Immunofluorescence analysis of MAb 3F4 to DENV-, JEV-, and YFV-infected Vero cells. (A) MAb 3F4 showed strong fluorescence with YF-17D virus-infected Vero cells but not with DENV-2- and JEV-infected Vero cells. (B) MAb 3F4 showed strong reactivity to wild-type YFV strains Baringo 1, Baringo 2, and 17D. Similarly, all seven of the remaining MAbs showed strong fluorescence with YFV strains and no fluorescence with DENV-2- or JEV-infected Vero cells (images not shown).