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Volume 54,
Issue 1,
1981
Volume 54, Issue 1, 1981
- Review Article
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- Animal
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A Virus of the Reoviridae in Established Cell Lines of Drosophila melanogaster
More LessSUMMARYA reovirus-like agent has been isolated from an established Drosophila melanogaster cell line 67j25D-G. The virion was 68 nm in diam. with a distinct outer capsid. The virus particles contained at least five polypeptides with mol. wt. of 30, 40, 70, 100 and 120 (all × 103) and 10 segments of double-stranded high mol. wt. RNA. Viruses of the same type were detected in several cell cultures of D. melanogaster obtained from different sources. The viral nucleic acid accounted for about 20% of the RNA in the cultured cells.
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Cleavage of Rauscher Leukaemia Virus (R-MuLV) Pr65gag by the Moloney Leukaemia Virus (M-MuLV) Proteolytic Activity Produces the R-MuLV-specific but not the M-MuLV-specific 40000 Dalton Intermediate Polypeptide
More LessSUMMARYAlthough the Pr65gag precursor polyproteins of Moloney murine leukaemia virus (M-MuLV) and of Rauscher murine leukaemia virus (R-MuLV) have the same apparent mol. wt. by SDS-polyacrylamide gel electrophoresis (SDS-PAGE), their initial ∼40000 dalton intermediate cleavage products differ in mol. wt., i.e. the M-MuLV product (Pr41.5gag) is 1500 daltons larger than the R-MuLV product (Pr40gag). We took advantage of this difference to show that in vitro cleavage of R-MuLV Pr65gag by the M-MuLV proteolytic activity gives rise to R-MuLV Pr40gag and not M-MuLV Pr41.5gag. This result suggests that the specificity for cleavage of the MuLV Pr65gag is built into the substrate.
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Morphological Components of Herpesvirus. III. Localization of Herpes Simplex Virus Type 1 Nucleocapsid Polypeptides by Immune Electron Microscopy
More LessSUMMARYHerpes simplex virus type 1 (HSV-1) nucleocapsids were observed in the electron microscope after their reaction with IgG’s purified from the sera of rabbits immunized with the individual nucleocapsid polypeptides. The combining sites of NC1, the major capsid protein (mol. wt. 154K), were distributed over the entire capsid surface. This result provides further evidence that NC1 represents the major hexamer constituent. NC2 (mol. wt. 50K) was less widely distributed and appeared to be located at capsid vertices; that antigen may be a constituent of the pentamers or of peripentameric hexamers. One or both of NC3 and NC4 (mol. wt. 40K and 38K) were also located all over the capsid, possibly at positions interior to those of NC1. One or both may represent the intercapsomeric fibrils, hexamer-associated protein or material associated with the pericore. The locations of the other nucleocapsid polypeptides could not be determined.
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Purification of Human Fibroblast Interferon by Zinc Chelate Chromatography
More LessSUMMARYHuman interferon was prepared by superinduction of cultures of either diploid embryonic skin and muscle cells or of the osteosarcoma cell line MG-63. The interferon so obtained was concentrated and partially purified by adsorption to controlled pore glass (CPG) beads at neutral pH and desorption by glycine-HCl buffer at pH 2. After neutralization, this interferon was applied to a column of zinc chelate which was eluted with buffers of decreasing pH. Most of the proteins eluted ahead of the interferon activity, which itself eluted in two distinct peaks. The first peak occurred in the effluent fractions around pH 5.9, and the second one in fractions around pH 5.2. The interferon found in fractions of pH 5.9 contained 5% of the original contaminating proteins. In contrast, the amount of total protein in the pH 5.2 peak was so small that it could not accurately be assayed by the fluorescamine method. Consequently, the interferon in the peak fraction was estimated to have a specific activity of about 2 × 109 units/mg. This material was radiolabelled and analysed by electrophoresis. A major peak of about 22000 mol. wt. with only minor contaminating proteins appeared on the autoradiographs. The total recovery of the zinc chelate chromatographical procedure was nearly 100%, and the interferon recovered from each peak behaved consistently on rechromatography.
Fibroblast interferon produced by most diploid cells contained less than 10% of the variant eluting at pH 5.9. MG-63 cells and high-passage cultures of some diploid cell strains produced up to 50% of this variant.
