Polykaryocyte induction by Newcastle disease virus propagated on different hosts

Department of Microbiology Emory University, Atlanta, Georgia 30322 U.S.A. Infection of cultured cells with Newcastle disease virus may result in the formation of multinucleated cells or polykaryocytes (Johnson & Scott, 1964). Polykaryocytes have been observed early (1 to 3 hr) after infection of cells with high multiplicities of Newcastle disease virus (Kohn, 1965). However, strains of Newcastle disease virus have different cell-fusing potencies (Kohn & Fuchs, 1969). We report here differences in the ability of Newcastle disease virus stocks propagated on chicken and human cells to induce early polykaryocyte formation. HeLa cells (obtained from Dr W. A. Cassel) were grown in Eagle's minimal essential medium (MEM) containing 10% calf serum. The os strain of Newcastle disease virus, assayed on HeLa cells as previously described (Ash & Bubel, 1966), was employed in all experiments. Virus titres were expressed in terms of haemadsorption focal units (h.f.u.)/ml. Received 30 September 1969; accepted 25 November 1969.