Association of RBD mutations with COVID-19 disease severity in the Iranian population.

The global public health is still at risk due to the COVID-19 pandemic, which was caused by SARS-CoV-2. Disease severity varies among patients and is influenced by mutations in the viral genome, particularly within the spike protein's receptor-binding domain (RBD). This study aimed to investigate the association between RBD mutations and disease severity and to shed light on the fundamental molecular mechanisms. Nasopharyngeal and oropharyngeal samples were obtained from 70 COVID-19 patients in Iran, including 35 mild and 35 deceased cases. The RBD region of the spike protein gene underwent amplification through reverse transcription-polymerase chain reaction (RT-PCR) and was subsequently sequenced using Sanger sequencing. The impact of RBD mutations on binding affinity to human ACE2 (hACE2) was assessed by molecular docking analyses. Sequence analysis identified seven nonsynonymous mutations within the RBD region. The N501Y mutation, which was the most prevalent, showed a significant correlation with disease severity. Molecular docking revealed that the N501Y substitution enhanced binding affinity to hACE2 by increasing hydrophobic interactions and altering the interaction patterns of neighboring residues. This study demonstrates that the N501Y mutation has an independent association with increased severity of COVID-19, likely due to its effect on strengthening the RBD-hACE2 interaction. Further studies involving larger cohorts and diverse populations are necessary to confirm these results and to explore their potential implications for disease management and therapeutic strategies.