Measurement of rabies virus N protein in rabies vaccines

In this study, we designed a capture ELISA using a monoclonal antibody specific for the N protein, the major protein of the rabies virus nucleocapsid, to measure the N protein content in rabies vaccines. Free N protein content was compared in the two types of rabies vaccine currently used in humans: suckling mouse brain (SMB) vaccine prepared from rabies virus-infected brain tissue, and tissue culture (TC) vaccine prepared from supernatants of rabies virus-infected cells. It was found that SMB vaccines contained considerably higher amounts of N protein than most of the TC vaccines. Possible implications concerning the efficacy of rabies vaccines are discussed.