- Volume 14, Issue 1, 1972
Volume 14, Issue 1, 1972
- Articles
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Effect of Concanavalin A on Cells Infected with Enveloped RNA Viruses
H. Becht, R. Rott and H.-D. KlenkSUMMARYA variety of cells infected with different enveloped RNA viruses are specifically agglutinated by Concanavalin A. The production of envelope-components seems to be essential for the agglutinability of cells infected with myxovirus. A strong flocculation of purified virus particles by Concanavalin A indicates that the specific receptor of the host cell membrane is incorporated into the virus envelope.
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Growth of Newcastle Disease and Herpes Virus and Interferon Production in a Monkey-Mouse Hybrid Line
More LessSUMMARYThe mean yield of NDV is about 0.1 p.f.u./cell in MKS-B mouse kidney cells, 100 p.f.u./cell in CV-1 monkey kidney cells and 70 p.f.u./cell in MK-CV111 clone 4, a hybrid line arising from the fusion of MKS-B and CV-1. The mean yield of herpes is about 2 p.f.u. in MKS-B, and 160 p.f.u. in both CV-1 and in MK-CV111 clone 4. The u.v. sensitivity of the capacity of cells to support NDV multiplication is the same for CV-1 and MK-CV111 clone 4 cells, but much lower for MKS-B cells, indicating that NDV replicates using at least some monkey functions of these hybrid cells.
NDV or Sindbis infected hybrids produce both mouse interferon (99%) and monkey interferon (1%), the molecular weights of which are the same as those of corresponding parental interferons.
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Some Biological Characteristics of Mycoplasmatales Virus-laidlawii 1
More LessSUMMARYMycoplasmatales virus-laidlawii 1 (MV-L1) produced plaques on lawns of 11 out of 17 strains of Acholeplasma laidlawii but not on 12 other mycoplasma species examined. Clones of A. laidlawii resistant to lysis by the virus could readily be obtained from survivors of the susceptible bni strain. These resistant clones carry virus apparently serologically similar to MV-L1 as does the susceptible bni strain itself.
The virus was sensitive to the action of u.v. light and chloroform but relatively insensitive to ether. Nonidet-P 40, heat and pH levels of between 8 and 10. MV-L1 passed readily through Millipore VS filters of 25 nm. pore diameter with loss of titre of 0.5 log p.f.u./ml. or less.
In one-step growth experiments the latent period was between 30 and 60 min. and the burst size varied from 4 to 213. Maximum yield was obtained when virus was added early in the logarithmic stage of acholeplasma growth. MV-L1 appeared to cause gradual lysis of the acholeplasma culture.
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Increased Interferon Release and Morphological Alteration in Human Cells by Repeated Exposure to Double-stranded RNA
More LessSUMMARYHuman skin fibroblasts produced interferon of high titre after exposure to double-stranded polyriboinosinic-ribocytidylic acid (In.Cn). In contrast to rabbit kidney cells, ten strains of human skin fibroblasts released more interferon after a second and third exposure to In. Cn than after the first one. It is speculated that this hyperreactivity is due to increased accumulation of an interferon precursor or to less effective synthesis of repressors of interferon production. Repeated exposure resulted in a cytopathic effect which was quantitatively related to the amount of interferon induced.
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Characterization of Subviral Components Resulting from Treatment of Rabies Virus with Tri(n-butyl) Phosphate
More LessSUMMARYThe pm strain of rabies virus was grown in human diploid WI-38 cells and labelled with the following radioactive substances: [14C]- or [3H]-d-glucosamine, [14C]-uridine, [14C]-stearic acid, [3H]-choline and a mixture of [14C]-amino acids. It was then purified and treated with 0.1% tri(n-butyl)phosphate (TNBP) in the presence of 0.1% Tween 80. All the stearic acid and choline and about 82% and 40%, respectively, of the d-glucosamine and amino acid (but none of the uridine) label was released from the virus. It was concluded that TNBP dissociates the lipids, most of the glycoproteins, and small quantities of non-glycosylated proteins from the virus leaving behind particles containing all of the virus RNA. These particles sedimented in sucrose gradients at the same rate as did intact virus; they had a higher buoyant density in CsCl gradients (1.304 compared with 1.244 g./cm3.) and they resembled intact virus in overall size and shape but lacked most of the surface projections. By polyacrylamide gel electrophoresis the following polypeptide species were identified in intact particles (tentative molecular weights are given in parentheses): glycoproteins (GP1 (78,000) and GP2 (65,000); nucleocapsid proteins NP1 (58,000) and NP2 (47,000) and two additional proteins MP (35,000) and CP (22,000). Treatment with TNBP released nearly all GP1 and GP2 and small quantities of MP. Particles obtained by treatment of the virus with the proteolytic enzyme bromelain also lacked the surface projections (and the glycoproteins GP1 and GP2) but retained the lipids.
