On enteropathogenic bovine coronavirus

A single amino acid change within antigenic domain II of the spike protein of bovine coronavirus confers resistance to virus neutralization

The spike glycoprotein is a major neutralizing antigen of bovine coronavirus (BCV). Conformational neutralizing epitopes of group A and group B monoclonal antibodies (MAbs) have previously been mapped to two domains at amino acids 351 to 403 (domain I) and amino acids 517 to 621 (domain II). To further map antigenic sites, neutralization escape mutants of BCV were selected with a group A MAb which has both in vitro and in vivo virus-neutralizing ability. The escape mutants were demonstrated to be neutralization resistant to the selecting group A MAb and remained sensitive to neutralization by a group B MAb. In radioimmunoprecipitation assays, the spike proteins of neutralization escape mutants were shown to have lost their reactivities with the selecting group A MAb. Sequence analysis of the spike protein genes of the escape mutants identified a single nucleotide substitution of C to T at position 1583, resulting in the change of alanine to valine at amino acid position 528 (A528V). The mutation occurs in domain II and in a location which corresponds to the hypervariable region of the spike protein of the coronavirus mouse hepatitis virus. Experimental introduction of the A528V mutation into the wild-type spike protein resulted in the loss of MAb binding of the mutant protein, confirming that the single point mutation was responsible for the escape of BCV from immunological selective pressure.

Monoclonal antibodies to bovine coronavirus: characteristics and topographical mapping of neutralizing epitopes on the E2 and E3 glycoproteins

Monoclonal antibodies to the Quebec isolate of bovine coronavirus were produced and characterized. Monoclonal antibodies to both the E2 and the E3 glycoproteins were found to efficiently neutralize virus in vitro. None of the monoclonal antibodies directed against the E1 glycoprotein neutralized virus infectivity. Neutralizing monoclonal antibodies to the E2 glycoprotein were all found to immunoprecipitate gp190, gp100, and their intracellular precursor protein gp170. Neutralizing monoclonal antibodies to the E3 glycoprotein immunoprecipitated gp124 and showed differential reactivity to its precursor proteins gp59 and gp118. These monoclonal antibodies also showed differential reactivity to an apparent degradation product of E3. Neutralizing monoclonal antibodies to E2 bound to two distinct nonoverlapping antigenic domains as defined by competitive binding assays. Neutralizing monoclonal antibodies to the E3 glycoprotein also bound to two distinct antigenic sites as defined by competitive binding assays plus a third site which overlapped these regions. Other results indicated that one domain on the E3 glycoprotein could be further subdivided into two epitopes. Thus four epitopes could be defined by E3-specific monoclonal antibodies.

Oligonucleotide fingerprints of antigenically related bovine coronavirus and human coronavirus OC43

Virion RNAs from the bovine enteric coronavirus and the human respiratory coronavirus OC43 were compared by one dimensional gel electrophoresis and by oligonucleotide fingerprinting. For each virus, approximately 55 per cent of the RNA migrated as a 6.8 Md species, 10 per cent as a 0.68 Md species, and 15 per cent as heterogeneous small molecular weight RNA. A sequence homology of greater than 96 per cent was observed between the 6.8 Md species from the two viruses. The 0.68 Md RNA is apparently an intravirion, subgenomic, polyadenylated molecule based on RNAse studies, oligo (dT)-cellulose chromatography, and hybridization to a cDNA clone of the 3' terminal 1.19 Kb region of the bovine coronavirus genome.