- Volume 66, Issue 3, 1985
Volume 66, Issue 3, 1985
- Review Article
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- Articles
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- Animal
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Purification and Characterization of the Respiratory Syncytial Virus Fusion Protein
More LessSUMMARYThe fusion protein of respiratory syncytial virus was purified by affinity chromatography using a monoclonal antibody. Under various conditions the protein was recovered as a 145K dimer or a 70K monomer. The 70K monomer was composed of disulphide-linked fragments of 48K and 23K. Polyclonal rabbit serum produced to the dimerized fusion protein neutralized virus but did not inhibit fusion, while rabbit serum to the 2-mercaptoethanol-treated dimerized protein neutralized virus and inhibited fusion of infected cells. Only the latter serum strongly recognized the 23K fragment when studied by Western blot analysis.
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Respiratory Syncytial Virus Polypeptides. IV. The Oligosaccharides of the Glycoproteins
More LessSUMMARYThe cell-associated glycoproteins of respiratory syncytial (RS) virus included GP1 (90K), VP70 (70K), VGP48 (48K) and GP26 (26K). Although present in infected cells, there was no VP70 in purified virus. Trypsin treatment of infected cells removed 80 to 90% of VP70 as well as its products VGP48 and GP26. This suggested that most of the VP70 in the cell is located on the plasma membrane. The glycoproteins of purified RS virus (GP1, VGP48 and GP26) contain mannose, galactose and fucose as well as glucosamine, but the quantity of mannose in GP1 is low when compared to that of the other three sugars. The effects that follow the treatment of infected cells with the glycosylation inhibitors tunicamycin and monensin, and the treatment of the immunoprecipitated product of pulse-chase experiments with endonuclease H demonstrated that VP70 and its products contained N-linked oligosaccharides, and that the oligosaccharides of the mature VGP48 subunit were of the complex type, while GP1 contained both N- and O-linked oligosaccharides. The non-glycosylated forms of VP70 and GP1 have estimated mol. wt. of 50K and 33K respectively. Therefore, the carbohydrate contribution to the mol. wt. of VP70 and GP1, as determined by PAGE, was equivalent to 20K for the former and 57K for the latter. The majority of the GP1 oligosaccharides were O-linked, a form of sugar linkage not previously found among paramyxoviruses.
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cDNA Cloning of the Messenger RNAs of Five Genes of Canine Distemper Virus
More LessSUMMARYMessenger RNAs from Vero cells infected with the Onderstepoort strain of canine distemper virus (CDV) were cloned into the PstI site of plasmid pAT153. Total polyadenylated RNA was used and resulting clones were screened with 32P-labelled cDNA probes from infected and mock-infected cells. The virus specificity of the clones was proven by Northern blot hybridization and by ability to select radioactive virus mRNAs labelled in vivo in the presence of actinomycin D. Clones from the N, P and M genes of CDV were identified by hybrid select translation; clones which presumably represent the H and F genes were also obtained. The clones allowed a designation of the major viral mRNA bands. Bicistronic mRNAs were identified, and their selection by various clones suggests a gene order of 3′-N-P-M-70K-65K-L-5′ for this virus.
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Preparation and Characterization of Monoclonal Antibodies Directed against Four Structural Components of Canine Distemper Virus
More LessSUMMARYMouse hybridomas producing antibodies against structural proteins of canine distemper virus (CDV) were produced by fusion of Sp2/0 myeloma cells with spleen cells from BALB/c mice immunized with purified preparations of Vero cell-grown CDV. Ascites fluids collected after intraperitoneal inoculation with 149 CDV antibody-producing hybridoma cell lines were characterized by different serological tests. By immune precipitation tests with [35S]methionine-labelled extracellular virions and intracellular virus polypeptides, 57 clones were found to produce antibodies against the nucleocapsid protein (NP), 22 against the polymerase (P) protein, 10 against the fusion (F) protein and nine against the large uncleaved glycoprotein (named H in analogy with measles virus). By competitive binding enzyme-linked immunosorbent assay (ELISA) tests with monoclonal antibodies against each structural component, a minimum of 18, six, three and seven separate antigenic determinants were identified on the NP, P, F and H proteins, respectively. The reactions of clones directed against F and H surface components of the virus were tested for their ability to inhibit the infectivity of both CDV and measles virus in the absence and presence of anti-γ-globulin. In addition, the inhibitory activity of the clones on measles haemagglutinating (HA) and haemolysis (HL) activity were examined. Monoclonal antibodies against six of the seven antigenic determinants of the H protein could neutralize the infectivity of the virus. After addition of anti-γ-globulin to the test, increases of titres varying from twofold to several hundredfold were observed with the different clones. None of all the clones against H could block measles virus infectivity, HA or HL activity. The 10 clones directed against the F protein could not neutralize the infectivity of CDV even in the presence of anti-γ-globulin. Further, the antibodies could not inhibit measles HA and HL activity in the absence of anti-γ-globulin. However, after the addition of anti-γ-globulin, antibodies against two of the three sites were found to block measles virus HL activity. The reactions of all clones were tested in immune fluorescence, ELISA and immune precipitation tests with three strains of CDV. Each strain had a few unique antigenic sites. Variation was found in four, one and three different antigenic sites of the NP, P and H proteins, respectively.
