- Volume 67, Issue 7, 1986
Volume 67, Issue 7, 1986
- Review Article
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- Animal
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Antigenic Structure of Polioviruses of Serotypes 1, 2 and 3
More LessSummaryThe antigenic sites recognized by monoclonal antibodies with neutralizing activity for the Sabin vaccine strains of poliovirus of serotypes 1, 2 and 3 have been studied by the isolation and characterization of mutants resistant to neutralization by antibody. Three distinct sites have been identified which are designated site 1, site 2 and site 3. Site 1 includes a region of 12 amino acids of VP1, from residues 89 to 100, and a corresponding region of VP1 has been identified as an antigenic site for poliovirus 2. This site was strongly immunodominant in type 2 and type 3 but was not detected for poliovirus 1. Site 2 is a complex site including residues 220 to 222 from VP1 (site 2a) with residues including 169 and 170 and others of VP2 (site 2b). Both site 2a and site 2b have been detected in type 1 poliovirus, while as yet only site 2b has been detected in type 3 poliovirus. Site 3 is a complex site including residues 286 to 290 from VP1 (site 3a) with residues including 58 and 59 and others of VP3 (site 3b). Both sites 3a and 3b have been detected in type 3 poliovirus, while as yet only site 3b has been detected in type 1 poliovirus.
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A Morphological Study of the Replication of Breda Virus (Proposed Family Toroviridae) in Bovine Intestinal Cells
More LessSummaryThe morphological aspects of Breda virus serotype 2 replication in intestinal cells of gnotobiotic calves were investigated by electron microscopy. Ultrastructural findings suggest a morphogenetic pathway involving cytoplasmic vesicles, the Golgi apparatus and the cell nucleus. Virus uptake probably occurs via a receptor-mediated endocytosis-like mechanism. Endocytotic vesicles then carry virus to an as yet undetermined site of uncoating. Masses of tubules having the same diameters as Breda virion cores are found in nuclei, suggesting a role for the cell nucleus in replication of nucleocapsids. Similar tubules, as well as complete virions, were found in the Golgi region, the apparent site of virus assembly. Virus-containing Golgi vesicles then presumably move to cell surfaces where they fuse with apical and baso-lateral cell membranes to release virions in a way that permits more than one viral replicative cycle to occur without damage to host cell integrity. Virions are elongated with rounded ends and measure 42 × 100.5 nm. The morphogenesis and replication of Breda virus most closely resembles that of Berne virus of the proposed family Toroviridae.
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Morphogenesis of Berne Virus (Proposed Family Toroviridae)
More LessSummaryIn equine dermis cells infected with Berne virus particles were first detected 10 h after infection. Virions were encountered in all parts of the Golgi system and, infrequently, in the rough endoplasmic reticulum. A unique form of budding of preassembled rigid tubular nucleocapsids was demonstrated. Masses of tubular nucleocapsids of a lesser diameter and electrondensity were prominent in the cytoplasm and the nucleus of infected cells. Within the Golgi system and cytoplasmic cisternae virions appeared as straight or slightly curved rods. Extremely long, aberrant virions (250 nm) were occasionally seen. The proper torovirion morphology was observed in extracellular particles and in vacuoles near the cell surface.
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A Filamentous Distribution for the Herpes Simplex Virus Type 2-encoded Major DNA-binding Protein
More LessSummaryMonoclonal antibodies reacting with the herpes simplex virus (HSV)-encoded major DNA-binding protein defined an intracellular filamentous network. This network was associated predominantly with the infected cell nucleus and occurred in cells infected with HSV type 2. It did not co-distribute with microfilaments, microtubules or intermediate filaments, and DNA synthesis was required for its formation. We suggest explanations for the occurrence and function of this novel filamentous network structure.
