Recombinant SARS-CoV-2 nucleocapsid protein

This Nucleoprotein (nucleocapsid protein) of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is expressed in insect cells. The Nucleocapsid protein is not important for determination of neutralizing IgG antibodies. However, the recombinant SARS-CoV-2 Nucleocapsid Protein, S9991 antigen in combination with monoclonal antibodies directed against neutralizing epitopes such as the ACE2 binding domain could be used in a competitive setup for determining neutralizing antibodies. The nucleocapsid protein is quite conserved. Using nucleocapsid protein for acute / early antibodies such as IgA/ IgM should make it possible to detect antibodies directed against the variants of concern in a satisfactory way at an early stage of illness.
For IgM detection, a mixture of nucleocapsid and spike proteins is recommended.