Emerging variants of concern (VOCs) are driving the COVID-19 pandemic 1 , 2 . Experimental assessments of replication and transmission of major VOCs and progenitors are needed to understand the mechanisms of replication and transmission of VOCs 3 . Here we show that the spike protein (S) from Alpha (also known as B.1.1.7) and Beta (B.1.351) VOCs had a greater affinity towards the human angiotensin-converting enzyme 2 (ACE2) receptor than that of the progenitor variant S(D614G) in vitro. Progenitor variant virus expressing S(D614G) (wt-S 614G ) and the Alpha variant showed similar replication kinetics in human nasal airway epithelial cultures, whereas the Beta variant was outcompeted by both. In vivo, competition experiments showed a clear fitness advantage of Alpha over wt-S 614G in ferrets and two mouse models—the substitutions in S were major drivers of the fitness advantage. In hamsters, which support high viral replication levels, Alpha and wt-S 614G showed similar fitness. By contrast, Beta was outcompeted by Alpha and wt-S 614G in hamsters and in mice expressing human ACE2. Our study highlights the importance of using multiple models to characterize fitness of VOCs and demonstrates that Alpha is adapted for replication in the upper respiratory tract and shows enhanced transmission in vivo in restrictive models, whereas Beta does not overcome Alpha or wt-S 614G in naive animals. The Alpha variant of SARS-CoV-2 outcompetes progenitor SARS-CoV-2 in upper respiratory tract replication competition in vivo.
【저자키워드】 SARS-CoV-2, viral infection, Experimental models of disease, 【초록키워드】 ACE2, VoC, hamsters, B.1.351, COVID-19 pandemic, variant, variants of concern, Transmission, nasal, in vitro, virus, Spike protein, airway, Replication, human ACE2, Viral, B.1.1.7, mice, ferret, VOCs, substitutions, Alpha, Beta, fitness, receptor, experiment, Alpha variant, hamster, respiratory, Beta variant, assessment, in vivo, epithelial, upper respiratory tract, mechanism, angiotensin, progenitor, Support, human Angiotensin-converting enzyme, similar replication kinetics, Substitution, ferrets, cultures, driving, high viral replication, highlight, greater, the spike protein, overcome, expressing, driver, 【제목키워드】 SARS-CoV-2 variant, enhanced,