Cells infected with Ebola virus (EBOV) release large amounts of viral glycoproteins; however, how these proteins contribute to pathogenesis is unknown. Now, Escudero-Pérez et al. show that one of these proteins, termed shed GP, binds to uninfected dendritic cells (DCs) and macrophages, in a process dependent on the glycosylation pattern of shed GP and on cellular Toll-like receptor 4 (TLR4). The binding of shed GP resulted in the activation of DCs and macrophages, and induced the release of cytokines, which were sufficient to increase the permeability of endothelial barriers. These data suggest that the release of shed GP from infected cells leads to the dysregulation of the host immune response and the modulation of remote target cells, such as endothelial cells, resulting in increased inflammation and vascular permeability, which are two characteristics of fatal EBOV infection.