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At least 1,369 records · Page 76Linked to original sources
PubMed1990

Altered phosphorylation pattern of simian virus 40 T antigen expressed in insect cells by using a baculovirus vector.

The phosphorylation pattern of simian virus 40 (SV40) large tumor (T) antigen purified from insect cells infected with a recombinant baculovirus was compared with that reported previously for T antigen from SV40-infected monkey cells. The specific activity of metabolic phosphate labeling of baculovirus T antigen was reduced, and the phosphopeptide map of the baculovirus protein, while qualitatively similar to that of lytic T, revealed several quantitative differences. The most striking difference was the prominence in the baculovirus map of peptides containing phosphothreonine 124. These peptides are known to arise from other phosphopeptides upon dephosphorylation of neighboring serines, suggesting that baculovirus T may be underphosphorylated at these serines and perhaps other sites. Functional assays used to further investigate the phosphorylation state of the baculovirus protein included SV40 DNA binding after enzymatic dephosphorylation with alkaline phosphatase and after phosphorylation by a murine homolog of cdc2 protein kinase. The results imply that baculovirus T antigen is underphosphorylated, in particular at those serine residues whose phosphorylation is responsible for down regulation of DNA-binding activity at site II in the core origin of DNA replication. In contrast, no evidence for a functionally significant underphosphorylation at threonine 124 could be found.

Animals↗
PubMed1993

Action of some new insect growth regulators on mosquito vectors. Part II: Geraniol based diethers.

Biological activity of saturated diethers viz. 1-benzyloxy/phenoxy-8-alkoxy and 1-alkoxy-8-benzyloxy-3,7-dimethyl-1, 8-octanes (IIa-IIq) prepared from Geraniol, were studied on three mosquito species and the bug Dysdercus koenigii. These diethers exhibited oviposition deterrent and developmental inhibition activities of greater magnitudes than the compounds based on citronellol reported in Part I of this paper. Some of these new compounds inhibit development of mosquitoes at 0.05 ppm and deter oviposition at 0.05 per cent doses. Tests were extended to field simulated conditions in selected cases.

Acyclic Monoterpenes↗
PubMed1990

Expression, characterization, and purification of a phosphorylated rabies nucleoprotein synthesized in insect cells by baculovirus vectors.

A baculovirus expression vector (AcNPV3) derived from the nuclear polyhedrosis virus of Autographa californica (AcNPV) was prepared containing the complete coding region of the nucleoprotein (N) gene of rabies virus (Gif-sur-Yvette clone of the CVS strain). The gene was placed under the control of the AcNPV polyhedrin promoter and was expressed to high levels (66 mg N protein/liter of 2 x 10(9) cells) by the derived recombinant virus using a Spodoptera frugiperda cell line. Using available antisera, it was established that the antigenic characteristics of the N protein were similar by comparison with those of the native N protein of rabies virus. Characterization of the expressed protein established that, like the N protein of mammalian cell-grown CVS virus, the N protein was phosphorylated. The expressed rabies N protein induced antibodies in mice that reacted strongly with the rabies viral protein. The expressed nucleoprotein was recovered from the insect cells by differential centrifugation followed by ion exchange chromatography. The expressed rabies N protein represents a source of authentic protein suitable for virus diagnosis as well as structural studies.

Animals↗
PubMed2025

Spiroplasma endosymbiont reduction of host lipid synthesis and Stomoxyn-like peptide contribute to trypanosome resistance in the tsetse fly Glossina fuscipes.

