Abstract
Bovine coronavirus (BCoV) causes severe diarrhea in newborn calves, is associated with winter dysentery in adult cattle and respiratory infections in calves and feedlot cattle. The BCoV S protein plays a fundamental role in viral attachment and entry into the host cell, and is cleaved into two subunits termed S1 (amino terminal) and S2 (carboxy terminal). The present study describes a strategy for the sequencing of the BCoV S1 gene directly from fecal diarrheic specimens that were previously identified as BCoV positive by RT-PCR assay for N gene detection. A consensus sequence of 2681 nucleotides was obtained through direct sequencing of seven overlapping PCR fragments of the S gene. The samples did not undergo cell culture passage prior to PCR amplification and sequencing. The structural analysis was based on the genomic differences between Brazilian strains and other known BCoV from different geographical regions. The phylogenetic analysis of the entire S1 gene showed that the BCoV Brazilian strains were more distant from the Mebus strain (97.8% identity for nucleotides and 96.8% identity for amino acids) and more similar to the BCoV-ENT strain (98.7% for nucleotides and 98.7% for amino acids). Based on the phylogenetic analysis of the hypervariable region of the S1 subunit, these strains clustered with the American (BCoV-ENT, 182NS) and Canadian (BCQ20, BCQ2070, BCQ9, BCQ571, BCQ1523) calf diarrhea and the Canadian winter dysentery (BCQ7373, BCQ2590) strains, but clustered on a separate branch of the Korean and respiratory BCoV strains. The BCoV strains of the present study were not clustered in the same branch of previously published Brazilian strains (AY606193, AY606194). These data agree with the genealogical construction and suggest that at least two different BCoV strains are circulating in Brazil.
Highlights
Bovine coronavirus (BCoV) is a member of the family Coronaviridae, order Nidovirales, that causes severe diarrhea in neonatal calves and winter dysentery in adult cattle and has been associated with respiratory infections in calves and feedlot cattle [1]
BCoV belongs to the antigenic group 2 of the coronaviruses that includes murine hepatitis coronaviruses (MHV), porcine hemagglutinating encephalomyelitis virus (HEV), rat coronavirus (RtCoV), and human respiratory coronavirus (HCoV-OC43) [2]
The amino-terminal S1 subunit forms the globular head of the mature protein and contains a receptor binding domain (RBD) as well as a hypervariable region (HVR)
Summary
Bovine coronavirus (BCoV) is a member of the family Coronaviridae, order Nidovirales, that causes severe diarrhea in neonatal calves and winter dysentery in adult cattle and has been associated with respiratory infections in calves and feedlot cattle [1]. The present study describes a strategy for direct sequencing of the S1 gene of BCoV from fecal samples and molecular analysis based on the genomic differences between Brazilian strains and other BCoVs from different geographical regions. For the construction of the dendrogram only strains with published full-length S sequences (Mebus, BCoV-ENT, LSU, OK514-3, LY-138, F15, Vaccine, and L9) were included in the analysis.
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More From: Brazilian Journal of Medical and Biological Research
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