[Molecular cloning and expression of the severe acute respiratory syndrome-associated coronavirus nucleocapsid protein and its clinical application].

Lu, Jian; Zhou, Bai-ping; Zhou, Yu-sen; Jiang, Xiao-ling; Wen, Li-xia; Le, Xiao-hua; Li, Bing; Xu, Liu-mei; Li, Li-xiong

OBJECTIVE To clone and express nucleocapsid (N) protein of the severe acute respiratory syndrome (SARS)-associated coronavirus, and to evaluate its antigenicity and application value in the development of serological diagnostic test for SARS. METHODS SARS-associated coronavirus N protein gene was amplified from its genomic RNA by reverse transcript nested polymerase chain reaction (RT-nested-PCR) and cloned into pBAD/Thio-TOPO prokaryotic expression vector. The recombinant N fusion protein was expressed and purified, and its antigenicity and specificity was analyzed by Western Blot, to establish the recombinant N protein-based ELISA for detection of IgG antibodies to SARS-associated coronavirus, and SARS-associated coronavirus lysates-based ELISA was compared parallelly. RESULTS The recombinant expression vector produced high level of the N fusion protein after induction, and that protein was purified successfully by affinity chromatography and displayed higher antigenicity and specificity as compared with whole virus lysates. CONCLUSION The recombinant SARS-associated coronavirus N protein possessed better antigenicity and specificity and could be employed to establish a new, sensitive, and specific ELISA for SARS diagnosis.