Abstract
Variations in epitopes on structural proteins of four isolates of parainfluenza virus type 4 (PIV-4) and the Mr of polypeptides in these isolates were determined by radioimmune precipitation assay with monoclonal antibodies to parainfluenza virus type 4A (PIV-4A) and type 4B (PIV-4B). Three isolates antigenically resembled the prototype PIV-4A and the sizes of their structural proteins were 72K (HN protein), 61K (F0 protein), 61K (NP protein) and 40K (M protein). However, one virus isolate showed marked antigenic differences from both the 4A and 4B prototype viruses, particularly with regard to properties of the HN and F proteins. In addition, both the NP and F0 proteins of this isolate had a slightly increased Mr of 63K.