Vaccinal and wild strains of Newcastle Disease virus (NDV) were analyzed for cell receptor binding and fusogenic biological properties associated with their HN (hemagglutimn-neuraminidase) and F (fusion protein) surface structures respectively. The evaluation of the biological activities of HN and F was carried out respectively by deterntination of hemagglutinating titers and hemolysis percentages, using erythrocytes from various animal origins at different pH values. Significant differences in hemag- glutination titersfor some strains of NDV were detected, when interacting with goose, sheep, guineapig and human "O" group erythrocytes at neutral pH. Diversity of hemolysis percentages was observed between different NDV strains at acid pH. These analysis were developed to evaluate particular aspects of the actual influence of the receptor specificity and pH on the receptor binding and fusogenic processes of Newcastle Disease viruses.
