SARS-CoV and SARS-CoV2 share absolutely the same cleavage junctions, almost the same sequence (96%) of their main protease, a high degree (76%) of similarity in the amino acid sequence of their S protein, a similar S2′ cleavage site, a similar spectrum of cells they can enter, and the similarity of the most residues essential for binding ACE2 [16], [17], [18]. Also, both of them utilize the same domain of S1B to interact with the ACE2 receptor. However, they differ in proteolytic processing to some degree. Study [16] of the human embryonic kidney (HEK) cell line, 293 T, has shown that a signal for the S2 subunit is present in cells inoculated with SARS-2-S, but not in cells inoculated with SARS-S.