Identification of haemagglutinin-neuraminidase antibody binding sites by Western blot analysis of antibody-resistant mutants and partial digest fragments of Newcastle disease virus.

A collection of monoclonal antibodies (MAbs) which react with the haemagglutinin-neuraminidase (HN) protein of Newcastle disease virus (NDV) has been used to isolate MAb-resistant mutants of the Beaudette C strain of NDV. The patterns of cross-reactivity of the HN proteins of these mutants against the collection of MAbs determined by Western blotting allowed the MAbs to be sorted into different groups. Protease V8 partial digest fragments of purified wild-type virions and subsequent reaction against the collection of MAbs using Western blotting provided an alternative method of grouping MAbs which broadly agreed with the former method. Chemical cleavage of the HN protein at aspartate-proline bonds followed by Western blotting of the fragments allowed the approximate position of certain MAb binding sites to be determined.