As endohelial cells are the first target of NiV infection, we have initially studied a permissivity of HUVEC cultures to NiV infection. We established the HUVEC cell culture and assessed their purity at passage 2, either by cell immunostaining or flow cytometry using two endothelial-specific markers, Von Willebrand Factor (VWF) stored in cytoplasmic Weibel-Palade bodies, and CD31 (PECAM-1) localized in homophilic intercellular contacts, which gave us reproducibly satisfactory results (Fig. S1 ). We then analyzed the expression of NiV receptors, production of viral specific RNAs, generation of the cytopatic effect and production of viral particles (Fig. 1) . The expression of mRNA specific for NiV entry receptors ephrinB2 and B3 [12, 13, 14] was readily detected in these cells, at levels close to those in the astroglioma cell line U373, which was also highly permissive to NiV infection [15] (Fig. 1C ). Production of NiV structural genes coding for nucleoprotein, matrix, fusion protein, glycoprotein and polymerase increased rapidly during the infection, following a gradient characteristic of paramyxoviruses, with highest expression of the first gene represented in the genome, N, and lowest for the gene coding for the polymerase (Fig. 1D ). Formation of large syncytia was rapidly detected in HUVECs (Fig. 1B ) and the highest level of the production of infectious particles was obtained 24H after infection, as most of the cells were lysed 48 h p.i. in this cell type (Fig. 1E) . Therefore, NiV infects rapidly HUVECs and induces a significant cytopathic effect.