The contribution of lectins to the interaction between oral Newcastle disease vaccine and grains.

Successful oral vaccination of chickens with Newcastle disease (ND) depends on the survival of vaccine virus on the grains that are used as carriers. Some interactions between grains and the V4 strain of ND virus (NDV) were studied. Crude saline washings were prepared from several grains - rice (unhusked, brown, white and boiled white), sorghum, millet, wheat, maize and barley - and tested for lectin activity, as indicated by agglutination of chicken erythrocytes. Only washings from unhusked rice, sorghum and millet failed to haemagglutinate. None of the crude washings antagonised the haemagglutinating activity of NDV, and the washing from white rice produced an 8-fold enhancement. The presence of lectins in the washings from rice, wheat and barley was confirmed by purifying a substance with N-acetyl-D-glucosamine specificity. Only the crude extract from white rice had any profound effect on infectivity, reducing the infectivity titre by 99.99%. It is not known if the viricidal substance is identical with the lectin. Of 9 commercial lectins tested, only ConA bound the V4 virus.