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Bruce A. Webb - One of the best experts on this subject based on the ideXlab platform.
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Shared and species-specific features among ichnovirus genomes
Virology, 2007Co-Authors: Kohjiro Tanaka, Andrea Makkay, Don Stoltz, Michel Cusson, Walter E. Barney, Renée Lapointe, Bruce A. WebbAbstract:Abstract During egg-laying, some endoparasitic wasps transmit a Polydnavirus to their caterpillar host, causing physiological disturbances that benefit the wasp larva. Members of the two recognized Polydnavirus taxa, ichnovirus (IV) and bracovirus (BV), have large, segmented, dsDNA genomes containing virulence genes expanded into families. A recent comparison of IV and BV genomes revealed taxon-specific features, but the IV database consisted primarily of the genome sequence of a single species, the Campoletis sonorensis IV (CsIV). Here we describe analyses of two additional IV genomes, the Hyposoter fugitivus IV (HfIV) and the Tranosema rostrale IV (TrIV), which we compare to the sequence previously reported for CsIV. The three IV genomes share several features including a low coding density, a strong A + T bias, similar estimated aggregate genome sizes (∼ 250 kb) and the presence of nested genome segments. In addition, all three IV genomes contain members of six conserved gene families: repeat element, cysteine motif, viral innexin, viral ankyrin, N-family, and a newly defined putative family, the polar-residue-rich proteins. The three genomes, however, differ in their degree of segmentation, in within-family gene frequency and in the presence, in TrIV, of a unique gene family ( TrV ). These interspecific variations may reflect differences in parasite/host biology, including virus-induced pathologies in the latter.
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response of immunocompetent and immunosuppressed spodoptera littoralis larvae to baculovirus infection
Journal of General Virology, 2006Co-Authors: Hadassah Rivkin, Bruce A. Webb, Jeremy A Kroemer, Alexander Bronshtein, Eduard Belausov, Nor ChejanovskyAbstract:The Mediterranean lepidopteran pest Spodoptera littoralis is highly resistant to infection with the Autographa californica multiple nucleopolyhedrovirus (AcMNPV) via the oral route, but highly sensitive to infection with budded virus (BV) via the intrahaemocoelic route. To study the fate of AcMNPV infection in S. littoralis, vHSGFP, an AcMNPV recombinant that expresses the reporter green fluorescent protein gene under the control of the Drosophila heat-shock promoter, and high-resolution fluorescence microscopy were utilized. S. littoralis fourth-instar larvae infected orally with vHSGFP showed melanization and encapsulation of virus-infected tracheoblast cells serving the midgut columnar cells. At 72 h post-infection, the viral foci were removed during the moult clearing the infection. Thus, oral infection was restricted by immune responses to the midgut and midgut-associated tracheal cells. By contrast, injection of BV into the haemocoel resulted in successful infection of tracheoblasts, followed by spread of the virus through the tracheal epidermis to other tissues. However, in contrast to fully permissive infections where tracheoblasts and haemocytes are equally susceptible to infection, a severe limitation to vHSGFP infection of haemocytes was observed. To investigate the resistance of S. littoralis haemocytes to BV infection with AcMNPV, the larval immune system was suppressed with the Chelonus inanitus Polydnavirus or a putatively immunosuppressive Polydnavirus gene, P-vank-1. Both treatments increased the susceptibility of S. littoralis larvae to AcMNPV. It is concluded that the resistance of S. littoralis to AcMNPV infection involves both humoral and cellular immune responses that act at the gut and haemocyte levels. The results also support the hypothesis that tracheolar cells mediate establishment of systemic baculovirus infections in lepidopteran larvae. The finding that Polydnaviruses and their encoded genes synergize baculovirus infection also provides an approach to dissecting the responses of the lepidopteran immune system to viruses by using specific Polydnavirus immunosuppressive genes.
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Polydnavirus genes and genomes: emerging gene families and new insights into Polydnavirus replication.
Annual review of entomology, 2004Co-Authors: Jeremy A Kroemer, Bruce A. WebbAbstract:Polydnavirus genome sequencing is providing new insights into viral genome organization and viral gene function. Sequence analyses demonstrate that the genomes of these viral mutualists are largely noncoding but maintain genes and gene families that are unrelated to other viral genes. Interestingly, these organizational patterns in Polydnavirus genomes are evident in both the bracovirus and ichnovirus genera, even though these two genera are evolutionarily unrelated. The identity and function of some Polydnavirus gene families are considered with some functions experimentally supported and others implied by homology relationships with known insect genes. The evidence relative to Polydnavirus origins and evolution is considered but remains an area of speculation. However, sequencing of these viral genomes has been informative and provides opportunities for productive investigation of these unusual mutualistic insect viruses.