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Molecular Cloning and Restriction Endonuclease Mapping of the Rat Cytomegalovirus Genome
More LessSummaryRat cytomegalovirus (RCMV) DNA was cleaved by restriction endonuclease EcoRI into 24 fragments ranging in mol. wt. from 34 × 106 to 0.20 × 106, of which 18 fragments could be cloned in plasmid pACYC 184. Restriction endonuclease XbaI cleaved the RCMV genome into 28 fragments, ranging in size from 44 × 106 to 0.81 × 106, of which 24 fragments were cloned in plasmid pSP62-PL. Among the restriction fragments that could not be cloned were two major terminal colinear fragments, EcoRI-A (34 × 106) and XbaI-A (44 × 106). Thus, the complete sets of recombinant plasmids spanned about 70% of the RCMV genome. Our mapping results including determination of the termini of the genome, characterization of double digestion products of restriction fragments and cross-hybridization of 35S-labelled (cloned) EcoRI and XbaI fragments to Southern blots of EcoRI-, XbaI- or BglII-cleaved RCMV DNA, allowed us to construct the EcoRI and XbaI restriction maps of RCMV DNA. Since no cross-hybridization between internal fragments was seen, it is concluded that the RCMV genome consists of a long unique sequence of 224 kilobases without internal inverted repeat sequences, which is similar to the structures of murine and guinea-pig CMV DNA but unlike that of human CMV DNA. In a minor population (approx. 20%) of the RCMV DNA, one terminus was found to be larger by 0.35 × 106 mol. wt. The nature of this fragment is unclear at the moment.
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African Swine Fever Virus Gene Expression in Infected Vero Cells
More LessSummaryPolypeptides synthesized in Vero cells infected with African swine fever virus (ASFV) can be divided into early and late classes on the basis of their sensitivity to cytosine arabinoside. As ASFV does not inhibit cell protein synthesis until late in infection, immunoprecipitation was used to identify virus-specific polypeptides. Eighteen early and 15 late polypeptides were detected by polyacrylamide gel electrophoresis. Early polypeptides can be further divided into those which are transiently expressed at early times and the majority which are synthesized throughout infection. In vitro translation products of RNAs from infected cells at different stages of infection were compared with in vivo products after immunoprecipitation. A good correspondence was observed between the invivo and in vitro patterns. Alle arly RNAs translated in vitro were synthesized in the presence of cytosine arabinoside and cycloheximide and can therefore be classified as immediate early RNAs. Only two polypeptides transcribed from early RNA were not present among late RNA products. No evidence was obtained for a discrete class of delayed early RNAs.
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Conservation of Potential Phosphorylation Sites in the NS Proteins of the New Jersey and Indiana Serotypes of Vesicular Stomatitis Virus
More LessSummaryA full length cDNA copy of the NS mRNA of the Missouri strain (Hazelhurst subtype, New Jersey serotype) of vesicular stomatitis virus (VSV) has been cloned and sequenced. The mRNA is 856 nucleotides long (excluding polyadenylic acid) and encodes a protein of 274 amino acids (mol. wt. 31000). Comparison with the NS gene of the Ogden strain (Concan subtype, New Jersey serotype) showed 15% difference at the nucleotide level and 10% difference at the amino acid level; the majority of the changes were located in the 3′ half of the mRNA. Comparison with the NS genes of two strains representing the Indiana serotype showed about 50% nucleotide and 33% amino acid sequence homology between the serotypes. In a four-way comparison of the proteins, two regions of higher homology were noted which may be of functional importance. Eighteen potential phosphorylation sites (Ser or Thr) were conserved between the four proteins; five of these sites correspond to the residues which have been suggested to be constitutively phosphorylated and may be essential for NS activity.
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The Myeloproliferative Sarcoma Virus Retains Transforming Functions after Introduction of a Dominant Selectable Marker Gene
SummaryThe dominant neomycin resistance gene (neoR) was introduced into the genome of the myeloproliferative sarcoma virus (MPSV), a replication-defective retrovirus carrying the mos oncogene. The resulting selectable neoR-MPSV virus did not lose its acute transforming property, unlike the results of attempts by other groups to insert marker genes into oncogenic viruses. NeoR-MPSV DNA was used to generate infectious virus by transfection followed by rescue with Friend or Moloney murine leukaemia virus. Infection of fibroblasts with this virus resulted in morphologically transformed cells which were resistant to the neomycin analogue G418. Segregation of the two functions (transformation and G418 resistance) was not observed in more than 500 independent viral transfers to fibroblasts. Furthermore, neoR-MPSV retained the leukaemogenesis-inducing properties of the wild-type virus. Myeloproliferation and G418-resistance transfer did not segregate after passage in mice.
