Susceptibility of sheep to experimental co-infection with the ancestral lineage of SARS-CoV-2 and its alpha variant

ABSTRACT

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible for a global pandemic that has had significant impacts on human health and economies worldwide. SARS-CoV-2 is highly transmissible and the cause of coronavirus disease 2019 in humans. A wide range of animal species have also been shown to be susceptible to SARS-CoV-2 by experimental and/or natural infections. Sheep are a commonly farmed domestic ruminant that have not been thoroughly investigated for their susceptibility to SARS-CoV-2. Therefore, we performed in vitro and in vivo studies which consisted of infection of ruminant-derived cells and experimental challenge of sheep to investigate their susceptibility to SARS-CoV-2. Our results showed that sheep-derived kidney cells support SARS-CoV-2 replication. Furthermore, the experimental challenge of sheep demonstrated limited infection with viral RNA shed in nasal and oral swabs at 1 and 3-days post challenge (DPC); viral RNA was also detected in the respiratory tract and lymphoid tissues at 4 and 8 DPC. Sero-reactivity was observed in some of the principal infected sheep but not the contact sentinels, indicating that transmission to co-mingled naïve sheep was not highly efficient; however, viral RNA was detected in respiratory tract tissues of sentinel animals at 21 DPC. Furthermore, we used a challenge inoculum consisting of a mixture of two SARS-CoV-2 isolates, representatives of the ancestral lineage A and the B.1.1.7-like alpha variant of concern, to study competition of the two virus strains. Our results indicate that sheep show low susceptibility to SARS-CoV-2 infection and that the alpha variant outcompeted the lineage A strain.

KEYWORDS:

• SARS-CoV-2
• sheep
• ovine
• ruminant
• susceptibility
• transmission
• co-infection

Acknowledgements

We thank the staff of KSU Biosecurity Research Institute, the histology laboratory at the Kansas State Veterinary Diagnostic Laboratory (KSVDL), members of the Histology and Immunohistochemistry sections at the Louisiana Animal Disease Diagnostic Laboratory (LADDL), the Comparative Medicine Group staff at Kansas State University and technical support from Emily Gilbert-Esparza, Yonghai Li and Cassidy Keating of KSU, and Jeana Owens and Dane Jasperson from USDA-ARS. The SARS-CoV-2 strains USA/CA-5574/2020 and USA/WA1/2020 were obtained through BEI Resources (catalog # NR-52281 and #54011). We also thank Dr Kyeong-Ok Chang for the Vero E6/TMPRSS2 cells used in these studies.

Disclosure statement

Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture. USDA is an equal opportunity provider and employer. The JAR laboratory received support from Tonix Pharmaceuticals, Xing Technologies and Zoetis, outside of the reported work. JAR is inventor of patents and patent applications on the use of antivirals and vaccines for the treatment and prevention of virus infections, owned by Kansas State University, KS, or the Icahn School of Medicine at Mount Sinai, New York. The AG-S laboratory has received research support from Pfizer, Senhwa Biosciences, Kenall Manufacturing, Avimex, Johnson & Johnson, Dynavax, 7Hills Pharma, Pharmamar, ImmunityBio, Accurius, Nanocomposix, Hexamer, N-fold LLC, Model Medicines, Atea Pharma, and Merck, outside of the reported work. AG-S has consulting agreements for the following companies involving cash and/or stock: Vivaldi Biosciences, Contrafect, 7Hills Pharma, Avimex, Vaxalto, Pagoda, Accurius, Esperovax, Farmak, Applied Biological Laboratories, Pharmamar and Pfizer, outside of the reported work. AG-S is inventor of patents and patent applications on the use of antivirals and vaccines for the treatment and prevention of virus infections, owned by the Icahn School of Medicine at Mount Sinai, New York.

Additional information

Funding

Funding for this study was partially provided through grants from the National Bio and Agro-Defense Facility (NBAF) Transition Fund from the State of Kansas (JAR), the AMP Core of the Center of Emerging and Zoonotic Infectious Diseases (CEZID) from National Institute of General Medical Sciences (NIGMS) under award number P20GM130448 (JAR, IM), the NIAID Centers of Excellence for Influenza Research and Surveillance under contract number HHSN 272201400006C (JAR), the United States Department of Agriculture (USDA)-NIFA (A1711 Program) under award number 2020-67015-33157, the German Federal Ministry of Health (BMG) COVID-19 Research and development funding to WHO R&D Blueprint (JAR), the NIAID supported Center of Excellence for Influenza Research and Response (CEIRR, contract number 75N93021C00016 to JAR), and the USDA Animal Plant Health Inspection Service’s National Bio- and Agro-defense Facility Scientist Training Program (KC, CM). This study was also partially supported by the Louisiana State University, School of Veterinary Medicine start-up fund under award number PG 002165 (UBRB), the USDA-Agricultural Research Service (DM, WCW), the Center for Research for Influenza Pathogenesis and Transmission (CRIPT), an NIAID supported Center of Excellence for Influenza Research and Response (CEIRR, contract # 75N93021C00014 to AG-S), and by the generous support of the JPB Foundation, the Open Philanthropy Project (research grant 2020-215611 [5384]) and anonymous donors to AG-S.