Monoclonal antibodies to three structural proteins of Newcastle disease virus: biological characterization with particular reference to the conformational change of envelope glycoproteins associated with proteolytic cleavage.

Monoclonal antibodies (MAbs) to the haemagglutinin-neuraminidase (HN), fusion (F) and matrix (M) proteins of Newcastle disease virus were prepared and characterized. At least three non-overlapping or partially overlapping antigenic sites were delineated on the HN, three on the F and three on the M proteins by competitive binding assays. Antigenic sites on the HN and F proteins roughly represented functional domains defined by serological tests. Two antigenic sites on the F protein were involved in virus neutralizing and haemolysis-inhibiting activity. These antigenic determinants were readily affected by treatment with certain surfactants and acetone. Proteolytic cleavage of the HN and F proteins was associated with conformational change, revealed by altered reactivity with MAbs and by altered topological arrangements of some epitopes. None of the anti-M MAbs inhibited any biological activities of the virus.