Antigenic and genomic relationships among turkey and bovine enteric coronaviruses

Antigenic and genomic relationships among tissue culture-adapted turkey enteric coronavirus (TCV) isolates, three strains of avian infectious bronchitis virus (IBV), and mammalian coronaviruses were investigated. Immunoblotting and immunoprecipitation experiments using polyclonal antisera showed that the four major structural proteins of TCV cross-reacted with the four homologous proteins of bovine enteric coronavirus (BCV), the N and M proteins of mouse hepatitis virus serotype 3, and the N protein of IBV. Close antigenic relationships between TCV and BCV were also established by seroneutralization and hemagglutination-inhibition. Of 49 monoclonal antibodies produced against either TCV or BCV, 11 differentiated the two viruses. Five of these monoclonal antibodies had neutralizing activities and were directed to either the peplomeric S (gp200-gp100) or hemagglutinin HE (gp140-gp65) glycoproteins. BCV cDNA probes tested on purified viral preparations and coronavirus-positive (by electron microscopy) fecal samples from diarrheic turkey poults confirmed the relatedness of TCV and BCV. The two viruses produced distinct cytopathic changes in HRT-18 cells in the presence of trypsin, whereas only TCV isolates were able to reproduce the clinical symptoms in turkey poults. Their matrix (M) proteins undergo different glycosylation processes.