SARS-CoV-2 replicates in respiratory ex vivo organ cultures of domestic ruminant species

Abstract

There is strong evidence that severe acute respiratory syndrome 2 virus (SARS-CoV-2), the causative agent of the coronavirus disease 2019 (COVID-19) pandemic, originated from an animal reservoir. However, the exact mechanisms of emergence, the host species involved, and the risk to domestic and agricultural animals are largely unknown. Some domestic animal species, including cats and ferrets, have been demonstrated to be susceptible to SARS-CoV-2 infection, while others, such as pigs and chickens, are not. Importantly, the susceptibility of ruminants to SARS-CoV-2 is unknown, even though they often live in close proximity to humans. We investigated the replication and tissue tropism of two different SARS-CoV-2 isolates in the respiratory tract of three farm animal species - cattle, sheep, and pigs - using respiratory ex vivo organ cultures (EVOCs). We demonstrate that the respiratory tissues of cattle and sheep, but not of pigs, sustain viral replication in vitro of both isolates and that SARS-CoV-2 binds efficiently to ACE2-expressing cells of the respiratory tract of both ruminant species. Intriguingly, SARS-CoV-2 isolates containing an amino acid substitution at site 614 of the spike protein (mutation D614?G) replicated at higher magnitude in ex vivo tissues of both ruminant species, supporting previous results obtained using human cells. These results suggest that additional in vivo experiments involving several ruminant species are warranted to determine the potential role in the epidemiology of this virus.