Identification of linear B-cell epitopes on the phosphoprotein of canine distemper virus using four monoclonal antibodies.

The highly contagious canine distemper virus (CDV) is a non-segmented single-stranded negative-sense RNA virus, which belongs to the Morbillivirus genus of the Paramyxoviridae family. The phosphoprotein (P) of CDV plays the important role in the virus replication and pathogenesis. In this study, we characterized four monoclonal antibodies (MAbs), designated as Pc7, Pc8, Pc11 and Pc25 MAbs against the P protein of CDV-PS strain. A series of overlapping P protein-derived peptides representing the CDV-PS phosphoprotein (aa232-507) were screened to identify linear peptide epitopes recognized by each MAb. Finally, four epitopes, 238SHGMGIVAGSTN249 (E2-9), 264GPSVSAENVRQ274 (E6-2), 390INPELRPIIGR400 (E27-2) and 252TQSALKSTG260 (E4-9), are minimal linear epitopes recognized by the Pc7, Pc8, Pc11 and Pc25 MAbs, respectively. Each identified B-cell epitope was able to be recognized by CDV positive dog serum. Alignment analysis of the amino acid sequences indicated that the linear B-cell epitope of the Pc11 MAb is relatively conserved among different CDV strains, but the linear B-cell epitopes recognized by Pc7, Pc8 and Pc25 MAbs are not conserved among CDV strains. Our results revealed that the E27-2 peptide might be a common B-cell binding epitope of CDV antibodies. These findings may provide a useful basis for the development of new diagnostic assays for CDV.