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Establishment of Persistent Infection in Mouse Cells by Sindbis Virus and its Temperature-sensitive Mutants
More LessSUMMARYThe ability of wild-type (wt) Sindbis virus and six temperature-sensitive (ts) mutants to establish persistent infection in mouse L cells and a line of mouse embryo (ME) cells was determined. The wt established persistent infection in both ME cells and L cells at 39 °C. At 30 °C the wt established persistent infection in L cells but not ME cells, which did not recover from the initial infection. For the ts mutants, both cell lines survived the initial infection at 39 °C (the restrictive temperature) but the virus was eventually eliminated. At 30 °C (the permissive temperature) in L cells all mutants established persistent infection. In ME cells at 30 °C, RNA− mutants (unable to synthesize virus-specified RNA at 39 °C) established persistent infection whereas the cells did not recover from infection with RNA+ mutants (able to synthesize virus-specified RNA at 39 °C). The wt virus was less cytopathic in L cells than in BHK or ME cells. Interferon was produced by both L and ME cells at 30 °C and 39 °C, but its activity could not be detected in either cell line at 30 °C.
It is proposed that establishment of persistent infection is dependent on reduced cytopathogenicity in the early stage of infection, and that further evolution of the virus then occurs to a less cytopathic form. Elimination of the virus at 39 °C is probably due to the action of interferon.
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Genetic Variation of Neurotropic and Non-neurotropic Murine Coronaviruses
More LessSUMMARYThe murine coronavirus strains MHV JHM, MHV 1, MHV 2, MHV 3 and MHV A59 were tested for their neurovirulence in weanling rats. The strain JHM was found to be highly neurovirulent for weanling rats, whereas the other strains were not, or only slightly, neurovirulent. MHV 1 caused no lesions in weanling rats. The other strains (MHV 2, MHV 3 and MHV A59) induced predominantly subclinical infections in weanling rats as demonstrated by an increase of antibodies and inflammatory lesions in the liver. Analysis of these strains by cross-neutralization revealed variable degrees of antigenic relationship between these viruses which were not related to their neurovirulence. However, when these strains were compared by analysing the T1-RNase-resistant oligonucleotides of virion RNA, the highly neurovirulent strain JHM was found to differ significantly in its nucleotide sequence from the other less-neurovirulent strains.
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Antigenic and Biological Relationships between Human Coronavirus OC43 and Neonatal Calf Diarrhoea Coronavirus
More LessSUMMARYMonospecific antisera were prepared in mice to human coronavirus OC43 and neonatal calf diarrhoea coronavirus (NCDCV) which had been previously adapted to growth in suckling mouse brain. Brain suspension from infected suckling mice was used as immunogen. The antigenic relationship between OC43 and NCDCV was studied by the indirect immunoperoxidase antibody technique, by the haemagglutination-inhibition (HI) test and a new infectious centre-reduction neutralization test. In mouse immune sera, a two-way cross-reaction between OC43 and NCDCV was detected. However, the antigenic relationship appeared to be closer for internal (as shown by immunoperoxidase staining) as compared to surface antigens (as shown by HI and neutralization). In primary infections of natural hosts there was a high degree of cross-reactivity between the two coronavirus strains for both surface and internal antigens, and homologous and heterologous titres were consistently within an eightfold dilution difference by all tests. Most human adults and calves had antibody to both OC43 and NCDCV and geometric mean titres of homologous antibody were higher than titres of heterologous antibody. Although OC43 and NCDCV share antigenic determinants, they possessed several different biological properties, including plaque morphology by the infectious centre assay, agglutination of 1-day-old chick erythrocytes and resistance of haemagglutinin to physical and chemical treatments.
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Differential Distribution of Virus and Histological Damage in the Lower Respiratory Tract of Ferrets Infected with Influenza Viruses of Differing Virulence
More LessSUMMARYThe distribution of four strains of influenza virus [A/PR/8/34 (H0N1) and clone 64d (attenuated for ferrets) and clones 64c and 7a (virulent for ferrets) of the recombinant virus A/PR/8/34-A/England/939/69 (H3N2)] in the lower respiratory tract (trachea, bronchi and the hilar, intermediate and outer alveolar zones of the lung) of ferrets was monitored daily for 4 days after intranasal inoculation. On day 1, some animals had high virus titres in all the tissues but in other animals virus was undetectable, irrespective of the virus strain. Two days after inoculation increase of virus contents of all tissues tended to be restricted. On days 3 and 4, the virulent clones (64c and 7a), in contrast to the attenuated strains (A/PR/8/34 and clone 64d), consistently infected the lower respiratory tissues. However, for all infected animals the virus contents of the hilar zones of the lungs were higher than those in the intermediate zones, while the alveolar zones were relatively free from virus. Quantitative estimations of the mild histological damage occurring in the lower respiratory tract 3 to 6 days after inoculation also indicated that bronchial and bronchiolar tissue were more susceptible to influenza virus than alveolar tissue and that clones 64c and 7a produced more damage than the other two strains. In agreement with the relative viral contents of clones 64c and 7a in the bronchi and in the hilar and intermediate zones of the lung, clone 64c produced more damage than clone 7a in the bronchi and less in the bronchioles of the lung parenchyma.