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Amino Acid Sequences of Haemagglutinins of Influenza Viruses of the H3 Subtype Isolated from Horses
More LessSUMMARYThe amino acid sequence of the haemagglutinin of A/equine/Miami/63 (H3N8), the prototype influenza virus of the H3 subtype from horses, is deduced from the nucleotide sequence of virus RNA and compared with the sequences of haemagglutinins of viruses of this subtype isolated from humans [X-31 (H3N2)] and from birds [A/duck/Ukraine/63 (H3N8)] and with the sequence of the haemagglutinin of A/equine/Fontainebleau/79 (H3N8) a virus isolated from a recent outbreak of equine influenza. The amino acid sequence differences detected are discussed with reference to the structure of the molecules, their antigenicity and antigenic drift in influenza viruses isolated from horses.
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Phosphopeptide Fingerprints of Nucleoproteins of Various Influenza A Virus Strains Grown in Different Host Cells
More LessSUMMARYMDCK, HeLa, L or primary chick embryo cells were infected with different influenza A virus strains and labelled with [32P]orthophosphate. The nucleoprotein was immunoprecipitated and digested by trypsin. The resulting tryptic fingerprints were strain-specific and dependent on the host cell in which the virus strains had been propagated. Virus mutants had different fingerprints. It is suggested that specific cellular protein phosphokinases are involved in virus replication and that these may determine host range and cell tropism by site-specific phosphorylation of viral phosphoproteins.
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Synthesis of Bunyavirus-specific Proteins in a Continuous Cell Line (XTC-2) Derived from Xenopus laevis
More LessSUMMARYThe XTC-2 cell line, derived from Xenopus laevis, supported the replication of representative viruses from each of the four genera in the family Bunyaviridae. Generally, viral titres were higher in XTC-2 cells than in other susceptible cell lines, and for some viruses plaques were detected earlier in XTC-2 cells. The XTC-2 cell line permitted comparative analyses of bunyavirus-specific protein synthesis. The patterns of synthesis of viral proteins, characteristic of each of the genera, were observed with representative viruses. These studies provided biochemical characterization of two Scottish isolates, which support the inclusion of Clo Mor virus in the Nairovirus genus and St Abb’s Head (M349) virus in the Uukuvirus genus.
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Entry of Poliovirus Type 1 and Mouse Elberfeld (ME) Virus into HEp-2 Cells: Receptor-mediated Endocytosis and Endosomal or Lysosomal Uncoating
More LessSUMMARYPoliovirus type 1 appeared from electron microscope studies to enter HEp-2 cells by receptor-mediated endocytosis. On adsorption the virus was evently distributed over the cell surface, with some preference for the microvilli and their bases. Invagination of the cell surface membrane with the attached virus commenced at coated pits and led to the formation of virus-containing coated vesicles in the cytoplasm. These coated vesicles fused with intracellular vesicles to form endosomes. When cells infected with poliovirus or Mouse Elberfeld virus were treated with the weak bases chloroquine, NH4Cl or the ionophore monensin to raise the intraendosomal and intralysosomal pH above 6, virus-directed macromolecular synthesis and production of progeny were prevented. These results suggest that the virus genomes are released to the cytoplasm via endosomes and/or lysosomes by a pH-dependent process.