Tsetse flies (Glossina spp.) vector African trypanosomes that cause devastating diseases in humans and domestic animals. Within the Glossina genus, species in the Palpalis subgroup exhibit greater resistance to trypanosome infections compared to those in the Morsitans subgroup. Varying microbiota composition and species-specific genetic traits can significantly influence the efficiency of parasite transmission. Notably, infections with the endosymbiotic bacterium Spiroplasma have been documented in several Palpalis subgroup species, including Glossina fuscipes fuscipes (Gff). While Spiroplasma infections in Gff are known to hinder trypanosome transmission, the underlying mechanisms remain unknown. To investigate Spiroplasma-mediated factors affecting Gff vector competence, we conducted high-throughput RNA sequencing of the gut tissue along with functional assays. Our findings reveal elevated oxidative stress in the gut environment in the presence of Spiroplasma, evidenced by increased expression of nitric oxide synthase, which catalyzes the production of trypanocidal nitric oxide. Additionally, we observed impaired lipid biosynthesis leading to a reduction of this important class of nutrients essential for parasite and host physiologies. In contrast, trypanosome infections in Gff's midgut significantly upregulated various immunity-related genes, including a small peptide, Stomoxyn-like, homologous to Stomoxyn first discovered in the stable fly, Stomoxys calcitrans. We observed that the Stomoxyn-like locus is exclusive to the genomes of Palpalis subgroup tsetse species. GffStomoxyn is constitutively expressed in the cardia (proventriculus) and synthetic GffStomoxyn exhibits potent activity against Escherichia coli and bloodstream form of Trypanosoma brucei parasites, while showing no effect against insect stage procyclic forms or tsetse's commensal endosymbiont Sodalis in vitro. Reducing GffStomoxyn levels significantly increased trypanosome infection prevalence, indicating its potential trypanocidal role in vivo. Collectively, our results suggest that the enhanced resistance to trypanosomes observed in Spiroplasma-infected Gff may be due to the reduced lipid availability necessary for parasite metabolic maintenance. Furthermore, GffStomoxyn could play a crucial role in the initial immune response(s) against mammalian parasites early in the infection process in the gut and prevent gut colonization. We discuss the molecular characteristics of GffStomoxyn, its spatial and temporal expression regulation and its microbicidal activity against Trypanosome parasites. Our findings reinforce the nutritional influences of microbiota on host physiology and host-pathogen dynamics.

Animals↗
PubMed1991

Action of some insect growth regulators on mosquito vectors: Part I--Citronellol based diethers.

New series of compounds starting from common terpenoids (Geraniol, citronellol) have been examined for biological activity on mosquito larvae. Many of these exhibited development disruption on eggs as well larvae. Some also affected adult oviposition behaviour. Developmental disturbances were classified as JH type by inducing typical metamorphosis inhibition in Dysdercus koenigii in the standard Hemipteran JH bioassay. Where indicated simulated field trials were also undertaken. This report describes results of bioevaluation of the citronellol based compounds. The results indicate that these show multifarious activity against mosquitoes but at relatively high doses, suggesting that exploration of further structural variety is needed before truly promising analogues can be obtained.

Acyclic Monoterpenes↗
PubMed1990

Assembly of double-shelled, viruslike particles of bluetongue virus by the simultaneous expression of four structural proteins.

Bluetongue is a disease of ruminants. The etiologic agent is bluetongue virus (BTV), a gnat-transmitted member of the Orbivirus genus of the Reoviridae. The virus has a genome of 10 double-stranded RNA species L1 to L3, M4 to M6, S7 to S10). The L2 and M5 genes of BTV which encode the outer capsid proteins VP2 and VP5, respectively, were inserted into a recombinant baculovirus downstream of duplicated copies of the baculovirus polyhedrin promoter. Insect cells coinfected with this virus plus a recombinant baculovirus expressing the two major core proteins VP3 and VP7 of BTV (T.J. French and P. Roy, J. Virol. 64:1530-1536, 1990) synthesized noninfectious, double-shelled, viruslike particles. When purified, these particles were found to have the same size and appearance as authentic BTV virions and exhibited high levels of hemagglutination activity. Antibodies raised to the expressed particles contained high titers of neutralizing activity against the homologous BTV serotype. The assembly of these bluetongue viruslike particles after the simultaneous expression of four separate proteins is indicative of the potential of this technology for the production of a new generation of viral vaccines and for the study of complex, multiprotein structures.

