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PubMed2003

Isolation and characterisation of the rabies virus N degrees-P complex produced in insect cells.

When the nucleoprotein (N) of nonsegmented negative-strand RNA viruses is expressed in insect cells, it binds to cellular RNA and forms N-RNA complexes just like viral nucleocapsids. However, in virus-infected cells, N is prevented from binding to cellular RNA because a soluble complex is formed between N and the viral phosphoprotein (P), the N degrees -P complex. N is only released from this complex for binding to newly made viral or complementary RNA. We coexpressed rabies virus N and P proteins in insect cells and purified the N degrees -P complex. Characterisation by gel filtration, polyacrylamide gel electrophoresis, analytical ultracentrifugation, native mass spectroscopy, and electron microscopy showed that the complex consists of one N protein plus two P proteins, i.e., an N degrees -P(2) complex.

Animals↗
PubMed1976

Strain selection during serial passage of Trichoplusia in nuclear polyhedrosis virus.

Two strains of a nuclear polyhedrosis virus (NPV) of Trichoplusia ni were isolated on the basis of plaque morphology. They are designated as MP (having greater than 30 polyhedra per nucleus) and FP (having fewer than 10 polyhedra per nucleus). Serial, undiluted passage of plaque, purified MP nonoccluded. Virus (NOV) in tissue culture led to the production of the FP phenotype detectable at passage 9. With continued serial, undiluted passage, FP became the predominant strain. Comparative growth curves showed that FP NOV are released faster than MP NOV. MP morphology was not observed after 14 serial, undiluted passages of plaque-purified FP. By the plaque neutralization assay, NOV from both strains of virus was neutralized by the homologus and heterologous antisera. The FP phenotype was observed when FP virus was grown in culture at 17, 22, and 27 C. Hence, the FP phenotype was not considered to be the result of temperature-inhibited crystallization of polyhedrin under standard tissue culture conditions. The NOV of both strains killed insects when injected directly into the hemocoele of T. ni larvae. Only MP inclusion bodies were virulent per os. The FP inclusion bodies fed to cabbage looper larvae did not kill, and no infectious agent could be detected in the hemolymph. Electron micrographs of MP polyhedra showed bundles of nucleocapsids of normal length within the polyhedra, whereas FP polyhedra contained heterogeneous, electron-dense material, which could account for their lack of pathogenicity.

Animals↗
PubMed1989

Expression and purification of biologically active v-sis/platelet-derived growth factor B protein by using a baculovirus vector system.

Malignant transformation induced by simian sarcoma virus is mediated by its v-sis protein, the monkey homolog of the platelet-derived growth factor (PDGF) B chain. By use of an appropriately engineered baculovirus expression vector, the v-sis protein was expressed in the insect cell line Spodoptera frugiperda (Sf9) at a level 50- to 100-fold higher than that observed with overexpression in mammalian-cell transfectants. The sis protein produced by Sf9 cells underwent processing similar to that observed in mammalian cells, including efficient disulfide-linked dimer formation. Moreover, the recombinant sis protein was capable of binding PDGF receptors and inducing DNA synthesis as efficiently as PDGF-B synthesized by mammalian cells. A significant fraction of sis protein was released from Sf9 cells, which made possible a one-step immunoaffinity purification to near homogeneity with a 40% recovery of biological activity. These results demonstrate that a protein whose normal processing requires both intrachain and interchain disulfide-bridge formation can be efficiently expressed in a biologically active form in insect cells by using a baculovirus vector system.

Amino Acid Sequence↗
PubMed2003

Flock house virus replicates and expresses green fluorescent protein in mosquitoes.

Flock house virus (FHV) is a non-enveloped, positive-sense RNA virus of insect origin that belongs to the family Nodaviridae. FHV has been shown to overcome the kingdom barrier and to replicate in plants, insects, yeast and mammalian cells. Although of insect origin, FHV has not previously been shown to replicate in mosquitoes. We have tested FHV replication in vitro in C6/36 cells (derived from neonatal Aedes albopictus) and in vivo in four different genera of mosquitoes, Aedes, Culex, Anopheles and Armigeres. FHV replicated to high titres in C6/36 cells that had been subcloned to support maximum growth of FHV. When adult mosquitoes were orally fed or injected with the virus, FHV antigen was detected in various tissues and infectious virus was recovered. Vectors developed from an infectious cDNA clone of a defective-interfering RNA, derived from FHV genomic RNA2, expressed green fluorescent protein in Drosophila cells and adult mosquitoes. This demonstrates the potential of FHV-based vectors for expression of foreign genes in mosquitoes and possibly other insects.