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Mouse Interferon Alpha Beta Genes Are Linked at the Centromere Proximal Region of Chromosome 4
More LessSUMMARYIn order to determine the chromosomal localization of the murine interferon-α (MuIFN-α) and murine interferon-β (MuIFN-β) genes the DNAs of a panel of somatic cell hybrids were analysed by Southern blot hybridization. The hybrid cells were derived from E36 Chinese hamster cells and GRSL or GR MaTu mouse cells and retained all hamster chromosomes but segregated mouse chromosomes. The MuIFN-α probe used was a 0.7 kb HindIII-EcoRI fragment derived from the MuIFN-α1 gene which hybridized with both mouse and hamster DNA. However, four fragments present in EcoRI digests of mouse DNA were clearly absent from the hybridization profile of EcoRI-digested hamster DNA and could be used for detection of MuIFN-α sequences in the hybrid cells. The MuIFN-β probe, a 0.5 kb BglII-BamHI fragment derived from the MuIFN-β gene, hybridized with a 2.6 kb EcoRI fragment of mouse DNA and only weakly cross-hybridized with a 4.8 kb EcoRI fragment in hamster DNA. Southern blot analysis of DNA from mouse/hamster hybrids compared with the analysis of chromosome markers showed that both the MuIFN-α and the MuIFN-β genes are located on chromosome 4. Analysis of DNA from hybrids that contained only part of chromosome 4 indicated that the MuIFN-α gene family and the MuIFN-β gene are situated at the centromere-proximal region of the chromosome.
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Effect of Borna Disease Virus Infection on Athymic Rats
More LessSUMMARYHomozygous athymic nude rats (rnu/rnu) infected intracerebrally with Borna disease virus produced relatively high titres of infectious virus in the central nervous system. However, no clinical signs of disease or pathological alterations could be found during a 100 day observation period. In contrast, heterozygous euthymic albino littermates (rnu/+), which were used as controls, reacted in a similar manner to immunocompetent Lewis rats. They developed behavioural alterations which coincided with encephalitis and retinitis. The results obtained confirm our previous concept that the genesis of Borna disease, at least in rats, is attributed to a cellular immune response.
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Cytomegalovirus Infection of Human Teratocarcinoma Cells in Culture
More LessSUMMARYWhereas human cytomegalovirus (HCMV) did not replicate in human embryonal carcinoma (EC) cells, it did replicate in some of the differentiated cells arising following the exposure of TERA-2-derived human EC cells to retinoic acid. On the other hand, retinoic acid did not induce a permissive state in several other diverse human cell lines, including an EC line, 2102Ep, which did not differentiate in response to this agent. Also, both TERA-2 and 2102Ep EC cells differentiated to a limited extent when grown at low cell density and a few of these cells became permissive for HCMV. Thus, susceptibility is the result of differentiation and not due to a direct effect of retinoic acid on viral replication. The nature of the block to HCMV replication in human EC cells is unknown, but viral DNA could be detected in the nucleus within an hour of infection and there was an increased anchorage-independent growth of undifferentiated and differentiated cells following HCMV infection. Viral replication is not subject to a general block in these cells, since another herpesvirus, herpes simplex virus type 1, replicated well.
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Herpes Simplex Virus Sequences Involved in the Initiation of Oncogenic Morphological Transformation of Rat Cells Are Not Required for Maintenance of the Transformed State
More LessSUMMARYWe have determined the herpes simplex virus (HSV) type 2 DNA sequences responsible for the initiation of morphological transformation and have investigated the retention and expression of these sequences in morphologically transformed cells and in tumours derived from these cells. All the transformed cells analysed were selected by a focus formation assay and are oncogenic in the inbred host rat. Cloned HindIII and BglII fragments from the HSV-2 genome were assayed for the ability to initiate morphological transformation of rat embryo cells. Only the HindIII a (map units 0.52 to 0.72) and the BglII n (0.582 to 0.612) clones gave transformed foci. This shows that the BglII n region is responsible for initiation of transformation. Southern blot analysis of DNA extracted from these transformed cells and from tumours derived from these transformed cells revealed that neither the BglII n fragment nor fragments of 500 bp mapping within it are detected at the level of one copy per cell and therefore need not be retained in the cell to maintain the oncogenic phenotype. In addition there was no evidence of expression of the HSV-specified ribonucleotide reductase activity which is partially encoded within the BglII n fragment of HSV-2. We also analysed DNA from rat embryo cells transformed by ts mutants of HSV-2 (HG52) or HSV-1 (HFEM or 17) at non-permissive temperature or by virus at supraoptimal temperature or by sheared virus DNA and DNA from tumours derived from lines of these transformed cells. In addition, we cloned both transformed and tumour cell lines and analysed these similarly. In no case could we detect HSV DNA sequences at the level of one copy per cell.
