WOUND-TUMOR VIRUS ANTIGENS IN THE INTERNAL ORGANS OF AN INSECT VECTOR.
Explore the source record for details and available documents.
Animals↗
SEARCH · Search PubMed
Results for “Insect Viruses”
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.
Evolution and phylogeny of insect endogenous retroviruses.
BACKGROUND: The genome of invertebrates is rich in retroelements which are structurally reminiscent of the retroviruses of vertebrates. Those containing three open reading frames (ORFs), including an env-like gene, may well be considered as endogenous retroviruses. Further support to this similarity has been provided by the ability of the env-like gene of DmeGypV (the Gypsy endogenous retrovirus of Drosophila melanogaster) to promote infection of Drosophila cells by a pseudotyped vertebrate retrovirus vector. RESULTS: To gain insights into their evolutionary story, a sample of thirteen insect endogenous retroviruses, which represents the largest sample analysed until now, was studied by computer-assisted comparison of the translated products of their gag, pol and env genes, as well as their LTR structural features. We found that the three phylogenetic trees based respectively on Gag, Pol and Env common motifs are congruent, which suggest a monophyletic origin for these elements. CONCLUSIONS: We showed that most of the insect endogenous retroviruses belong to a major clade group which can be further divided into two main subgroups which also differ by the sequence of their primer binding sites (PBS). We propose to name IERV-K and IERV-S these two major subgroups of Insect Endogenous Retro Viruses (or Insect ERrantiVirus, according to the ICTV nomenclature) which respectively use Lys and Ser tRNAs to prime reverse transcription.
Amino Acid Motifs↗
Generation of replication-competent hepatitis B virus nucleocapsids in insect cells.
The double-stranded DNA genome of human hepatitis B virus (HBV) and related hepadnaviruses is reverse transcribed from a pregenomic RNA by a viral polymerase (Pol) harboring both priming and RNA- and DNA-dependent elongation activities. Although hepadnavirus replication occurs inside viral nucleocapsids, or cores, biochemical systems for analyzing this reaction are currently limited to unencapsidated Pols expressed in heterologous systems. Here, we describe cis and trans classes of replicative HBV cores, produced in the recombinant baculovirus system via coexpression of HBV core and Pol proteins from either a single RNA (i.e., in cis) or two distinct RNAs (in trans). Upon isolation from insect cells, cis and trans cores contained Pol-linked HBV minus-strand DNA with 5' ends mapping to the authentic elongation origin DR1 and also plus-strand DNA species. Only trans cores, however, were highly active for the de novo priming and reverse transcription of authentic HBV minus strands in in vitro endogenous polymerase assays. This reaction strictly required HBV Pol but not the epsilon stem-loop element, although the presence of one epsilon, or better, two epsilons, enhanced minus-strand synthesis up to 10-fold. Compared to unencapsidated Pol enzymes, encapsidated Pol appeared to be (i) highly processive, able to extend minus-strand DNAs of 400 nucleotides from DR1 in vitro, and (ii) more active for HBV plus-strand synthesis. These observations suggest possible contributions to the replication process from the HBV core protein. These novel core reagents should facilitate the analysis of HBV replication in its natural environment, the interior of the capsid, and also fuel the development of new anti-HBV drug screens.
Animals↗
A baculovirus dual expression vector derived from the Autographa californica nuclear polyhedrosis virus polyhedrin and p10 promoters: co-expression of two influenza virus genes in insect cells.
A baculovirus transfer vector, pAcUW3, was developed to facilitate the insertion of two influenza virus genes, those encoding the haemagglutinin (HA) and neuraminidase (NA) membrane glycoproteins, into the Autographa californica nuclear polyhedrosis virus genome in a single cotransfection experiment. The NA gene was inserted in place of the polyhedrin coding sequences under the control of the polyhedrin promoter, whereas the HA gene was placed under the control of a copy of the p10 promoter at a site upstream of and in opposite orientation to the polyhedrin promoter. After infection of Spodoptera frugiperda cells with the recombinant virus, AcUW3HANA, both HA and NA were expressed in the very late phase of infection and were shown to be functional in appropriate assays. Immunofluorescence assays demonstrated their localization at the surface of infected insect cells. The expression of both foreign genes in the recombinant virus was found to be stable for at least 12 passages in cell culture.
