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PubMed1992

Failure of dengue viruses to replicate in Culex quinquefasciatus (Diptera: Culicidae).

Culex quinquefasciatus (Say) and Aedes aegypti (L.) were parenterally infected with dengue viruses and virus replication was monitored at intervals after infection in each species. Dengue viruses replicated rapidly in Ae. aegypti, reaching a peak titer of 10(6)-10(7) mosquito infectious dose 50 (MID50) per mosquito. In Cx. quinquefasciatus, however, dengue virus replication did not occur. We conclude that this mosquito species is refractory to infection with dengue viruses and, therefore, does not serve as a vector in nature.

Aedes↗
PubMed1982

Bromodeoxyuridine-induced mutants of Autographa californica nuclear polyhedrosis virus defective in occlusion body formation.

Twelve temperature-sensitive (ts) and two morphology mutants of Autographa californica nuclear polyhedrosis virus were generated using the mutagen 5-bromo-2'-deoxyuridine (BrdUrd). The ts mutants grew normally at 25 degrees C but exhibited abnormal occlusion body formation when grown at 33 degrees C whereas the morphology mutants produced an abnormal cytopathic effect at 25 degrees C and 33 degrees C. None of the mutants was severely restricted for production of non-occluded virus; thus, with the eight ts mutants and the two morphology mutants incubated at 33 degrees C the drop in titre was 0.5 to 3.0 log10 from that at 25 degrees C. The mutants fell into three groups based on the amount of polyhedrin synthesized at 25 degrees C and 33 degrees C in infected cells. The eight ts mutants were combined with ts mutants constructed in a previous series of experiments and the collection was sorted into complementation groups. The collection comprised ten groups and the new mutants were sorted into seven of these. It is concluded that gene products of these complementation groups have essential roles in occlusion body formation.

Bromodeoxyuridine↗
PubMed1986

Properties of a novel DNA virus from the tsetse fly, Glossina pallidipes.

Virus particles were isolated from hypertrophied salivary glands of the tsetse fly, Glossina pallidipes collected near Mombasa, Kenya. Purified virus particles were rod-shaped, 57 nm wide by 700 to 1300 nm long. Particle lengths fell into two size classes, with 'short' particles averaging 869 nm and 'long' particles 1175 nm. The virus particles morphologically resembled elongated baculovirus nucleocapsids although, unlike baculoviruses, no fully enveloped virions were found in purified preparations. The particles contained double-stranded DNA which appeared to be linear when analysed by electrophoresis in agarose gels, ethidium bromide-caesium chloride gradient centrifugation or electron microscopy (EM). There was some evidence for the DNA being heterogeneous in size from EM studies and from the observation that restriction enzyme analysis failed to provide a clear profile of DNA fragments. Protein from purified virions contained at least 12 polypeptides with a major component of 39 000 mol. wt. These results suggest that the virus cannot be placed in any of the existing taxonomic groupings of DNA viruses.

Animals↗
PubMed1992

Two novel viruses associated with severe disease symptoms of the green stinkbug Nezara viridula.

Two viruses were isolated from green stinkbugs (Nezara viridula) with severe disease symptoms. These viruses have been named N. viridula virus type 1 (NVV-1) and NVV-2 according to their relative sedimentation coefficients. NVV-1 is a small picorna-like virus with a diameter of 29 nm, a buoyant density in CsCl of 1.34 g/ml and a sedimentation coefficient of 153S. NVV-1 particles contain a 9.4 kb ssRNA segment and have three coat proteins of M(r)s 32,100, 31,500 and 30,700. NVV-2 sediments as two components on sucrose gradients; the top 104S component consists almost entirely of 41 nm empty capsids and the faster sedimenting 177S component consists of intact 39 nm spherical particles. NVV-2 particles have a buoyant density in CsCl of 1.39 g/ml and consist of one major protein of M(r) 73,800 and at least two minor proteins of M(r)s 13,500 and 16,500. Only one dsRNA segment of 6.2 kb was identified. The properties of NVV-2 are similar to those of the Totiviridae. Individual stinkbugs were infected with either NVV-1 or NVV-2, or with a mixture of the two viruses. Re-infection of virus-free stinkbugs with the mixture resulted in typical disease symptoms. Both viruses were vertically transmitted through the eggs and insects were infected by surface contamination of their food source.

