- Volume 41, Issue 1, 1978
Volume 41, Issue 1, 1978
- Review Article
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- Articles
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Quantification of Cell Fusion by Twenty-one Strains of Newcastle Disease Virus Using Flow Microfluorometry
More LessSUMMARYThe cell-fusing ability of Newcastle disease virus (NDV) was quantified using flow microfluorometry (FMF). The rate of polykaryocyte formation, fusion dependence on multiplicity of infection, and cell fusion differences for 21 NDV strains were measured using this technique. No correlation was found between the virulence of a virus strain and its cell fusion index calculated from the FMF data.
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Suppression of the Synthesis of Cellular Macromolecules by Herpes Simplex Virus
More LessSUMMARYSynthesis of cellular protein was substantially inhibited within I h of infection with herpes simplex virus, type 2, strain G (HSV-2). The inhibition also occurred, although no virus-specific protein synthesis was detected, after infection with u.v. irradiated virus and in cytoplasts that had been enucleated before infection. The inhibitory activity could not be distinguished from infectivity by dilution, sedimentation or reaction with γ-globulin. HSV-2 also suppressed the synthesis of Sendai virus proteins, but not those specified by HSV-1.
Host protein synthesis was no more sensitive than virus protein synthesis to an increased concentration of NaCl in the medium, nor could the suppression of host synthesis be prevented by adding excess MgCl2 to the medium or by omitting CaCl2 or NaCl. It was accompanied by the breakdown of polyribosomes, which also occurred in the presence of cycloheximide but not at 4 °C. The breakdown yielded ribosomes that were sensitive to a high salt concentration, unlike those produced by treatment of polyribosomes with RNase. The synthesis of cellular DNA and RNA was also inhibited following infection with u.v.-inactivated virus.
It is concluded that the suppression of host protein synthesis (and probably also of host DNA and RNA synthesis) is caused by a constituent of the infecting virus particles. The mechanism is obscure but probably does not depend on the leakage out of the cell of Mg2+ or into the cell of Ca2+ or Na+ ions, nor on the specific inhibition of initiation of host polypeptide chains, nor on RNase-like attack on host polyribosomes.
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Estimates of Molecular Weights of Nepovirus RNA Species by Polyacrylamide Gel Electrophoresis under Denaturing Conditions
More LessSUMMARYThe mol. wt. of the RNA components of twelve nepoviruses were estimated by electrophoresis at 60 °C in 2·0% polyacrylamide gels containing 8 m-urea. This method gave estimates of RNA mol. wt. that were very reproducible and those for RNA-2 are considered more accurate than values published hitherto. Most of the viruses fell into one of three clusters with RNA-2 mol. wt. of about 1·45 × 106, 1·65 × 106 and 2·0 × 106. For all the viruses, the estimates for RNA-1 (2·08 to 2·19 × 106) were considerably lower than previously published values but may not be more accurate. Three viruses had additional RNA components (RNA-3) with mol. wt. 0·4 to 0·5 × 106. The implications of these findings for the packaging of the RNA molecules and for classification of the viruses is discussed.
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Factors Influencing the Infection of Barley Mesophyll Protoplasts with Brome Mosaic Virus RNA
More LessSUMMARYOne of the most critical factors for the infection of barley protoplasts with brome mosaic virus (BMV) RNA was the osmotic strength of the medium during protoplast isolation and inoculation. Infection was most efficient when protoplasts were isolated and inoculated in 0·5 m-mannitol and then washed with 0·7 m-mannitol; less infection occurred when the protoplasts were isolated in 0·5 or 0·7 m-mannitol and inoculated and washed in 0·7 m-mannitol. Other conditions optimal for infection were inoculum containing 1 μg/ml BMV RNA or less, 1 μg/ml poly-l-ornithine, 20 mm-potassium citrate buffer at pH 4·7 and 0·5 mm-CaCl2, and inoculation at 0 °C. Up to 90% of protoplasts were infected in these conditions. Osmotic shock produced by increase of mannitol concentration immediately before inoculation induced invagination suggestive of pinocytosis, and this seemed to be associated with efficient infection of barley protoplasts with BMV. The discrepancy between the effect of this osmotic shock on the infection of barley protoplasts with BMV and its RNA, and the mechanism of infection are discussed.
