Spike residue 403 affects binding of coronavirus spikes to human ACE2

The bat sarbecovirus RaTG13 is a close relative of SARS-CoV-2, the cause of the COVID-19 pandemic. However, this bat virus was most likely unable to directly infect humans since its Spike (S) protein does not interact efficiently with the human ACE2 receptor. Here, we show that a single T403R mutation increases binding of RaTG13 S to human ACE2 and allows VSV pseudotyped infection of human lung cells and intestinal organoids. Conversely, mutation of R403T in the SARS-CoV-2 S reduces pseudotyped infection and viral replication. The T403R RaTG13 S is neutralized by sera from individuals vaccinated against COVID-19 indicating that vaccination might protect against future zoonoses. Our data suggest that a positively charged amino acid at position 403 in the S protein is critical for efficient utilization of human ACE2 by S proteins of bat coronaviruses. This finding could help to better predict the zoonotic potential of animal coronaviruses.

Fabian Zech, Daniel Schnierthauer, Christoph Jung, Alexandra Herrmann, Arne Cordsmeier, Qinya Xie, Rayhane Nchioua, Caterina Prelli Bozzo, Meta Volcic, Lennart Koepke, Janis A Müller, Jana Krüger, Sandra Heller, Steffen Stenger, Markus Hoffmann, Stefan Pöhlmann, Alexander Kleger, Timo Jacob, Karl-Klaus Conzelmann, Armin Enserink, Konstantin M J Sparrer, Frank Kirchhoff