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High Yield Growth and Purification of Human Parainfluenza Type 3 Virus and Initial Analysis of Viral Structural Proteins
More LessSUMMARYStructural proteins from a large-plaque variant (LPV) of human parainfluenza type 3 virus were analysed by electrophoresis on Laemmli-type polyacrylamide gels. High virus concentrations were obtained by growth in BS-C-1 cells cultivated on microcarrier beads. Purification of the virus in composite equilibrium gradients of potassium tartrate:glycerol resulted in 25% recovery of input infectivity and a preparation containing <0.08% of input host cell protein and RNA. Parainfluenza type 3 virus equilibrated at a density of 1.20 g/ml in these gradients. Analysis by polyacrylamide gel electrophoresis of 3H-glucosamine-labelled virus taken from peak gradient fractions revealed 8 or 9 major virion peptides, ranging in mol. wt. from 17 × 103 to 125 × 103 (17K to 125K), two of which were glycoproteins. The sum of the estimated mol. wt. of these peptides, 501.5K to 570.5K, does not exceed the estimated genomic potential of other paramyxoviruses.
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Action of Nucleotide Derivatives on Translation in Encephalomyocarditis Virus-infected Mouse Cells
More LessSUMMARYThe infection of animal cells by encephalomycocarditis (EMC) virus lead to a drastic change in membrane permeability towards low mol. wt. compounds. Addition of the nucleotide analogue GppCH2p to the culture medium resulted in a specific inhibition of protein synthesis in EMC virus-infected 3T6 cells. This inhibition was not observed when GTP or ATP were present nor in control mock-infected 3T6 cells. The induction of membrane leakiness after viral infection was not specific for 3T6 cells, as it was also detected in mouse L cells, hamster BHK-21 cells and monkey CV1 cells. The inhibitory action produced by GppCH2p in virus-infected cells was fully reversed upon addition of fresh medium. Moreover, analysis of the proteins synthesized after medium replacement showed a preferential synthesis of cellular proteins. The presence of zinc ions resulted in an inhibition of the cleavage of large viral polypeptide precursors to mature viral proteins. Under these conditions, membrane leakiness as measured by GppCH2p, was not observed. However, this seems to be an effect of zinc ions themselves on the membrane, because inhibition of mature protein formation by other means, such as the presence of amino acid analogues, did not prevent inhibition of translation by GppCH2p in virus-infected cells.
Addition of the cap analogues 7mGppp and 2′-O′-mGppp, resulted in specific stimulation of viral protein synthesis in EMC virus-infected 3T6 cells. On the other hand, the presence of 7mGp had no effect on translation. We propose that a specific capping of viral mRNA takes place in the presence of these compounds, and leads to increased stability and greater efficiency in the translation of viral mRNA.
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Comparisons of Belmont Virus, a Possible Bunyavirus Unique to Australia, with Bunyamwera Virus
More LessSummaryBelmont virus is an arbovirus isolated from mosquitoes and has a preference for marsupial hosts. The diameter of virions by negative staining (122 nm before fixation and 91 nm after fixation) was greater than that of Bunyamwera virus (94 nm and 79 nm respectively). However, the particles of both viruses appeared morphologically identical and sedimented at the same rate in sucrose density gradients. Belmont virus had a tripartite segmented RNA genome (28S, 24S and 11S) similar to Bunyamwera virus RNA (33S, 26S and 16S). The mol. wt. of these RNA species of Belmont virus measured by gel electrophoresis were 3.2 × 106, 2.4 × 106 and 0.3 × 106 compared to 2.9 × 106, 1.8 × 106 and 0.3 × 106 for the L, M and S species of Bunyamwera virus RNA. Both viruses comprised four structural proteins of the same relative proportions and corresponding mol. wt. For Bunyamwera virus, these were 145 × 103 (L), 104 × 103 (G1), 32 × 103 (G2) and 22 × 103 (N). The equivalent proteins of Belmont virus had mol. wt. of 147 × 103 (P147), 107 × 103 (G107), 28 × 103 (P28) and 25 × 103 (P25). Under conditions in which the envelope glycoproteins G1 and G2 of Bunyamwera virus were labelled in glucosamine, only G107 of Belmont virus was labelled. However, both G107 and P28 of Belmont virus were solubilized by non-ionic detergent and were then separable from the nucleocapsid containing all the RNA and P25. Chymotrypsin treatment of Belmont virus digested only G107, leaving a residue of P25 and P28, and of visible spikes. Similarly, G2 and the spikes of Bunyamwera virus resisted digestion with chymotrypsin. It was concluded that P28 is an envelope protein, equivalent to G2. Belmont virus thus appears to be a typical member of the Bunyaviridae but is unique in that it lacks carbohydrate in the small envelope protein (P28).
