A sensitive and specific antigen detection assay for Middle East respiratory syndrome coronavirus

Chen, Yixin; Chan, Kwok-Hung; Kang, Yahong; Chen, Honglin; Luk, Hayes KH; Poon, Rosana WS; Chan, Jasper FW; Yuen, Kwok-Yung; Xia, Ningshao; Lau, Susanna KP; Woo, Patrick CY

The full-length NP gene of MERS-CoV was cloned and expressed in E. coli strain ER2566 with a stretch of six histidine residues at both the N and C termini. The MERS-CoV-rNP, with a molecular weight of 46 kDa, was purified by Ni-NTA affinity chromatography and was used to immunize BALB/c mice. Western blot showed that mouse anti-MERS-CoV-rNP immune sera had good reactivity with MERS-CoV and MERS-CoV-rNP, indicating that the expressed MERS-CoV-rNP has similar antigenicity to native NP of MERS-CoV ( Figure 1 ). As a control, the mouse anti-MERS-CoV-rNP immune sera did not react with influenza A virus strain CA/04 (Figure 1 ). The high ELISA titer of mouse anti-MERS-CoV-rNP immune sera confirmed that the MERS-CoV-rNP has good immunogenicity in BALB/c mice, indicating that the MERS-CoV-rNP was useful for generation of anti-MERS-CoV-rNP MAbs (Figure 2 ).