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A teratocyte gene from a parasitic wasp that is associated with inhibition of insect growth and development inhibits host protein synthesis
Insect molecular biology, 2003Co-Authors: Douglas L. Dahlman, R. L. Rana, E. J. Schepers, T. Schepers, F. A. Diluna, Bruce A. WebbAbstract:After parasitization, some wasps induce hosts prematurely to initiate metamorphic development that is then suspended in a postwandering, prepupal state. Following egression of the parasite larva, the host remains in this developmentally arrested state until death. Teratocytes, cells released at egg hatch from extra-embryonic serosal membranes of some wasp parasites, inhibit growth and development when injected into host larvae independent of other parasite factors (e.g. venom, Polydnavirus). Synthesis of some developmentally regulated, abundantly expressed Heliothis virescens host proteins is inhibited in hosts parasitized by Microplitis croceipes and by teratocyte injection. A cDNA encoding a 13.9 kDa protein (TSP14) that inhibited protein synthesis, growth and development was isolated from a protein fraction secreted by teratocytes. TSP14 appears to be responsible, in part, for the teratocyte-mediated inhibition of host growth and development. Interestingly, this cDNA encoded a cysteine-rich amino acid motif similar to that described from Campoletis sonorensis Polydnavirus, a mutualistic virus that enables wasp parasitization of lepidopteran larvae. Moreover, TSP14 inhibited protein synthesis in a dose-dependent manner in rabbit reticulocyte lysate and wheat germ extract translation systems. We hypothesize that some wasp parasites inhibit translation as a general means to regulate and redirect lepidopteran host physiology to support endoparasite development.
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Perspectives on Polydnavirus origins and evolution
Advances in virus research, 2002Co-Authors: Matthew W Turnbull, Bruce A. WebbAbstract:Publisher Summary This chapter discusses the origin and evolution of Polydnavirus (PDV) that exists in obligate mutualisms with some parasitic Hymenoptera. A given PDV species replicates only in a single wasp species, and all members of that wasp species carry the associated virus. Two genera of PDVs are recognized––the bracoviruses (BVs) and the ichnoviruses (IVs)–– associated with braconid and ichneumonid wasps, respectively. The PDV genera have similar genome organization and replication/transmission pathways but have no known genetic similarity. Viral gene expression in insects parasitized by PDV-carrying wasps causes physiological alterations that are essential for parasitoid survival and development. PDV life cycles have been described as having “two arms.” PDVs replicate from proviral DNA in specialized cells of the wasp oviduct. Virus replication is first detected in the late pupal stage with virus released from calyx cells by budding or cell lysis and accumulating to high concentrations in the oviduct lumen. PDVs provide an interesting system for viral evolutionary studies. The unique life cycle involves coevolution with two hosts––one mutualistic and one pathogenic––thus, imposing both reductive and diversifying selection pressures on viral genes.
B Lanzrein - One of the best experts on this subject based on the ideXlab platform.
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Changes in the haemolymph proteome of Spodoptera littoralis induced by the parasitoid Chelonus inanitus or its Polydnavirus and physiological implications
Journal of insect physiology, 2005Co-Authors: Martha Kaeslin, Rita Pfister-wilhelm, Daniel Molina, B LanzreinAbstract:The egg-larval parasitoid Chelonus inanitus induces in its host Spodoptera littoralis two major developmental effects, namely a precocious onset of metamorphosis followed by a developmental arrest in the prepupal stage. Along with each egg, the wasp injects Polydnavirus and venom into the host egg. The Polydnavirus has been shown to play a major role in inducing the developmental arrest while the parasitoid larva is instrumental in inducing the precocious onset of metamorphosis. Here we report that experimental dilution of haemolymph of Polydnavirus-containing larvae can partially prevent the developmental arrest while injection of native, but not of heat-treated, haemolymph or plasma from Polydnavirus-containing larvae into nonparasitized larvae could induce developmental arrest in 14-15% of the larvae. This illustrates that heat-labile factors present in haemolymph play a role in causing developmental arrest. Injection of parasitoid medium increased the proportion of larvae entering metamorphosis precociously while injection of antibodies against a parasitoid-released protein had the opposite effect; this indicates that this protein and possibly other parasitoid-released substances are involved in inducing the precocious onset of metamorphosis. Analysis of the plasma proteome of nonparasitized, parasitized and Polydnavirus-containing larvae revealed that the developmental effects are associated with only minor differences: eleven low abundant viral or virus-induced proteins and five parasitoid-released proteins were seen at specific stages of the host.
