- Volume 58, Issue 1, 1982
Volume 58, Issue 1, 1982
- Bacterial
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Condensed DNA Structures Derived from Bacteriophage Heads
More LessSUMMARYBacteriophage λ particles were rendered osmotically fragile by incubation, spread over hypophase and examined by electron microscopy. When water was used as hypophase, condensed structures were released from the phage heads and treatment of these with cytochrome c or several alternative proteins resulted in the release of free, relaxed DNA. Phage were pretreated with nitrogen mustard, a bifunctional alkylating agent; when the condensed structures from such phage particles were treated with protein, DNA was released in small supercoiled domains. This confirmed a previous finding that bacteriophage DNA has a supercoiled topology and suggests that the winding pattern of DNA in the phage might involve small domains of coiled DNA analogous to nucleosomes. Such a conformation could be consistent with other studies on the arrangement of DNA in phage heads if the domains have parallel axes.
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- Animal
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Non-structural Proteins in Newcastle Disease Virus-infected Cells
More LessSUMMARYExamination of pulse-labelled Newcastle disease virus (NDV)-infected chick embryo fibroblasts (CEF) by two-dimensional polyacrylamide gel electrophoresis revealed the presence of two virus-coded non-structural polypeptides of mol. wt. 36K and 33K. Longer pulses and pulse–chase incubations revealed the production of an additional, glycosylated, non-structural polypeptide of mol. wt. 40K (gp40). Kinetic arguments suggest that 36K and 33K are primary translation products but that gp40 is not. 36K was stable in chase incubations, but 33K was not. Partial digest peptide analysis showed that gp40 and an additional glycosylated polypeptide gp62, which is sometimes present (Chambers & Samson, 1980), are related to the HN polypeptide. Partial digest peptide analysis of the 36K polypeptide generated only a few peptides, which were not sufficient to conclude whether 36K was related to the major virus polypeptides, and since polypeptide 33K was metabolically unstable, insufficient radioactivity was incorporated for peptide studies. Extensive strain-dependent variation in the isoelectric points and mol. wt. of all the NDV polypeptides which are soluble in the isoelectric focusing gels, including 36K and 33K, is reported. This variation, and the insensitivity of the synthesis of 36K and 33K to actinomycin D, show that both non-structural polypeptides are virus-coded.
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Comparison of the Oligosaccharide Structure of the Glycoprotein of Vesicular Stomatitis Virus and a Thermolabile Mutant (tl-17)
More LessSUMMARYAs a means of examining the extent to which the polypeptide structure of a virus glycoprotein contributes to the overall structure and composition of the carbohydrate moieties, we have made a detailed comparison of the structure of the oligosaccharide moieties of wild-type vesicular stomatitis virus (VSV) glycoprotein with those of a glycoprotein-defective mutant of VSV, tl-17 (VSV). Characterization of the oligosaccharides by ion-exchange and gel filtration chromatography after sequential enzymic degradation reveals similar structures in the wt and mutant glycoproteins. However, the altered polypeptide structure of the tl-17 glycoprotein affects the extent of addition of sialic acid and fucose, both of which are added late in the maturation of the glycoprotein.
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Control of Interferon mRNA Levels and Interferon Yields in Butyrate and 5′-Bromodeoxyuridine-treated Namalwa Cells
More LessSUMMARYTreatment of Namalwa cells with butyrate or 5′-bromodeoxyuridine (BrdUrd) before induction with Sendai virus caused an increase in the production of both interferon (IFN) and interferon mRNA (IFN mRNA). However, the increase in IFN mRNA did not completely account for the increase in IFN yield. The treatments did not affect the time course of IFN mRNA transcription and translation, or the association of IFN mRNA with polysomes. Likewise, the treatments did not alter the post-translational fate of the IFN produced. We conclude that butyrate and BrdUrd affect IFN production at the level of transcription or processing of IFN mRNA and suggest that increased efficiency of translation provides an additional level of control.
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Monoclonal Antibodies to Sindbis Virus Glycoprotein E1 can Neutralize, Enhance Infectivity, and Independently Inhibit Haemagglutination or Haemolysis
More LessSUMMARYTwo monoclonal antibodies raised against Sindbis virus were shown to be specific for the envelope glycoprotein E1 by radioimmunoprecipitation (RIP). They had a number of contrasting biological properties. One of them was capable of neutralizing virus infectivity and inhibiting haemagglutination, while the other had no significant neutralizing or haemagglutination-inhibiting capability, but did inhibit virus-mediated haemolysis. Both monoclonal antibodies could enhance virus infectivity of Fc receptor-bearing macrophage-like cells when present at suitable dilutions.
