Dose-dependent response to infection with SARS-CoV-2 in the ferret model: evidence of protection to re-challenge
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Abstract
In December 2019 an outbreak of coronavirus disease (COVID-19) emerged in Wuhan, China. The causative agent was subsequently identified and named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) which rapidly spread worldwide causing a pandemic. Currently there are no licensed vaccines or therapeutics available against SARS-CoV-2 but numerous candidate vaccines are in development and repurposed drugs are being tested in the clinic. There is a vital need for authentic COVID-19 animal models to further our understanding of pathogenesis and viral spread in addition to pre-clinical evaluation of candidate interventions.
Here we report a dose titration study of SARS-CoV-2 to determine the most suitable infectious dose to use in the ferret model. We show that a high (5×10 6 pfu) and medium (5×10 4 pfu) dose of SARS-CoV-2 induces consistent upper respiratory tract (URT) viral RNA shedding in both groups of six challenged animals, whilst a low dose (5×10 2 pfu) resulted in only one of six displaying signs of URT viral RNA replication. The URT shedding lasted up to 21 days in the high dose animals with intermittent positive signal from day 14. Sequential culls revealed distinct pathological signs of mild multifocal bronchopneumonia in approximately 5-15% of the lung, observed on day 3 in high and medium dosed animals, with presence of mild broncho-interstitial pneumonia on day 7 onwards. No obvious elevated temperature or signs of coughing or dyspnoea were observed although animals did present with a consistent post-viral fatigue lasting from day 9-14 in the medium and high dose groups. After virus shedding ceased, re-challenged ferrets were shown to be fully protected from acute lung pathology. The endpoints of URT viral RNA replication in addition to distinct lung pathology and post viral fatigue were observed most consistently in the high dose group. This ferret model of SARS-CoV-2 infection presents a mild clinical disease (as displayed by 80% of patients infected with SARS-CoV-2). In addition, intermittent viral shedding on days 14-21 parallel observations reported in a minority of clinical cases.
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SciScore for 10.1101/2020.05.29.123810: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
Institutional Review Board Statement IACUC: All experimental work was conducted under the authority of a UK Home Office approved project licence that had been subject to local ethical review at PHE Porton Down by the Animal Welfare and Ethical Review Body (AWERB) as required by the Home Office Animals (Scientific Procedures) Act 1986. Randomization Experimental Design: Before the start of the experiment animals were randomly assigned to challenge groups, to minimise bias. Blinding not detected. Power Analysis not detected. Sex as a biological variable Animals: Twenty-two healthy, female ferrets ( Cell Line Authentication not detected. Table 2: Resources
Experimental Models: Cell Lines Sentences Resources Viruses … SciScore for 10.1101/2020.05.29.123810: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
Institutional Review Board Statement IACUC: All experimental work was conducted under the authority of a UK Home Office approved project licence that had been subject to local ethical review at PHE Porton Down by the Animal Welfare and Ethical Review Body (AWERB) as required by the Home Office Animals (Scientific Procedures) Act 1986. Randomization Experimental Design: Before the start of the experiment animals were randomly assigned to challenge groups, to minimise bias. Blinding not detected. Power Analysis not detected. Sex as a biological variable Animals: Twenty-two healthy, female ferrets ( Cell Line Authentication not detected. Table 2: Resources
Experimental Models: Cell Lines Sentences Resources Viruses and Cells: SARS-CoV-2 Victoria/01/202026 was generously provided by The Doherty Institute, Melbourne, Australia at P1 and passaged twice in Vero/hSLAM cells [ECACC 04091501] Whole genome sequencing was performed, on the challenge isolate, using both Nanopore and Illumina as described previously40. Vero/hSLAMsuggested: ECACC Cat# 04091501, RRID:CVCL_L037)Virus titre was determined by plaque assay on Vero/E6 cells [ECACC 85020206]. Vero/E6suggested: JCRB Cat# JCRB1819, RRID:CVCL_YQ49)SARS-CoV-2 virus plaque assay: Samples were diluted in serum-free MEM containing antibiotic/antimycotic (Life Technologies) and incubated in 24-well plates (Nunc, ThermoFisher Scientific, Loughborough, UK) with Vero E6 cell monolayers. Vero E6suggested: RRID:CVCL_XD71)Software and Algorithms Sentences Resources Viruses and Cells: SARS-CoV-2 Victoria/01/202026 was generously provided by The Doherty Institute, Melbourne, Australia at P1 and passaged twice in Vero/hSLAM cells [ECACC 04091501] Whole genome sequencing was performed, on the challenge isolate, using both Nanopore and Illumina as described previously40. Nanoporesuggested: NoneResults from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).
Results from LimitationRecognizer: An explicit section about the limitations of the techniques employed in this study was not found. We encourage authors to address study limitations.Results from TrialIdentifier: No clinical trial numbers were referenced.
Results from Barzooka: We did not find any issues relating to the usage of bar graphs.
Results from JetFighter: We did not find any issues relating to colormaps.
Results from rtransparent:- Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
- Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
- No protocol registration statement was detected.
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