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Cloning, characterization and analysis by RNA interference of various genes of the Chelonus inanitus Polydnavirus.
Journal of General Virology, 2005Co-Authors: Marianne Bonvin, Marc Annaheim, Dorothee Marti, Stefan Wyder, Dejan Kojic, B LanzreinAbstract:Successful parasitism of some endoparasitic wasps depends on an obligately symbiotic association with Polydnaviruses. These unique viruses have a segmented genome consisting of circles of double-stranded (ds) DNA and do not replicate in the parasitized host. They are produced in the wasp's ovary and injected into the host along with the egg. Chelonus inanitus is an egg–larval parasitoid; its Polydnavirus (CiV) has been shown to protect the parasitoid larva from the host's immune system and to induce developmental arrest in the prepupal stage. The genome of CiV consists of at least 10–12 segments and five have been sequenced up to now. Here, the complete (CiV12g2) or partial (CiV12g1, CiV16.8g1) cloning of three new CiV genes is reported. All three occur only on one viral segment and have no similarity to other known Polydnavirus genes, with the exception of a high similarity of CiV12g1 to CiV14g1 and CiV12g2 to CiV14g2. Furthermore, the first attempt of in vivo application of RNA interference to study the function of Polydnavirus genes is shown. Injection of dsRNA of two late- and one early- and late-expressed CiV genes into CiV/venom-containing host eggs partially rescued last-instar larvae from developmental arrest. Injection of the same dsRNAs into parasitized eggs partially reduced parasitoid survival, mainly by preventing the successful emergence of the parasitoid from the host. These viral genes thus seem to be involved in inducing developmental arrest and in keeping the cuticle soft, which appears to be necessary for parasitoid emergence and host feeding.
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Stage-dependent expression of Chelonus inanitus Polydnavirus genes in the host and the parasitoid
Journal of insect physiology, 2004Co-Authors: Marianne Bonvin, Martha Kaeslin, Marc Annaheim, Stefan Wyder, Dejan Kojic, Fabian Blank, Irene Wehrle, B LanzreinAbstract:Abstract Chelonus inanitus (Braconidae) is a solitary egg–larval parasitoid of Spodoptera littoralis (Noctuidae). Along with the egg it also injects Polydnaviruses (CiV) and venom, which are prerequisites for successful parasitoid development. CiV protects the parasitoid from encapsulation by the host's immune system and induces a developmental arrest in the prepupal stage. The Polydnavirus genome consists of several double-stranded circular DNA segments. Proviral DNA is integrated in the wasp's genome and virus replication is restricted to the wasp's ovary. Here, the analysis of eight CiV genes located on five different segments revealed four patterns of expression in the course of parasitization: early, late, persistent but variable, and early and late. The comparison between parasitized and CiV/venom only containing hosts indicated that the presence of the parasitoid larva modulates transcript levels. Haemocytes, fat body and nervous tissue contained viral transcripts, values being highest in haemocytes. Small amounts of CiV transcripts were also observed in parasitoid larvae and pupae, suggesting transcription from the proviral integrated form of viral DNA. This is the first comparative analysis of the expression patterns of several viral genes in both parasitized and CiV/venom only containing hosts over the entire period of parasitization, and it reveals intricate interactions between the parasitoid, the Polydnavirus and the host.
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Characterization of two genes of the Polydnavirus of Chelonus inanitus and their stage-specific expression in the host Spodoptera littoralis.