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Replication of Oryctes Baculovirus in Cell Culture: Viral Morphogenesis, Infectivity and Protein Synthesis
More LessSUMMARYThe sequence of events in the replication of Oryctes baculovirus in DSIR-HA-1179 cells began with the uptake of virus particles by pinocytosis at the plasma membrane. Seven h after infection, enveloped virus particles were observed inside a cleared area in the nucleus. Virus was released from cells by budding through the plasma membrane where a second unit membrane was acquired. The infectivity of virus particles with a single envelope purified from within cells was not significantly different from that of virus which had acquired the second envelope by budding. Twenty-seven structural virus proteins were identified by gradient polyacrylamide gel electrophoresis. The synthesis of eight of the major structural proteins was detected by pulse labelling infected cells with l-[35S]methionine. No late protein synthesis, as observed in subgroup A baculoviruses, was detected in this subgroup C baculovirus.
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Baculovirus Replication: Uptake of Trichoplusia ni Nuclear Polyhedrosis Virus Particles by Insect Cells
X. Wang and D. C. KellySUMMARYThe uptake of two forms of Trichoplusia ni multiple nucleocapsid nuclear polyhedrosis virus by Spodoptera frugiperda cells in culture has been evaluated. Subtle differences in the Mg2+ and Ca2+ requirements for the uptake of cell-released virus (CRV) and polyhedron-derived virus (PDV) exist; otherwise, both forms of the virus appeared similar in their mode of uptake. Entry occurs by fusion of the plasma membrane of the cell with the envelope surrounding the virus nucleocapsid at neutral pH. The receptor turnover for the virus probably occurs rapidly since saturation of receptor sites for the virus was not achieved. The binding and penetration of the virus, and the uncoating and transport of the viral genome to the nucleus is rapid. Uncoating occurs predominantly in the cytoplasm. The lower infectivity of PDV, compared with CRV, for cells in culture may happen because this form of the virus accumulates in cell vacuoles and is unable to proceed with infection.
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Synthesis of Proteins and Glycoproteins in Dengue Type 2 Virus-infected Vero and Aedes albopictus Cells
More LessSUMMARYFifteen proteins were detected in Vero cells infected by dengue type 2 (DEN-2) virus that were not observed in mock-infected cells, namely P98, p82, P67, GP60, gp54, GP46, p30, p28, gp22, GP20, p18, gp16, p15, p14 and gp13. With the exceptions of gp54 and gp13, polypeptides corresponding to those listed above were also observed in DEN-2 virus-infected Aedes albopictus C6/36 cells. Pulse-chase labelling experiments suggested a possible precursor-product relationship between p30 and p28, and between gp22 and GP20. Peptide mapping and immunoprecipitation experiments showed that the major glycoproteins GP60, GP46 and GP20 were unrelated. Immunoprecipitations of infected cells with antiserum prepared against the DEN-2 soluble complement-fixing (SCF) antigen demonstrated that this antigen is equivalent to the non-structural glycoprotein GP46. The envelope glycoprotein (E) from virus grown in C6/36 cells migrated faster through polyacrylamide gels containing SDS than E from virus grown in Vero cells. [3H]Mannose-labelled glycopeptides of GP60, GP46 and GP20 were separated by gel filtration and by electrophoresis in Tris-borate gels; in addition, the polypeptides synthesized in infected cells in the presence of tunicamycin were analysed. The results revealed heterogeneity among the glycan units of GP60 and GP46.
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Sequences of the Nucleocapsid Genes from Two Strains of Avian Infectious Bronchitis Virus
More LessSUMMARYcDNAs prepared from viral genomic RNA purified from two strains of infectious bronchitis virus (IBV) (Beaudette and M41) have been cloned into pBR322. Three of these clones, which contain the complete sequences of mRNA A for both strains, except for the leader sequences which are only present on the subgenomic messenger RNAs, have been sequenced using the dideoxy method. The sequences are similar for both strains, each containing a single long open reading frame of 1227 bases which predicts a polypeptide of molecular weight approximately 45000. The genome position and size of this predicted polypeptide are consistent with it being the gene for the nucleocapsid protein. The amino acid sequence shows considerable homology with those of the nucleocapsids of murine hepatitis virus strains A59 and JHM. The major difference between the sequences determined for the two IBV strains is that the 3′ non-coding region of the Beaudette strain contains a 184 base segment which is not present in the M41 strain.