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Structural Analysis of p28 Adult T-Cell Leukaemia-associated Antigen
SummaryThe 28000 mol. wt. polypeptide (p28) of adult T-cell leukaemia-associated antigen encoded by the 24S defective human T-cell leukaemia virus (HTLV-I) is associated with protein kinase activity. We have determined the nucleotide sequence of this defective HTLV-I provirus and found that it contains a portion of the gag gene (p19 and part of p24), the pX region, and two long terminal repeats, one at each end. The predicted p28 gag-pX fused protein consists of 190 amino acids and its mol. wt. was calculated as 21055. The results of peptide mapping analysis showing that p28 contains p19 supported the nucleotide sequence data. That p28 was encoded by this defective provirus was also demonstrated by transient expression of p28 polypeptide in COS 7 cells transfected with a recombinant plasmid containing a simian virus 40 early promoter and the p28-coding region of the 24S HTLV-I.
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The Antigenic Relationship between Measles, Canine Distemper and Rinderpest Viruses Studied with Monoclonal Antibodies
SummaryMonoclonal antibodies (MAbs) were used to delineate the antigenic relationship between the three morbillivirus types: measles virus (MV), canine distemper virus (CDV) and rinderpest virus (RPV). Panels of six to 31 MAbs against the haemagglutinin (H), fusion (F), nucleocapsid protein (NP), phosphoprotein (P) and matrix (M) proteins of MV and the H, F, NP and P proteins of CDV were employed. Nine strains of MV, three strains of CDV and four strains of RPV were examined by radioimmunoprecipitation assay and immune fluorescence for reactivity with the heterologous MAbs. Overall, the NP and in particular the F proteins of the morbilliviruses showed a high degree of epitopic homology; the P and M proteins showed a partial epitopic homology, with the greatest variation between the M proteins of CDV and MV; the H proteins showed a low degree of epitopic homology and then only between MV and RPV. These data indicate that the major cross-protecting antigen in heterotypic vaccination amongst morbilliviruses is the F antigen. The epitopic relationships found between morbilliviruses as identified by the MAbs were classified as follows. (i) Group-specific epitopes were present on all strains of the three morbillivirus types. (ii) Group-cross-reactive epitopes were present on only some of the strains from each morbillivirus type (these epitopes identified the presence of intratypic strain variation in all proteins of all three virus types). (iii) Type-specific epitopes, i.e. MV unique or CDV unique, were found only on the homologous morbillivirus type. (iv) CDV-RPV intertypic and MV-RPV intertypic epitopes were, respectively, epitopes shared by CDV and RPV but not with any MV strain, and epitopes shared by MV and RPV but not with any CDV strain. These cross-reactivities and type-specific reactions were obtained with the internal viral proteins (M, P and NP). The epitopes of the F proteins were mainly group-specific and no CDV-RPV or MV-RPV intertypic epitopes were found. The epitopes of the H protein were either type-specific or MV-RPV intertypic. These data support the proposed evolutionary relationship between the morbilliviruses.
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Genetic Variation within a Neutralizing Domain on the Haemagglutinin—Neuraminidase Glycoprotein of Newcastle Disease Virus
More LessSummaryPreviously, a panel of monoclonal antibodies recognizing epitopes in four antigenic sites on the haemagglutinin—neuraminidase (HN) glycoprotein of the Australia-Victoria strain of Newcastle disease virus were used in strain comparisons. Epitopes in three sites were found to be conserved while the epitope recognized by the single antibody to site 3 was not. A new panel of antibodies is described, two of which bind to epitopes in site 3 and six of which bind to a site (site 1,4) that overlaps with sites 1 and 4 as determined by analyses of variants, temperature-sensitive mutants, and strains by assays of neutralization of infectivity and binding in a radioimmunoassay. Neutralization of heterologous strains with the panel of antibodies revealed that both new site 3 epitopes are also highly divergent, while three additional epitopes outside site 3 (those in site 1,4) are highly conserved. The new site 3 antibodies can bind to virions of several heterologous strains without neutralizing infectivity. Thus, of the 10 epitopes we have now examined, all of three in site 3 are specific with respect to neutralization of infectivity for th ehomologous strain, while all of seven in other sites are conserved in heterologous strains. This suggests that the strain specificity originally described for a single site 3 epitope is, instead, a property of a much more extensive, poorly conserved domain on the HN molecule.
