Effects of Ebola Virus Glycoproteins on Endothelial Cell Activation and Barrier Function

Abstract

Ebola virus causes severe hemorrhagic fever with high mortality rates in humans and nonhuman primates. Vascular instability and dysregulation are disease-decisive symptoms during severe infection. While the transmembrane glycoprotein GP 1,2 has been shown to cause endothelial cell destruction, the role of the soluble glycoproteins in pathogenesis is largely unknown; however, they are hypothesized to be of biological relevance in terms of target cell activation and/or increase of endothelial permeability. Here we show that virus-like particles (VLPs) consisting of the Ebola virus matrix protein VP40 and GP 1,2 were able to activate endothelial cells and induce a decrease in barrier function as determined by impedance spectroscopy and hydraulic conductivity measurements. In contrast, the soluble glycoproteins sGP and ⌬-peptide did not activate endothelial cells or change the endothelial barrier function. The VLP-induced decrease in barrier function was further enhanced by the cytokine tumor necrosis factor alpha (TNF-␣), which is known to induce a long-lasting decrease in endothelial cell barrier function and is hypothesized to play a key role in Ebola virus pathogenesis. Surprisingly, sGP, but not ⌬-peptide, induced a recovery of endothelial barrier function following treatment with TNF-␣. Our results demonstrate that Ebola virus GP 1,2 in its particle-associated form mediates endothelial cell activation and a decrease in endothelial cell barrier function. Furthermore, sGP, the major soluble glycoprotein of Ebola virus, seems to possess an anti-inflammatory role by protecting the endothelial cell barrier function.

Genome comparison of virulent and avirulent strains of the Pichinde arenavirus

“…Sequence changes in the viral HA glycoprotein have been shown to alter its receptor binding specificity that allows the virus to "jump" host species [19,45,47]. The Ebola GP glycoprotein is another example of a major determinant of viral tropism and virulence [12,13,49].…”

Inhibition of Ebola virus glycoprotein-mediated cytotoxicity by targeting its transmembrane domain and cholesterol

“…The ectopic expression of GP is sufficient to induce the detachment of adherent cells 32 , and a mucin-like domain within subunit GP 1 has been suggested to strongly impact this process 6 . Cell detachment accounts for the loss of the endothelial barrier of infected blood vessels, which putatively leads to vascular leakage and contributes to the high pathogenicity of the virus 6,9 . Ebola virions are filamentous in shape, and the matrix protein VP40 and GP are sufficient to produce protrusions at the plasma membrane of adherent cells 33,34 .…”

“…The dysregulation of the immune response and a heavy inflammatory reaction, described as a 'cytokine storm', are induced on EBOV infection 5 . Whether the detachment of infected endothelial cells and the concomitant leakage of the endothelial barrier are important factors in the pathogenesis of Ebola virus disease remains controversial [6][7][8][9][10][11] . Among other factors, the cytotoxicity of EBOV has been attributed to the envelope glycoprotein (GP) 6 ; however, the molecular mechanism underlying the pathogenicity of this virus is unclear.…”

Dérégulation de l’hémostase dans les infections à filovirus

“…Des nécroses similaires, avec dépôt de fibrine, ont également été décrites dans la pulpe blanche et la pulpe rouge de la rate, modifiant souvent l'architecture de cet organe. De plus, bien que les cellules endothéliales en culture soient facilement infectées par le virus, il y a peu de preuves d'une réplication virale dans ces cellules in vivo avant les dernières étapes de la maladie [26]. Une nécrose multifocale est observée dans les tissus lymphoïdes ; celle-ci ne résulte pas directement de l'infection par le virus -les lymphocytes ne sont pas infectables -, mais provient d'un emballement du système immunitaire, qui, lui, est responsable de l'apoptose massive des lymphocytes [16,17,21,27].…”

“…Étonnamment, la sGP, une protéine spécifique au virus Ebola, semble exercer un rôle protecteur vis-à-vis des effets du TNF sur ces cellules. La glycoprotéine structurale a, quant à elle, montré des propriétés inverses [26]. De plus, l'activation des cellules endothéliales induit l'expression à leur surface du facteur tissulaire, qui, comme nous l'avons décrit précédemment, déclenche la coagulation.…”