In silico binding affinity of the spike protein with ACE2 and the relative evolutionary distance of S gene may be potential factors rapidly obtained for the initial risk of SARS-CoV-2

Objectives: In this research, we aimed to find potential factors which are rapidly obtained for the risk of the coming new variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), when their genetic substitutions were detected in late 2022. Methods: We first performed molecular docking simulation analyses of the spike proteins with human angiotensin-converting enzyme 2 (ACE2) by using ZDOCK program to determine the binding affinities to human cells of three new variants of SARS-CoV-2: Omicron BQ.1, XBB, and XBB.1.5. We then investigated the three variants to determine the relative evolutionary distance of the spike protein gene (S gene) from the Wuhan, Omicron BA.1, and Omicron BA.4/5 variants. Results: The results indicated that Omicron BQ.1. had a highest binding affinity but had the shortest evolutionary distance from BA.4/5. The XBB variant had a lower binding affinity and long evolutionary distances from all the three variants. However, the XBB.1.5 variant had the highest binding affinity of the spike protein with ACE2 and the longest evolutionary distance of the S gene. Conclusion: This result suggested that in silico binding affinity of the spike protein with ACE2 and the relative evolutionary distance of S gene may be potential factors for the risk of SARS-CoV-2 variants based on the comparison of infectivity of BQ.1, XBB, and XBB.1.5.