Binding of the plant lectins, concanavalin A (con A), wheat germ agglutinin, soybean agglutinin and Lens culinaris agglutinin to the surface of cells infected with different Newcastle disease virus (NDV) strains inhibited virus release. Binding of succinyl con A with a lower valency than native tetrameric con A to the surface of infected cells did not inhibit virus release. It was proposed that binding of multivalent lectin molecules to the surface of infected cells impairs assembly of the virus envelope and the budding of new virus particles by the formation of cross linkages and lattice formation between protein molecules on the cell surface. Binding of the same lectins to NDV infected cells also caused significant inhibition of virus induced cell fusion. In contrast, treatment of cells with a phytohaemagglutinin preparation from Phaseolus vulgaris enhanced NDV induced cell fusion. A new form of NDV induced c.p.e. was observed in lectin treated cells involving extensive damage and fragmentation of cell nuclei. This c.p.e. was also found in lectin treated cells infected with the avirulent NDV strains F and Queensland which normally induce only limited cell damage. The possible mechanisms underlying the varied effects of different lectins on NDV release and cytopathogenicity are discussed.
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