Journal of General Virology, 2002Co-Authors: Andrea Johner, B LanzreinAbstract:Chelonus inanitus (Braconidae, Hymenoptera) is a solitary egg-larval parasitoid of Spodoptera littoralis. Along with the egg the female wasp injects Polydnaviruses, which are prerequisites for successful parasitoid development. The Polydnavirus genome is segmented and consists of double-stranded circular DNA. Proviral DNA is integrated in the wasp’s genome; virus replication is restricted to the wasp’s ovary and does not occur in the parasitized host. The Polydnavirus of C. inanitus (CiV) protects the parasitoid larva from encapsulation by the host’s immune system and causes a developmental arrest of the host in the prepupal stage. Here we report on the first two cloned CiV genes, which are named CiV14g1 and CiV14g2 because of their localization on segment CiV14. The cDNA of CiV14g1 has a size of 2036 bp; the gene contains seven exons interrupted by six introns of similar size and encodes a putative polypeptide of 548 amino acids. The cDNA of CiV14g2 has a size of 618 bp; the gene consists of three exons and encodes a putative peptide of 77 amino acids. Transcript quantities of both genes are very low up to the penultimate larval instar of the host. In the last instar, at the stage of pupal cell formation, CiV14g1 expression increases about 5-fold and CiV14g2 expression about a 1000-fold. These are the first data to show strong upregulation of Polydnavirus genes towards the end of parasitization. These two genes might be involved in the reduction of host ecdysteroids observed at this stage.
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overview of parasitism associated effects on host haemocytes in larval parasitoids and comparison with effects of the egg larval parasitoid chelonus inanitus on its host spodoptera littoralis
Journal of Insect Physiology, 1998Co-Authors: Peter Stettler, Rita Pfisterwilhelm, Tina Trenczek, Toni Wyler, B LanzreinAbstract:In the first part we review the effects of larval endoparasitoids and their Polydnavirus and venom on the immune system of their hosts. In all systems investigated, haemocyte spreading and encapsulation activity was reduced; in some cases effects on total (THC) or differential (DHC) haemocyte count as well as modification of haemocyte morphology and ultrastructure were also documented. In many cases Polydnavirus (and venom) were shown to play a major role in abrogation of the host's immune reaction. In the second part we present the first investigation of effects of parasitism and Polydnavirus/venom on the immune system of the host for an egg-larval parasitoid, Chelonus inanitus. We observed that in 4th and 5th instar larvae, i.e. 7 to 10 days after parasitization, neither haemocyte spreading and encapsulation activity, nor DHC, nor haemocyte ultrastructure were altered. After parasitization with X-ray irradiated wasps, which inject Polydnavirus and venom and infertile eggs, there was no alteration of the above mentioned parameters. Nevertheless, parasitoid larvae implanted into 4th instar larvae which developed from eggs parasitized with X-ray irradiated wasps were not encapsulated, whereas co-injected latex beads were. These results show that parasitism by this egg-larval parasitoid does not generally suppress the host's immune system but that Polydnavirus/venom injected at oviposition prevent, by, as yet unknown mechanisms, encapsulation of the parasitoid larva.
Michael R Strand - One of the best experts on this subject based on the ideXlab platform.
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Polydnavirus Gene Products that Interact with the Host Immune System
Parasitoid Viruses, 2012Co-Authors: Michael R StrandAbstract:Publisher Summary This chapter discusses the Polydnavirus gene products that interact with the host immune system. The Polydnaviridae is divided into the genus bracovirus (BV), which is associated with wasps in seven subfamilies of the Braconidae and the genus ichnovirus (IV), which is associated with wasps in two subfamilies of the Ichneumonidae. Strict vertical transmission as proviruses results in each wasp species carrying a genetically unique Polydnavirus (PDV) isolate. Most PDV-carrying wasps also parasitize only one or a small number of host species, which are primarily larval or egg stage Lepidoptera. All PDV-carrying wasps inject the encapsidated form of their virus into host insects when they oviposit. Virions rapidly infect different host tissues and within 1–2 h begin expressing viral gene products. PDVs do not replicate in the wasp's host but a number of the genes they express are implicated in causing physiological alterations of benefit to developing offspring. Among the most important of these alterations is preventing the host's immune system from killing wasp eggs and larvae.
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A limited role in parasitism for Microplitis demolitor Polydnavirus.