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Circular Dichroism Studies on Turnip Rosette Virus
More LessSUMMARYCircular dichroism studies show that the RNA of turnip rosette virus (TRosV), both within the particles and free in solution, has considerable base pairing. The protein of TRosV is characterized by a relatively high proportion of β-structure and low proportion of α-helix. Swelling of the virus particles by raising the pH and removing divalent cations causes slight changes in the conformation of the RNA and some changes in the protein conformation.
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Prostaglandins Enhance Spread of Herpes Simplex Virus in Cell Cultures
More LessSUMMARYStimuli such as u.v. light or trauma which induce recurrence of herpes simplex may act by affecting virus replication in the skin. Such stimuli release pharmacologically active agents in the skin, including prostaglandins (PGs) such as PGE2. These agents, and other compounds which alter levels of adenosine cyclic monophosphate (cyclic AMP), were tested for their effect on the replication of herpes simplex virus (HSV) in Vero cells.
Prostaglandin E2 (PGE2) and prostaglandin F2α both increase the size of HSV plaques; PGE2 also increases the yield of virus inoculated at low m.o.i. Moreover, inhibitors of prostaglandin synthesis decrease plaque size and inhibit the growth of virus inoculated at low m.o.i.; such inhibition can be partially overcome by adding PGE2. Analysis of the results suggest that prostaglandins can enhance cell-to-cell spread of HSV, but that cyclic AMP is probably not involved in this effect.
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Protection of Mice Against Viral Infection by Corynebacterium parvum and Bordetella pertussis
More LessSUMMARYMice could be significantly protected against infection with herpes simplex virus (HSV) by i.p. or i.v. injection of killed Corynebacterium parvum 7 days before infection. This protection was seen in inbred strains of mice with a different degree of sensitivity to HSV and after both i.p. and i.v. infection. Resistant mice immuno-suppressed by X-irradiation and showing an increased susceptibility to HSV could also be protected by a previous injection of C. parvum. Elevated levels of interferon were demonstrated in the serum of mice injected with C. parvum 5 to 12 days previously. Four different strains of anaerobic coryneforms were compared and only those which were able to induce a systemic activation of the lymphoreticular system (as reflected by splenomegaly) protected against HSV infection. Protection against HSV-infection could also be demonstrated by using killed Bordetella pertussis. C. parvum also protected against Semliki Forest virus infection in two different strains of mice.
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Pre-lytic Release of Foot-and-Mouth Disease Virus in Cytoplasmic Blebs
More LessSUMMARYThe pre-lytic release mechanism of foot-and-mouth disease virus was investigated by immunofluorescence, acridine orange staining, and electron microscopy in infected bovine and porcine kidney coverslip cultures. Cells with cytoplasmic fluorescence and which were positive for single stranded RNA with acridine orange staining were observed at 2 h after infection. Scanning electron microscopy showed cytoplasmic blebs in all cultures examined 2 h after infection. Rounded cells with virus inclusions began to appear 3 h after infection. Rounded cells and cytoplasmic blebs were shown to have single stranded RNA by acridine orange staining. Immunofluorescence and transmission electron microscopy with immunoferritin tagging demonstrated foot-and-mouth disease virus in cytoplasmic blebs. This study presents evidence for a pre-lytic release of foot-and-mouth disease virus through virus-containing cytoplasmic blebs emerging from infected cells.