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Inhibition of Semliki Forest Virus Penetration by Lysosomotropic Weak Bases
More LessSUMMARYThe effect of five lysosomotropic weak bases (chloroquine, amantadine, tributylamine, methylamine and NH4Cl) on Semliki Forest virus (SFV) infection has been studied in BHK-21 cells. When present at concentrations equal to or greater than 0.1, 0.5, 2, 15 and 15 mm respectively, the agents inhibited SFV infection by more than 90%. The effect was reversible and involved a process occurring within the first 60 min of virus–cell contact. The agents did not have a direct virucidal effect nor did they affect virus binding to the cells, receptor-mediated endocytosis of prebound virus, intracellular distribution of virus after endocytosis, or the low pH-induced membrane fusion activity of the virus spike glycoproteins. The step blocked by chloroquine and NH4Cl occurred intracellularly and was identified as the release of the virus nucleocapsid into the cytoplasm or the uncoating process. On the basis of these results, our previous studies on SFV entry, and the known effects of lipophilic amines on lysosomes, we conclude that the agents affect entry by a common mechanism: they prevent the transfer of the virus nucleocapsid into the cytoplasm by increasing the lysosomal pH above the critical value needed to trigger a low pH-dependent fusion reaction between the membranes of the lysosome and the virus.
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Characterization of Heavy Particles of Adeno-associated Virus Type 1
More LessSUMMARYThe temperature-sensitive mutant ts4 of adenovirus type 2 (Ad-2) is capable of complementing adeno-associated virus type 1 (AAV-1) in HEp2, KB and HEK cells at 34 °C and 39 °C when used as a helper virus. Heavy non-infectious AAV-1 particles can be generated by using the mutant ts4 in HEp2 cells. When AAV-1 is grown in serial passages in HEp2 cells, both the wild-type Ad-2 and the mutant ts4 give rise to heavy, less infectious AAV-1 particles. The heavy AAV-1 particles generated by Ad-2 in advanced serial passages retain the property of having CF and IF antigens, but the AAV-1 generated by the mutant in advanced serial passages lose this property. There is no appreciable difference in the particle counts made by electron microscopy of AAV-1 preparations generated either by Ad-2 or the mutant ts4. Analysis by polyacrylamide gel electrophoresis of purified heavy AAV generated by ts4 indicates that in late passage an additional polypeptide of higher mol. wt. than the three structural polypeptides is detected.
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Adenovirus–Cell Interactions Early After Infection: In vitro Characteristics and Tumourigenicity of Adenovirus Type 2-transformed Rat Liver Epithelial Cells
More LessSUMMARYCloned rat liver epithelial cells (clone C3) were semi-permissive for adenovirus type 2 (Ad-2) and non-permissive for adenovirus type 12 (Ad-12). Ad-2-infected C3 cells were shown to produce hexon and fibre protein, but at an m.o.i. of 20 a maximum virus yield of only 2.4 p.f.u. per cell was obtained. Forty-eight h after infection with Ad-12 ‘early’ virus proteins (major species 8K and 60K), but no ‘late’ proteins (virus structural proteins) could be identified.
Of six Ad-2-transformed epithelial lines isolated from clone C3 only one was tumourigenic in syngeneic rats, whereas all six transformants produced tumours in athymic nude mice. There was a remarkable variation in the morphology of the Ad-2-transformed liver cells, ranging from an epithelial morphology similar to C3 cells to cells with a distinct lymphoid morphology.
The in vitro and in vivo behaviour of the Ad-2-transformed clone C3 cells reported in this communication, taken together with our previous report on the characteristics of Ad-12-transformed C3 cells, clearly show that the differences observed between Ad-2- and Ad-12-transformed rat embryo cells were also observed in our studies using cloned rat liver epithelial cultures. Our findings clearly rule out the hypothesis that the heterogeneity of Ad-2 transformation events is the result of the transformation in vitro of different types of target cell.
