SEARCH · Search PubMed
Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
The phenomena and steps of replication of insect pathogenic viruses (baculoviruses : nuclear polyhedrosis viruses) in their natural hosts and in insect cell cultures are described.
In contrast to insect viruses, animal viruses can produce considerable amounts of progeny virus in cells undergoing apoptosis. Nevertheless, viruses in general have acquired the ability to escape apoptosis of infected cells. These facts indicate that the role of apoptosis in virus infection is different in insect virus and animal virus, although both viruses need to avoid apoptosis of the infected cells for a viral life cycle in nature. In animal virus infection, the primary role of apoptosis is considered not to be a premature lysis of the infected cells (and the following abortion of virus multiplication) but to allow the dying cells to be phagocytosed by macrophages. This phagocytosis is able to prevent dysregulated inflammatory reactions at the site of virus infection and to initiate a specific immune response against the infected virus.
The regions of RNA-2 of Cowpea mosaic virus (CPMV) that encode the Large (L) and Small (S) coat proteins were expressed either individually or together in Spodoptera frugiperda (sf21) cells using baculovirus vectors. Co-expression of the two coat proteins from separate promoters in the same construct resulted in the formation of virus-like particles whose morphology closely resembled that of native CPMV virions. No such particles were formed when the individual L and S proteins were expressed. Sucrose gradient centrifugation of the virus-like particles showed that they had the sedimentation characteristics of empty (protein-only) shells. The results confirm that the 60 kDa L-S fusion is not an obligate intermediate in the virion assembly pathway and indicate that expression of the coat proteins in insect cells will provide a fruitful route for the study of CPMV morphogenesis.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Serological tests were done to examine the relationships between twelve picorna-like viruses of insects. The results of the tests indicated that the majority of the viruses are unrelated. However, cricket paralysis virus, isolated from Australian wild field crickets, appeared to be identical to Drosophila C virus, independently isolated in France. Cricket paralysis virus was infective for adults of Drosophila melanogaster and its infectivity towards Galleria melonella was neutralised by Drosophila C virus antiserum. It is therefore concluded that cricket paralysis virus and Drosophila C virus are very closely related if not identical.
The major structural protein (MSP--apparent molecular weight 49,000) of insect iridescent virus type 22 (isolated from blackflies--Simulium spp.) was resolved from disrupted, purified virus particles by SDS-PAGE and transferred to nitrocellulose by Western blotting. The portion of the blot containing the MSP was identified and excised. Tryptic peptides, generated by digestion in situ, were purified by HPLC. Three of these peptides were sequenced and an oligonucleotide gene probe was designed using one of them. A SalI clone of IV22 DNA was identified as MSP-specific by hybridization. DNA from this and an overlapping DNA clone was sequenced and a large open reading frame was positively identified as the MSP coding sequence by comparison with the tryptic peptide sequences. The molecular weight of the predicted protein product of this gene is 51,993, comparable with the apparent weight obtained by SDS-PAGE. In infected Spodoptera frugiperda (Sf) cells MSP is synthesized from 12 hr postinfection onwards. The identification of this gene and analysis of its expression opens the way to elucidating the control of late gene expression in an insect iridescent virus.
The gene encoding the complete glycoprotein of vesicular stomatitis virus (VSV, Indiana serotype G protein) with potential asparagine-linked glycans at amino acid residues 179 and 338 was inserted into a baculovirus transfer vector pAcYM1, derived from the nuclear polyhedrosis virus of Autographa californica (AcNPV). The gene was placed under the control of the AcNPV polyhedrin promotor and expressed by the derived recombinant viruses to high levels in Spodoptera frugiperda cell lines. The principal product was the glycosylated version of the G protein, although some alternative (including probable degradation) forms of the protein were also observed. Similar recombinant viruses were prepared with deletion of one, the other, or both glycosylation sites of the VSV G protein. All forms expressed VSV G protein derivatives and mediated cell fusion and the production of syncytia at low pH. The fusogenic properties of the VSV G protein expressed on the surface of insect cells was prevented using anti-VSV sera, or by elevating the pH above 6.2. A reduction of the pH to 5.5, or 5.0, accelerated the rate of syncytia formation.
The bluetongue virus core particles have been shown to contain an RNA-directed RNA polymerase (1). To identify the protein responsible for the virion RNA polymerase activity, the complete 3.9 Kb DNA clone representing the largest RNA segment 1 (L1) of bluetongue virus (BTV-10) was placed under control of the polyhedrin promoter of Autographa californica nuclear polyhedrosis virus (AcNPV). The derived recombinant virus was used to infect Spodoptera frugiperda cells. As demonstrated by stained polyacrylamide gel electrophoresis and by the use of bluetongue virus antibody, infected insect cells synthesized the largest protein of BTV-10 (VP1, 150 k Da). Antibody raised in rabbit to recombinant VP1 protein recognized bluetongue virus VP1 protein. The recombinant virus infected cell lysate had significantly inducible levels of RNA polymerase enzymatic activity as determined by a poly (U)-oligo (A) polymerase assay. The availability of enzymatically active bluetongue virus RNA polymerase provides a system in which we can precisely delineate the role this protein plays in the regulation of bluetongue replication.