Animals↗
Glycoprotein E2 of classical swine fever virus: expression in insect cells and identification as a ribonuclease.
Two regions of amino acids homologous to the ribonuclease catalysis domain of the fungal RNases T2 of Aspergillus oryzae and Rh of Rhizopus niveus and the plant S-glycoproteins of Nicotiana alata are perfectly conserved in the amino acid sequence of the envelope glycoprotein E2 of classical swine fever virus (CSFV). To analyze the functional significance of these conserved sequences, the gene encoding E2 was inserted into the p10 locus of baculovirus and expressed in insect cells. Recombinant virus BacCE2 generated a protein which was similar in size (42 to 46 kDa) to wild-type E2 synthesized in swine kidney cells infected with CSFV. Recombinant E2 was purified by immunoaffinity chromatography from the lysate of cells infected with BacCE2 and assayed for RNase activity. RNase activity coeluted with the E2 fraction, indicating that ribonuclease activity is an inherent property of E2. The ribonuclease-specific activity of the protein fraction containing pure E2 was comparable to that of the N. alata S-glycoproteins.
Amino Acid Sequence↗
The emergence of new plant diseases. The case of insect-transmitted plant viruses.
Explore the source record for details and available documents.
Animals↗
[Use of a novel baculovirus vector to express nucleoprotein gene of Crimean-Congo hemorrhagic fever virus in both insect and mammalian cells].
OBJECTIVE: To construct a novel baculovirus vector which is capable of promoting the high-yield expression of foreign gene in mammalian cells and to express by this vector the nucleoprotein (NP) gene of Crimean-Congo hemorrhagic fever virus (CCHFV) Chinese isolate (Xinjiang hemorrhagic fever virus, XHFV) BA88166 in insect and Vero cells. METHODS: Human cytomegalovirus (CMV) immediate early (IE) promoter was ligated to the baculovirus vector pFastBac1 downstream of the polyhedrin promoter to give rise to the novel vector pCB1. XHFV NP gene was cloned to this vector and was well expressed in COS-7 cells and Vero cells by means of recombinant plasmid transfection and baculovirus infection. RESULTS: The XHFV NP gene in vector pCB1 could be well expressed in mammalian cells. Vero cells infected with recombinant baculovirus harboring NP gene could be employed as antigens to detect XHF serum specimens whose results were in good correlation with those of ELISA and in parallel with clinical diagnoses. CONCLUSIONS: This novel baculovirus vector is able to express the foreign gene efficiently in both insect and mammalian cells, which provides not only the convenient diagnostic antigens but also the potential for developing recombinant virus vaccines and gene therapies.
Animals↗
A possible overwintering mechanism for bluetongue virus in the absence of the insect vector.
Bluetongue virus (BTV) and several other Orbivirus species are transmitted between mammalian hosts via bites from adults of certain species of Culicoides midges. However, BTV can survive for 9-12 months (typically during the winter), in the absence of adult vectors, with no detectable cases of viraemia, disease or seroconversion in the host. The survival of the virus from one 'vector season' to the next is called 'overwintering' but the mechanism involved is not fully understood. It is demonstrated that BTV can persistently infect ovine gammadelta T-cells in vitro, a process that may also occur during infection and viraemia in mammalian hosts, thus providing a mechanism for virus persistence. Interaction of persistently BTV-infected gammadelta T-cells with antibody to the gammadelta T-cell-specific surface molecule WC-1 resulted in conversion to a lytic infection and increased virus release. Skin fibroblasts induce a similar conversion, indicating that they express a counter ligand for WC-1. Feeding of Culicoides midges induces skin inflammation, which is accompanied by recruitment of large numbers of activated gammadelta T-cells. The interaction of persistently infected gammadelta T-cells with skin fibroblasts would result in increased virus production at 'biting sites', favouring transmission to the insect vector. This suggested mechanism might also involve up-regulation of the WC-1 ligand at inflamed sites. It has been shown previously that cleavage of virus surface proteins by protease enzymes (which may also be associated with inflammation) generates infectious subvirus particles that have enhanced infectivity (100 times) for the insect vector.
