Isolation and characterization of a coronavirus from elk calves with diarrhea

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Abstract
This is the first report of the isolation of a coronavirus from elk calves. Two fecal samples from elk calves with diarrhea were shown to be positive for coronavirus-like particles by electron microscopy, and the particles were propagated in the human rectal tumor-18 cell line. After 24 h, syncytia were observed, and cell culture supernatants from both samples showed hemagglutinating activity with mouse erythrocytes. Cells infected with both elk coronavirus (ECV) isolates reacted with Z3A5, a monoclonal antibody against the spike protein of bovine coronavirus (BCV), on an indirect fluorescent antibody test. The protein profiles of both ECV isolates were similar to that of BCV as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis. On Northern blot analysis, the transcriptional pattern of ECV was typical of coronaviruses, with a nested set of transcripts with common 3' end sequences. Based on a published nucleoprotein gene sequence for BCV (Mebus isolate), we arbitrarily designed two primers for amplification by PCR. After cloning, the nucleoprotein was sequenced and a high degree of homology (99%) between the nucleoprotein gene sequences of ECV and BCV was observed. Thus, ECV is closely related genetically and antigenically to BCV and will be a new member of antigenic group 2 of the mammalian coronaviruses, which possess hemagglutinin-esterase protein.