A study published in Nature (DOI: 10.1038/s41586-024-07636-1) uses deep mutational scanning to analyze how mutations in the SARS-CoV-2 spike protein affect viral properties such as ACE2 binding, cell entry, and serum neutralization. The research focuses on two SARS-CoV-2 variants, XBB.1.5 and BA.2, and examines over 9,000 mutations across their spike proteins. The findings reveal that mutations outside the receptor-binding domain (RBD) can significantly impact ACE2 binding and serum neutralization. Notably, mutations in the RBD at specific sites (357, 420, 440, 456, and 473) are strongly associated with serum escape, although their effects vary among individuals. The study also identifies non-RBD mutations that affect ACE2 binding, suggesting they may modulate RBD conformation. The research demonstrates that the growth rates of SARS-CoV-2 clades can be partially explained by the effects of spike mutations on viral phenotypes. The study highlights the importance of understanding how mutations affect viral fitness and immune evasion. The deep mutational scanning approach enables the identification of mutations that enhance or reduce ACE2 binding and serum neutralization. The results show that non-RBD mutations can have significant effects on neutralization, with some mutations shifting the RBD to a conformation that escapes certain antibodies. The study also shows that mutations in the N-terminal domain (NTD) and RBD can influence viral fitness. The findings suggest that mutations outside the RBD can affect ACE2 binding and neutralization, and that these mutations may play a role in the evolution of SARS-CoV-2. The research provides insights into the molecular mechanisms underlying viral evolution and highlights the importance of understanding how mutations affect viral properties. The study's results have implications for predicting the future evolution of SARS-CoV-2 and developing strategies to combat viral variants.A study published in Nature (DOI: 10.1038/s41586-024-07636-1) uses deep mutational scanning to analyze how mutations in the SARS-CoV-2 spike protein affect viral properties such as ACE2 binding, cell entry, and serum neutralization. The research focuses on two SARS-CoV-2 variants, XBB.1.5 and BA.2, and examines over 9,000 mutations across their spike proteins. The findings reveal that mutations outside the receptor-binding domain (RBD) can significantly impact ACE2 binding and serum neutralization. Notably, mutations in the RBD at specific sites (357, 420, 440, 456, and 473) are strongly associated with serum escape, although their effects vary among individuals. The study also identifies non-RBD mutations that affect ACE2 binding, suggesting they may modulate RBD conformation. The research demonstrates that the growth rates of SARS-CoV-2 clades can be partially explained by the effects of spike mutations on viral phenotypes. The study highlights the importance of understanding how mutations affect viral fitness and immune evasion. The deep mutational scanning approach enables the identification of mutations that enhance or reduce ACE2 binding and serum neutralization. The results show that non-RBD mutations can have significant effects on neutralization, with some mutations shifting the RBD to a conformation that escapes certain antibodies. The study also shows that mutations in the N-terminal domain (NTD) and RBD can influence viral fitness. The findings suggest that mutations outside the RBD can affect ACE2 binding and neutralization, and that these mutations may play a role in the evolution of SARS-CoV-2. The research provides insights into the molecular mechanisms underlying viral evolution and highlights the importance of understanding how mutations affect viral properties. The study's results have implications for predicting the future evolution of SARS-CoV-2 and developing strategies to combat viral variants.