Indirect Enzyme-Linked Immunosorbent Assay based on the nucleocapsid protein of SARS-like coronaviruses

The nucleocapsid protein (N) is a major structural protein of coronaviruses. The N protein of bat SARS-like coronavirus (SL-CoV) has a high similarity with that of SARS-CoV. In this study, the SL-CoV N protein was expressed in Escherichia coli, purified and used as antigen. An Indirect Enzyme-Linked Immunosorbent Assay (indirect ELISA) was developed for detection of SARS- or SL-CoV infections in bat populations. The detection of 573 bat sera with this indirect ELISA demonstrated that SL-CoVs consistently circulate in Rhinilophus species, further supporting the proposal that bats are natural reservoirs of SL-CoVs. This method uses 1–2 μl of serum sample and can be used for preliminary screening of infections by SARS- or SL-CoV with a small amount of serum sample.