Biological and molecular differentiation between coronaviruses associated with neonatal calf diarrhoea and winter dysentery in adult cattle.

Cytopathic coronaviruses were isolated in HRT-18 cells from bloody faecal samples collected from cows in Québec dairy herds with classical winter dysentery (WD). The formation of polykaryons in the infected cell cultures was found to be dependent on the presence of trypsin in the medium. Virus identification was confirmed by indirect immunofluorescence and indirect protein A-gold immunoelectron microscopy using rabbit hyperimmune serum, as well as monoclonal antibodies directed against the spike (S) and hemagglutinin-esterase (HE) glycoproteins of the prototype Mebus strain of bovine coronavirus (BCV-Meb). Four WD isolates differed from BCV-Meb by their ability to agglutinate rat erythrocytes at 4 and 37 degrees C, their higher receptor destroying enzyme activity, but lower acetylesterase activity. The WD isolates were serologically indistinguishable from the reference BCV-Meb strain by virus neutralization and Western immunoblotting, but could be differentiated by hemagglutination-inhibition. Sequence analysis of the PCR-amplified HE gene of a plaque-purified WD isolate (BCQ-2590) revealed sufficient number of nucleotide and amino acid substitutions which may explain this antigenic variability.