with purified human mAb (100 nM, ‘second mAb’) for 1 h at 37°C before their addition to mAb-coated plates. Bound rVSV-PUUV-Gn/Gc was detected by incubation with a streptavidin-HRP conjugate (Thermo Scientific). Competition levels were determined by reduction of rVSV binding in presence of a competitor mAb compared to rVSV binding in the absence of competition (rVSV complexed with human IgG1 [Sigma-Aldrich]). Antibodies with >75% reduction of rVSV binding were considered to be in competition with pre-complexed mAbs.