Animals↗
PubMed1997

Biological and molecular features of the relationships between Diadromus pulchellus ascovirus, a parasitoid hymenopteran wasp (Diadromus pulchellus) and its lepidopteran host, Acrolepiopsis assectella.

The Diadromus pulchellus ascovirus (DpAV) has been isolated from laboratory strains of Diadromus pulchellus and in natural wild populations collected from the Antibes locality (southern France). The DpAV genome was found in the cells of the head, thorax and abdomen of this hymenopteran wasp. DpAV virions are present in the female genitalia and are transmitted to the nymphal lepidopteran host, Acrolepiopsis assectella, at each oviposition of the female wasp. The presence of the DpAV genome in all Diadromus somatic cells suggests that it is inherited by vertical transmission. DpAV is amplified in the host tissues during the larval development of D. pulchellus in A. assectella. Cell lysis due to amplification of the virus does not prevent the development of the hymenopteran larva. Virus amplification appears to be slower in nymphs parasitized by D. pulchellus than in nymphs artificially infected with DpAV alone. Lysis of the nymphal cells due to viral replication seems to be synchronous with egg hatching and the development of the hymenopteran larva. The features of DpAV and its relationship with the parasitoid wasp D. pulchellus during its development are compared to those of the ichnoviruses.

Animals↗
PubMed1967

Mutations, chromosomal aberrations, and tumors in insects treated with oncogenic virus.

An increased incidence of lethal mutations, visible mutations, chromosomal losses, chromosomal nondisjunctions, and tumors resulted when drosophila were placed in medium containing Rous-sarcoma virus. In the group treated, a few mosaics of the eye and translocations appeared as well. There is a suggestion, from preliminary data, that the size of chromosomal puffs may be reduced by this RNA virus, but the difference is not significant. Tests for the persistence of virus in progeny have been negative so far.

Animals↗
PubMed1971

Pathway of infection of mosquito iridescent virus. I. Preliminary observations on the fate of ingested virus.

Mosquito iridescent virus (MIV) is ingested in large amounts by first- and second-instar Aedes taeniorhynchus larvae without causing a high rate of infection. Electron microscope studies have been undertaken to determine the fate of ingested virus. Preliminary observations suggest that most, if not all, ingested particles are degraded shortly after entering the midgut. MIV and other virus particles employed in this study were apparently unable to penetrate the peritrophic membrane; consequently, none was observed inside, or in contact with, midgut epithelial cells.

Aedes↗
PubMed1979

Plaque assay of baculoviruses employing an agarose-nutrient overlay.

Four baculoviruses produced visible plaques in the Spodoptera frugiperda cell line when cell monolayers were infected and overlayed with a simplified, agarose-nutrient formulation. Macroscopic plaques were first detected 4 days postinoculation, and by 10 days plaques ranging from 0.5 to 3 mm in diameter were seen. Dose-response experiments indicated that a single particle initiated the formation of a plaque, because a linear response was demonstrated with increased dosage.

Animals↗
PubMed1980

The mechanism of arbovirus transovarial transmission in mosquitoes: San Angelo virus in Aedes albopictùs.

The mechanism of transovarial transmission of San Angelo (SA) virus in Aedes albopictus was investigated.A mosquito line with SA virus filial infection rates of almost 100% was developed by selection. Results of crosses and back-crosses between this transovarial transmission-efficient line and noninfected mosquitoes indicated that SA virus was transmitted in Ae. albopictus by maternal inheritance. The infection status of the male parent was of no consequence; the virus was passed from generation to generation through the females. Transovarially infected mosquitoes contained less virus than insects infected by inoculation. The behavior of SA virus in Ae. albopictus was similar to that of sigma virus in Drosophila melanogaster, suggesting that some females in the transovarial transmission-efficient line had developed a chronic infection of their germinal cells (oogonia). Serial transovarial passage of SA virus in Ae. albopictus did not alter its plaque morphology, infectivity for mosquitoes, or pathogenicity for vertebrates. Transovarially infected mosquitoes transmitted the virus by bite to mice.

Aedes↗
PubMed1976

Influence of temperature corresponding to that of the vector on Tahyna virus.

The behaviour of uncloned, low-passage Tahyna virus in an Aedes albopictus (AA) cell line at 28 and 20 degrees C was studied in the course of 10 passages. The virus multiplied at both temperatures without any apparent effect on the host cell. At 28 and 20 degrees C reduction of plaque size, decrease of peripheral virulence and weakening of thermostability were observed. Differences between both temperatures were only in the intensity of these changes.