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Proteins and Glycoproteins Specified by Bunyamwera Virus and by Belmont Virus, a Possible Bunyavirus, in Mammalian Cells
More LessSUMMARYPurified preparations of Belmont virus were shown to be very similar morphologically and biochemically to those of Bunyamwera virus. Comparisons of the synthesis of virus-specifed proteins in Vero and BHK-21 cells confirm the close taxonomic relationship. Total protein synthesis was inhibited 95% by 23 h post-infection with Belmont virus; a similar reduction occurred earlier in Bunyamwera virus-infected cells. This inhibition was multiplicity dependent, and synthesis of the host protein component was inhibited more severely. When cells were labelled late during infection at an m.o.i. of 1, the four structural proteins were readily resolved by gel electrophoresis. A small possibly non-structural protein (p14 for Belmont, p13 for Bunyamwera) was also identified late in infection in both hosts. As in the virion, the small envelope protein (P28) of Belmont virus was not glycosylated, whereas the large envelope protein G107, and the corresponding G1 and G2 of Bunyamwera virus, were labelled intracellularly in mannose, galactose and glucosamine. The kinetics of synthesis of the proteins for both viruses were similar, the events occurring earlier in Bunyamwera virus-infected cells. The nucleoprotein N was the most prominent at 3 to 5 h post-infection and remained so; G1 or the large envelope protein was also prominent early, but later more label was apparently incorporated into G2 or the small envelope protein. Pulse-chase experiments provided no evidence of precursor proteins. The relationship of the four or five identified virus-specified translation products to the three bunyavirus messenger RNAs remains obscure.
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Purification of Measles Virus Glycoproteins and their Integration into Artificial Lipid Membranes
More LessSUMMARYWe report a simple method for the isolation of the measles virus glycoproteins, and their subsequent incorporation into artificial lipid bilayers. The two viral glycoprotins, HA and F, were isolated in preparative amounts from disrupted purified virus by lentil lectin affinity chromatography. The proteins were reconstituted into single bilayer lipid vesicles by: (i) exchanging the non-dialysable detergent Nonidet P40 (NP40) for a dialysable one, octylglucoside, while the proteins were immobilized on the lectin column and (ii) co-dialysis of the eluted glycoproteins in octylglucoside with phosphatidylcholine. The resultant ‘virosomes’ had visible ‘spikes’ and possessed haemagglutinating activity. These measles virosomes should provide a useful reagent for studying immune responses to measles virus, independent of the immunosuppressive effects of the whole virus.
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Antigen and Polypeptide Synthesis by Temperature-sensitive Mutants of Respiratory Syncytial Virus
More LessSUMMARYA revised nomenclature for the polypeptides of respiratory syncytial (RS) virus has been devised on the basis of comparison of the Long, A2 and RSN-2 strains by slab-gel electrophoresis. Seven polypeptides, now designated VP200, VGP48, VPN41, VPP32, VPM27, VP25 and VP10, were observed in preparations of all three strains of RS virus, irrespective of the host cell of origin. In addition, a slowly migrating glycopolypeptide GP1 was prominent in partially purified RS virus of the Long and A2 strains obtained from Hep-2 cells, and to a lesser extent from BS-C-1 cells. In the case of the RSN-2 strain, this polypeptide was only resolved clearly in virus obtained from Hep-2 cells. GP1 was an atypical glycopolypeptide in that 35S-methionine incorporation was poor relative to 3H-glucosamine incorporation.
The ts mutants of RS virus exhibited four distinct phenotypes with respect to intracellular polypeptide synthesis and antigen production at 39 °C. Mutants ts 17 (complementation group B′) and ts 19 (group E) were almost completely restricted, suggesting defective early functions. Mutants ts A1 (group A), ts A7 (group C) and ts 1 (group D) synthesized antigen and polypeptides normally, but the amount of antigen at the cell surface was reduced, suggesting maturation defects. In addition, the VPP32 of ts 1 (group D) exhibited an aberrant mobility, confirming its viral specificity. The remaining mutants, representing groups B, F and G exhibited generally impaired synthesis at 39 °C.