Journal of insect physiology, 1998Co-Authors: Dominique Trudeau, Michael R. Strand, Michael R StrandAbstract:Spodoptera frugiperda larvae stung by Microplitis demolitor undergo physiological alterations characteristic of parasitism. However, despite these physiological modifications, parasitized S. frugiperda larvae never yield adult wasps. Our original hypothesis that unsuccessful parasitism was due to a transcriptionally inactive Polydnavirus proved untrue. Microplitis demolitor Polydnavirus (MdPDV) successfully infected and expressed, albeit transiently, in S. frugiperda hemocytes. MdPDV expression was most abundant in the first three days of parasitism, then sharply declined on Day 4 post-parasitization and continued to decline for the remainder of the study. During the period of MdPDV expression, S. frugiperda hemocytes were non-adherent, incapable of spreading in vitro and did not encapsulate M. demolitor eggs in vivo. Concurrent with diminishing viral expresssion, S. frugiperda hemocytes regained their ability to adhere and spread in vitro and encapsulated M. demolitor eggs in vivo. Although MdPDV disrupted S. frugiperda's encapsulation response for the first three days post-parasitization, M. demolitor was unable to develop in this noctuid species. Failure to develop was independant of viral activity, all M. demolitor eggs oviposited in S. frugiperda larvae failed to complete embryogenesis and died within 24 hour of oviposition. S. frugiperda larvae infected with MdPDV exhibited alterations in development very similar to other lepidopterans that are permissive hosts for M. demolitor. In addition, MdPDV DNA persisted in Spodoptera frugiperda hemocytes in the absence of viral expression.
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two microplitis demolitor Polydnavirus mrnas expressed in hemocytes of pseudoplusia includens contain a common cysteine rich domain
Journal of Virology, 1997Co-Authors: Michael R Strand, R A Witherell, Michael R Strand, D. TrudeauAbstract:Microplitis demolitor is a Polydnavirus-carrying wasp that parasitizes the larval stage of Pseudoplusia includens. A previous study indicated that M. demolitor Polydnavirus (MdPDV) infects primarily hemocytes in parasitized hosts. Thereafter, several alterations that compromise the immune response of P. includens toward the developing parasitoid occur in hemocytes. In this study, we identified two MdPDV mRNAs (1.0 and 1.5 kb) expressed in P. includens hemocytes that have homology to the viral genomic clone pMd-2. Corresponding 1.0- and 1.5-kb cDNA clones (MdPi455 and MdPi59) were isolated from an MdPDV-infected hemocyte cDNA library. Nucleotide sequence analysis of the cDNA clones confirmed that the 1.5- and 1.0-kb mRNAs have significant regions of homology. Sequence alignment revealed that the gene, OMd1.0, encoding the 1.0-kb mRNA is present in pMd-2. This gene contains two introns and three exons that agree with the sequence for MdPi455. In contrast, the 1.5-kb mRNA is likely encoded by a related gene located on the same MdPDV genomic DNA as is OMd1.0. The predicted peptide sequences for the 1.0- and 1.5-kb transcripts contain a cysteine-rich region at their 5' ends that have some similarity with epidermal growth factor-like motifs. Hybridization studies revealed that both mRNAs are expressed in granular cells and plasmatocytes, the primary classes of hemocytes involved in defense against M. demolitor and other parasites.
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parasitism by microplitis demolitor induces alterations in the juvenile hormone titers and juvenile hormone esterase activity of its host pseudoplusia includens
Journal of Insect Physiology, 1996Co-Authors: B A Dover, Michael R Strand, Meena M Balgopal, Walter G Goodman, Michael R StrandAbstract:Microplitis demolitor is a Polydnavirus-carrying parasitoid that attacks the larval stage of Pseudoplusia includens and other noctuids. Parasitism or injection of wasp components like Polydnavirus and teratocytes has a juvenilizing effect on P. includens development. Here we measured hemolymph juvenile hormone (JH) titers and juvenile hormone esterase activity in P. includens larvae after parasitism or injection of wasp components. Results were compared to nonparasitized larvae. During the fifth stadium, JH titers of nonparasitized larvae fluctuated between 0.08 and 0.50 ng/ml, whereas titers in parasitized larvae never fell below 2 ng/ml. P. includens larvae injected with calyx fluid plus venom or calyx fluid plus venom and teratocytes exhibited JH titers intermediate between parasitized and nonparasitized larvae. Nonparasitized larvae exhibited two peaks of JH esterase activity. The first occurred between 12 and 48 h in association with cessation of larval feeding, while the second occurred immediately before pupation. In contrast, levels of JH metabolism remained at low levels in parasitized larvae and larvae injected with calyx fluid plus venom or calyx fluid, venom and teratocytes. Only trace amounts of JH were detected in in vitro assays of teratocytes or M. demolitor larvae suggesting neither released JH into the hemolymph of parasitized larvae. Although calyx fluid plus venom and teratocytes did not elevate JH titers to the levels measured in parasitized larvae, their effects on formation of larval-pupal intermediates by P. includens were similar to those generated by exogenous application of methoprene or JH.
