Dialyzable Factor in Normal Allantoic Fluid Inhibiting Hemagglutination Patterns with Newcastle Disease Virus. ∗

Abstract

Summary

An inhibitor of hemagglutination present in allantoic fluid suspensions of certain strains of Newcastle disease virus was largely removed by dialysis so that definite and reproducible hemagglutination patterns were obtained with virus suspensions which had previously appeared to be nonagglutinating. The inhibiting factor was present in normal allantoic fluid of 13-day-old eggs and in the dialysate of dialyzed normal allantoic fluids. The inhibiting activity was 8-16 times more effective at 4°C than at 25°C but the inhibitor was resistant to heating at 100°C for 30 minutes. It was not destroyed by receptor destroying enzyme. The inhibitor was 4 times as effective when mixed with the red blood cells before addition of the virus as when the inhibitor and virus were mixed before adding the red cells. Erythrocytes mixed with inhibitor for varying periods regained their agglutinability if washed free of inhibitor. Moreover, the inhibitor removed from such erythrocytes retained its inhibitory titer undiminished. NDV did not destroy or reduce the inhibitory capacity when allowed to mix with inhibitor for 2 hours at 25°C.