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At least 235 records · Page 13Linked to original sources
PubMed2005

Trypanosoma rangeli interactions within the vector Rhodnius prolixus: a mini review.

This article is an integrative mini review of the research on the interactions between Trypanosoma rangeli and the insect vector, Rhodnius prolixus. Special attention is given to the interactions of these parasites with the gut environment, gut walls, with hemolymph invasion, hemocytes, hemocyte microaggregations, prophenoloxidase-activating system, superoxide, and nitric acid generation and eicosanoid pathways. We described factors affecting vectorial capacity and suggested that T. rangeli may modulate the hemocoelic invasion and the survival of the parasites by overcoming the cellular and humoral defense reactions of the insect vector at different physiological events. The mechanisms of these interactions and their significance for parasite transmission are discussed.

Animals↗
PubMed1986

Expression of the influenza virus haemagglutinin in insect cells by a baculovirus vector.

The insect baculovirus Autographa californica nuclear polyhedrosis virus (AcNPV) has played a major role in studies on the molecular biology of insect DNA viruses. Recently, this system has been effectively adapted as a highly efficient vector in insect cells for the expression of several mammalian genes. A cDNA sequence of the influenza (fowl plague) virus haemagglutinin gene has been inserted into the BamHI site of the pAc373 polyhedrin vector. Spodoptera frugiperda cells were co-transfected with this construct, pAc-HA651, and authentic AcNPV DNA. Recombinant virus was selected by adsorption of transfected cells to erythrocytes followed by serial plaque passages on S. frugiperda cells. We have determined the site of insertion of the haemagglutinin gene into the AcNPV genome by restriction enzyme cleavage and Southern blot hybridization analyses using haemagglutinin cDNA as a probe. The influenza haemagglutinin gene is located in the polyhedrin gene of AcNPV DNA. Immunofluorescent labelling, immunoprecipitation and immunoblot analyses with specific antisera revealed that S. frugiperda cells produce immune reactive haemagglutinin after infection with the recombinant virus. The haemagglutinin is expressed at the cell surface and has haemolytic capacity that has been activated by post-translational proteolytic cleavage. When chickens were immunized with S. frugiperda cells expressing haemagglutinin, they developed haemagglutinin-inhibiting and neutralizing antibodies and were protected from infection with fowl plague virus. These observations demonstrate that the haemagglutinin is processed in insect cells in a similar fashion as in fowl plaque virus-infected vertebrate cells and that it has full biological activity.

Amino Acid Sequence↗
PubMed2003

Spiralin is not essential for helicity, motility, or pathogenicity but is required for efficient transmission of Spiroplasma citri by its leafhopper vector Circulifer haematoceps.

Spiralin is the most abundant protein at the surface of the plant pathogenic mollicute Spiroplasma citri and hence might play a role in the interactions of the spiroplasma with its host plant and/or its insect vector. To study spiralin function, mutants were produced by inactivating the spiralin gene through homologous recombination. A spiralin-green fluorescent protein (GFP) translational fusion was engineered and introduced into S. citri by using an oriC-based targeting vector. According to the strategy used, integration of the plasmid by a single-crossover recombination at the spiralin gene resulted in the expression of the spiralin-GFP fusion protein. Two distinct mutants were isolated. Western and colony immunoblot analyses showed that one mutant (GII3-9a5) did produce the spiralin-GFP fusion protein, which was found not to fluoresce, whereas the other (GII3-9a2) produced neither the fusion protein nor the wild-type spiralin. Both mutants displayed helical morphology and motility, similarly to the wild-type strain GII-3. Genomic DNA analyses revealed that GII3-9a5 was unstable and that GII3-9a2 was probably derived from GII3-9a5 by a double-crossover recombination between plasmid sequences integrated into the GII3-9a5 chromosome and free plasmid. When injected into the leafhopper vector Circulifer haematoceps, the spiralinless mutant GII3-9a2 multiplied to high titers in the insects (1.1 x 10(6) to 2.8 x 10(6) CFU/insect) but was transmitted to the host plant 100 times less efficiently than the wild-type strain. As a result, not all plants were infected, and symptom production in these plants was delayed for 2 to 4 weeks compared to that in the wild-type strain. In the infected plants however, the mutant multiplied to high titers (1.2 x 10(6) to 1.4 x 10(7) CFU/g of midribs) and produced the typical symptoms of the disease. These results indicate that spiralin is not essential for pathogenicity but is required for efficient transmission of S. citri by its insect vector.

Animals↗
PubMed1999

Semliki Forest virus as an expression vector in insect cell lines.