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Association of Moloney Murine Leukaemia Virus Proteins: An Assay for Hydrophobic Protein–Protein Interactions
More LessSUMMARYProtein–protein interaction of Moloney murine leukaemia virus was studied by an assay where one protein preparation was coupled covalently to Sepharose, and binding of radiolabelled proteins to the protein–Sepharose was examined. It was found that the virus proteins gp70, p30, p15E and p15 in solution could associate weakly to disrupted virus particles and to p30. However, when the disrupted virus particles and p30 were coupled to Sepharose in the presence of Triton X-100, stronger binding of the four proteins was observed. Only low or no binding of p12 and p10 was observed to these protein–Sepharoses. The results are discussed with respect to the assembly and structure of the virus particle.
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Restriction Endonuclease Mapping of Unintegrated Proviral DNA of Kirsten Murine Sarcoma Virus
More LessSUMMARYLinear unintegrated Kirsten murine sarcoma virus DNA synthesized after acute infection of NIH/3T3 cells or by detergent-disrupted virions, was studied by restriction enzyme cleavage and agarose gel electrophoresis. Labelled DNA (cDNA) synthesized by reverse transcription of a virion RNA template was used to detect viral DNA sequences by filter hybridization. The sites of cleavage for eleven enzymes were located on the genome. Hybridization studies using a cDNA probe specific for the 3′ end of the genome defined the orientation of the physical map with respect to virion RNA and identified terminally redundant sequences on the genome. Further evidence for terminal redundancy was obtained by restriction mapping of linear and circular viral DNA, where the duplication was shown to be 0.34 × 106 (500 base pairs) in length and in a tandem orientation. Circular viral DNA was found predominantly in the nucleus of acutely infected cells and it existed in two major size classes. The larger size class represented an exact circularization of linear DNA (with no other sequence permutation) whilst in the smaller DNA species one of the terminally redundant sequences was absent.
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Mouse Mammary Tumour Virus and Polyoma Virus Information in Mammary Tumours of Athymic Mice Inoculated with Polyoma Virus
More LessSUMMARYPolyoma virus inoculation of athymic mice results in the development of mammary tumours with a much higher incidence than the development of salivary gland tumours, the latter being the most common for immunocompetent normal mice. The possibility existed that polyoma virus might act as a co-carcinogen in activating the expression of mouse mammary tumour virus (MMTV). Molecular hybridization studies, however, showed that the mammary tumour development was accompanied by neither the amplification of MMTV genomic sequences nor by their more extensive transcription. In contrast, tumour tissue contained about 60 to 100 copies of polyoma virus genome equivalents per cell and some of these sequences were apparently transcribed into RNA. While these results do not rule out the transient involvement of MMTV expression in mammary tumour development, it appeared that the mammary gland cells were directly transformed by polyoma virus. Apparently, polyoma virus displayed a tropism in athymic mice that was different from that in normal mice.
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Characterization of Xenotropic and Dual-tropic Type C Retroviruses Isolated from Abelson Tumour
More LessSUMMARYTumours induced in Balb/c mice by Abelson virus complex were found to contain a xenotropic virus (A-X-MuLV) and an NB-tropic, dual-tropic virus (NBX), in addition to the Moloney leukaemia virus (M-MuLV) and the defective, transforming Abelson virus genome. Both A-X-MuLV and NBX virus were presumably present in a genomically masked form and could be recovered only by co-cultivation of tumour cells with permissive cells. Only about 0.87% and 0.13% of the viruses in the co-culture supernatant represented A-X-MuLV and NBX virus respectively; the majority were m-MuLV. The NBX virus acted more efficiently than the HIX virus (Fischinger et al., 1975) as helper to rescue murine sarcoma virus (MSV) from S+L− cells of hamster, rat and mouse origin, whereas the converse was true for those of cat and human origin. The interference and neutralization patterns suggested that the NBX virus was an env gene recombinant between A-X-MuLV and m-MuLV. The fact that NBX virus cross-reacted in radioimmunoassays with gp70s of both m-MuLV and Balb:virus-2 provides evidence for the recombinant nature of the NBX gp70-coding gene which was probably derived from both m-MuLV and a virus similar to Balb:virus-2 or A-X-MuLV. The presence of a unique antigenic determinant on the gp70 of NBX virus is also suggested. Both A-X-MuLV and NBX virus cross-reacted with type-specific p12s of m-MuLV and Balb:virus-2, suggesting that the gag gene coding for p12 of NBX virus was derived from the A-X-MuLV, which was itself a recombinant, its p12-coding gene being derived from both Balb:virus-2-like virus and m-MuLV. The NBX virus was not oncogenic when tested in newborn Balb/c mice.
