Abstract
Members of the family Filoviridae, including Ebola virus (EBOV) and Marburg virus (MARV), cause severe hemorrhagic fever in humans and nonhuman primates. Given their high lethality, a comprehensive understanding of filoviral pathogenesis is urgently needed. In the present studies, we revealed that the exchange protein directly activated by cAMP 1 (EPAC1) gene deletion protects vasculature in ex vivo explants from EBOV infection. Importantly, pharmacological inhibition of EPAC1 using EPAC-specific inhibitors (ESIs) mimicked the EPAC1 knockout phenotype in the ex vivo model. ESI treatment dramatically decreased EBOV infectivity in both ex vivo vasculature and in vitro vascular endothelial cells (ECs). Furthermore, postexposure protection of ECs against EBOV infection was conferred using ESIs. Protective efficacy of ESIs in ECs was observed also in MARV infection. Additional studies using a vesicular stomatitis virus pseudotype that expresses EBOV glycoprotein (EGP-VSV) confirmed that ESIs reduced infection in ECs. Ultrastructural studies suggested that ESIs blocked EGP-VSV internalization via inhibition of macropinocytosis. The inactivation of EPAC1 affects the early stage of viral entry after viral binding to the cell surface, but before early endosome formation, in a phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K)-dependent manner. Our study delineated a new critical role of EPAC1 during EBOV uptake into ECs.
Highlights
Members of the family Filoviridae, including Ebola virus (EBOV) and Marburg virus (MARV), cause severe hemorrhagic fever in humans and nonhuman primates, with case-fatality in humans ranging from 57% to 90% [1,2,3,4,5,6]
At 72 h postexposure with EBOV, it was observed that the endothelium in aortic rings from KO mice was protected from infection compared to the infected endothelium in aortic rings from KO mice was protected from infection compared to the infected aortic rings isolated from WT mice (p < 0.005) (Figure 1A,B and Figure S2)
This observation was aortic rings isolated from WT mice (p < 0.005) (Figures 1A,B and S2). This observation was further further validated by an in vitro EBOV infection model of mouse brain microvascular endothelial cell (BMEC) prepared from KO or WT
Summary
Members of the family Filoviridae, including Ebola virus (EBOV) and Marburg virus (MARV), cause severe hemorrhagic fever in humans and nonhuman primates, with case-fatality in humans ranging from 57% to 90% [1,2,3,4,5,6]. All human outbreaks of EBOV have been traced to equatorial. Viruses 2018, 10, 563 infection in humans on record occurred in West Africa. 15 May 2018 in the eastern Democratic Republic of the Congo in Central Africa, a week after the western outbreak in the country was over [7]. Neither vaccines nor postexposure treatments have been FDA-approved for combating filoviral infections [11,12,13,14]. Given their high lethality, a comprehensive understanding of filoviral pathogenesis and the development of novel mechanism-based prophylactic and therapeutic countermeasures are urgently needed
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