RESUMO
In this study, we attempted to define differences in the hemagglutinin-esterase (HE) glycoprotein between 11 bovine coronaviruses (BCV) recent (post-1991) and past (pre-1991) isolates from neonatal calf diarrhoea (NCD) and winter dysentery (WD) syndromes as a basis for strain differentiation related to the clinical source of the isolates. The five WD-associated BCV isolates studied could be distinguished from past NCD-isolates by their hemagglutinating (HA) properties at 4 degrees and 37 degrees C, their receptor-destroying enzyme (RDE) activities with rat erythrocytes and lack of reactivity of these NCD isolates to four HA inhibiting (HAI) monoclonal antibodies (MAbs) directed against the HE glycoprotein of the reference WD-associated BCQ.2590 Quebec strain. Although minor or no differences could be demonstrated by comparing biological properties of the HE of WD-isolates to those of recent NCD-isolates, past NCD isolates lacked reactivity with the WD HAI MAbs, whereas recent NCD isolates displayed two distinct reactivity patterns. Attempts to define sequence differences in the HE genes of the WD and NCD strains revealed high nucleotide (NT) identities with only scattered amino acid differences, seemingly unrelated to the clinical origin of the isolates or HAI MAb reactivities.
Assuntos
Doenças dos Bovinos/virologia , Infecções por Coronavirus/veterinária , Coronavirus Bovino/genética , Coronavirus Bovino/imunologia , Diarreia/veterinária , Disenteria/veterinária , Hemaglutininas Virais/genética , Hemaglutininas Virais/imunologia , Proteínas Virais de Fusão/genética , Proteínas Virais de Fusão/imunologia , Substituição de Aminoácidos , Animais , Anticorpos Monoclonais , Anticorpos Antivirais , Variação Antigênica , Sequência de Bases , Bovinos , Infecções por Coronavirus/virologia , Coronavirus Bovino/isolamento & purificação , Primers do DNA/genética , Diarreia/virologia , Disenteria/virologia , Variação Genética , Genoma Viral , Dados de Sequência Molecular , Especificidade da Espécie , SíndromeRESUMO
Bovine coronavirus isolates associated with recent outbreaks of respiratory disease in Ontario and Quebec dairy farms were compared to reference strains known to be responsible for neonatal calf diarrhea (NCD) or winter dysentery (WD) of adult cattle. In respect to their hemagglutinating properties and their higher RDE activities with rat erythrocytes, WDBCoV strains differed from NCDBCoV strains and respiratory bovine coronaviruses RBCoV strains. Serologically, three MAbs directed to the HE glycoprotein of the WDBCoV strain BCQ.2590 recognized two serogroups amongst NCDBCoV strains by hemagglutination inhibition, whereas only one of the MAbs failed to react toward three of the four RBCoV isolates tested. Sequencing analysis of the S (S1 portion), HE, ORF4 and ORF5 genes of BCoV isolates associated with different clinical syndromes indicated that neither insertions or deletions could explain their distinct tropism. For the HE glycoprotein, a total of 15 amino acids (aa) substitutions were identified by comparing field isolates to the prototype Mebus strain. Two specific proline substitutions were identified for virulent strains being located in the signal peptides (aa 5) and aa position 367; one specific aa change was revealed at position 66 for RBCoV field isolates. Analysis of the S1 portion of the S glycoprotein revealed a total of eight aa changes specific to enteropathogenic (EBCoV) strains and eight aa changes specific to RBCoV strains. For all BCoV isolates studied, the region located between the S and M genes (ORF4) apparently encodes for two non-structural (ns) proteins of 4.9 and 4.8 kDa. A specific non-sense mutation was identified for the nucleotide at position 88 of the putative 4.9 kDa protein gene of RBCoV isolates resulting in 29 rather that 43 aa residues. The ORF5, which encodes a 12.7 ns protein and the 9.5 kDa E protein, was highly conserved amongst the BCoV field isolates.