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Antigenic Structure of Transmissible Gastroenteritis Virus. II. Domains in the Peplomer Glycoprotein
More LessSummaryThe antigenic structure of the peplomer glycoprotein E2 of the porcine transmissible gastroenteritis coronavirus (TGEV) was explored using a panel of 23 hybridoma antibodies (MAbs). The topography of the epitopes was established by means of a competition radioimmunoassay. Four main antigenic sites, termed A, B, C and D, were thus clearly delineated. Most of the neutralization-mediating determinants were found to cluster in the A-B area, which has been shown to be highly conserved among TGEV strains. Cooperative enhancement of binding to sites B and D was observed following attachment of MAbs relevant to site A. Additional epitopes were identified on E2 by MAbs that selectively recognized its intracellular precursor. Functional mapping was also performed using neutralization-resistant variants. Analysis of their reactivity confirmed part of the epitope linkages defined by the first approach. The overall lower frequency of such variants altered at site A suggested that some of the epitopes may play an essential function.
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Identification of a 17000 Molecular Weight Antigenic Polypeptide in Transmissible Gastroenteritis Virus-infected Cells
More LessSummaryPulse labelling of cells with [35S]methionine at different times after infection followed by SDS-PAGE was used to resolve and to identify polypeptides designated as specific to transmissible gastroenteritis virus (TGEV)-infected swine testicular (ST) cell cultures. The major TGEV structural proteins, with apparent molecular weights of 200000 (200K), 47K and 30K were detected in radiolabelled cell extracts by 6 h post-infection. Additionally, a 17K major polypeptide was present in infected cells but not in mock-infected control cultures. Labelling with [3H]glucosamine revealed only the 200K and 30K proteins to be glycosylated. TGEV-primed porcine lymphocytes, secondarily stimulated in vitro with sucrose gradient-purified virus, produced antibody only to the two glycoproteins (gp) indicating that the 17K polypeptide is not a surface feature of the virion. Two pigs were infected oronasally with the virulent Miller strain of TGEV and their sera were analysed by immunoprecipitation. At 25 days post-infection convalescent sera responded strongly to gp30 and gp200 and there was a weak initial response to the 17K polypeptide. Serum immunoglobulins at 60 days post-infection reacted strongly to the 17K protein while the antibody response to gp30 was significantly reduced and that to gp200 was slightly reduced.
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Infectious Bronchitis Immunity: Its Study in Chickens Experimentally Infected with Mixtures of Infectious Bronchitis Virus and Escherichia coli
More LessSummaryThe live infectious bronchitis (IB) vaccine, H120, protected chickens against intranasal challenge with a mixture of Escherichia coli strains (E. coli Pool) and IB virus (IBV) strains of the same (Massachusetts) serotype as H120; it usually also protected against challenge with the E. coli Pool and IBV strains of other serological types. When these challenge strains were themselves used as vaccines they usually protected against challenge with a mixture of the E. coli Pool and an IBV strainof the Massachusetts serotype (VF69-149) or an IBV strain not of the Massachusetts serotype (HVI-116). Poor protection, when observed, was most common inthose experiments involving a minority of the IBV strains that had been incriminated in recent outbreaks of disease in vaccinated flocks of chickens. Much lower concentrations of IBV strain VF69-149 and E. coli O18 were found in the nose, trachea and spleen of H120-vaccinated chickens killed at different times after they were given a mixture of these organisms than were found in these sites in similarly challenged unvaccinated chickens. Some protection against challenge with IBV and the E. coli Pool was also observedin chickens vaccinated with an inactivated IBV strain; it was much less effective than that obtained following vaccination with the corresponding live IBV strain.
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Coronavirus IBV: Virus Retaining Spike Glycopolypeptide S2 but Not S1 Is Unable to Induce Virus-neutralizing or Haemagglutination-inhibiting Antibody, or Induce Chicken Tracheal Protection
More LessSummaryAvian infectious bronchitis coronavirus (IBV) inactivated by β-propiolactone induce partial protection of the trachea in up to 40% of chickens following one intramuscular inoculation 4 to 6 weeks prior to challenge. Retention of an intact tracheal ciliated epithelium 4 days after challenge was the criterion of protection. There was no correlation between protection and serum titres of virus-neutralizing (VN) and haemagglutination-inhibiting (HI) antibody, which were maximal at about 4 weeks after inoculation. Virus from which the S1 but not the S2 (spike-anchoring) spike glycopolypeptide had been removed by urea did not induce protection or VN or HI antibody. Four intramuscular inoculations of monomeric S1 induced VN and HI antibody in two and four chickens respectively. These results indicate that VN and HI antibodies are induced primarily by S1, that intact spikes are a major requirement for the induction of protective immunity and that this propertyis probably associated with S1.