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Correlation of the Virus Sequence Content and Biological Properties of Cells Carrying the Herpes Simplex Virus Type 2 Thymidine Kinase Gene
A. Minson, S. E. Bell and K. BastowSUMMARYSeven cell lines, transformed to a thymidine kinase-positive phenotype with herpes simplex virus type 2 (HSV-2) DNA fragments, have been examined to determine their virus-specific DNA sequence content. The results are consistent with the reported map position of the HSV-2 thymidine kinase gene. Different cell lines contained different amounts of non-selected virus-specific sequences and this correlated with the ability of some cell lines to compensate the deficiencies in some temperature-sensitive (ts) mutants of HSV-1 and HSV-2. The cell lines were also examined for their ability to synthesize elevated levels of thymidine kinase in response to infection with a thymidine kinase-negative virus mutant. Of the seven cell lines, two failed to respond to infection in this way and these cell lines lacked sequences on the upstream side of the kinase gene which were present in the remaining cell lines.
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Analysis of Polypeptides of the Tree Shrew (Tupaia) Herpesvirus by Gel Electrophoresis
More LessSUMMARYThe virion polypeptide composition of three independently isolated tree shrew herpesviruses (THV) was analysed by SDS-polyacrylamide slab gel electrophoresis and by a two-dimensional technique using isoelectric focusing. Two of the virus isolates analysed were from malignant tumours; the other isolate (THV, strain 1) was from an apparently healthy animal. The polypeptide patterns of the three purified Tupaia herpesvirus isolates were remarkably similar, each consisting of at least 35 polypeptides ranging in mol. wt. from 12000 to 230000. Whilst the majority of analogous polypeptides of the three viruses were of indistinguishable electrophoretic mobility, some (e.g. polypeptides of 82K to 86K) showed small differences in apparent mol. wt. which were characteristic of the virus strain. Comparative SDS-polyacrylamide gel electrophoresis made it possible to distinguish the Tupaia herpesvirus isolates from each other. At least five glycoproteins were found in purified THV virions. The two-dimensional electropherograms revealed at least 47 discernible protein spots, some of which were specific for a given THV isolate and which were detectable even in lysates of THV-infected cells.
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Proteins Specified by Herpesvirus Saimiri: Purification and Properties of a Single Polypeptide which Elicits Virus-neutralizing Antibody
More LessSUMMARYA virus-specified polypeptide of 160000 mol. wt. (160K) was purified more than 1000-fold from the soluble proteins present in the culture medium of cells productively infected with herpesvirus saimiri (HVS). Purified preparations of the 160K polypeptide gave rise to high titre precipitating and neutralizing antibodies in immunized rabbits, which cross-neutralized independent isolates of HVS (neutralization rate constants, k, of between 3.8 and 4.8) and specifically precipitated the 160K polypeptide from extracts of cells infected with the homologous or heterologous strains of this virus. Antiserum to the 160K polypeptide of HVS also gave low (k = 0.02) levels of neutralization of the related herpesvirus ateles. Purified preparations of the 160K polypeptide were capable of removing most or all of the neutralizing antibody sera of squirrel monkeys with naturally acquired antibodies to HVS. The 160K polypeptide was previously shown to form part of the surface of enveloped virus particles. However, we show here that the 160K polypeptide is not extensively glycosylated in infected cells. The majority of glucosamine incorporation specific to HVS-infected cells was into eight regions with apparent mol. wt. of 170K to 220K, 125K to 145K, 115K to 120K, 83K to 88K, 65K to 75K, 52K to 58K, 25K to 27K and 12.5K to 13K. It remains possible that alternative cleaved or glycosylated forms of the 160K polypeptide are also present on the virus particle or that precipitating antibody to 160K and virus-neutralizing antibodies are not identical. However, our inability to detect precipitating antibody to virus-induced proteins or glycoproteins other than the 160K polypeptide and the high titre of neutralizing antibody present in this serum, provides reasonable evidence that it is the antibodies which react with the 160K polypeptide that are responsible for virus neutralization.
