The recurrent Spike A222V mutation in SARS-CoV-2 enhances replication in primary deer lung cells

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infects humans and animals and is therefore a pathogen of grave concern within a One Health framework. Identifying animal-adaptive mutations is critical to preserving One Health, as these mutations could also lead to the persistence of SARS-CoV-2 in animal reservoirs with continual spillover to humans. Therefore, we sought to pair experimental evolution and epidemiological data to identify putative human- and animal-adaptive viral residues and determine their impact on replication-competent SARS-CoV-2 in both human and animal cells. We passaged SARS-CoV-2 in cells expressing human, dog, cat, mink, and white-tailed deer ACE2 and sequenced the passaged populations. In addition, we searched SARS-CoV-2 sequences for mutations following patterns of convergent evolution that were common to both human- and animal-derived SARS-CoV-2 sequences. We identified the epidemiologically relevant Spike A222V mutation from our passaging experiment in cells expressing cat ACE2, a mutation that has also arisen independently across eight lineages of SARS-CoV-2 from human- and animal-derived sequences. To assess its impact on replication in human and animal cells, we constructed SARS-CoV-2 Spike A222V in the Wuhan-Hu-1 backbone with Spike D614G; this virus replicated similarly to the WT SARS-CoV-2 in human lung epithelial cells. In contrast, SARS-CoV-2 Spike A222V demonstrated an advantage in replication in primary deer lung cells, which was not mediated by the deer ACE2 receptor. Infection via the human, dog, cat, and mink ACE2 receptor resulted in reduced replication of SARS-CoV-2 Spike A222V. Our experiments identified Spike A222V as a putatively deer-adaptive mutation. Future studies should assess Spike A222V's relevance to transmission within deer and to other animal species in contact with deer.