Animals↗
PubMed2003

The potential of virulent Wolbachia to modulate disease transmission by insects.

A virulent strain of Wolbachia has recently been identified in Drosophila that drastically reduces adult lifespan. It has been proposed that this phenotype might be introduced into insect disease vector populations to reduce pathogen transmission. Here we model the requirements for spread of such an agent and the associated reduction in disease transmission. First, a simulation of mosquito population age structure was used to describe the age distribution of mosquitoes transmitting dengue virus. Second, given varying levels of cytoplasmic incompatibility and fecundity effect, the maximum possible longevity reduction that would allow Wolbachia to invade was obtained. Finally, the two models were combined to estimate the reduction in disease transmission according to different introduction frequencies. With strong CI and limited effect of fecundity, an introduction of Wolbachia with an initial frequency of 0.4 could result in a 60-80% reduction of transmitting mosquitoes. Greater reductions are possible at higher initial release rates.

Age Factors↗
PubMed1988

Expression of the human EGF receptor with ligand-stimulatable kinase activity in insect cells using a baculovirus vector.

The mechanism by which the binding of epidermal growth factor (EGF) to specific cell surface receptors induces a range of biological responses remains poorly understood. An important part of the study of signal transduction in this system involves the production of sufficient native and mutant EGF receptor species for X-ray crystallographic and spectroscopic analysis. Baculovirus vectors containing the cDNA encoding the human EGF receptor protein have here been utilized to infect insect cells. This results in expression of a 155-kb transmembrane protein which is recognized by four antibodies against different regions of the human EGF receptor. Studies with tunicamycin, monensen and endoglycosidase H show the difference in size between the recombinant and the native receptor is due to alterations in glycocsylation. Studies of [125I] EGF binding shows a Kd of 2 X 10(-9) M in intact infected insect cells which falls to 2 X 10(-7) M upon detergent solubilization. The recombinant protein exhibits an EGF-stimulated tyrosine protein kinase activity and an analysis of tryptic peptides shows that the phosphate acceptor sites are similar to those of the EGF receptor isolated from A431 cells. These observations indicate that functional EGF receptor can be expressed in insect cells, and furthermore, this system can be used for large-scale production.

Animals↗
PubMed2000

Efficacy of three insect repellents against the malaria vector Anopheles arabiensis.

Three commercial repellents marketed in South Africa: Bio-Skincare (BSC, oils of coconut, jojoba, rapeseed and vitamin E), Mosiguard towelletes with 0.574 g quwenling (p-menthane-3,8-diol, PMD) and the standard deet (15% diethyl-3-methylbenzamide, Tabard lotion), were compared against a laboratory colony of the mosquito Anopheles arabiensis Patton (Diptera: Culicidae), the predominant malaria vector in South Africa. Human forearms were treated with 1.2 g BSC, 0.8 g PMD towelette or 0.5 g deet and exposed to 200 hungry An. arabiensis females for 1 min, at intervals of 1-6 h post-treatment. Tests were conducted by three adult male volunteers (aged 30-45 years, crossover controlled test design for 3 consecutive days), using their left arm for treatment and right arm for untreated control. Biting rates averaged 39-52 bites/min on untreated arms. All three repellents provided complete protection against An. arabiensis for up to 3-4 h post-application; deet and PMD gave 90-100% protection up to 5-6h, but BSC declined to only 52% protection 6h post-treatment. These results are interpreted to show that all three repellent products give satisfactory levels of personal protection against An. arabiensis for 4-5 h, justifying further evaluation in the field.

Adult↗
PubMed1992

The role of temperature and nutritional status in flight initiation by Triatoma infestans.