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Coronavirus IBV: Removal of Spike Glycopolypeptide S1 by Urea Abolishes Infectivity and Haemagglutination but Not Attachment to Cells
More LessSummaryUrea has been used to remove the S1 spike glycopolypeptide from avian infectious bronchitis virus (IBV) strains M41 and Beaudette, without removing the S2 spike-anchoring glycopolypeptide. Reduction of the pH to 2.9 did not cause release of S1 although some S1 was released spontaneously from IBV Beaudette at pH 7.4. Virus that lacked S1 was no longer infectious or able to cause haemagglutination (HA). However, radiolabelled IBV that lacked S1 attached to erythrocytes and chick kidney cells to the same or similar extent as did intact virus. Treatment of IBV with a phospholipase C preparation, required to make IBV cause HA, did not increase binding of IBV to erythrocytes. The results indicate that while the attachment to cells of virus that lacks S1 is qualitatively different from that of intact virus, the decline in infectivity is the consequence of the loss of some other spike function.
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Integration of Region X of Hepatitis B Virus Genome in Human Primary Hepatocellular Carcinomas Propagated in Nude Mice
SummaryTissues of human primary hepatocellular carcinoma (PHC) from six patients infected with hepatitis B virus (HBV) were propagated in nude mice, as well as a strain of hepatitis B surface antigen-positive PHC (PLC/PRF/5). Integration of viral DNA into chromosomal DNA of tumour cells was evaluated by the capacity to hybridize with radiolabelled DNA probes, each representing fundamental partsof the HBV genome, that is S and C genes and regions pre-S and X. All PHC cells possessed region X integrated in their chromosomes. However, integration of the S gene, C gene and region pre-S was found in only six of the seven PHCs. Based on these findings, the integration of region X seems to be most closely associated with carcinogenesis in HBV infection.
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Gibbon Ape Leukaemia Virus RNA in Leukaemic T-Lymphoid Cell Lines: Expression of a Novel RNA Transcript
More LessSummaryFibroblast cell lines infected in vitro with different strains of gibbon ape leukaemia virus or the related woolly monkey virus (SSAV) synthesized two RNA species of approximately 8=.4 kb and 2.9 kb. The former, a complete RNA, represents the gap-pol mRNA, while the latter is a spliced transcript lacking gag and pol, and represents the env mRNA. In contrast, RNA from one T-lymphoid cell line derived from a gibbon ape T-lymphocytic leukaemia (UCD-144) expressed a viral mRNA in addition to gag-pol and env mRNA. This RNA is 6.4 kb and lacks at least 3=.0 kb of sequences derived from the internal region of the viral genome, including most or all of the pol gene. These data, as well as data from Southern blots of UCD-144 DNA, suggest that the 6.4 kb mRNA could represent a transcript from a defective recombinant provirus and may contain cell-derived sequences.
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Mapping of the Major Glycoprotein Gene of Human Cytomegalovirus
More LessSummaryThe gene coding for the most abundant glycoprotein (gp58) of human cytomegalovirus (HCMV), strain AD169, was physically mapped on the viral genome. A monospecific rabbit antiserum against gp58 was used to screen a cDNA library that was constructed from poly(A)+ RNA of HCMV-infected cells in the prokaryotic expression vector λ gt11. A cDNA clone was identified which synthesized part of the glycoprotein. It allowed localization of the coding region within the right terminal sequence of the HindIII-F fragment between map coordinates 0.344 and 0.380 of HCMV virion DNA.
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Characterization of Glycoprotein Complexes Present in Human Cytomegalovirus Envelopes
More LessSummaryThree disulphide cross-bridged glycoprotein complexes were immunoprecipitated from purified human cytomegalovirus envelopes using a monoclonal antibody with a specificity for a glycoprotein of mol. wt. 52 × 103. These complexes were isolated by electroelution after polyacrylamide gel electrophoresis (PAGE) under non-reducing conditions. Compositional analysis of each complex by PAGE under reducing conditions showed that at least two distinct complexes,one containing glycoproteins with mol. wt. of 52 × 103 and 95 × 103 and the other with glycoproteins of 52 × 103 and 130 × 103, were present. The results obtained indicated that one of these complexes could also exist as a dimer.