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Coronavirus MHV-JHM mRNA 5 Has a Sequence Arrangement which Potentially Allows Translation of a Second, Downstream Open Reading Frame
More LessSUMMARYThe sequence of a 5′-proximal region of mRNA 5 of coronavirus MHV-JHM was determined by chain-terminator sequencing of cDNA subcloned in M13. The sequence contained two long open reading frames of 321 bases and 264 bases, overlapping by five bases but in different frames. Both open reading frames are initiated by AUG codons in sequence contexts that are relatively infrequently used as initiator codons. The smaller, downstream open reading frame encoded a neutral protein (mol. wt. 10200) with a hydrophobic amino terminus. The larger, 5′-proximal open reading frame encoded a basic protein (mol. wt. 12400) which lacks internal methionine residues. With the exception of the AUG codon initiating the downstream open reading frame, no internal AUG codons were found within the sequence covered by the upstream open reading frame. These results suggest that the MHV-JHM mRNA 5 is translated to produce two proteins by a mechanism involving internal initiation of protein synthesis. Preliminary evidence is presented showing that the downstream open reading frame is functional in vivo.
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Coding Sequence of Coronavirus MHV-JHM mRNA 4
More LessSUMMARYA coding sequence at the 5′ end of mRNA 4 of the coronavirus MHV-JHM was determined by M13/chain-terminator sequencing of cloned cDNA. An open reading frame of 417 bases with the potential to encode a polypeptide of mol. wt. 15200 (139 residues) was identified. The 3′ end of the open reading frame overlapped by 16 bases the start of an open reading frame found in mRNA 5. The translation product of mRNA 4 was predicted to be a basic polypeptide rich in threonine. It had a large hydrophobic region near the amino terminus and a basic carboxy terminus. An intracellular, virus-specific polypeptide, which has been previously described as having a mol. wt. of 14000 to 14500 has the size and charge characteristics of such a translation product.
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Peptide Mapping of Envelope-related Glycoproteins Specified by the Flaviviruses Kunjin and West Nile
More LessSUMMARYGlycoproteins detected in Vero cells infected by the flaviviruses West Nile and Kunjin were examined by gel electrophoresis and peptide mapping. Two major glycoproteins, gp66 and gp54, were observed in West Nile virus-infected cells labelled for short time periods with [3H]mannose. A third glycoprotein, gp58, was present in smaller amounts. Pulse-labelling experiments suggested that gp66 was a precursor of gp54. Peptide mapping of [3H]leucine-labelled gp66, gp54 and the envelope glycoprotein E of West Nile virus demonstrated that gp66 and gp54 were related to E, and that the peptides of gp54 were a subset of those of gp66. Peptide mapping of the corresponding Kunjin virus-specified glycoproteins (gp66, gp59 and gp53) showed that the [3H]leucine-labelled peptides of gp53 and gp59 were similar and were contained within gp66. Since we have shown previously that gp59 and gp53 are related to E of Kunjin virus, we conclude that cells infected by West Nile or Kunjin viruses contain a similar set of E-related glycoproteins.
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Lack of Quantitative Correlation between the Neutralization of Poliovirus and the Antibody-mediated pI Shift of the Virions
More LessSUMMARYThe effect of mono- and polyclonal antibodies on the infectivity and pI (isoelectric pH) of type 1 poliovirus was studied. According to Mandel’s hypothesis, the isoelectric pH of poliovirus should change to about pI 4 upon neutralization. However, several antibodies did not follow this rule. Moreover, when antibodies did shift the pI, no quantitative correlation existed between the extent of neutralization and the amount of poliovirus shifted to low pI.
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Human Papillomavirus Type 16 Recombinant DNA Is Maintained as an Autonomously Replicating Episome in Monkey Kidney Cells
More LessSUMMARYHuman papillomavirus type 16 (HPV16) DNA cloned in the expression vector pSV2-neo has been shown to be maintained in transfected monkey kidney cells as an autonomously replicating episome at a level of 2 to 10 copies per cell. Integration of pSV2-neo/HPV16 DNA with the host genome occurred in transfected mouse fibroblasts. Neither type of cell appeared to be phenotypically transformed.
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Recombinants between Vaccinia and Ectromelia Viruses Bearing the Specific Pathogenicity Markers of Both Parents
More LessSUMMARYNineteen recombinants between vaccinia virus (VV) DNA− temperature-sensitive mutants and ectromelia virus (EMV) were characterized with respect to their biological properties and genome structure. Four of these recombinants acquired the pathogenicity for mice characteristic of EMV, while the pathogenicity for rabbits characteristic of VV was not only preserved, but even enhanced. Most unexpectedly, these recombinants with ‘double pathogenicity’, as well as four other recombinants, acquired a stable genetic trait which was not typical of the parental viruses, i.e. the ability to form haemorrhagic lesions on the chorioallantoic membrane of chick embryos. Approximate mapping of the genomes of these recombinants with restriction endonucleases showed that their DNA contained mostly VV sequences with a single detected insert of EMV DNA. In the ‘double pathogenicity’ recombinants, this insert was located in the central part of the genome, and its minimal size was about 16 Mdal.
