Abstract
Newcastle disease virus grown in embryonated eggs was separated and purified by sucrose density gradient centrifugation into two distinct types of particles, B and T, the former being normal virus particles with high activities of hemagglutination, hemolysis, neuraminidase and infectivity, the latter being non-infectious virus particles with low activities of hemolysis and neuraminidase but high hemagglutination activity. B and T particles were shown to share a common antigen by immunodiffusion test. T particles were deficient in viral RNA, since they contained only 13s RNA in a small amount, whereas B particles possessed a large amount of 57s RNA and a small amount of 13s RNA. T particles interfered with the multiplication of normal Newcastle disease virus in primary cultures of chick embryo cells.