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Fc Receptor(s) Induced by Human Cytomegalovirus Bind Differentially with Human Immunoglobulin G Subclasses
More LessSummaryThe IgG subclass specificity of Fc receptor(s) induced on cells by infection with human cytomegalovirus (HCMV) was studied in a binding assay by using infected cells and purified iodinated IgG of various subclasses from HCMV seronegative healthy adult donors. All four human IgG subclasses bound to HCMV-infected cells, with the following relative magnitudes: IgG1 ⩾ IgG4 > IgG2 > IgG3. The IgG subclass specificity of the Fc receptor was further analysed in an inhibition assay by using fragments prepared from purified human IgG by papain digestion, and using unlabelled subclass proteins. Fc but not Fab fragments inhibited the binding of 125I-labelled human IgG to HCMV-infected cells. The biological role of the Fc receptor in HCMV infection is discussed.
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A Neutralizing Monoclonal Antibody to Respiratory Syncytial Virus which Binds to Both F1 and F2 Components of the Fusion Protein
More LessSummaryA virus-neutralizing monoclonal antibody (1E3) specifically immunoprecipitated the 70000 mol. wt. (70K) fusion (F) protein from respiratory syncytial (RS) virus-infected HeLa cells. Western blotting analysis of polypeptides from such cells separated by SDS-polyacrylamide gel electrophoresis (SDS-PAGE) under reducing conditions revealed that 1E3 was peculiar in that it bound to both F1 (50K) and F2 (20K) components of the F protein. Antibody subsequently eluted from either the F1 or the F2 regions of immunoblots re-bound to both F1 and F2 regions of the SDS-PAGE blot. These results show that monoclonal antibody 1E3 reacts with an epitope which is found on both F1 and F2 subunits of RS virus fusion protein.
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Persistence of BK Virus in Human Foetal Pancreas Cells
More LessSummaryHigh multiplicity BK virus (BKV) infection of primary cells derived from human foetal pancreas resulted in massive cytopathology and subsequent outgrowth of cells. Intranuclear BKV T-antigen was present in all cells and viral antigen was detected in 10 to 30% of these cells. The subcultured cells yielded BKV in the supernatant (approx. 105 TCID50/ml) and in the cells free viral DNA was present (approx. 10% of total cellular DNA content). Analysis of the viral DNA indicated the presence of deleted and rearranged BKV DNA molecules. Although all cells continuously expressed BKV T-antigen they did not exhibit the transformed phenotype. This persistent infection of human foetal pancreas cells represents a novel type of in vitro interaction between BKV and human cells which may correspond to the in vivo findings on BKV tropism for pancreatic cells.
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- Plant
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Comparison of the in vitro Translation Products of Wild-type and a Deletion Mutant of Soil-borne Wheat Mosaic Virus
More LessSummaryA wild-type isolate (WT) of soil-borne wheat mosaic virus (SBWMV, isolate JT) (RNA I 6.9 kb and RNA II 3.6 kb) was successively transferred to wheat plants by mechanical inoculation and a deletion mutant (DM) (RNA I 6.9 kb and RNA II 2.1 kb) was produced. In wheat germ extracts, RNA I of both WT and DM directed synthesis of polypeptides having mol. wt. of 220000 (220K) and 150K, and RNA II of both WT and DM directed synthesis of 25K and 19K polypeptides. Incubation in wheat germ extracts of WT or DM virions purified with an alkaline buffer also gave 220K, 25K and 19K polypeptides as major products and a 150K polypeptide as a minor product. In rabbit reticulocyte lysates, RNA I of both WT and DM directed synthesis of only the 220K polypeptide, whereas WT RNA II produced 100K, 46K, 25K and 19K polypeptides and DM RNA II, 31K, 25K and 19K polypeptides. SBWMV DM antiserum precipitated polypeptides of 100K, 31K, 25K and 19K but not 220K and 46K. The 19K polypeptide was identified as the capsid protein from its electrophoretic mobility and its reaction with antiserum to virus particles. Thus, the differences between the in vitro translation products of WT and DM SBWMV were confined only to those coded by RNA II.
