An ELISA based on recombinant spike protein S for the detection of antibodies to transmissible gastroenteritis virus of swine-like canine coronaviruses

Recombinant canine coronaviruses, resembling the transmissible gastroenteritis virus of swine (TGEV) in a 5′ fragment of the S glycoprotein, have been detected recently and showed to be present in canine populations. The 5′ fragment of the S protein (S′) of a TGEV-like canine coronavirus (CCoV), strain 174/06, was expressed in an Escherichia coli cell-free system. The purified recombinant polypeptide was employed to develop an ELISA test for the detection of TGEV-like CCoV-specific antibodies in dog sera. Four canine sera positive for TGEV-like CCoV, six sera positive to classical CCoV-II strains and 10 negative control sera were examined. The recombinant S′ was not recognized by antibodies to classical CCoV-II, as only sera from dogs infected experimentally with TGEV-like CCoV reacted strongly with the recombinant S′ polypeptide whereas dog sera with antibodies to classical CCoV-II did not react. As classical CCoV-II and TEGV-like CCoVs are related antigenically, the recombinant S′ ELISA is a useful method to investigate serologically the prevalence of TGEV-like CCoVs in dogs.