Host genetic diversity enables Ebola hemorrhagic fever pathogenesis and resistance

Abstract

Existing mouse models of lethal Ebola virus infection do not reproduce hallmark symptoms of Ebola hemorrhagic fever, neither delayed blood coagulation and disseminated intravascular coagulation nor death from shock, thus restricting pathogenesis studies to nonhuman primates. Here we show that mice from the Collaborative Cross panel of recombinant inbred mice exhibit distinct disease phenotypes after mouse-adapted Ebola virus infection. Phenotypes range from complete resistance to lethal disease to severe hemorrhagic fever characterized by prolonged coagulation times and 100% mortality. Inflammatory signaling was associated with vascular permeability and endothelial activation, and resistance to lethal infection arose by induction of lymphocyte differentiation and cellular adhesion, probably mediated by the susceptibility allele Tek. These data indicate that genetic background determines susceptibility to Ebola hemorrhagic fever.

Figure 1. Distinct Morbidity and Mortality Following MA-EBOV Infection in CC-RIX Mouse Lines

A. Percent of starting body weight over course of infection in susceptible (red squares) and resistant mice (blue circles). Data shown are mean ± SEM from five mice per CC-RIX line. B. Kaplan-Meier survival curve for susceptible (red) and resistant (blue) mice. Five mice were used for each CC-RIX line. C,D,E,F. Gross appearance of liver at necropsy in uninfected susceptible (C) and resistant (E) mice, and on day 5 post-infection in susceptible (D) and resistant (F) mice.

Figure 2. MA-EBOV Replication in CC-RIX Mouse Lines

A,B. Quantitative real-time PCR showing expression of MA-EBOV genomes relative to mouse 18S rRNA in spleen (A) and liver (B). Data shown are mean ± SEM for three mice per time point per RIX line. C,D. Titration of infectious MA-EBOV in organ homogenates from spleen (C) and liver (D) quantified as focus forming units per milliliter. No infectious virus was detected prior to day 3 p.i. Data shown are mean ± SEM from two experiments using 2–3 mice per time point per CC-RIX line. E,F,G,H. Immunohistochemical staining for VP40 in resistant liver (E,F) and susceptible liver (G,H). Arrow indicates representative hepatocyte morphology. (t-test, *p<0.05)

Figure 3. Quantification of Coagulopathy and Hemorrhage in CC-RIX Mouse Lines

A,B,C. Coagulation times in seconds for thrombin (A), prothrombin (B), and activated partial thromboplastin (C) over course of MA-EBOV infection. D. Serum fibrinogen levels in CC-RIX mice over course of MA-EBOV infection. All data shown are the mean ± SEM for 2 experiments including 2–5 animals per time point. (ANOVA with Tukey’s HSD post-hoc. *p<0.05, **p<0.05, ***p<0.0000001).

Figure 4. Distinct Host Responses Associated with Disease Phenotype

A,B. Number of differentially expressed genes (DEG) either up-regulated (positive y-axis) or down-regulated (negative y-axis) relative to time-matched mock-infected samples in spleen (A) and liver (B).