The single-stranded, plus-sense severe acute respiratory syndrome coronavirus 2 (SARS–CoV-2) genome encodes nonstructural replicase polyproteins as well as structural proteins such as spike (S), nucleocapsid (N), membrane (M) and envelop (E) proteins. N protein is abundantly expressed and highly immunogenic during SARS-COV-2 infection. The middle or C-terminal region of the N protein has been shown to elicit antibody production during the immune response. S protein is a transmembrane homotrimeric class I fusion glycoprotein; the S1 subunit binds to angiotensin-converting enzyme II (ACE2) and S2 subunit is involved in the fusion of viral and host cell membranes. The distal S1 subunit contains a receptor binding domain (RBD), whose hinge-like conformational movement is required for ACE2 receptor binding and refolding of S2 for membrane fusion. S and its RBD have been the targets for the design and development of vaccines to prevent SARS-CoV-2 infection and rechallenge.   ​