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Effects of n-Butyrate on Epstein—Barr Virus-carrying Lymphoma Lines
More LessSUMMARYn-Butyrate has been shown to induce Epstein—Barr virus (EBV) antigen synthesis in certain EBV-carrying lymphoma lines (Luka et al., 1979). We have studied the effect of n-butyrate on two EBV-positive Burkitt lymphoma lines by immunofluorescence and electron microscopy. In the producer line P3HR-1, the drug induced not only early antigen (EA) and virus capsid antigen (VCA) synthesis, as shown before, but also increased the number of cells containing virus particles. The transition from VCA expression to the formation of virus particles was much more effective in treated cells than in EBV antigen-producing cells of the same line. The productive cycle was associated with the development of characteristic morphological changes. In the non-producer Raji cells, n-butyrate induced EA in only a minor fraction of the cells. There were, however, clear signs of differentiation in the direction of plasma cells. Two days after the addition of n-butyrate 80% of the Raji cells could be classified as plasmablasts. After 72 h, 20% of the cells appeared as typical plasma cells.
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Involvement of Natural Killer Cells in the Pathogenesis of Murine Cytomegalovirus Interstitial Pneumonitis and the Immune Response to Infection
More LessSUMMARYThe significance of the natural killer (NK) cell response to murine cytomegalovirus (MCMV) infection was evaluated in C3H/HeN mice. This strain was selected for study after preliminary demonstration that the NK cell response, occurring between 3 and 6 days post-infection was relatively high in comparison to other mouse strains studied. A dose—response effect of hydrocortisone treatment on suppression of this response was found. A dose of hydrocortisone, given subcutaneously on two successive days, which was found to markedly inhibit the NK cell response, had no effect on development of serum interferon or antibody levels, or spleen cytotoxic T cell activity under the conditions studied. Suppression of the NK cell response by this treatment, however, was accompanied by enhanced spleen and pulmonary virus replication in vivo and increased susceptibility of mice to lethal infection. MCMV interstitial pneumonitis was characterized histologically and lung lymphocytes studied at 4 days post-infection were found to have increased NK cell activity. Treatment of mice with hydrocortisone was found to inhibit development of gross and histological evidence of pneumonitis. These findings indicate that NK cells are involved in the pathogenesis of MCMV interstitial pneumonitis and may function early in infection to restrict the extent of virus replication.
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2′–5′ Oligo(A) Synthetase Levels in Interferon-sensitive or -resistant Lymphoid Cells
More LessSUMMARYThe activity of 2′–5′ oligo(A) synthetase has been measured both in control and interferon-treated lymphoid cells. While control or interferon-treated Raji and Namalwa cells exhibit low activity of the 2′–5′ oligo(A) synthetase, the activity of this enzyme is increased 20-fold when Daudi cells are treated with the same dose of human interferon. The same enzyme is induced by interferon in R3HR-1 cells to a lesser extent.
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Caprine Arthritis-Encephalitis Virus Infection of Caprine Monocytes
More LessSUMMARYMonocyte-enriched cultures of goat peripheral blood leukocytes were exposed to caprine arthritis-encephalitis virus (CAEV) at an m.o.i. of 8 TCID50 per cell as measured in goat synovial membrane cell cultures. At the time of infection, 90% of the adherent cells displayed characteristic macrophage markers of phagocytic activity and cytoplasmic non-specific esterase. A productive infection was established, with extracellular infectious virus titres reaching a maximum of 105.2 TCID50 per ml at day 4 post-infection. Synthesis of CAEV antigens was detected by direct immunofluorescence and it was shown that 85% of the adherent cells contained virus antigen by day 6 post-infection. A cytopathic effect, characterized by giant cell formation and cell death, developed concomitantly with increased virus replication.
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Oligopeptide Mapping of NP Proteins of Influenza A Viruses
More LessSUMMARYOligopeptide mapping of nucleoproteins (NP proteins) of 54 strains of influenza A virus showed the presence of both common and individual oligopeptides. Using the distribution of variable oligopeptides as the criterion, NP proteins were subdivided into four groups (NP0, NP1, NP2 and NP3). The NP0 group is composed of H0N1 influenza viruses and the majority of animal influenza viruses. The NP1 group contains H1N1 (except A/California/78) and H2N2 influenza viruses isolated from man as well as H1N1 influenza viruses recently isolated from animals. A/New Jersey/76 (Hsw1N1) influenza virus also belongs to the NP1 group. The NP2 group consists of H3N2 influenza viruses isolated from man and animals. A/California/78 (H1N1) influenza virus also falls into the NP2 group. The NP3 group contains NP proteins of four animal influenza viruses with the antigenic formulas Hsw1N2, Hsw1Nav2, Hav6Nav5 and Heq2Neq2.
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