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CHARACTERIZATION OF MONOCLONAL ANTIBODIES TO HEMOCYTES OF PSEUDOPLUSIA INCLUDENS
Journal of Insect Physiology, 1996Co-Authors: Michael R Strand, Michael R Strand, Jena A. JohnsonAbstract:Abstract A panel of monoclonal antibodies (MAbs) was generated against hemocytes from unparasitized Pseudoplusia includens and P. includens parasitized by the Polydnavirus- carrying parasitoid Microplitis demolitor. Of 862 hybridomas generated, 107 lines secreted antibodies to one or more classes of hemocytes. For the current study, 21 lines were cloned, 11 lines were isotyped and three MAbs were characterized. MAb 48F2D5 specifically labeled granular cells, MAb 52F3A5 labeled plasmatocytes and MAb 55F2G7 only labeled hemocytes inoculated with M. demolitor Polydnavirus (MdPDV). Western blot analysis indicated that each MAb recognized specific antigens when cell proteins were separated on SDS-PAGE gels. Using immunofluorescence microscopy, differences were noted in the proportion of granular cells and plasmatocytes present in parasitized hosts and in the proportion of each cell type labeled by MAb 55F2G7. Double-labeling experiments further suggested that the proportion of granular cells infected by MdPDV declined between 24 h and 7 days post-parasitism while the proportion of infected plasmatocytes did not.
B A Webb - One of the best experts on this subject based on the ideXlab platform.
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promoter analysis of a cysteine rich campoletis sonorensis Polydnavirus gene
Journal of General Virology, 1997Co-Authors: L Cuit, B A WebbAbstract:Promoter activity of the Campoletis sonorensis Polydnavirus (CsPDV) WHv1.6 gene was analysed by transient transfection assays in insect cell culture using constructs expressing the CAT gene. Deletions of the WHv1.6 gene promoter were used to define promoter regions important for expression. Progressive deletion of the regions upstream of the TATA box reduced the promoter activity, whereas deletions eliminating the TATA box abolished promoter activity. Cis-activating elements were detected up to 1 kb upstream of the WHv1.6 transcription initiation site (TIS). Promoter elements increasing transcription were detected between -444 and -550 bp and between -831 and -1035 bp relative to the TIS. Analysis of the 3' flanking sequences of the WHv1.6 gene indicated that the polyadenylation signals were the only important elements affecting expression in the constructs. Comparison of promoter regions of four cysteine-rich CsPDV genes revealed homologous sequences that may be important for transcriptional regulation of Polydnavirus gene expression in parasitized Heliothis virescens larvae.
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Apparent functional role for a cysteine-rich Polydnavirus protein in suppression of the insect cellular immune response.
Journal of virology, 1994Co-Authors: B A WebbAbstract:Polydnaviruses suppress the cellular immune response and inhibit growth and development in their lepidopteran host, allowing survival of their endoparasitic hymenopteran host. Characterization of genes disrupting insect physiological systems is a major objective in the study of Polydnaviruses. Recently, a cysteine-rich gene family encoding a motif composed of invariable cysteine residues flanking hypervariable intercysteine amino acids was described (S.D. Dib-Hajj, B.A. Webb, and M.D. Summers, Proc. Natl. Acad. Sci. USA 90:3765-3769, 1993). They noted similarities to the positive selection pressure for mutations within the vertebrate major histocompatibility complex (MHC) class II genes and speculated that this class of Polydnavirus genes may target and disrupt the insect immune system. To study the functional activity of this family of predicted cysteine-rich proteins, the VHv1.1 gene product was produced from bacterial and baculovirus expression systems. Polyclonal antiserum produced from the bacterial fusion protein reacted with a 30-kDa protein from hemocytes, cell-free plasma, and fat body of parasitized larvae. Immunofluorescence analysis of hemocytes from parasitized insects detected the 30-kDa protein bound to granulocytes and plasmacytes. To assay the functional activity of the 30-kDa VHv1.1 protein, a recombinant baculovirus was constructed allowing in vivo expression of the 30-kDa Polydnavirus protein from infected insects. Expression of the VHv1.1 protein from the baculovirus system reduced the encapsulation response to washed wasp eggs relative to controls. The experimental evidence demonstrates that Campoletis sonorensis Polydnavirus-infected cells secrete VHv1.1 into the hemolymph, where it binds to hemocytes and is associated with the inhibition of the cellular immune response.