Studies were undertaken to determine if replication-deficient Semliki Forest virus expression vectors could be successfully used to express foreign gene constructs in insect cell lines. Using green fluorescent protein (GFP) as a marker we recorded infection levels of nearly 100% in the Aedes albopictus cell lines C6/36 and Aa23T, as well as in the Ae. aegypti cell line MOS20. The virus was capable of infecting an Anopheles gambiae cell line MOS55. The amount of GFP protein produced in each cell line was quantified. Northern analysis of viral transcription revealed the presence of novel transcripts in Aa23T, C6/36, and MOS55 cell lines, but not in the BHK or MOS20. The initial characterization of these transcripts is described.

Aedes↗
PubMed2006

Insulated piggyBac vectors for insect transgenesis.

BACKGROUND: Germ-line transformation of insects is now a widely used method for analyzing gene function and for the development of genetically modified strains suitable for pest control programs. The most widely used transposable element for the germ-line transformation of insects is piggyBac. The site of integration of the transgene can influence gene expression due to the effects of nearby transcription enhancers or silent heterochromatic regions. Position effects can be minimized by flanking a transgene with insulator elements. The scs/scs' and gypsy insulators from Drosophila melanogaster as well as the chicken beta-globin HS4 insulator function in both Drosophila and mammalian cells. RESULTS: To minimize position effects we have created a set of piggyBac transformation vectors that contain either the scs/scs', gypsy or chicken beta-globin HS4 insulators. The vectors contain either fluorescent protein or eye color marker genes and have been successfully used for germ-line transformation of Drosophila melanogaster. A set of the scs/scs' vectors contains the coral reef fluorescent protein marker genes AmCyan, ZsGreen and DsRed that have not been optimized for translation in human cells. These marker genes are controlled by a combined GMR-3xP3 enhancer/promoter that gives particularly strong expression in the eyes. This is also the first report of the use of the ZsGreen and AmCyan reef fluorescent proteins as transformation markers in insects. CONCLUSION: The insulated piggyBac vectors should protect transgenes against position effects and thus facilitate fine control of gene expression in a wide spectrum of insect species. These vectors may also be used for transgenesis in other invertebrate species.

Animals↗
PubMed2006

Gene drive systems for insect disease vectors.

The elegant mechanisms by which naturally occurring selfish genetic elements, such as transposable elements, meiotic drive genes, homing endonuclease genes and Wolbachia, spread at the expense of their hosts provide some of the most fascinating and remarkable subjects in evolutionary genetics. These elements also have enormous untapped potential to be used in the control of some of the world's most devastating diseases. Effective gene drive systems for spreading genes that can block the transmission of insect-borne pathogens are much needed. Here we explore the potential of natural gene drive systems and discuss the artificial constructs that could be envisaged for this purpose.

Animals↗
PubMed2003

Monoclonal antibody MG96 completely blocks Plasmodium yoelii development in Anopheles stephensi.

In spite of research efforts to develop vaccines against the causative agent of human malaria, Plasmodium falciparum, effective control remains elusive. The predominant vaccine strategy focuses on targeting parasite blood stages in the vertebrate host. An alternative approach has been the development of transmission-blocking vaccines (TBVs). TBVs target antigens on parasite sexual stages that persist within the insect vector, anopheline mosquitoes, or target mosquito midgut proteins that are presumed to mediate parasite development. By blocking parasite development within the insect vector, TBVs effectively disrupt transmission and the resultant cascade of secondary infections. Using a mosquito midgut-specific mouse monoclonal antibody (MG96), we have partially characterized membrane-bound midgut glycoproteins in Anopheles gambiae and Anopheles stephensi. These proteins are present on the microvilli of midgut epithelial cells in both blood-fed and unfed mosquitoes, suggesting that the expression of the protein is not induced as a result of blood feeding. MG96 exhibits a dose-dependent blocking effect against Plasmodium yoelii development in An. stephensi. We achieved 100% blocking of parasite development in the mosquito midgut. Preliminary deglycosylation assays indicate that the epitope recognized by MG96 is a complex oligosaccharide. Future investigation of the carbohydrate epitope as well as gene identification should provide valuable insight into the possible mechanisms of ookinete attachment and invasion of mosquito midgut epithelial cells.

Animals↗
PubMed1993

Some aspects of Phlebotomus papatasi (Scopoli) in greater Cairo, Egypt.

Exogenous and indigenous cases of zoonotic cutaneous leishmaniasis are reported in several Egyptian Governorates particularly those in the Nile Delta, Phlebotomus paptasi (Scopoli) is the only proven insect vector. This paper was intended to study the seasonal abundance, nocturnal activity and breeding sites as well as other relevant behaviour aiming to throw some light on this insect vector. The results showed that: (a) the seasonal activity started in April and ended in November or beginning of December. (b) female outnumbered male indoors (7.4:1) and V.V. outdoors (0.14:1). (c) blood fed females were 97.7% indoors and 29.4% outdoors. (d) the nocturnal activity ranged between 6 p.m. to 6 a.m. indoors and 8 p.m. to 6 a.m. outdoors. (e) the immature stages of Phlebotomus were successfully recovered from rodent burrows and poultry sheds.