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Novel Influenza A Viruses Isolated from Canadian Feral Ducks: Including Strains Antigenically Related to Swine Influenza (Hsw1N1) Viruses
More LessSUMMARYTwelve influenza A viruses, antigenically related to the H0, H1 and Hsw1 subtypes, were isolated from cloacal samples of feral ducks in Canada. Antigenic comparisons showed that these viruses were most closely related to the recent Hsw1N1 isolates from man and pigs, whereas in vivo pathogenicity tests revealed differences between the Hsw1N1 viruses from the ducks and those from humans and pigs.
Antigenic characterization of 94 additional influenza A viruses from the ducks showed four haemagglutinin subtypes (Hav1, Hav4, Hav5 and Hav7), an unclassified haemagglutinin, and six neuraminidase subtypes (N1, N2, Neq2, Nav1, Nav2 and Nav5) in various combinations, some of which are novel and have not previously been reported. Three of these duck influenza viruses possessed a haemag-glutinin antigenically related to that of classical fowl plague virus. A much higher percentage of virus isolations were from juvenile ducks (18·5%) than from adults (5 %). All of the ducks, from which viruses were isolated, appeared healthy at the time of sampling. Serological studies on a limited number of humans and domestic birds living in close proximity to the Canadian ducks revealed no evidence of interspecies transmission.
Our findings suggest that these birds serve as a substantial reservoir of antigenically diverse influenza viruses, including isolates antigenically related to the current human and animal influenza viruses. This reservoir in nature may be perpetuated by a cycle involving annual infection of juvenile birds followed by transmission to the remaining susceptible birds until the next congregation during the breeding season.
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Suppression of Interferon Production in Mouse Spleen Cells by Cytochalasin D
More LessSUMMARYCytochalasin D is thought to impair microfilament function. The present study has investigated its effects on four different systems in which interferon is formed, namely (1) mouse fibroblasts induced with virus (2) mouse spleen cells induced with virus, or (3) with endotoxin or (4) by allogeneic stimulation.
Cytochalasin D did not suppress formation of interferon by fibroblasts (L cells) or spleen cells stimulated with either HVJ or NDV. However it did suppress production of interferon by spleen cells in response to endotoxin or an allogeneic stimulation; here its action was apparently not on the secretion of interferon, but on some earlier event. It also suppressed the production of interferon by mouse spleen cells induced with HVJ if this had been u.v. irradiated for more than 15 min: this suggests that cytochalasin D sensitive structures do play some role in interferon production by mouse spleen cells when stimulated with HVJ, as well as when they are stimulated with endotoxin or an allogeneic stimulus.
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A New, Rapid Procedure for the Concentration of C-type Viruses from Large Quantities of Culture Media: Ultrafiltration by Diaflo Membrane and Purification by Ficoll Gradient Centrifugation
More LessSUMMARYThe Amicon TCIR recycle system with Diaflo PM30 filters provided a rapid, simple and inexpensive method for the concentration of baboon endogenous virus from a large quantity of culture medium from chronically infected cells. The recovery of infectivity and virion RNA-dependent DNA polymerase activity was substantially better than after the conventional concentration methods of ultra-centrifugation or precipitation with ammonium sulphate or polyethylene glycol 6000. The combination of ultrafiltration and Ficoll gradient centrifugation is recommended as a general procedure for the purification of fragile C-type viruses.
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The Role of Macrophages in Mice Infected with Murine Cytomegalovirus
More LessSUMMARYQuantitative studies were made of the infection of mouse peritoneal macrophages in vitro by cytomegalovirus, using virus assays and immunofluorescence. The efficiency of infection was low. Broth-induced peritoneal macrophages were about four times more resistant to infection than unstimulated macrophages and it was even more difficult to infect activated macrophages taken from mice 6 days after intravenous infection. Peritoneal macrophages (unstimulated) were infected at least 15 times more readily by tissue culture-passed (attenuated) virus than by salivary gland (virulent) virus, but macrophages prevented the spread of tissue culture virus to underlying susceptible mouse embryo fibroblasts, whereas they did so much less effectively with virulent salivary gland virus.
