Journal of General Virology - Volume 11, Issue 1, 1971

Spermine, oxidized by partially purified serum amine oxidase, inactivated influenza, Newcastle disease and Sendai viruses. The rate of inactivation, determined by assaying the production of haemagglutinins in chick embryos, depended upon the concentration of the drug, temperature, and exposure time. Under appropriate conditions a complete inactivation of all the viruses was observed. Oxidized spermidine was also inhibitory, but at higher concentrations. Completely inactivated Newcastle disease and Sendai viruses agglutinated red blood cells in vitro and fused Ehrlich ascites cells. Electron microscopy showed that oxidized spermine had little effect on the integrity of the inactivated viruses. The virucidal activity of oxidized spermine was abolished after reduction with sodium borohydride, implying the importance of aldehyde groups in the inactivation process.

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.

The failure of type 1 herpesvirus to form plaques in chick embryo cells distinguishes the type 1 virus from the type 2 virus. Herpesvirus type 2 forms plaques in these cells at titres equal to those obtained in rabbit kidney cells, while most type 1 strains fail to form plaques in chick embryo cells (Figueroa & Rawls, 1969). However, most type 1 virus isolates contain a small proportion of virus which does form plaques in chick embryo cells, and this proportion increases with passage of the isolates in tissue culture. The type 1 variants capable of forming plaques in chick embryo cells retain the biological and antigenic characteristics of the parental type 1 virus, but acquire a relative resistance to the DNA inhibitor ara-A (Lowry, Melnick & Rawls, 1970). The present study was undertaken to characterize the type 1 abortive infection in chick embryo cells.

The parainfluenza virus SV5 has been found to contain six proteins with mol. wts ranging from about 41,000 to 76,000 (Caliguiri, Klenk & Choppin, 1969; Mountcastle, Compans & Choppin, 1971). The nucleocapsid of the virus particle is composed of a single polypeptide chain with a mol. wt. of about 61,000 (Mountcastle et al. 1970); the other five proteins are presumably associated with the virus envelope. Two of the proteins are covalently linked to carbohydrate (Klenk, Caliguiri & Choppin, 1970). We report here that these glycoproteins comprise the spikes or projections on the surface of the SV5 virus particle.

The w3 strain of SV5 (Choppin, 1964) was grown in MDBK cells (Choppin, 1969) in reinforced Eagle's medium (Bablanian, Eggers & Tamm, 1965) with 2% calf serum. Cells were inoculated at a multiplicity of about 10 p.f.u./cell.

Holmes & Watson (1963), Dales & Silverberg (1969) and Hummeler, Tomassini & Zajac (1969) showed that herpes simplex virus enters the host cell by being engulfed via the phagocytic process. Equine abortion virus enters the cell similarly (Abodeely, Lawson & Randall, 1970). An alternative mechanism of virus entry has been proposed by Morgan, Rose & Mednis (1968) who suggest that the stages of herpes virus entry into the host cell consist of attachment, digestion of the virus envelope, digestion of the cell membrane, passage of the capsid into the cytoplasm, breakdown of the capsid with the subsequent release of the DNA core into the cytoplasm. We describe here the early stages of infection of kidney cells by infectious bovine rhinotracheitis virus, another member of the herpes virus group.

Infectious bovine rhinotracheitis virus was kindly supplied by the Cell Culture Division of the Naval Biomedical Laboratory, Oakland, California.

Studies in a number of laboratories have indicated that the internal protein components of adenovirus are basic in nature and possess some properties which are similar to the histones and protamines. Thus, they are acid-soluble, rich in arginine and have alanine as their major N-terminal amino acid (Russell, Laver & Sanderson, 1968; Prage, Pettersson & Philipson, 1968; Maizel, White & Scharff, 1968; Boulanger et al. 1970; Laver, 1970; Russell, McIntosh & Skehel, 1971). The possible function of these components in infection is of great interest; furthermore, they provide a relatively simple system in which to study the interaction of basic proteins and nucleic acids. As one approach to this problem, the changes in the metabolism of cellular histones as a result of infection by adenovirus have been examined by analysing the acid-soluble components of infected and control cells in polyacrylamide gel electrophoresis.