Human anti-SARS-CoV & CoV-2 NPantibody recognize human SARSCoronavirus Nucleocapsid protein (NP). Coronavirus NP localize to the cytoplasmand the nucleolus in both Virus-likeparticle (VLP) infected primary cells andin cells transfected with NP plasmid. NPhas abundant expression in coronavirusand is a highly immunogenicphosphoprotein. NP is also conserved insequence. Due to these characteristicsabove, the NP is an ideal marker fordiagnosis.