Fig. 1.

Structure of SARS-CoV-2 [Adapted from Encyclopedia Britannica, 2020] [5].The spike protein (S) enables binding to the trans-membrane ACE2 host receptor; the envelope (E) protein and the membrane (M) protein together form the viral envelope and determine its shape; the hemagglutinin esterase (HE) protein may look like another cell entry mechanism of novel CoVs; the nucleocapsid (N) protein in bound to the RNA genome of the virus to form the nucleocapsid [6]. For SARS-CoV-1 and SARS-CoV-2, the S protein is the key determinant for host tropism and pathogenicity. It is the focal target for neutralizing antibodies and thus of great concern with regard to immunological response and vaccine development [6]