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Small RNA Viruses Co-infecting the Pine Emperor Moth (Nudaurelia cytherea capensis)
More LessSUMMARYLarvae of the pine emperor moth, Nudaurelia cytherea capensis, naturally infected with Nudaurelia β virus (NβV), contained a second serologically unrelated virus which we have called Nudaurelia ω virus (NωV). NωV had a buoyant density of 1.285 g/ml in CsCl and yielded a single major polypeptide of 65000 daltons on gel electrophoresis. The particles of NωV were morphologically distinguishable from those of Nudaurelia viruses described by others, and tryptic peptide analyses indicated that NωV protein was distinct from that of NβV and NɛV. Both NωV and NβV contained a small stable fraction of particles with buoyant densities of about 1.33 g/ml.
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Effect of Heat Shock on Epstein–Barr Virus and Cytomegalovirus Expression
More LessSUMMARYThe effect of heat shock was investigated on lymphoblastoid cell lines Raji and P3HR1 harbouring Epstein-Barr virus (EBV) genomes, and on Vero cells abortively infected with human cytomegalovirus (HCMV). A heat shock at 44 °C for 10 min induced the appearance of EBV early antigens in Raji cells and increased the percentage of cells expressing EBV viral capsid antigens in P3HR1 cells. Heat shock performed on Vero cells just before HCMV infection resulted in an approximately fourfold increase in the number of cells exhibiting early nuclear antigens, and in the appearance of HCMV-induced Fc receptors.
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Comparative Electrophoretic Study of Polypeptides of Influenza A/H3N2 Viruses Isolated in Circumscribed Geographical Areas
More LessSUMMARYTwo distinct groups of influenza A/H3N2 viruses, closely related to A/Bangkok/1/79 and to A/Belgium/2/81, have been chosen from viruses isolated in Italy during 1981 to 1983 with the aim of analysing the biochemical composition of their polypeptides. The strains of each group have shown differences in electrophoretic migration rates in one or more proteins in comparison to the prototype viruses. Polypeptide mobility variations among isolates from circumscribed geographical areas and from single outbreaks have also been observed. In particular, there was a high degree of variability in the NS1 protein. The detection of biochemical differences among identical antigenic variants, probably the result of point mutations in polypeptide sequences or of genetic reassortment among different co-circulating human viruses, is a further expression of the peculiar ability of the influenza A virus to exhibit variation in internal proteins during its circulation.
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Extracellular Release of Enveloped Vaccinia Virus from Mouse Nasal Epithelial Cells in vivo
More LessSUMMARYThe release of vaccinia virus from mouse nasal epithelial cells infected in vivo was studied by electron microscopy. Intracellular naked vaccinia virus was enwrapped by Golgi membranes to form a double membrane intermediate. The outer membrane of the intermediate presumably fused with the plasma membrane, releasing extracellular enveloped virus. No signs of simple naked virus budding at the plasma membrane were observed. The majority of extracellular virus was enveloped and not naked.
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Polyethylene Glycol-mediated Infection of Cowpea Protoplasts with Sonchus Yellow Net Virus
More LessSUMMARYThe conditions favouring the infection of cowpea mesophyll protoplasts by Sonchus yellow net virus (SYNV) were determined. When 3 × 106 protoplasts were inoculated with 60 µg SYNV in 40% polyethylene glycol, 3 mm-CaCl2 at room temperature, over 90% of the surviving protoplasts became infected. Infectivity tests showed that the virus could be detected 12 h after inoculation.
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Cauliflower Mosaic Virus DNA Persists as Supercoiled Forms in Cultured Turnip Cells
More LessSUMMARYExplants taken from turnip leaves infected systemically with cauliflower mosaic virus (CaMV) proliferate callus tissue when cultured on an appropriate medium. CaMV DNA, detected by spot hybridization, was found to persist in these cultured cells for at least 45 days. Analysis of unencapsidated virus DNA by blot hybridization after agarose gel electrophoresis showed that the truncated DNA forms characteristic of infected leaf tissue were virtually absent from callus cells. These cells contained predominantly genome-length supercoiled CaMV DNA together with discrete subgenomic supercoiled forms.
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