The Mucin-Like Domain of the Ebola Glycoprotein Does Not Impact Virulence or Pathogenicity in Ferrets

Abstract

Background: Ebola virus (EBOV) is considered among the most dangerous viruses with case fatality rates approaching 90% depending on the outbreak. While several viral proteins (VPs) including VP24, VP35, and the soluble glycoprotein are understood to contribute to virulence, less is known of the contribution of the highly variable mucin-like domain (MLD) of EBOV. Early studies have defined a potential role in immune evasion of the MLD by providing a glycan shield to critical glycoprotein residues tied to viral entry. Nonetheless, little is known as to what direct role the MLD plays in acute EBOV disease (EVD).

Methods: We generated an infectious EBOV clone that lacks the MLD and assessed its virulence in ferrets compared with wild-type (WT) virus.

Results: No differences in growth kinetics were observed in vitro, nor were there any differences in time to death, viremia, or clinical picture in ferrets infected with recombinant EBOV (rEBOV)-WT or rEBOV-Δmucin.

Conclusions: The EBOV MLD does not play a critical role in acute pathogenesis of EVD in ferrets.

Keywords: Ebola virus; ferrets; mucin-like domain; reverse genetics.

Figure 1.

In vitro and in vivo characterization of Ebola virus (EBOV) and the EBOV mucin-like domain (MLD). A, Growth kinetics of wild-type recombinant EBOV (rEBOV-WT) and rEBOV-MLD in HUH-7 cells. B, Survival of ferrets infected with rEBOV-WT and rEBOV-Δmucin. C, Plasma viremia from ferrets infected with rEBOV-WT and rEBOV-Δmucin. D, Infectious virus burden in tissues from ferrets taken at time of euthanasia from animals infected with rEBOV-WT and rEBOV-Δmucin. *P ≤ .05. Abbreviations: Fr, frontal lobe; hpi, hours postinfection; ns, not significant; PFU, plaque-forming units; rEBOV-WT, wild-type recombinant Ebola virus.

Figure 2.

Representative gross pathology and histopathology of ferrets challenged with wild-type Ebola virus (EBOV) (A–F) and recombinant EBOV-Δmucin (G–L). A, Multifocal to coalescing hepatitis. B, Centrilobular vacuolar degeneration and necrotizing hepatitis (*) (hematoxylin and eosin staining [H&E], ×20 magnification). C, Immunohistochemistry (IHC) positive (brown) for anti-EBOV antigen of hepatocytes and endothelium (white arrow) (IHC, ×20). D, Petechial rash of the lower ventral abdomen (black arrows). E, Splenitis with lymphocytolysis of germinal centers (H&E, ×10). F, IHC positive (brown) for anti-EBOV antigen of mononuclear cells of the red and white pulp and endothelium (IHC, ×10). G, Multifocal to coalescing hepatitis. H, Centrilobular vacuolar degeneration and necrotizing hepatitis (*) and blood vessel (white arrow) (H&E, ×20). I, IHC positive (brown) for anti-EBOV antigen of hepatocytes and blood vessel endothelium (white arrow) (IHC, ×20). J, Petechial rash of the lower ventral abdomen (black arrows). K, Splenitis with lymphocytolysis of germinal centers and the periarteriolar sheaths (H&E, ×10). L, IHC positive (brown) for anti-EBOV antigen of mononuclear cells of the red and white pulp and endothelium (IHC, ×10). Full color version available online.