Development and Characterization of a Guinea Pig-Adapted Sudan Virus

Abstract

Infections with Sudan virus (SUDV), a member of the genus Ebolavirus, result in a severe hemorrhagic fever with a fatal outcome in over 50% of human cases. The paucity of prophylactics and therapeutics against SUDV is attributed to the lack of a small-animal model to screen promising compounds. By repeatedly passaging SUDV within the livers and spleens of guinea pigs in vivo, a guinea pig-adapted SUDV variant (SUDV-GA) uniformly lethal to these animals, with a 50% lethal dose (LD 50 ) of 5.3 ؋ 10 ؊2 50% tissue culture infective doses (TCID 50 ), was developed. Animals infected with SUDV-GA developed high viremia and died between 9 and 14 days postinfection. Several hallmarks of SUDV infection, including lymphadenopathy, increased liver enzyme activities, and coagulation abnormalities, were observed. Virological analyses and gross pathology, histopathology, and immunohistochemistry findings indicate that SUDV-GA replicates in the livers and spleens of infected animals similarly to SUDV infections in nonhuman primates. These developments will accelerate the development of specific medical countermeasures in preparation for a future disease outbreak due to SUDV. IMPORTANCE A disease outbreak due to Ebola virus (EBOV), suspected to have emerged duringDecember 2013 in Guinea, with over 11,000 dead and 28,000 infected, is finally winding down. Experimental EBOV vaccines and treatments were administered to patients under compassionate circumstances with promising results, and availability of an approved countermeasure appears to be close. However, the same range of experimental candidates against a potential disease outbreak caused by other members of the genus Ebolavirus, such as Sudan virus (SUDV), is not readily available. One bottleneck contributing to this situation is the lack of a small-animal model to screen promising drugs in an efficient and economical manner. To address this, we have generated a SUDV variant (SUDV-GA) that is uniformly lethal to guinea pigs. Animals infected with SUDV-GA develop disease similar to that of SUDV-infected humans and monkeys. We believe that this model will significantly accelerate the development of lifesaving measures against SUDV infections.

Post-exposure treatments for Ebola and Marburg virus infections

“…Small animals including mice, hamsters and guinea pigs have been used as animal models of filovirus haemorrhagic fever [226][227][228][229][230][231][232][233][234] . Mice and guinea pigs were historically used to screen post-exposure interventions against filoviruses, but these models have often failed to predict efficacy of candidate therapies in the more robust non-human primate (NHP) models 8,9 .…”

“…An important consideration for any filovirus vaccine is the ability to provide rapid protection, as outbreaks, epidemics and bioterrorist events do not allow time for a multiple-injection strategy. Several filovirus vaccines prevent infection in NHPs when used as single injections 232,233,247,253,254,257,258 . In particular, the rVSV filovirus vaccines are very potent in this regard and can completely protect NHPs against EBOV, even if administered as few as 7 days before high-dose EBOV (Makona strain) challenge 257 .…”

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

“…Viral RNA was also extracted from approximately 30 mg of harvested organs using the RNeasy kit (Qiagen) according to the manufacturer's instructions. Reverse transcription-quantitative PCR (RT-qPCR) was used to determine viral loads and was performed using an ABI StepOnePlus instrument as adapted from a protocol described previously (12). Sequences of the BDBV primers and probes used in this study are as follows: BEBOVGP F, 5=-GRATTCTRCAATTGCCC-3=; BEBOVGP R, 5=-TGR AATAGGATTATTACCCAAACAA-3=; BEBOVGPP FAM, 5=-FAM-G TGARCGCTTCAGRAAAACATCTTTYT-BHQ1-3=.…”

“…Since wild-type filovirus isolates are not lethal to immunocompetent rodents, host-adapted virus variants have been generated through sequential passaging in mice and guinea pigs to establish animal models for studying filovirus pathogenesis as well as evaluating vaccines and therapeutics. Using this method, small animal models have been developed for EBOV (7,8), Ravn virus (9), and Marburg virus (10,11), and recently a guinea pig model has been developed for Sudan virus (12). While these animal models have played a considerable role in the development of specific antivirals against filoviruses, the establishment of these animal models can be laborious and time-consuming, limiting the ability to study outbreak strains in a timely manner.…”

Rodent-Adapted Filoviruses and the Molecular Basis of Pathogenesis

“…Several different guinea pig-adapted filoviruses have been generated over the last two decades, and with the exception of guinea pig-adapted SUDV (GPA-SUDV), all of them required only a maximum of eight passages in adult guinea pigs before a lethal phenotype was achieved [69, 70, 74, 84–90]. GPA-SUDV, on the other hand, required 25 passages in guinea pigs before becoming lethal [88]. Disease caused by all guinea pig-adapted filoviruses is similar to EHF and MHF in humans and NHPs: The viruses replicate systemically and to high titers (albeit not as high as observed in mice or NHP models), causing significant pathology in multiple organs, especially the liver and spleen [69, 70, 85, 87–89].…”