Aedes↗
PubMedDate not supplied

[The circulation of viruses of the California encephalitis and Bunyamwera groups (Bunyaviridae, Bunyavirus) on the northeastern Russian plain].

In the Komi ASSR, 102.2 thousand mosquitoes, 207 small mammals, 1487 blood serum specimens from people, 793 cow blood sera, 140 blood serum specimens from reindeer were collected in June-August, 1988. Twenty seven virus strains isolated from mosquitoes were classified into Bunyaviridae family according to the data of electron microscopic studies. Identification of the isolates by CFT and IFA showed 18 of the strains to belong to California encephalitis complex and 9 to Bunyamwera complex. Serological studies by neutralization test demonstrates a high frequency of contact of the human population and domestic animals with viruses of the California complex practically in the entire study area: an average of 45% among human subjects, 48% among cattle and 33% among reindeer. Such high values of the immune portions indicate the activity of the discovered natural foci of this complex. The results for Batai virus from the Bunyamwera complex do not indicate its high activity: approximately 2% of positive findings in human subjects and about 4% in the cattle. The results permit a prognosis of California encephalitis and Bunyamwera complex viruses spread in the northern part of Western Siberia.

Animals↗
PubMed1979

Electron microscope study of mosquito densonucleosis virus maturation.

Maturation of mosquito densonucleosis virus (MDV) was studied in its natural host, Aedes aegypti L. larvae. First ultrastructural changes were observed in the cytoplasm of virus-infected cells. They consisted in the formation of paracrystalline structures containing particles 18--20 nm in diameter as well as microtubules 20 nm in diameter. Virogenic stromas and paracrystalline virion arrays were found in the nuclei of virus-infected cells.

Aedes↗
PubMed1992

Expression and secretion of Japanese encephalitis virus nonstructural protein NS1 by insect cells using a recombinant baculovirus.

The nonstructural protein NS1 of Japanese encephalitis virus (JEV) was expressed at a high level under the control of the polyhedrin promoter in Spodoptera frugiperda (Sf9) insect cells using a recombinant baculovirus. Recombinant NS1 was designed to contain its natural signal sequence at its N-terminus and no C-terminal hydrophobic domain that could act as a membrane anchor. This recombinant protein exhibited similar size to native NS1 expressed in Aedes albopictus (C6/36) insect cells infected with wild-type JEV. The signal sequence of NS1 allowed translocation of the protein into the endoplasmic reticulum where it underwent glycosylation. A small fraction of synthesized NS1 was able, in the absence of any other viral protein, to associate as a homodimer, showing similar characteristics to the native dimer. Interestingly, this recombinant dimeric form seemed to be exported and released in the extracellular medium of infected cell culture. During its transport, one of the two N-linked oligosaccharides of the polymannose type was processed to an endoglycosidase H-resistant form, suggesting that the protein had passed through the Golgi compartment before reaching the cell surface. Moreover, Triton X-114 partitioning analysis showed that monomeric NS1 behaved essentially as a hydrophilic protein, whereas both intracellular and extracellular dimeric NS1 were either free of or associated to membraneous components.

Animals↗
PubMed2006

Evolutionary origin of Venturia canescens virus-like particles.

Insect host-parasitoid interactions provide fascinating examples of evolutionary adaptations in which the parasitoid employs a variety of measures and countermeasures to overcome the immune responses of its host. Maternal factors introduced by the female wasps during egg deposition play an important role in interfering with cellular and humoral components of the host's immune defence. Some of these components actively suppress host immune components and some are believed to confer protection for the developing endoparasitoid by rather passive means. The Venturia canescens/Ephestia kuehniella parasitoid-host system is unique among other systems in that the cellular defence capacity of the host remains virtually intact after parasitization. This system raises some important questions that are discussed in this mini-review: If immune protection of the egg and the emerging larva is achieved by surface properties comprising glycoproteins and virus-like particles (VLPs) produced by the female wasp, why is the prophenoloxidase activating cascade blocked in parasitized caterpillars? Another question is the evolutionary origin of these particles, given that the functional role and structural features of V. canescens VLP proteins are more related to cellular proteins than to viruses.

Animals↗