SARS Coronavirus is an enveloped virus containing three outer structural proteins, namely the membrane (M), envelope (E), and spike (S) proteins. Spike (S)-glycoprotein of the virus interacts with a cellular receptor and mediates membrane fusion to allow viral entry into susceptible target cells. Accordingly, S-protein plays an important role in virus infection cycle and is the primary target of neutralizing antibodies. The E.Coli derived 35 kDa recombinant protein contains Nucleocapsid protein 1-49, 192-220 amino acids immunodominant regions. The 2 regions are separated with 3 glycine residues.