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
Seven hybridoma cell lines producing monoclonal antibodies (MAbs) to the hemagglutinin-esterase (HE) glycoprotein of bovine coronavirus (BCV) were obtained from BALB/c mice that were immunized with an enriched peplomeric fraction of the winter dysentery (WD)-associated strain BCQ.2590. The specificities of these MAbs to either the dimeric (140-kDa) or the monomeric (65-kDa) form of the HE glycoprotein were determined by Western immunoblotting experiments with purified virus and immunoprecipitation tests with [35S]methionine-labelled infected cell extracts. Four of these anti-HE MAbs inhibited the hemagglutinating activity of the virus and three weakly neutralized its infectivity in vitro. In addition, competition binding assays allowed for the definition of two independent antigenic domains (domains A and D) and two overlapping antigenic domains (domains B and C) for the HE glycoprotein of the WD-associated strain; epitopes located within antigenic domain A were not associated with hemagglutination inhibition (HAI) and virus neutralization activities. In HAI tests, the four anti-HA MAbs defined two distinct antigenic subgroups among 24 BCV field isolates that have been associated with either typical outbreaks of WD or neonatal calf diarrhea (NCD) in Quebec dairy herds from 1986 to 1996. The Quebec WD-associated strains of BCV, as well as some of the NCD-associated strains isolated since 1991, fell within a subgroup distinct from that of the prototype Mebus strain.
