, and/or protection than the other regions, such as full-length, S1, and RBD (Guo et al., 2005; Jiaming et al., 2017). Therefore, in terms of safety and efficacy, the RBD and/or S1 of S protein could be applied as critical targets for the development of subunit vaccine candidates against SARS-CoV, MERS-CoV, SARSr-CoV, and MERSr-CoV. Because of its conserved amino acid sequences and high homology among different virus strains (Elshabrawy et al., 2012; Zhou et al., 2018), the S2 subunit has potential to be used as a target for the development of universal vaccines against divergent virus strains.
In addition to the S protein, the N protein of SARS-CoV and MERS-CoV may se