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Structure and evolutionary implications of a "cysteine-rich" Campoletis sonorensis Polydnavirus gene family.
Proceedings of the National Academy of Sciences of the United States of America, 1993Co-Authors: S D Dib-hajj, B A Webb, Max D SummersAbstract:For successful parasitization, the female Campoletis sonorensis endoparasitic wasp injects a Polydnavirus into its host, Heliothis virescens, during oviposition. Viral gene expression induces immunosuppression and alters development of the host. We report here that three abundantly expressed genes, VHv1.1, WHv1.0, and WHv1.6, describes a Polydnavirus "cysteine-rich" gene family which may be important in inducing these host manifestations. These genes have a similar primary gene structure and their proteins contain cysteine motifs characteristic of snail ion-channel ligands, the omega-conotoxins. Like the omega-conotoxins, the intercysteine amino acid residues are hypervariable with only three identical amino acids in all motifs. The conservation of this domain in the three viral genes may reflect an important functional role for these viral proteins in the parasitization of H. virescens. The three genes also contain introns similar in sequence at comparable positions in their 5' untranslated leaders and coding sequences. VHv1.1 contains two cysteine motifs, and each motif is interrupted by an intron at the same position as in the cysteine motifs of WHv1.0 and WHv1.6. Intron 2 sequences of WHv1.0 and WHv1.6 are 92% identical, while the immediately flanking exon sequences encoding the cysteine motifs are only 76% identical. This provides an example of nuclear pre-mRNA introns which are more conserved than flanking exons among members of a gene family.
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Stimulation of Polydnavirus replication by 20-hydroxyecdysone
Experientia, 1992Co-Authors: B A Webb, M D SummersAbstract:During oviposition the endoparasitic waspCampoletis sonorensis, introduces a Polydnavirus into parasitized insects where viral gene expression is required for endoparasite survival. The Polydnavirus is integrated into wasp chromosomal DNA and replicates only in the ovary. Ecdysteroids regulate the developmental expression of many insect genes and may regulate Polydnavirus replication. Direct verification of viral replication was performed by dot blot hybridization and by amplifying DNA sequences containing the viral integration site; this ‘junction’ fragment cannot be amplified from integrated virus. Thoracic ligations and in vitro ecdysteroid treatments of wasp ovaries support the hypothesis that Polydnavirus DNA replication is regulated by ecdysteroid during parasite development.
Anne Nathalie Volkoff - One of the best experts on this subject based on the ideXlab platform.
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Les Polydnavirus, un exemple unique de machinerie virale domestiquée par des insectes parasitoïdes.
Virologie (Montrouge France), 2020Co-Authors: Ange Lorenzi, Anne Nathalie VolkoffAbstract:Polydnaviruses are unique mutualistic viruses associated with thousands of parasitoid wasps. They are characterized by a segmented packaged DNA genome and are necessary for parasitic success. Virus particles are produced in the wasp ovaries from a set of "viral" sequences integrated into the wasp genome. The Polydnavirus/wasp associations as observed today result from the integration of a viral genomes into the wasp genome during evolution. Recent years have been marked by the discovery of the viral ancestors of the two known types of Polydnavirus, bracovirus and ichnovirus, which has helped to shed some light on the evolution of the symbiosis. Some of the viral genes have been conserved in the genome of the parasitoid, allowing the latter to produce non-replicative viral particles, that contain DNA molecules encoding essentially "virulence" genes, probably of insect origin. Thus Polydnaviruses can be considered as endogenous viral elements (EVE) that have been domesticated by the wasp to become a "weapon" allowing its survival.
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Les Polydnavirus, un exemple unique de machinerie virale domestiquée par des insectes parasitoïdes.