The pathogenesis of infection was studied in intact mice by immunofluorescence, and the observations paralleled the in vitro findings. When large doses of salivary gland virus were injected intravenously, infected Kupffer cells (liver macrophages) were occasionally seen and the inoculated virus directly infected large numbers of hepatic cells. In similar experiments with tissue culture-passed virus, there was initial infection of occasional Kupffer cells, which only rarely gave rise to infected hepatic cells. Differences in the extent of Kupffer cell infection by the two strains of virus were not detected in these experiments. Salivary gland virus also usually failed to infect splenic or lymph node macrophages. Occasional infected mononuclear cells were seen in the blood, lung and bone marrow, but were not identified. Infected cells were very rarely seen in the thymus, even in suckling mice.
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Electrophoretic Properties of Cowpea Mosaic Virus (Severe Subgroup)
More LessSUMMARYParticles of the Puerto Rico isolate of cowpea mosaic virus (CPMV-PR), which belongs in the severe subgroup, had one electrophoretic form when analysed by 2·5% polyacrylamide gel electrophoresis and zone electrophoresis in sucrose gradients at pH 7·8, 7·5, and 5·5. The electrophoretic properties of CPMV-PR did not vary with time after inoculation but the virus could be converted to a slower migrating form by in vitro treatment with trypsin. The partial conversion by trypsin was accompanied by and was possibly the result of proteolytic conversion of the S protein subunit to a lower molecular mass form. Analysis of proteins of untreated CPMV-PR suggested that the S subunit of the virus could also be converted in vivo by plant proteases to a smaller form without any change in the particle net surface charge, while in vitro treatment with trypsin affected those S subunits not previously converted by plant proteases, by converting them to a form slightly larger and with a greater positive charge than the S subunit produced by action of the plant proteases. This hypothesis accounts both for the decrease in electrophoretic mobility and for the fact that the conversion was only partial.
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Comparison of Interferon Action in Interferon Resistant and Sensitive L1210 Cells
More LessSUMMARYTranslation inhibition, leu-tRNA aminoacylation and double-stranded RNA and ATP dependent phosphorylation were examined in interferon-treated and control cell-free lysates of leukaemic mouse L 1210 R and L 1210 S cells. No differences were observed between the respective interferon-treated and control cell-free extracts, except for the presence of an enhanced 67K dalton phosphoprotein fraction in interferon-treated L 1210 S cell-free extracts. In non-responding cell-free lysates, the lack of stimulation of a 67K dalton phosphoprotein fraction cannot be explained by the presence of an increased level of some inhibitory activity, such as a phosphatase.
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Optical Diffraction Analysis of Electron Microscope Images of Tubular Structures Found in Cells Infected with Herpes Simplex Virus Type 2
More LessSUMMARYOptical diffraction analysis was done on the electron micrographs of tubular structures found in cells infected with herpes simplex virus type 2. By this method, the helical arrangement of subunits forming a tubular structure was demonstrated.
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Tumour Specific Transplantation Antigen in Hamster Tumour Cells Induced with BK Virus
More LessSUMMARYImmunization of hamsters with purified BK virus (BKV) followed by transplantation of BKV-induced hamster tumour cells revealed a tumour specific trans-plantation antigen (TSTA) in these cells. The antigen did not cross-react with the TSTA of SV40 since immunization with BKV did not protect against challenge of SV40 tumour cells.
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Differences in Sialic Acid Content of Human Interferons
More LessSUMMARYHuman leucocyte, lymphoblastoid and fibroblast interferons were separately treated with sialidase and the effect of this on their isoelectric focusing was examined using a system in which full dissociation of complexes occurred. Both leucocyte and lymphoblastoid interferons showed a single form with an isoelectric point which was unaltered by treatment with sialidase. In contrast, fibroblast inter-feron showed three forms which were reduced to one by treatment with the enzyme.