Animals↗
Multiplication of tomato spotted wilt virus in its insect vector, Frankliniella occidentalis.
The accumulation of two proteins, the nucleocapsid (N) protein and a non-structural (NSs) protein both encoded by the S RNA of tomato spotted wilt virus (TSWV), was followed in larvae during development and in adults of Frankliniella occidentalis after ingesting the virus for short periods on infected plants. The amounts of both proteins increased, as shown by ELISA and Western blot analysis, within 2 days above the levels ingested, indicating multiplication of TSWV in these insects. Accumulation of these proteins and of virus particles was further confirmed by in situ immunolabelling of the salivary glands and other tissues of adult thrips. The accumulation of large amounts of N and NSs protein, the occurrence of several vesicles with virus particles in the salivary glands and the massive numbers of virus particles in the salivary gland ducts demonstrate that the salivary glands are a major site of TSWV replication. The occurrence of virus particles in the salivary vesicles is indicative of the involvement of the Golgi apparatus in the maturation of the virus particles and its transport to the salivary ducts.
Animals↗
[Differential diagnosis of virus diseases in insects. II].
Explore the source record for details and available documents.
Animals↗
Antibody response to the M2 protein of influenza A virus expressed in insect cells.
A recombinant baculovirus expressing the M2 protein from influenza A/Ann Arbor/6/60 (H2N2) virus (AA60 virus) was constructed. The expressed M2 protein was recognized by a monoclonal antibody specific for the M2 protein and comigrated with the M2 protein from cells infected with AA60 virus on SDS-polyacrylamide gels. Immunofluorescence studies indicated that the expressed M2 protein was present on the surface of Spodoptera frugiperda (Sf9) cells infected with the recombinant baculovirus. Immunoassays using the expressed M2 protein were able to detect antibodies to the M2 protein in serum samples from humans and ferrets infected with influenza A viruses.
Animals↗
Mechanical transmission of curly top virus to its insect vector by needle inoculation.
Explore the source record for details and available documents.
Animals↗
Expression of hepatitis A virus capsid sequences in insect cells.
A cDNA coding for hepatitis A virus (HAV) VP1 and portions of the flanking VP3 and P2 sequences was inserted into the genome of Autographa californica nuclear polyhedrosis virus under the control of the polyhedrin promoter and translational start codon. Cells infected with recombinant virus produced high levels of a 55 kDa protein, identified as containing HAV VP1 by reactivity with anti-VP1 serum. The expressed protein also reacted on immunoblots with human HAV convalescent sera as well as sera from rabbits immunized with intact HAV. This protein was found predominantly in the cytoplasm of infected insect cells, probably as an insoluble aggregate.
Animals↗
Identification of a very early promoter of insect Hz-1 virus using a novel dual-expression shuttle vector.
Very early promoters of viruses control the proper cascade expression of viral genes and are essential for completion of virus life cycles. These promoters are usually rare and weak and do not encode structural proteins. As a result, they are difficult to identify. In order to identify and clone the very early promoters of a large eukaryotic DNA virus, the Hz-1 virus, a novel cloning strategy was applied. This strategy is based on a dual-expression shuttle vector containing a promoter-less lacZ gene. Insertion of eukaryotic promoters upstream permits the efficient expression of LacZ in bacteria cells. The function of the putative promoters was then confirmed by their proper expression in insect cells. The first two productive infection-specific promoters of Hz-1 virus, contained within the shuttle vectors pTSV-2-129 and pTSV-2-49, were cloned from the HindIII-K and HindIII-A fragments of the Hz-1 viral genome, respectively. By primer extension analysis, an immediate and constitutive expression of the promoter in clone pTSV-2-129 was detected after viral infection. Identification of the productive infection-specific promoters has laid down important groundwork for future studies on the molecular mechanism of the transcriptional switch between productive and persistent infections of Hz-1 virus.
