Ruminant respiratory syncytial virus subgroup distiction using synthetic peptides from the extracellular central region of the attachment protein -G

Subgroup specific, peptide-based, enzyme immunoassays were developed from the unique extracellular, central region (residues 158--189) located between two mucin-like regions of the attachment protein-G from ovine and bovine respiratory syncytial viruses. Antigenic peptides [ovine (residues 173--189) and bovine (residues 171--187)] used to develop the enzyme immunoassays were identified by a combination of algorithms and epitope mapping from each G-glycoprotein. The negative threshold for each enzyme immunoassay was established as the mean optical density of indirect immunofluorescent antibody-negative bovine sera plus three standard deviations. The sensitivity, specificity, positive and negative predictive values of each enzyme immunoassay was determined by comparison with indirect immunofluorescence (gold standard). Antibody prevalence to the ovine and bovine subgroups of respiratory syncytial virus infections was determined from 1,102 bovine serum samples obtained from six diagnostic laboratories from the Northwest and Southeast United States. The Southeast had a higher prevalence of the bovine subgroup strains (69.5%) [compared to the Northwest (40.9%)], whereas the prevalence of the ovine strain was similar for the two regions [Southeast with 16.7% compared to the Northwest with 14.9%]. The overall prevalence was 56.6% for the bovine strain and 15.9% for the ovine strain. The immunoassays then were used to determine the prevalence of ruminant RSV subgroups in a herd of Rocky Mountain Bighorn Sheep. Antibody to the ovine-specific peptide was found in 68% of samples tested whereas 28% of serum samples reacted with the bovine-specific peptide. Results indicated that viruses from both subgroups (ovine and bovine) of ruminant respiratory syncytial virus infect bighorn sheep. The implications of all results were discussed.