Ferrets Infected with Bundibugyo Virus or Ebola Virus Recapitulate Important Aspects of Human Filovirus Disease

Abstract

Bundibugyo virus (BDBV) is the etiological agent of a severe hemorrhagic fever in humans with a case-fatality rate ranging from 25 to 36%. Despite having been known to the scientific and medical communities for almost 1 decade, there is a dearth of studies on this pathogen due to the lack of a small animal model. Domestic ferrets are commonly used to study other RNA viruses, including members of the order Mononegavirales. To investigate whether ferrets were susceptible to filovirus infections, ferrets were challenged with a clinical isolate of BDBV. Animals became viremic within 4 days and succumbed to infection between 8 and 9 days, and a petechial rash was observed with moribund ferrets. Furthermore, several hallmarks of human filoviral disease were recapitulated in the ferret model, including substantial decreases in lymphocyte and platelet counts and dysregulation of key biochemical markers related to hepatic/renal function, as well as coagulation abnormalities. Virological, histopathological, and immunohistochemical analyses confirmed uncontrolled BDBV replication in the major organs. Ferrets were also infected with Ebola virus (EBOV) to confirm their susceptibility to another filovirus species and to potentially establish a virus transmission model. Similar to what was seen with BDBV, important hallmarks of human filoviral disease were observed in EBOV-infected ferrets. This study demonstrates the potential of this small animal model for studying BDBV and EBOV using wild-type isolates and will accelerate efforts to understand filovirus pathogenesis and transmission as well as the development of specific vaccines and antivirals. IMPORTANCEThe 2013-2016 outbreak of Ebola virus in West Africa has highlighted the threat posed by filoviruses to global public health. Bundibugyo virus (BDBV) is a member of the genus Ebolavirus and has caused outbreaks in the past but is relatively understudied, likely due to the lack of a suitable small animal model. Such a model for BDBV is crucial to evaluating vaccines and therapies and potentially understanding transmission. To address this, we demonstrated that ferrets are susceptible models to BDBV infection as well as to Ebola virus infection and that no virus adaptation is required. Moreover, these animals develop a disease that is similar to that seen in humans and nonhuman primates. We believe that this will improve the ability to study BDBV and provide a platform to test vaccines and therapeutics.

Recently Identified Mutations in the Ebola Virus-Makona Genome Do Not Alter Pathogenicity in Animal Models

“…However, despite being promising, the current humanized mouse models are not uniform in their biological make-up and still in their infancies in general (Prescott and Feldmann, 2016). The same holds true for the recently published ferret model (Cross et al, 2016; Kozak et al, 2016), which also accommodates the use of wild-type isolates but suffers from being at a premature stage of development, with a lack of tools for ferrets and the more difficult holding and handling of ferrets in maximum containment. There are two commonly used EBOV nonhuman primate models, the cynomolgus and rhesus macaque, both of which do not perfectly recapitulate all but closely mimick most symptoms of human disease.…”

Antibodies from a Human Survivor Define Sites of Vulnerability for Broad Protection against Ebolaviruses

“…Finally, we tested the anti-BDBV efficacy of the two pan-ebolavirus bNAbs, ADI-15878 and ADI-15742, in the domestic ferret, which is the only described non-NHP model for BDBV challenge (Figures 7E and 7F) (Cross et al, 2016; Kozak et al, 2016). Animals received two doses of each bNAb.…”

Immunization-Elicited Broadly Protective Antibody Reveals Ebolavirus Fusion Loop as a Site of Vulnerability

“…A ferret model was recently developed that exhibits many features of filovirus disease in humans (Kozak et al, 2016). Since guinea pig studies indicated that a combination of CA45 and FVM04 is optimal for effective control of EBOV infection, we tested this cocktail in the BDBV ferret model.…”

“…All units were autoclavable and stainless steel in structure. Ferret challenge studies were performed as previously described (Kozak et al, 2016). Briefly, 6-month old male and female ferrets (Mustela putorius furo) (620–960 g) were infected by intramuscular route with 253 TCID 50 of Bundibugyo virus/H.sapiens-wt/UGA/2007 (BDBV, Genbank accession number KR063673.1).…”

“…Viral RNA was extracted using the QIAamp viral RNA mini kit (Qiagen) following the manufacturer’s instructions. Samples viral loads were determined using reverse transcription quantitative PCR (RT-qPCR) with an ABI StepOnePlus instrument as described previously (Kozak et al, 2016). …”