Alcohol Dehydrogenase↗
Attempted mechanical transmission of lumpy skin disease virus by biting insects.
The mosquitoes Anopheles stephensi Liston and Culex quinquefasciatus Say (Diptera: Culicidae), the stable fly Stomoxys calcitrans Linnaeus (Diptera: Muscidae) and the biting midge Culicoides nubeculosus Meigen (Diptera: Ceratopogonidae) were allowed to feed on either lumpy skin disease (LSD) infected animals or through a membrane on a bloodmeal containing lumpy skin disease virus (LSDV). These arthropods were then allowed to refeed on susceptible cattle at various intervals after the infective feed. Virus was detected in the insects by polymerase chain reaction immediately after feeding and at sufficiently high titre to enable transmission to occur. However, no transmission of virus from infected to susceptible animals by An. stephensi, S. calcitrans, C. nubeculosus and Cx. quinquefasciatus was observed.
Animals↗
Evolutionary and taxonomic implications of conserved structural motifs between picornaviruses and insect picorna-like viruses.
A comparison of the recently determined structure of an insect picorna-like virus, Cricket paralysis virus (CrPV), with that of the mammalian picornaviruses shows that several structural features are highly conserved between these viruses. These conserved features include the topology of the coat proteins, the conformation of most loops, and the general arrangement of the internally located N-terminal arms of the coat proteins. The conformational conservation of the N-termini of the three major coat proteins between CrPV and the picornaviruses suggests a putative ancestral T = 3 virus. Comparisons of the genome structure and amino-acid sequence of the coat proteins of CrPV with a number of other insect picorna-like viruses show that most of them belong to a novel group, recently given the interim name Cricket paralysis-like viruses. Two other insect picorna-like viruses, Infectious flacherie virus (IFV) and Sacbrood virus (SBV), for which the genome sequences have recently been determined, have very different coat protein sequences and a genome organization more like the picornaviruses. However, the position of the small VP4 protein in the structural protein polyprotein as well as the mechanism for its cleavage from VP3 upon assembly strongly suggests an evolutionary link to the "Cricket paralysis-like viruses". We propose that the picornaviruses, Cricket paralysis-like viruses and IFV/SBV group are a natural assemblage. The ancestor for this assemblage had a structure based upon the CrPV/picornavirus paradigm and a genome encoding a single major coat protein; gene duplication and rearrangements have subsequently produced the viruses that we observe today. We also discuss the possible relatives of the proposed assemblage and the likely implications of future structural studies that may be carried out on the putative relatives.
Amino Acid Motifs↗
ON THE DEVELOPMENT OF INSECT POLYHEDROSIS AND GRANULOSIS VIRUS PARTICLES.
Explore the source record for details and available documents.
Animals↗
Expression of the human immunodeficiency virus gag gene in insect cells.
Regions of the gag-pol gene of human immunodeficiency virus (HIV), the causative agent of AIDS, have been cloned into the polyhedrin gene of the baculovirus Autographa californica nuclear polyhedrosis virus. When these recombinant viruses were used to infect insect cells, the cells produced gag-related proteins which could be immunoprecipitated with serum from AIDS patients. The major proteins produced by Acgag1, which contained the entire gag gene and a small portion of the pol gene, had molecular weights of 55,000 and 40,000 Da. Acgag2, which contained a larger portion of the pol gene in addition to the gag coding sequences, produced a major protein of 24,000 Da and only minor amounts of the 55,000- and 40,000-Da proteins. The implications of these results with respect to proteolytic processing of HIV gag proteins as well as the potential diagnostic use of this system are discussed.
Animals↗