The isolated MAbs bind to cells infected with recombinant vaccinia viruses expressing various arenavirus GPCs as well as to cells infected with authentic LASV. (A to F) Immunofluorescence images of nonpermeabilized BSC40 cells infected with vaccinia viruses expressing different arenavirus GPCs. Cells were infected at an MOI of 1 overnight with different recombinant vaccinia viruses that express arenavirus GPCs and stained with the six MAbs at 30 µg/ml. The isolated MAbs bind to cells infected with recombinant vaccinia viruses expressing various arenavirus GPCs as well as to cells infected with authentic LASV. (A to F) Immunofluorescence images of nonpermeabilized BSC40 cells infected with vaccinia viruses expressing different arenavirus GPCs. Cells were infected at an MOI of 1 overnight with different recombinant vaccinia viruses that express arenavirus GPCs and stained with the six MAbs at 30 µg/ml. Naive mouse serum was used as a negative control, while polyclonal serum from a mouse vaccinated with LASV GPC, MOPV GPC, and MACV GPC was used as a positive control at a dilution of 1:100. (G) Immunofluorescence images of cells infected with wild-type VACV and stained with the six antibodies. Cells were infected at an MOI of 1 overnight with wild-type VACV and stained with the six antibodies. Serum from a mouse vaccinated with MVA was used as a positive control. (H) Immunofluorescence images of Vero.E6 cells infected with LASV strain Nig08-A18 and stained with the six different MAbs. Vero.E6 cells were infected with wild-type LASV in a BSL-4 facility for 24 h at an MOI of 0.1. Cells were fixed, permeabilized, and stained with 10 ng/µl of each MAb. Cell masks and cell nuclei (DAPI) were also stained, and the merged images are shown. Fatima Amanat et al. mSphere 2018; doi:10.1128/mSphere.00189-18