To characterize the antigenicity of nucleocapsid proteins(NP) derived from canine coronavirus(CCo V) and canine respiratory coronavirus(CRCo V) in China, the N genes of CCo V(CCo V-BJ70) and CRCo V(CRCo V-BJ202) were cloned from swabs obtained from diseased pet dogs in Beijing and then sequenced. The recombinant NPs(r NPs) were expressed in Escherichia coli and purified by nickel-affinity column and size exclusion chromatography. Sequencing data indicated that the N genes of CCo V-BJ70 and CRCo V-BJ202 belonging to two distinctly different groups were relatively conserved within each subgroup. Sodium dodecyl sulfate polyacrylamide gel electrophoresis(SDS-PAGE) results showed that r NPs of CCo V and CRCo V were expressed efficiently and isolated with a final purity of over 95%. Western blot analysis revealed the r NP from CRCo V could cross-react with mice antisera against human coronavirus(HCo V-229 E, NL63, OC43, HKU1), while r NP of CCo V had cross-reactivity with only anti-sera against viruses belonging to the same group(HCo V-229 E and NL63). In summary, CCo V and CRCo V r NPs were successfully expressed in E. coli and showed antigenic cross-reactivity with antisera raised against human coronaviruses. These findings indicate that further serologic studies on coronavirus infections at the animal-human interface are needed.
Shuai LuYingzhu ChenKun QinJianfang ZhouYongliang LouWenjie Tan
