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Volume 66,
Issue 5,
1985
Volume 66, Issue 5, 1985
- Animal
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Effect of Chloroquine on African Swine Fever Virus Infection
More LessSummaryWhen present during the whole infective cycle, the lysosomotropic drug, chloroquine, inhibited cytopathic changes and production of African swine fever virus (ASFV) in Vero cells. This inhibition decreased when the drug was added from 1 h to 4 h after infection. Chloroquine had no direct effect on the virus nor on viral adsorption and internalization. Electron microscopy showed that, in the presence of the drug, the virions were retained in large vacuoles having a lysosomal appearance. This inhibition was fully reversible, even when the drug was removed as late as 72 h after infection. The results support the hypothesis that ASFV enters the cells by adsorptive endocytosis and not by fusion with the plasma membrane.
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125I-labelled Human Interferons Alpha, Beta and Gamma: Comparative Receptor-binding Data
More LessSUMMARYBinding of 125I-labelled human recombinant DNA interferons (IFNs) alpha-2, beta and gamma was compared on various human lymphoid cells and embryonic fibroblasts. While binding constants were within an order of magnitude for all three interferons (10−10 to 10−9 m), no competition was observed between IFN-γ on the one hand and IFN-α2 and IFN-β on the other. However, consistent with previous reports, IFN-α2 and IFN-β competed for presumably common receptors. Depending on the cell type, binding sites for IFN-γ were expressed in different numbers compared to those for IFN-α2 and IFN-β. These direct comparative binding studies support the hypothesis that the receptor system for IFN-γ is unrelated to the IFN-α/β system.
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Evidence that IFN-α/β Induces Two Antiviral States Active Against Different Viruses
More LessSUMMARYIFN-α/β has been suggested to require only one round of mRNA and protein synthesis to induce an antiviral state. We have examined the mechanism of induction of the antiviral states shown against three types of viruses: mengovirus (plus strand, sense RNA), vesicular stomatitis virus (VSV, minus strand RNA), and vaccinia virus (DNA). Mouse L cells were treated with IFN-α/β and cycloheximide and then with actinomycin D on a schedule which allowed only one round of mRNA and protein synthesis. The cells were challenged with virus under single cycle growth conditions to determine the amount of antiviral activity against the particular challenge virus employed. These studies confirmed that most of the antiviral effect directed against VSV is achieved with one round of macromolecular synthesis. However, most of the antiviral effect directed against mengovirus and vaccinia virus seemed to require more than one round. These results suggest that IFN-α/β induces two different antiviral states: one requiring one round of synthesis which is primarily responsible for the inhibition observed for VSV; and another requiring more than one round of synthesis which is primarily responsible for the inhibition observed for mengovirus and vaccinia virus.
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Principal and Subsidiary Antigenic Sites of VP1 Involved in the Neutralization of Poliovirus Type 3
More LessSUMMARYThe characterization of over 300 mutants, derived from two strains of poliovirus type 3 and selected for resistance to neutralization by monoclonal antibodies, has led to the further definition of the major antigenic site involved in neutralization. The site encompasses amino acids 89 to 100 of VP1. A subsidiary antigenic site near the C-terminus of VP1 has been identified for the Sabin vaccine strain of poliovirus type 3. Of 59 monoclonal antibodies to poliovirus type 3 examined, 27 had virus-neutralizing activity and 25 of these were identified as directed against the major site on VP1 (designated site 1), indicating the immunodominant role of this site. One of the six monoclonal antibodies that recognized the subsidiary antigenic site on VP1 (designated site 2) possessed virus-neutralizing activity. The identification of the principal antigenic site of the virus provides a rational basis for attempts at the development of synthetic oligopeptide vaccines against poliovirus type 3.
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Cross-reactive Target Antigen in Cell-mediated Cytolysis of Cells Infected with a Temperature-sensitive Mutant of Sindbis Virus
More LessSUMMARYCytotoxic T lymphocytes (CTL) against alphavirus-infected L929 cells were generated in mice by two in vivo immunizations of one virus or by in vivo immunization followed by in vitro stimulation of splenocytes with infected peritoneal exudate cells or splenocytes. These CTL caused specific H-2-restricted cytolysis equally well with homologous, heterologous or Sindbis virus ts20 mutant-infected cells. Thus, specific CTL appear to be cross-reactive components in normal immunity to alphaviruses and the E1 glycoprotein is implicated as the target antigen.