Aedes↗
PubMed1988

Isolation of "exotic" Bhanja virus (Bunyaviridae) from ticks in the temperate zone.

One strain of Bhanja virus was isolated from Dermacentor marginatus male ticks collected from sheep in Slovak Karst, eastern Czechoslovakia (48 degrees 31'N, 20 degrees 28'E). In addition, three strains of Brezová virus (subtype of Tribec orbivirus, Reoviridae) were isolated from Ixodes ricinus ticks. The result represents the northernmost isolation of Bhanja virus and, moreover, its first recovery from D. marginatus in Europe. Cross-neutralization plaque reduction test revealed antigenic similarity of the Czechoslovak strain to the south-European isolates of Bhanja virus, but a more distant relationship to virus strains isolated in Africa and Asia.

Animals↗
PubMed2006

Horizontal and vertical transmission of viruses in the honey bee, Apis mellifera.

The most crucial stage in the dynamics of virus infections is the mode of virus transmission. In general, transmission of viruses can occur through two pathways: horizontal and vertical transmission. In horizontal transmission, viruses are transmitted among individuals of the same generation, while vertical transmission occurs from mothers to their offspring. Because of its highly organized social structure and crowded population density, the honey bee colony represents a risky environment for the spread of disease infection. Like other plant and animal viruses, bee viruses use different survival strategies, including utilization of both horizontal and vertical routes, to transmit and maintain levels in a host population. In this review, we explore the current knowledge about the honey bee viruses and transmission routes of bee viruses. In addition, different transmission strategies on the persistence and dynamics of host-pathogen interactions are also discussed.

Animals↗
PubMed1986

Molecular analysis of Campoletis sonorensis virus DNA in the lepidopteran host Heliothis virescens.

Nucleic acid hybridization techniques were used to analyse the fate of Campoletis sonorensis virus (CsV) DNAs in naturally parasitized and virus-injected Heliothis virescens larvae. Viral DNA persisted in injected H. virescens larvae from 0 to 10 days post-injection but no increase in the amount of viral DNA could be detected. Similarly, no increase in the amount of viral DNA was detected in naturally parasitized H. virescens larvae before the development of the C. sonorensis pupae. However, a dramatic increase of viral DNA was detected in pharate and newly emerged (0 to 48 h) adult C. sonorensis wasps. The results from these in vivo molecular analyses suggest that CsV replication does not occur in naturally parasitized or virus-injected H. virescens and that viral replication may be restricted to tissues of C. sonorensis wasps.

DNA Replication↗
PubMed1977

Polyamines contained by two densonucleosis viruses.

Densonucleosis viruses 1 and 2 both contain the three polyamines putrescine, spermidine, and spermine in complete virus particles but not in their respective top components. The polyamines, with spermidine predominant, comprise 1.41% of the virus particle by weight, which is sufficient to neutralize 26% of the single-stranded DNA contained within the particles.

Animals↗
PubMed1988

Molecular cloning and characterization of cytoplasmic polyhedrosis virus polyhedrin and a viable deletion mutant gene.

The double-stranded RNA genome of Bombyx mori cytoplasmic polyhedrosis virus (CPV) was converted to double-stranded DNA and cloned into plasmid pBR322. The complete nucleotide sequence of cloned genome segment 10, which encodes virus polyhedrin polypeptide, was determined. The CPV polyhedrin gene consists of 942 based pairs and possesses a long open reading frame that codes for a polypeptide of 248 amino acids (molecular weight, 28,500), consistent with an apparent molecular weight of 28,000 previously determined for purified polyhedrin. No sequence homology was found between CPV polyhedrin and polyhedrins from several nuclear polyhedrosis viruses. In addition to the polyhedrin gene, we completed the sequence analysis of a small deletion mutant gene derived from the polyhedrin gene. This mutant gene consists of two subset domains of the polyhedrin gene, i.e., the 5'-terminal 121 base pairs and the 3'-terminal 200 base pairs. An in vitro transcription demonstrated that the small mutant gene is transcribed by virion-associated RNA polymerases. These data confirm the importance of CPV terminal sequences in virus genome replication.

Amino Acid Sequence↗
PubMed1992

Expression of bovine immunodeficiency-like virus envelope glycoproteins by a recombinant baculovirus in insect cells.