Virologie, 2020Co-Authors: Ange Lorenzi, Anne Nathalie VolkoffAbstract:Les Polydnavirus illustrent un exemple unique d’interactions symbiotiques entre un virus et un organisme eucaryote. Ces sont des mutualistes obligatoires, associés à de nombreuses espèces d’hyménoptères parasitoïdes. Ils sont caractérisés par un génome encapsidé constitué de plusieurs molécules d’ADN et sont nécessaires à la réussite parasitaire. Les particules virales sont produites dans les ovaires à partir d’un corpus de séquences « virales » intégrées au génome de la guêpe. Les associations Polydnavirus/guêpe telles qu’observées aujourd’hui résultent d’événements d’intégration de génomes viraux dans le génome des guêpes survenus au cours de l’évolution. Ces dernières années ont été marquées par la découverte des ancêtres viraux des deux types de Polydnavirus connus, les Bracovirus et les Ichnovirus, ce qui a permis d’éclairer en partie l’évolution de la symbiose. Une partie des gènes viraux a été conservée dans le génome du parasitoïde, permettant à ce dernier de produire des particules virales non réplicatives, car contenant un génome constitué essentiellement de gènes dits de « virulence », probablement d’origine insecte. Les Polydnavirus peuvent être considérés comme des éléments endogènes viraux (EVE) qui ont été domestiqués par la guêpe pour devenir au fil du temps une « arme » garantissant sa survie.
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Establishment of cell lines from the wasp Hyposoter didymator (Hym., Ichneumonidae) containing the symbiotic Polydnavirus H. didymator ichnovirus.
Journal of General Virology, 2004Co-Authors: Janick Rocher, Marc Ravallec, Anne Nathalie Volkoff, Gérard Devauchelle, P. Barry, Dominique Ray, Martine Duonor-céruttiAbstract:Cell lines derived from Polydnavirus-associated wasps should constitute a valuable tool for investigations of Polydnavirus replication, but none is yet available. In this work, we describe the first cell lines, named Hd-AA, -AD, -BBA and -K, to have been established from the ichneumonid wasp Hyposoter didymator, associated with the Polydnavirus H. didymator ichnovirus (HdIV). Southern blot analysis indicated that the viral DNA was present in all four cell lines and co-localized with high molecular mass DNA, probably the wasp chromosomes. Northern blot analysis of mRNAs extracted from the AA cell line showed transcription of some HdIV-encoded genes, although at low level. The effects of ecdysone treatment, HdIV re-infection and 42 °C heat-shock were analysed in the AA cell line. No effect was detected at the DNA (virus replication) or RNA (gene expression) levels, which may be due to the limitation of the present available tools.
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Establishment of cell lines from the wasp Hyposoter didymator (Hym., Ichneumonidae) containing the symbiotic Polydnavirus H. didymator ichnovirus.
The Journal of general virology, 2004Co-Authors: Janick Rocher, Marc Ravallec, Anne Nathalie Volkoff, Gérard Devauchelle, P. Barry, Dominique Ray, Martine Duonor-céruttiAbstract:Cell lines derived from Polydnavirus-associated wasps should constitute a valuable tool for investigations of Polydnavirus replication, but none is yet available. In this work, we describe the first cell lines, named Hd-AA, -AD, -BBA and -K, to have been established from the ichneumonid wasp Hyposoter didymator, associated with the Polydnavirus H. didymator ichnovirus (HdIV). Southern blot analysis indicated that the viral DNA was present in all four cell lines and co-localized with high molecular mass DNA, probably the wasp chromosomes. Northern blot analysis of mRNAs extracted from the AA cell line showed transcription of some HdIV-encoded genes, although at low level. The effects of ecdysone treatment, HdIV re-infection and 42 degrees C heat-shock were analysed in the AA cell line. No effect was detected at the DNA (virus replication) or RNA (gene expression) levels, which may be due to the limitation of the present available tools.
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The replication of Hyposoter didymator Polydnavirus: Cytopathology of the calyx cells in the parasitoid
Biology of the Cell, 1995Co-Authors: Anne Nathalie Volkoff, Marc Ravallec, Janick Rocher, Jean-pierre Bossy, Pierre Cérutti, Martine Cerutti, Gérard DevauchelleAbstract:In the ichneumonid wasp Hyposoter didymator, a Polydnavirus was detected in the female reproductive tract. With the aim of studying the regulation of Polydnavirus replication, the location and the structure of the virus-producing cells were determined, and the virus replication process was followed inside the ovaries of young adult females observed in light and electron microscopy. The examination of ovaries of pupa females revealed that virus replication is initiated within the calyx just prior to adult emergence. This study revealed that the calyx appears to be a specialized virogenic tissue which also has, during late pupal life, a secretory function that alters the function of virus production.