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An RNA-dependent RNA Polymerase Associated with the Filamentous Nucleoproteins of Rice Stripe Virus
More LessSummaryFilamentous particles of rice stripe virus (RSV) were found to be associated with an RNA-dependent RNA polymerase activity. The enzyme catalysed the synthesis in vitro of single- and double-stranded RNAs corresponding in size with RNA found in RSV particles, as well as two other dsRNAs with mol. wt. of 1.0 × 106 and 0.56 × 106. The RSV polymerase activity required Mg2+, Mn2+ or Fe2+ but not Na+, K+ or NH+ 4 which were inhibitory at concentrations of more than 50 mm. The optimum pH of the polymerase was around 8.0 at the optimum temperature, 40°C. Detergent treatment of RSV particles did not enhance the polymerase activity. Purified RSV particles contained a minor polypeptide (mol. wt. 230000) as well as coat protein; the former may be the RSV polymerase. The taxonomy of RSV is discussed in relation to enveloped animal viruses with negative-stranded RNA, which also contain an RNA-dependent RNA polymerase in virus particles.
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The Nucleotide Sequence of Tomato Black Ring Virus RNA-2
More LessSummaryThe sequence of the 4662 nucleotides [excluding poly(A)] of RNA-2 of tomato black ring virus (TBRV) has been determined. Most of the sequence (4074 nucleotides) encodes a polypeptide of mol. wt. 150000 (150K). The 5′ and 3′ non-coding sequences are 287 and 301 nucleotides in length, differ from the coding sequence in base composition, and contain repeated sequences, some of which resemble oligonucleotides in the 3′ non-coding sequence of M-RNA of cowpea mosaic virus (CPMV). From its amino acid composition, the coat protein of TBRV was tentatively located in the C-terminal third of the 150K polypeptide. The amino acid sequence of the 150K polypeptide immediately N-terminal to the putative coat protein sequence was found to resemble parts of the 30K polypeptides of tobamoviruses and, to a lesser extent, part of the 105K polypeptide translation product of CPMV M-RNA.
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Serotype-specific and General Luteovirus Probes from Cloned cDNA Sequences of Barley Yellow Dwarf Virus
More LessSummaryGenome fragments from two serotypes of barley yellow dwarf virus (BYDV) were cloned and used as hybridization probes. Dot blot assays using 32P-labelled plasmid probes readily detected BYDV in crude sap extracts from infected plants and were at least as sensitive as ELISA. Some clones were specific for either the RPV or the PAV serotypes. Others hybridized not only with the RNA of both serotypes but also with those of three other luteoviruses (beet western yellows, potato leaf roll and soybean dwarf), but they did not hybridize with the RNA of a tobamovirus or Escherichia coli tRNA. These nucleic acid probes therefore have potential for the general diagnosis of infection by members of the luteovirus group as well as detection of specific BYDV serotype infections. The taxonomic implications of the observation that the genomes of different luteoviruses have some conserved regions are discused.
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Infectious and Non-infectious Mutants of Cauliflower Mosaic Virus DNA
SummaryMutants of cauliflower mosaic virus (CaMV), generated in vitro by modification of recombinant DNA plasmids containing the viral genome, either retained the ability to induce disease symptoms on turnip plants, produced less severe symptoms or failed to induce symptoms. Wild-type symptoms were produced by a variant CaMV DNA of the Cabbage S isolate that had 4 bp in open reading frame (ORF) III replaced with a 16 bp sequence. Less severe symptoms, due to a delay in symptom appearance relative to inoculation with wild-type DNA, were induced by a mutant with a frameshift mutation in ORF II (pSA103). CaMV DNA, recovered from plants infected with pSA103, contained a second mutation which restored the original translation reading frame. Nucleic acid hybridization to ‘squishes’ of leaf tissue from plants that had been inoculated with mutant DNAs that included DNAs modified in each of the six major ORFs of CaMV DNA revealed that only those plants that appeared diseased had detectable CaMV nucleic acid in uninoculated leaves. Replicated CaMV DNA was also not detected in non-encapsidated and virion DNA fractions from inoculated leaves of non-diseased plants.
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Volume 20 (1973)
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Volume 19 (1973)
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Volume 18 (1973)
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Volume 17 (1972)
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Volume 16 (1972)
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Volume 15 (1972)
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Volume 14 (1972)
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Volume 13 (1971)
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Volume 12 (1971)
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Volume 11 (1971)
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Volume 10 (1971)
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Volume 9 (1970)
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Volume 8 (1970)
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Volume 7 (1970)
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Volume 6 (1970)
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Volume 5 (1969)
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Volume 4 (1969)
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Volume 3 (1968)
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Volume 2 (1968)
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Volume 1 (1967)