Animals↗
PubMed2025

Small interfering RNAs generated from the terminal panhandle structure of negative-strand RNA virus promote viral infection.

Virus-derived small interfering RNAs (vsiRNAs) have been widely recognized to play an antiviral immunity role. However, it is unclear whether vsiRNAs can also play a positive role in viral infection. Here, we characterized three highly abundant vsiRNAs mapped to the genomic termini of rice stripe virus (RSV), a negative-strand RNA virus transmitted by insect vectors. The three vsiRNAs shared 11 nucleotides due to the conservative genomic termini and were likely generated from viral terminal panhandle structure, depending on both Dicer1 and Dicer2 in insects. In addition to targeting viral RNAs in a miRNA-like manner, the three vsiRNAs coordinately downregulated the expression of DOPA decarboxylase, thereby suppressing the prophenoloxidase immune reaction in insect vectors. In vsiRNA-silenced transgenic rice, the viral titer significantly decreased, indicating that these vsiRNAs promote RSV replication in rice. This study elucidates a unique function of vsiRNAs derived from the conserved panhandle structure of negative-strand RNA viruses in enhancing viral infection.

RNA, Small Interfering↗
PubMed1991

Genetic control of oral susceptibility to infection of Culicoides variipennis with bluetongue virus.

A family selection scheme, based on the progeny from individual females, was used to select several families of the insect vector Culicoides variipennis that were resistant or susceptible to oral infection with bluetongue virus. Genetic crosses between families showed results consistent with control by a single genetic locus (blu). Reciprocal crosses suggested a maternal effect in which the genotype of the mother determined the phenotype of the offspring. The dominant and recessive natures of the resistant (blu(r)) and susceptible (blu(s)) alleles were determined by the sex of the parent. The results provide the first evidence to suggest a genetic locus controlling insect vector competence for infection with an arbovirus.

Animals↗
PubMed1999

Species specific detection of Trypanosoma cruzi and Trypanosoma rangeli in vector and mammalian hosts by polymerase chain reaction amplification of kinetoplast minicircle DNA.

Several groups have recently developed molecular tests for the detection of Trypanosoma cruzi, the causative agent of Chagas' disease. Polymerase chain reaction (PCR) amplification of kinetoplast minicircle DNA sequences appears to be the most sensitive method. However, the specificity of PCR-based diagnostic methods was challenged when the complete sequence of Trypanosoma rangeli DNA minicircles was discovered. In the present study, we conducted. PCR experiments using the S35/S36 primers in Rhodnius prolixus and Balb/c mice with single and mixed infections of T. cruzi and/or T. rangeli. In single infections, the profile of each trypanosome was easily distinguishable in haemolymph, salivary gland and intestinal tissues and faeces of insect vectors. In mixed infections of anterior intestine (where T. rangeli is more predominant than T. cruzi), the DNA amplification profile of both parasites was observed simultaneously. Conversely, only the T. cruzi profile was observed in rectal ampulla (where T. cruzi is more abundant than T. rangeli). In mice with single infections of T. cruzi or T. rangeli, the profiles of amplified DNA were easily distinguishable in each case. The T. cruzi profile was dominant in most mixed infections, probably due to the fact that T. cruzi minicircles are more abundant and consequently compete more eagerly for annealing with the S35/S36 primers. In cases of mixed infections where T. rangeli was initially more abundant than T. cruzi, the specific T. rangeli 760 bp band was present for 7 days after infection and then this band and others ranging from 300 to 450 bp disappeared and only the typical T. cruzi 330 bp band remained. The S35/S36 primers used in polyacrylamide gel electrophoresis (PAGE) detected T. cruzi specifically, and prevented misdiagnosis due to the presence of T. rangeli. This technique can also be used to identify parasites in different stages of the infection (acute or chronic) in vertebrate hosts and to localize the parasites in the insect vector.

Animals↗
PubMed1989

Detection of Trypanosoma cruzi by DNA amplification using the polymerase chain reaction.

