Establishing a stable cell line for Lassa virus (LASV) replicon particle (VRP) propagation. A, Immunofluorescence staining for LASV glycoprotein 1 (GP1) and glycoprotein precursor (GPC) in Vero-LASV-GPCco cells. B, Spread of VRPs in Vero-LASV-GPCco cells. Cells were inoculated with VRPs at a multiplicity of infection of 0.05 (as quantified on Vero E6 cells). ZsGreen (ZsG) fluorescence was imaged in a fixed position of live cell monolayers on consecutive days.