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The Ratio of Plasma Membrane Cholesterol to Phospholipid and the Inhibition of Sindbis Virus Maturation by Low NaCl Medium
More LessSUMMARYSindbis virus maturation is inhibited by low NaCl medium in chick embryo cells and in one strain of BHK cells, but not in another strain of BHK cells which has a different passage history. The plasma membrane of the cells in which Sindbis virus maturation is resistant to low NaCl medium has a higher ratio of cholesterol to phospholipid than the other cells. Cholesterol-containing liposomes, but not cholesterol-free liposomes, can release Sindbis virus from low NaCl-inhibited cells. These results suggest that low NaCl medium may block Sindbis virus maturation by a mechanism which is influenced by the ratio of plasma membrane cholesterol to phospholipid.
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MRC-5 Cells, a Model for Junín Virus Persistent Infection
More LessSUMMARYPersistent infection of MRC-5 cells was established following inoculation with attenuated Junín virus (JV). In the acute phase of the infection both the pathogenic XJ and the attenuated XJ0 and XJC13 strains showed severe c.p.e. and free viral titres reached 105 p.f.u./ml. Recovery and establishment of persistently infected MRC-5 sublines (MRC-5Pl) proved a very common event and seemed to be independent of viral strain, m.o.i. employed or virus passage history. These MRC-5Pl sublines released virus throughout their life span and infectious centre assays performed at different passage levels with two sublines showed that 5 to 9% of the cells were producing virus. Heterotypic but not heterologous resistance to superinfection developed, as observed in persistent JV-heteroploid cell systems. Analysis of released JV showed that attenuation had not been markedly altered, but alteration in plaque morphology under methyl cellulose, appearance of temperature-sensitive mutants and alterations in mouse pathology imply that some properties of JV have been altered. Results presented here stress once again the ability of JV to establish persistent infections. The source and diploid characteristics of MRC-5 cells make them a satisfactory model for JV persistence studies.
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Infectivity Difference Between the Two Phenotypes of Autographa californica Nuclear Polyhedrosis Virus: Importance of the 64K Envelope Glycoprotein
More LessSUMMARYTwo phenotypes of Autographa californica nuclear polyhedrosis virus (AcNPV), occluded virus and budded virus (BV), are responsible for causing disease in Trichoplusia ni. Virus released from occlusion bodies by alkali (LOVAL) is more infectious in the gut than in the haemocoel whereas BV is more infectious in the haemocoel than in the gut. Reduction of infectivity of BV in the haemocoel by the monoclonal antibody AcV1 to a level comparable to LOVAL clearly implicates its target, a 64K phosphoglycoprotein abundant in the BV envelope but not detected in LOVAL, as being involved in BV×s greater infectivity in that location. Homologous antiserum reduces the infectivity of LOVAL in the gut to that of LOVAL in the haemocoel, suggesting an analogous envelope component may account for its greater infectivity in the gut.
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- Plant
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Pseudorecombinants between Cloned DNAs of Two Isolates of Cassava Latent Virus
More LessSUMMARYInfective clones of the Nigerian isolate of cassava latent virus (CLV) have been obtained. The apparent molecular weight of the capsid protein of this isolate is slightly higher than that produced in plants infected with cloned DNAs of the Kenyan isolate of CLV. Pseudorecombinant experiments using heterologous combinations of cloned DNAs have confirmed that the physical properties of the capsid protein are encoded on DNA 1 and at least some determinants of symptom induction are also located on this DNA. Comparison between the nucleotide sequences of the open reading frames encoding the two capsid proteins shows several nucleotide differences which affect the amino acid composition but which do not significantly alter the potential molecular weight of the product. In vitro translation of poly(A)+ RNAs shows that the differences in electrophoretic mobility are not due to differences in host-directed post-translational processing.
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Properties of Sweet Potato Feathery Mottle Virus RNA and Capsid Protein
More LessSUMMARYSweet potato feathery mottle virus (SPFMV) shares many biological and cytopathological characteristics with viruses in the potyvirus group. However, the native virion lengths for strains of SPFMV range from 810 to 865 nm. This is similar to the length attained by other potyvirus virions after reaction with divalent cations. In this paper we show that the SPFMV genome is an infective, polyadenylated, probably single-stranded RNA molecule with a molecular weight of 3.65 × 106 and that the coat protein has a molecular weight of 3.8 × 104. These properties also resemble those of potyviruses.
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A Dot Immunobinding Assay for the Detection of Tobacco Mosaic Virus in Infected Tissues
More LessSUMMARYA dot immunobinding assay (DIBA) was modified for the rapid detection of plant viruses in infected tissues by avoiding non-specific reactions and minimizing the amounts of antibodies used. With this method, less than 1 ng of tobacco mosaic virus could be detected in several milligrams of infected tobacco leaves. This simple, rapid and sensitive assay should prove to be a useful and practical diagnostic technique for plant virus diseases.
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