Flight initiation in Triatoma infestans is associated with low nutritional status and increases with rising temperature; it appears to be largely independent of bug age and sex. A predictive model for the probability of flight initiation was constructed based on weight:length ratios of the bugs and maximum ambient temperature, both of which can be ascertained in the field. The model accurately predicted the proportion of bugs initiating flight in > 85% of the groups used in our study. The predictive equation was found to give significant fits with two independent data sets. From our results it might be expected that flight would be rare during colder (< 20 degrees C) months but that 5-10% of the normal population of an infested house would fly on any given night during the hotter months when temperatures approach 30 degrees C. If bug nutritional status falls significantly, this proportion could be expected to rise to 30%.

Animal Nutritional Physiological Phenomena↗
PubMed2001

Germline transformation of the malaria vector, Anopheles gambiae, with the piggyBac transposable element.

Germline transformation of the major African malaria vector, Anopheles gambiae, was achieved using the piggyBac transposable element marked with the enhanced green fluorescent protein (EGFP) injected into mosquito embryos. Two G1 generation male mosquitoes expressing EGFP were identified among 34 143 larvae screened. Genomic Southern data and sequencing of the piggyBac insertion boundaries showed that these two males arose from one piggyBac insertion event in the injected G0 embryos. Genetic cross data suggest that the insertion site of the element either resulted in, or is tightly linked to, a recessive lethal. This was demonstrated by a deficiency in the number of EGFP-expressing offspring from inbred crosses but expected ratios in outcrosses to non-transformed individuals and failure to establish a pure-breeding line. The insertion was weakly linked to the collarless locus on chromosome 2 and was shown by in situ hybridization to be located in division 28D of that chromosome. Particularly high levels of expression were observed uniformly in salivary glands and, in most individuals, in the anterior stomach. An improvement in the injection technique at the end of the studies resulted in increased G0 hatching, transient expression and EGFP-expression rates among G1 progeny.

3' Flanking Region↗
PubMed2002

Germ-line transformation of the South American malaria vector, Anopheles albimanus, with a piggyBac/EGFP transposon vector is routine and highly efficient.

Stable and efficient germ-line transformation was achieved in the South American malaria vector, Anopheles albimanus, using a piggyBac vector marked with an enhanced green fluorescent protein gene regulated by the Drosophila melanogaster polyubiquitin promoter. Transgenic mosquitoes were identified from four independent experiments at frequencies ranging from 20 to 43% per fertile G0. Fluorescence was observable throughout the body of larvae and pupae, and abdominal segments of adults. Transgenic lines analysed by Southern hybridization had one to six germ-line integrations, with most lines having three or more integrations. Hybridized transposon vector fragments and insertion site sequences were consistent with precise piggyBac-mediated integrations, although this was not verified for all lines. The piggyBac/PUbnlsEGFP vector appears to be a robust transformation system for this anopheline species, in contrast to the use of a piggyBac vector in An. gambiae. Further tests are needed to determine if differences in anopheline transformation efficiency are due to the marker systems or to organismal or cellular factors specific to the species.

Animals↗
PubMed2001

Modulation of host immunity by haematophagous arthropods.

The medical and veterinary public-health importance of haematophagous arthropods is immense and continuing to increase because of the emergence of new vector-borne infectious agents and the resurgence of well known ones. Control of blood-feeding arthropods and the pathogens they transmit is compounded by drug, insecticide and acaricide resistance. Novel control strategies are needed. Immunological control is one very promising approach to these problems. In order to develop anti-arthropod vaccines that block pathogen transmission and establishment, the immunological interactions occurring at the interface of the blood-feeding arthropod and host must be characterized. An important component of these interactions is arthropod modulation of the host's innate and acquired, specific immune defences. This review discusses current knowledge regarding the ability of haematophagous arthropods to alter their hosts' immune defences, the impact of those changes on pathogen transmission, the molecular bases for the immunomodulation, and strategies for identification of the molecules in arthropod saliva that are responsible for the immunomodulation.

Animals↗