Absence of surface filaments in ts mutant-infected cells at 39 °C confirmed their virus-specific nature.
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Comparative Mitogenic Effects of Herpes Simplex Virus and Mycoplasma on Murine Lymphocytes
More LessSUMMARYPrevious work indicated that herpes simplex virus type 1 (HSV-1) is a mitogen for mouse spleen cultures, as monitored by uptake of 3H-thymidine. We observed variable responses of mouse spleen cultures to different viral preparations. The variable responses, which did not follow normal dose—response relationships, were not due to HSV-1 strain differences, altered response kinetics or the presence or absence of defective viral particles, but to mycoplasma contamination of viral stocks. Mycoplasma-free (MF) HSV-1 stocks were prepared by transfection of MF NHF cells with HSV-1 DNA. MF HSV-1 infection of spleen cultures resulted in a five- to sixfold stimulation of DNA synthesis and stimulation of a polyclonal antibody response. Heat treatment (56 °C for 1 h) and antibiotics were used to distinguish mycoplasma and HSV-1-induced spleen culture mitogenic responses. The mycoplasma-induced mitogenic activity was found to be heat labile and sensitive to gentamicin and chloramphenicol. In contrast, the HSV-1-induced response was not affected by gentamicin or chloramphenicol and heat treatment resulted in only a 50% loss of activity.
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The Detection of Epstein—Barr Virus Receptors Utilizing Radiolabelled Virus
More LessSUMMARYEpstein—Barr virus (EBV) was labelled with 3H-thymidine and purified about 1000-fold from the culture medium by ultracentrifugation on 5 to 30% dextran grandients. The presence of the virus was monitored by radioactivity and Epstein—Barr virus-determined nuclear antigen (EBNA) induction in sensitive indicator cells (Ramos). Peaks for both activities occurred in the 17 to 18% dextran fractions. Unlabelled virus recovered in the peak fraction was labelled with 125I. Both thymidine and 125I-labelled purified virus bound quantitatively to receptor-positive Burkitt lymphoma-derived cell lines but not to EBV-receptor-negative T-lymphocyte-derived cell lines. Thymidine-labelled virus that was allowed to bind to Raji cells was present in the interior of briefly trypsinized cells after 3 h incubation at 37 °C. The results provide a convenient method for detecting the EBV receptor by radioactively labelled virus.
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Temperature-sensitive Mutant of Newcastle Disease Virus which has an Altered Nucleocapsid-associated Protein
More LessSUMMARYAnalysis of six temperature-sensitive (ts) mutants of Newcastle disease virus (NDV) representing each of six complementation groups by both SDS-polyacrylamide gel electrophoresis (SDS-PAGE) and two-dimensional gel electrophoresis revealed that in only one mutant was there an alteration in the isoelectric point of a protein. This altered protein was the nucleocapsid-associated protein, NAP. In addition, the mobility of the haemagglutinin—neuraminidase protein, HN, was decreased on non-reduced SDS-PAGE in this mutant.
All independent ts + clones derived from this mutant had normal NAP but HN protein migrated at the decreased rate. Haemagglutinating activity of wild-type (ts +) and ts virions was equally thermostable. Wild-type and ts + clones derived from this ts mutant were RNA (+) at both permissive and non-permissive temperatures, whereas the ts mutant was RNA(-) at the non-permissive temperature. This ts mutant appears to be a double mutant in both HN and NAP genes, the latter only being a temperature-sensitive lesion which affects virus-directed RNA synthesis.
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Isolation of Cowpox Virus Clones Deficient in Production of Type A Inclusions: Relationship to the Production of Diffusible LS Antigen
More LessSUMMARYCowpox virus clones (A− clones) deficient in production of type A inclusions were isolated from two cowpox strains, Amsterdam and 53. These clones did not differ from their parents in major markers such as pock morphology in chorioallantoic membranes and pathogenicity in the rabbit skin. However, the LS antigens induced by A− clones developed precipitin lines in agar gel diffusion tests, while the antigens from their parents failed to precipitate. Immunofluorescence and agar gel diffusion tests revealed that antigens detectable by antisera against purified type A inclusions and LS antigens were closely related to each other. These findings suggest that the A− clones might be variants of cowpox virus which have lost the ability to assemble LS antigens into type A inclusions.
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