The polymerase chain reaction was used to amplify a 188-base pair (bp) segment of the repetitive 195-bp nuclear DNA sequence of Trypanosoma cruzi that is the most abundant sequence in this organism. The reaction amplified this repetitive element in four T. cruzi isolates from widely separated geographic regions. No amplification of the 188-bp fragment occurred when DNAs extracted from Leishmania spp., African trypanosomes, or blood samples from mice and humans were used. Amplification of one-half of the DNA from a single T. cruzi parasite produced an amount of the 188-bp element that was readily visible in a gel stained with ethidium bromide. Hybridization of a radiolabeled probe to membrane-bound amplification products increased the sensitivity to a level at which 1/200 of the DNA in a single parasite could be detected. T. cruzi DNA was readily detected in DNA extracted from the abdominal contents of infected insect vectors reared in the laboratory. No parasite DNA was detected in the blood samples of two individuals known to be infected with T. cruzi, possibly because in such patients the number of circulating parasites are extremely low or because parasitemias are intermittent. These results represent a considerable increase in sensitivity over previously reported methods for the detection of T. cruzi infections. Polymerase chain reaction amplification can be used to evaluate large numbers of samples in a single day and thus should be useful in large-scale studies of the prevalence of T. cruzi in both insect vectors and mammalian hosts.

Animals↗
PubMed2000

Complementation of a glucose transporter mutant of Schizosaccharomyces pombe by a novel Trypanosoma brucei gene.

The African trypanosome Trypanosoma brucei has a digenetic life cycle that involves the insect vector and the mammalian host. This is underscored by biochemical switches in its nutritional requirements. In the insect vector, the parasite relies on amino acid catabolism, but in the mammalian host, it derives its energy exclusively from blood glucose. Glucose transport is facilitated, and constitutes the rate-limiting step in ATP synthesis. Here, we report the cloning of a novel glucose transporter-related gene by heterologous screening of a lambdaEMBL4 genomic library of T. brucei EATRO 164 using a rat liver glucose transporter cDNA clone. Genomic analysis shows that the gene is present as a single copy within the parasite genome. The gene encodes a protein with an estimated molecular mass of 55.9 kDa, which shares only segmental homology with members of the glucose transporter superfamily. Several potential post-translational modification sites including phosphorylation, N-glycosylation, and cotranslational myristoylation sites also punctuate the sequence. It is distinguished from classical transporter proteins by the absence of putative hydrophobic membrane-spanning domains. However, this protein was capable of complementing Schizosaccharomyces pombe glucose transporter mutants. The rescued phenotype conferred the ability of the cells to grow on a broad range of sugars, both monosaccharides and disaccharides. The kinetics of glucose uptake reflected those in T. brucei. In addition to complementation in yeast, we also showed that the gene enhanced glucose uptake in cultured mammalian cells.

Amino Acid Sequence↗
PubMed1996

Hermes, a functional non-Drosophilid insect gene vector from Musca domestica.

Hermes is a short inverted repeat-type transposable element from the house fly, Musca domestica. Using an extra-chromosomal transpositional recombination assay, we show that Hermes elements can accurately transpose in M. domestica embryos. To test the ability of Hermes to function in species distantly related to M. domestica we used a nonautonomous Hermes element containing the Drosophila melanogaster while (w+) gene and created D. melanogaster germline transformants. Transgenic G1 insects were recovered from 34.6% of the fertile G0 adults developing from microinjected w- embryos. This transformation rate is comparable with that observed using P or hobo vectors in D. melanogaster, however, many instances of multiple-element insertions and large clusters were observed. Genetic mapping, Southern blotting, polytene chromosome in situ hybridization and DNA sequence analyses confirmed that Hermes elements were chromosomally integrated in transgenic insects. Our data demonstrate that Hermes elements transpose at high rates in D. melanogaster and may be an effective gene vector and gene-tagging agent in this species and distantly related species of medical and agricultural importance.

Animals↗
PubMed2005

Baculovirus as a highly efficient expression vector in insect and mammalian cells.

Baculovirus has been widely used for the production of recombinant proteins in insect cells. Since the finding that baculovirus can efficiently transduce mammalian cells, the applications of baculovirus have been greatly expanded. The prospects and drawbacks of baculovirus-mediated gene expression, either in insect or in mammalian cells, are reviewed. Recent progresses in expanding the applications to studies of gene regulation, viral vector preparation, in vivo and ex vivo gene therapy studies, generation of vaccine vectors, etc are discussed and the efforts directed towards overcoming the existing bottlenecks are particularly emphasized.

Animals↗
PubMed1976

Public health advantages of biological insect controls.

Biological control is not new, it is simply newly appreciated. This renewed appreciation stems from the widespread insecticide treadmill which is largely a product of insecticide disruption of the balance of insect communities. Biological control is a natural phenomenon; the regulation of plant and animal numbers by natural enemies. In this broad sense, biological control is vital to public health because it keeps the myriad insect species from out-competing us. It also has direct public health advantages as where natural enemies are manipulated to control disease vectoring insects. Insecticide distruption of biological control by insecticides and the resulting pesticide treadmill have serious public health implications. One is the increased pesticide load in the environment. The other is the acceleration of pesticide resistance in disease vectoring insects. The treadmill and its associated hazards will not abate so long as chemical control dominates our pest management strategy.

Environmental Health↗