Abstract
Neutralizing monoclonal antibodies incorporated into plaque assay overlay medium were used to select antibody-resistant (AbR) mutants of both the Herts (using antifusion protein monoclonal 481) and Beaudette C (using anti-haemagglutinin-neuraminidase protein monoclonal 445) strains of Newcastle disease virus at the permissive temperature of 34 degrees C. Certain of the Herts, but none of the Beaudette C, AbR mutants were also temperature-sensitive (ts-) and failed to form plaques at the non-permissive temperature of 41.5 degrees C. [35S]Methionine-labelled proteins from chick embryo fibroblasts infected with wild-type, ts+ AbR and ts- AbR virus when separated by two-dimensional polyacrylamide gel electrophoresis revealed a variety of changes in the isoelectric point of the fusion protein F (using monoclonal 481) and the haemagglutinin-neuraminidase protein HN (using monoclonal 445). The ts+ 'revertants' of ts- AbR mutants remained AbR and also showed changed isoelectric points in the F protein.