Explore the source record for details and available documents.
Nodamura virus multiplied in mosquito cell lines, as determined by infectivivity assays in adult honey bees (Apis mellifera) and wax moth larvae (Galleria mellonella). Titres of more than 10-7 and 10-5 bee LD50 /ml were obtained in culture fluids of Aedes albopictus and Aedes aegypti cells respectively after 10 days. Comparable titres were obtained after several months, during which the cultures were subdivided up to six times. Nodamura virus also multiplied in BHK cells and yielded titres of 10-4-8 to 10-6-6 mouse LD50/ml and 10-5-1 to 10-7-1 wax moth LD50/ml in culture fluid 1 to 4 days after infection. No c.p.e. was observed in infected cells.
Explore the source record for details and available documents.
The toxic effect of insect iridescent virus type 6 - chilo iridescent virus - (CIV) was investigated using Balb/c mice (strain ByJ Ico and Kisslegg). The animals were inoculated with CIV intraperitoneally (1 X 10(9) to 9.2 X 10(11) TCID50/animal). The animals which were administered with 1 X 10(11) to 9 X 10(11) TCID50 of CIV per animal, developed acute clinical illness and died during 18 to 80 h post infection. Histopathological and electronmicroscopic examinations of the liver tissues of those animals which died and/or were sacrificed when moribund showed acute degenerative hepatitis leading to death. No evidence for viral replication was found in the liver cells affected. A mortality rate between 21.1% and 100% was recorded for CIV, depending on the strain and number of mice used and the dose of virus administered. The toxic effect of CIV was eliminated or reduced extensively using heat denaturation or treatment of CIV with sodium dodecylsulphate or proteinase K. This indicates that the nature of the factor causing toxic degenerative cell damage is a protein.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
The DNA of the granulosis virus of the Indian meal moth, Plodia interpunctella, was characterized by physical chemical and electron microscopic techniques. Twenty-five percent of the DNA extracted from purified virus was isolated as supercoiled circular molecules. The remaining 75% consisted of relaxed circular molecules. These molecular forms were indicated by the production of two radioactive bands during sedimentation of (3)H-labeled granulosis virus DNA in alkaline sucrose gradients or in equilibrium density gradients of neutral cesium chloride/propidium iodide. Electron microscopic visualization of the DNA that banded at the higher density in the latter gradients revealed supercoiled structures whereas that of DNA that banded at the lower density demonstrated relaxed circular molecules. The superhelical molecules were converted to relaxed circles by treatment with pancreatic DNase. The molecular weight of the viral DNA was calculated to be 81 x 10(6) by sedimentation in neutral sucrose and 78 x 10(6) by sedimentation in alkaline sucrose. The molecular weight estimated from length measurements in electron micrographs was 76 x 10(6). The buoyant density of the granulosis virus DNA was 1.703 g/cm(3) and that of its insect host DNA was 1.697 g/cm(3). Equilibrium sedimentation in cesium chloride and thermal denaturation indicated G + C contents of 44% and 39% for the viral and host DNA, respectively.
The sequences of 50 RNA-dependent RNA polymerases (RDRPs) from 43 positive strand and 7 double strand RNA (dsRNA) viruses have been compared. The alignment permitted calculation of distances among the 50 viruses and a resultant dendrogram based on every amino acid, rather than just those amino acids in the conserved motifs. Remarkably, a large subgroup of these viruses, including vertebrate, plant, and insect viruses, forms a single cluster whose only common characteristic is exploitation of insect hosts or vectors. This similarity may be due to molecular constraints associated with a present and/or past ability to infect insects and/or to common descent from insect viruses. If common descent is important, as it appears to be, all the positive strand RNA viruses of eucaryotes except for the picornaviruses may have evolved from an ancestral dsRNA virus. Viral RDRPs appear to be inherited as modules rather than as portions of single RNA segments, implying that RNA recombination has played an important role in their dissemination.
Expression of the murine leukaemia virus (MLV) major Gag antigen p65(Gag) using the baculovirus expression system leads to efficient assembly and release of virus-like particles (VLP) representative of immature MLV. Expression of p180(Gag-Pol), facilitated normally in mammalian cells by readthrough of the p65(Gag) termination codon, also occurs efficiently in insect cells to provide a source of the MLV protease and a pattern of p65(Gag) processing similar to that observed in mammalian cells. VLP release from p180(Gag-Pol)-expressing cells however remains essentially immature with disproportionate levels of the uncleaved p65(Gag) precursor when compared to the intracellular Gag profile. Changing the p65(Gag) termination codon altered the level of p65(Gag) and p180(Gag-Pol) within expressing cells but did not alter the pattern of released VLP, which remained immature. Coexpression of p65(Gag) with a fixed readthrough p180(Gag-Pol) also led to only immature VLP release despite high intracellular protease levels. Our data suggest a mechanism that preferentially selects uncleaved p65(Gag) for the assembly of MLV in this heterologous expression system and implies that, in addition to their relative levels, active sorting of the correct p65(Gag) and p180(Gag-Pol) ratios may occur in producer cells.