- Volume 11, Issue 1, 1971

The molecular weights of the protein subunits of Odontoglossum ringspot virus, belladonna mottle virus and brome mosaic virus were estimated by the equilibrium centrifugation method of Yphantis to be 17,300, 20,700 and 17,200, respectively.

Solutions of the virus protein subunit monomers were prepared by suspending the virus particles in neutral buffers containing 6m-urea and Cleland’s reagent; preliminary tests with well-characterized proteins showed that the urea solution decreased the partial specific volume of the proteins by about 0.02 to 0.03 g./ml.

In solvents without urea brome mosaic virus dimer subunits had a molecular weight of about 40,000.

The cytopathic effects produced by seven strains of Newcastle disease virus grown in chick embryo cell culture were examined. The principal form of cytopathic effect involved the formation of multinucleate cells (polykaryocytes) by cell fusion. The capacity of the different Newcastle disease virus strains to induce cell fusion was related directly to their virulence for chicks and fertile eggs. The virulent (velogenic) strains herts, warwick and texas produced significantly greater polykaryocytosis than the mesogenic strain beaudette c which, in turn, produced greater polykaryocytosis than the avirulent (lentogenic) vaccine strain f. The lentogenic strains queensland and ulster failed to produce detectable cytopathic effects. Distinct morphological differences were noted in the polykaryocytes produced by the different strains. The ability to form plaques and plaque size in chick embryo monolayers was also related to the virulence of the virus strains.

Nine strains of Newcastle disease virus were examined for their ability to inhibit cellular protein synthesis and to cause cell fusion. Inhibition of cellular protein synthesis was confined to infection with virulent strains (herts, warwick, texas, h, field pheasant) and the mesogenic strain beaudette c. No inhibition of synthesis was recorded with avirulent strains (ulster, f, queensland). Inhibition of cellular protein synthesis required virus protein synthesis within 3 hr of infection and could be inhibited by parafluorophenylalanine and Congo red. Cell fusion and haemadsorption by the various Newcastle disease virus strains also required virus-induced protein synthesis and were inhibited by cycloheximide, parafluorophenylalanine and Congo red. However, neither virus-induced inhibition of cellular protein synthesis nor cell fusion required new virus RNA synthesis, since azauridine did not affect these processes. The importance of virus-induced proteins in the inhibition of protein synthesis and cell fusion is discussed.

Purified preparations of adenovirus were readily disrupted by heating them for a short time in the presence of sodium deoxycholate. The inner complex of proteins and virus DNA (cores) was partially purified by velocity gradient centrifugation in sucrose or glycerol. Further purification was achieved by equilibrium centrifugation on a preformed gradient of ‘Urografin’. Acrylamide gel electrophoresis showed that the cores contained principally two protein components one of which could be removed at the last stage of purification. The core preparations were infective at an extremely low efficiency, the infectivity being sensitive to DNase, trypsin and to various antivirus sera.