In addition to the S protein, the N protein of SARS-CoV and MERS-CoV may serve as an additional target for the development of subunit vaccines. Unlike S protein, the N protein has no ability to elicit neutralizing antibodies to block virus-receptor interaction and neutralize viral infection, but it may induce specific antibody and cellular immune responses (Liu et al., 2006; Zheng et al., 2009). Several immunodominant B-cell and T-cell epitopes have been identified in the N protein of SARS-CoV and MERS-CoV, some of which are conserved in mice, non-human primates, and humans (Liu et al., 2006; Chan et al., 2011; Veit et al., 2018). Other proteins, such as M protein, can be used as potential targets of SARS-CoV and MERS-CoV subunit vaccines. Notably, SARS-CoV M protein-derived peptides have immunogenicity to induce high-titer antibody responses in the immunized animals (He et al., 2005b), suggesting the potential for utilizing this protein to develop subunit vaccines.