Agglutination of Mammalian Erythrocytes by Newcastle Disease Virus. ∗

Abstract

Summary and conclusions

The ability of NDV to induce agglutination of mammalian erythrocytes of certain species is a character possessed by some but not all strains of the virus. The erythrocytes of certain individuals of such species as the cow, the horse, and the sheep are more susceptible than those of others to agglutination by NDV. Agglutination of mammalian red blood cells, as a rule, may be recorded accurately as the per cent of individuals whose cells are susceptible to the action of a given strain of NDV and not as a uniformly negative or positive result. This percentage of erythrocyte susceptible individuals may range from zero in some species to 100% in others but in most species lies between these extremes so that its consideration is warranted in every instance. It was demonstrated that the pH may affect the agglutination of mammalian red blood cells and, consequently, alter the interpretation of the test. If suitable controls of the variables of the test are included and the source of red blood cells is properly selected many strains of NDV may be differentiated by their mammalian agglutination range or spectrum.

The mechanism underlying these observations has not been investigated. The most obvious explanation predicates differences in the agglutinative activity of the virus strains, possibly associated with variable levels of enzyme production or activity. Chu would hold accountable differences in the levels of one or more inhibitors of hemagglutination. In either case, the activity or lack of activity seems to be associated with lines or strains of virus. The differing hemagglutinative susceptibility of individual donors suggests that the mechanisms involved are rather complex.

The phenomenon of agglutination of mammalian erythrocytes has practical application in maintaining the identity of stock strains of virus and possibly also in determining probable intermingling of the viruses of live vaccines and wild strains in field outbreaks of Newcastle disease.