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Mink Lung Cells: A Non-primate Cell Line Highly Susceptible for Varicella-Zoster Virus
More LessSUMMARYMink lung cells (MvILu) are highly susceptible to varicella-zoster virus (VZV). The titres of cell-free VZV suspensions reached 1·0 × 107 p.f.u./ml at 3 days postinfection, with subsequent cell degeneration, if MvILu cells were infected with a multiplicity of infectious virus of 0·01 p.f.u./cell. In contrast, during the same period and under the same conditions the titres of cell-free VZV were 102 to 103 times lower when grown on human foreskin fibroblasts. A fast and reliable plaque assay and a neutralization test for VZV on MvILu cells, were developed.
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Structural Polypeptides of Machupo Virus
More LessSUMMARYThe structural proteins of an arenavirus pathogen, Machupo virus, were compared to the structural proteins of two previously characterized non-pathogenic arenaviruses, Pichinde and Tacaribe, in SDS-polyacrylamide gels. Similarities in mol. wt. of the major structural proteins from both pathogenic and non-pathogenic viruses were apparent; however, some differences in the number of glycosylation properties of minor proteins were observed.
Machupo virions contain two major protein species. The most prominent is a non-glycosylated protein with a mol. wt. of 68000, while the other was a glycosylated protein with a mol. wt. of 41000. Minor amounts of other proteins (mol. wt. 84000, 74000, 50000 and 15000) and a glycolipid were also observed.
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The ocr Gene Function of Bacterial Viruses T3 and T7 Prevents Host-controlled Modification
More LessSUMMARYOn pre-infection of the host Escherichia coli B with u.v.-inactivated T3 or T7 phage able to express their early genes (like 0·3), B-specific modification of super-infecting, successfully multiplying viruses does not take place. The ocr gene function (gene 0·3) of T3 and T7 not only prevents host-specific DNA restriction but also modification, probably by inhibiting the same late step in the interaction between the restriction enzyme and DNA.
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Evidence for a Precursor-Product Relationship Between Intracytoplasmic A Particles and Mouse Mammary Tumour Virus Cores
More LessSUMMARYThis report presents evidence which supports a relationship between intracytoplasmic A particles (CAP) and mouse mammary tumour virus (MMTV). Three MMTV-specific antigenic determinants in CAP (MMTV p27, p14 and p10) were detected by immunodiffusion. No structural proteins of comparable mol. wt. were found in CAP; however, exposure of CAP to trypsin resulted in the cleavage of the CAP structural proteins to MMTV-like polypeptides. This process was accompanied by the preservation of MMTV-specific antigenic determinants. Disulphide bonds were necessary for the structural maintenance of CAP. Reducing agents destroyed the organized structure of CAP, whereupon processing of CAP proteins to MMTV-like polypeptides by trypsin was prevented. CAP p82, possessed only MMTV p27 antigenic determinants, while CAP polypeptides p20-18 possessed p10 antigenic determinants. Following processing of CAP structural proteins by trypsin, MMTV-specific p27 antigenic determinants were shifted from CAP p82 to CAP p27; MMTV-p10 antigenic determinants were found with CAP p15-10. These results suggest a model wherein CAP structural proteins are modified by protease during maturation, resulting in the shift of their proteins to sizes consistent with those which have been currently identified as the major internal components of the virion and that this phenomenon is largely predicated on the folding of CAP proteins into the morphologically intact A particle.
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Induction of Infectious Virus DNA and Virus Particles by Mitomycin C in SV40-Transformed Mouse Cells
More LessSUMMARYA line of SV40-transformed mouse cells (SV/3T3-4E) was isolated and four clones were derived from this line. Spontaneous production of small amounts of infectious SV40 DNA was detected in the parental line and in three out of the four clones tested, although no synthesis of virions could be demonstrated. The yields of SV40 DNA were significantly enhanced following treatment of these cells with mitomycin C and infectious virus particles became detectable occasionally.
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