The bovine immunodeficiency-like virus (BIV) env open reading frame (ORF) contains both sequences encoding env and sequences for exon 1 of the putative rev gene. Recombinant baculoviruses incorporating BIV env ORF sequences were constructed to characterize the expression, processing, and immunogenicity of products of the BIV env ORF in insect cells and to develop reagents to study native BIV Env glycoproteins. A recombinant baculovirus containing the entire env ORF synthesized a nonglycosylated, 20-kDa, BIV-specific protein, apparently unrelated to native BIV Env proteins. In contrast, a recombinant baculovirus containing a truncated env ORF in which the coding sequences for rev exon 1 were deleted synthesized three size classes of glycosylated proteins in insect cells related to the BIV Env precursor (gp145), surface (gp100), and transmembrane (gp45) glycoproteins observed in BIV-infected mammalian cells. Oligomers of recombinant BIV Env proteins also formed in these baculovirus-infected insect cells. Immunofluorescence staining of intact insect cells infected by the baculovirus expressing BIV Env with BIV-specific serum demonstrated that the recombinant Env glycoproteins were expressed on the cell surface. Antisera raised to recombinant Env glycoproteins immunoprecipitated native gp145, gp100, and gp45 in BIV-infected bovine cells similar to sera from animals naturally or experimentally infected with BIV.

Animals↗
PubMed1983

Autographa californica nuclear polyhedrosis virus (AcNPV) DNA does not persist in mass cultures of mammalian cells.

Autographa californica nuclear polyhedrosis virus (AcNPV) is one of the most extensively studied baculoviruses. We have investigated whether AcNPV or its DNA can replicate and/or persist in cultures of mammalian cells. Human HeLa cells or primary human embryonic kidney cells, simian CV1 cells, hamster BHK21 (B3) cells or Muntiacus muntjak cells growing in monolayer cultures were used in these studies. Cells were inoculated with AcNPV at multiplicities ranging from 0.1 to 100 PFU/cell. Subsequently, the inoculated cells were investigated for virus production and for the replication and the persistence of viral DNA. Extracts of inoculated cells were also screened for the occurrence of AcNPV-specific RNA. AcNPV does not multiply in any of the cell lines studied. Viral DNA replication or transcription could not be detected by blotting and nucleic acid hybridization experiments using nick-translated, cloned viral probes. Furthermore, there was no evidence for the persistence of viral DNA or of fragments of viral DNA in mass cultures of mammalian cells. A puzzling homology between pBR322 plasmid DNA and human, simian, and hamster DNAs was detected. Since mammalian cells can take up and integrate any foreign DNA at very low frequency, it cannot be ruled out by the approach chosen that a very small number of cells might have incorporated and fixed viral DNA in their genomes. As this caveat is always pertinent for any population of cells exposed to foreign DNA, this reservation does not appear to be of particular significance in safety considerations when working with baculoviruses or any virus for that matter.

Animals↗
PubMed1989

Location and nucleotide sequence of the 25K protein missing from baculovirus few polyhedra (FP) mutants.

Wild-type and few polyhedra (FP) mutants of the baculovirus Autographa californica nuclear polyhedrosis virus (AcMNPV) were studied to identify and sequence the gene encoding the 25-kDa (25K) protein normally present in AcMNPV-infected Spodoptera frugiperda cells but which is often missing from FP mutant-infected cells. Our previous study had mapped two overlapping late transcripts to the insertion site of host cell DNA within the HindIII-I fragment (33.8 to 37.7 map units) of wild-type AcMNPV. An FP mutant, AcFP875-2, had a 1.6-kbp insertion of S. frugiperda DNA near the 5' end of these transcripts which by S1 analysis were shown to initiate within the host cell sequence. Primer extension analysis revealed that the transcription start for this gene in wild-type virus occurred within a conserved 12-base sequence found near the transcription start sites of several baculovirus late and hyper-expressed genes. A similar 12-base sequence was found at the transcription start site within this 1.6-kbp pair host cell DNA sequence in AcFP875-2. mRNAs from wild-type virus-infected cells were hybridization-selected using a 542-bp SalI subfragment of the 3.2-kbp EcoRI-HindIII fragment (35.0 to 37.7 map units). These mRNAs directed the synthesis of a 25K protein which in size was identical to the 25K protein in wild-type virus-infected cells and the translation product of a 1.15-kb cRNA transcribed from a RsaI fragment (36.4 to 37.4 map units). Comparison of gel band patterns following partial proteolysis of the translation product of the 1.15 cRNA and the 25K protein from wild-type virus-infected cells revealed that the two proteins were closely related if not identical. Nucleotide sequence analysis within this EcoRI-HindIII fragment revealed an open reading frame which encodes a 25K protein. Insertion of the Escherichia coli lacZ gene encoding the beta-galactosidase enzyme into the transcribed portion of this EcoRI-HindIII fragment yielded a recombinant virus which lacked a 25K protein and exhibited an altered (FP) plaque phenotype.

Animals↗