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Basis for the Probit Analysis of an Interferon Plaque Reduction Assay
More LessSUMMARYThe number of plaque forming units (p.f.u.) of virus dispensed on to interferon-treated monolayers in a plaque reduction assay has been assumed to follow a Poisson distribution with the mean estimated from plaque counts on untreated monolayers. From these considerations, plaque counts have been assigned weights and the probit regression line calculated by the method of maximum likelihood. A chisquare analysis of plaque reduction data indicates agreement with the calculated line and does not refute the assumptions leading to the use of Poisson weighting coefficients or a log-normal distribution of p.f.u. ‘tolerances’ to interferon. This implies that the most precise estimate of dose occurs where plaques develop from 27% of the added p.f.u. The calculation of a weighted probit regression line from interferon plaque reduction data has several advantages: all the data from an experiment can be properly utilized; the variance and confidence interval of the interferon titres can be obtained; a direct comparison of dose-responses and titres can be made between different samples; a measure of the reliability of an experiment can be obtained by chi-square analysis.
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Defective Virus RNA Synthesis and Production of Incomplete Influenza Virus in Chick Embryo Cells
More LessSUMMARYVirus particles released from chick embryo cells infected with equine influenza virus at high multiplicity in the first 10 hr after infection contained the complete RNA component of infectious virus. Virus released later (20 to 30 hr after infection) was of von Magnus type and contained the RNAs of incomplete virus. It is concluded that the formation of von Magnus virus in chick embryo cells is due to a defective synthesis of virus RNA components and not due to a defective assembly and release of virus particles.
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Experimental Study on the Transmission of Sendai Virus in Specific Pathogen-free Mice
More LessSUMMARYUsing the sero-conversion test Sendai virus was shown to transmit rapidly in specific pathogen-free (SPF) mice. Transmission of virus was closely related to the titre in nasal tissue of one infector. The transmitted virus grew without any preferential distribution in the respiratory tissues and gradually disappeared within 2 weeks of contact infection. Under our experimental conditions direct contact with the infector was the most important factor in transmission.
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In Vitro Immune Responses of Spleen Cells from Friend Virus Infected Mice
More LessSUMMARYThe primary immune response to sheep erythrocytes of spleen cells cultured from mice infected with Friend virus was compared with that of normal spleen cell cultures. Significant depression of the response, as measured by the production of haemolytic plaque-forming cells, was first observed when mice had been infected for 3 days prior to cell culture. This depression became more severe as the infection period was prolonged.
After 4 days infection in vivo the peak of the in vitro response was reduced to a mean of 11% of normal values. No depression was observed during the first 48 hr of the development of the response in such cultures.
The immune defect was shown to exist only in the non-adherent (lymphocyte-like) fraction of the spleen.
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Studies on the Structural Proteins of Semliki Forest Virus
More LessSUMMARYA method is described for the growth of Semliki Forest virus in suspensions of primary chick embryo fibroblasts and for its subsequent purification. The overall purification of the virus was approximately 250-fold with a 40 to 50% recovery of haemagglutination activity. Analysis of purified Semliki Forest virus by SDS-polyacrylamide gel electrophoresis showed the presence of two distinct protein bands. The protein of the virus envelope has a molecular weight of approximately 51,000 and is a glycoprotein. The lighter protein, with a molecular weight of approximately 32,000, is associated with the nucleocapsid core of the virion and does not appear to contain carbohydrate. Preparative SDS-polyacrylamide gel electrophoresis through a discontinuous gel system yielded mg. quantities of each of the two structural proteins. Amino acid analysis revealed that the envelope protein is relatively rich in hydrophobic amino acids, whereas the core protein is rich in hydrophilic amino acids, particularly lysine and glutamate. The N-terminal amino acid of the envelope protein is valine and that of the core protein is lysine. By employing the dansyl technique, tryptic peptide maps of the envelope and core proteins of Semliki Forest virus were obtained. Approximately 25 soluble tryptic peptides were obtained from the envelope protein and approximately 38 from the core protein.
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