Most CoVs share a similar viral structure, similar infection pathway, and a similar structure of the S proteins [41], suggesting that similar research strategies should also be applicable for the 2019-nCoV. For example, the study of MERS-CoV vaccines was accelerated by virtue of strategies that had been established for SARS-CoV [42]. It has been reported that the 2019-nCoV is also genetically close to SARS-CoV [43,44]. Therefore, to predict whether vaccines developed for SARS-CoV will also be effective against 2019-nCoV infection, the full length S protein sequences from the 2019-nCoV, a SARS-CoV, and two genetically similar bat CoV strains were selected for alignment (Fig. 1 ). The results indicated more than 50% homology of the viruses. However, the most variable residues are located in S1, a critical vaccine target, implying that neutralizing antibodies that were so effective against SARS-CoV infection may fail to recognize the 2019-nCoV, and that multiple amino acid differences at the receptor binding motif may modify virus tropism, a possible reason for cross-species transmission.
Fig. 1 Comparison of S protein sequences of coronaviruses. Multiple alignment of full amino acid sequences of S protein from 2019-nCoV (GISAID accession no. EPI_ISL_402124), SARS-CoV (GenBank accession no. AY278489), bat-SL-CoVZC45 (GenBank accession no. MG772933.1), and bat-SL-CoVZXC21 (GenBank accession no. MG772934.1) was performed and displayed with clustalx1.83 and MEGA4 respectively. ‘‘-” represents the unconfirmed amino acid residues, “.” represents the identical amino acid residues. The functional domains were labeled based on the research on SARS-CoV [41]; light blue box was for RBD region; dark blue box for receptor binding motif (RBM); light purple box for HR1; and dark purple box for HR2, respectively. Double underlined regions in HR1 and HR2 are fusion cores, which are critical regions responsible for the formation of stable six-helical bundles between HR1 and HR2.