Loss of furin cleavage site attenuates SARS-CoV-2 pathogenesis.

Johnson, Bryan A; Xie, Xuping; Bailey, Adam L; Kalveram, Birte; Lokugamage, Kumari G; Muruato, Antonio; Zou, Jing; Zhang, Xianwen; Juelich, Terry; Smith, Jennifer K; Zhang, Lihong; Bopp, Nathen; Schindewolf, Craig; Vu, Michelle; Vanderheiden, Abigail; Winkler, Emma S; Swetnam, Daniele; Plante, Jessica A; Aguilar, Patricia; Plante, Kenneth S; Popov, Vsevolod; Lee, Benhur; Weaver, Scott C; Suthar, Mehul S; Routh, Andrew L; Ren, Ping; Ku, Zhiqiang; An, Zhiqiang; Debbink, Kari; Diamond, Michael S; Shi, Pei Yong; Freiberg, Alexander N; Menachery, Vineet D

SARS-CoV-2, a novel coronavirus (CoV)-producing worldwide pandemic1, has a furin cleavage site (PRRAR) in its spike protein that is absent in other group 2B CoVs2. To explore whether the furin cleavage site contributes to infection and pathogenesis, we generated a mutant SARS-CoV-2 deleting the furin cleavage site (ΔPRRA). SARS-CoV-2 ΔPRRA replicates had faster kinetics, improved fitness in Vero E6 cells, and reduced spike protein processing as compared to parental SARS-CoV-2. However, the ΔPRRA mutant had reduced replication in a human respiratory cell line and was attenuated in both hamster and K18-hACE2 transgenic mouse models of SARS-CoV-2 pathogenesis. Despite reduced disease, the ΔPRRA mutant conferred protection against rechallenge with the parental SARS-CoV-2. Importantly, COVID-19 patient sera and receptor-binding domain (RBD) monoclonal antibodies had lower neutralization values against the ΔPRRA mutant versus parental SARS-CoV-2, likely due to increased particle/PFU ratio. Together, these results demonstrate a critical role for the furin cleavage site in SARS-CoV-2 infection and highlight the importance of this site in evaluating antibody neutralization activity.