Abstract
Three human and six bovine parainfluenza virus type 3 (PIV3) strains were examined by the use of 60 monoclonal antibodies (MAbs). Fifty-three MAbs to the human C243 strain were directed against six, four, nine and seven epitopes of the haemagglutininneuraminidase (HN), fusion (F), nucleocapsid (N) and matrix proteins, respectively. Seven MAbs to the bovine strain were directed against three epitopes of the HN protein and three epitopes of the F protein. Each strain was characterized in ELISA and immunofluorescence tests with all MAbs and in a haemagglutination inhibition assay with the anti-HN MAbs. There were marked differences between human and bovine viruses, primarily in the HN protein where five epitopes differed. One epitope of the F and one of the N protein also differed. Bovine PIV3 was found to be a homogeneous subtype and distinct from human PIV3.