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In JoVE (2)
- Protocol voor Dengue Infecties in Muggen (A. aegypti) en Infectie Fenotype Bepaling
- Protocol voor Plasmodium falciparum Infecties in Muggen en Infection Fenotype Bepaling
Other Publications (18)
- Journal of Insect Physiology
- Applied and Environmental Microbiology
- Insect Biochemistry and Molecular Biology
- Science (New York, N.Y.)
- Proceedings. Biological Sciences / The Royal Society
- PLoS Pathogens
- Science (New York, N.Y.)
- Science (New York, N.Y.)
- Developmental and Comparative Immunology
- BMC Genomics
- PLoS Pathogens
- BMC Genomics
- PLoS Neglected Tropical Diseases
- PLoS Pathogens
- BMC Genomics
- PLoS Pathogens
- Proceedings of the National Academy of Sciences of the United States of America
- PloS One
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Articles by Zhiyong Xi in JoVE
Protocol voor Dengue Infecties in Muggen (A. aegypti) en Infectie Fenotype Bepaling
Suchismita Das, Lindsey Garver, Jose Ruiz Ramirez, Zhiyong Xi, George Dimopoulos
Malaria Research Institute, Bloomberg School of Public Health, Johns Hopkins University
Zodra een gen is geïdentificeerd als potentieel refractaire voor het dengue virus moet worden geëvalueerd voor zijn rol in het voorkomen van virale infecties in de mug. Dit protocol illustreert hoe de mate van dengue infecties van muggen kunnen worden getest. De technieken voor het groeien van het virus in de cultuur, membraan voeden muggen menselijk bloed, en het testen van virale titers in de mug middendarm worden gedemonstreerd.
Protocol voor Plasmodium falciparum Infecties in Muggen en Infection Fenotype Bepaling
Zhiyong Xi, Suchismita Das, Lindsey Garver, George Dimopoulos
Malaria Research Institute, Bloomberg School of Public Health, Johns Hopkins University
Zodra een gen is geïdentificeerd als potentieel vuurvaste voor malaria, dient te worden geëvalueerd voor zijn rol in het voorkomen van Plasmodium besmettingen binnen de mug. Dit protocol illustreert hoe de mate van plasmodium infecties van muggen kunnen worden getest. De technieken voor de voorbereiding van de gametocyt cultuur, membraan voeden muggen menselijk bloed, en het testen van virale titers in de mug middendarm worden gedemonstreerd.
Other articles by Zhiyong Xi on PubMed
Journal of Insect Physiology. Apr, 2005 | Pubmed ID: 15890182
Quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) was used to study developmental expression and hormonal regulation of the juvenile hormone esterase gene (DmJhe) in the fruit fly, Drosophila melanogaster. The levels of DmJhe mRNA were low during the embryonic stage. A peak of Dmjhe mRNA was detected in the first, second and third instar larvae. The Dmjhe mRNA levels also increased soon after pupal ecdysis. The Dmjhe mRNA was detected in both male and female adult flies. The peaks of Dmjhe mRNA observed in the larvae coincided with the peaks of juvenile hormone (JH). In contrast, the mRNA for ecdysone-induced transcription factor, Drosophila hormone receptor 3 (DHR3) showed peaks of expression that coincided with the ecdysteroid peaks in embryo, larva and pupa. JH III induced Dmjhe mRNA but not DHR3 mRNA in explanted tissues cultured in Grace's medium. 20-hydroxyecdysone induced DHR3 mRNA and suppressed JH III induction of DmJhe mRNA. These studies show that the expression of jhe in D. melanogaster is regulated by both JH and 20E.
Characterization of Wolbachia Transfection Efficiency by Using Microinjection of Embryonic Cytoplasm and Embryo Homogenate
Applied and Environmental Microbiology. Jun, 2005 | Pubmed ID: 15933022
Wolbachia spp. are intracellular alpha proteobacteria closely related to Rickettsia. The maternally inherited infections occur in a wide range of invertebrates, causing several reproductive abnormalities, including cytoplasmic incompatibility. The artificial transfer of Wolbachia between hosts (transfection) is used both for basic research examining the Wolbachia-host interaction and for applied strategies that use Wolbachia infections to affect harmful insect populations. Commonly employed transfection techniques use embryonic microinjection to transfer Wolbachia-infected embryo cytoplasm or embryo homogenate. Although microinjections of both embryonic cytoplasm and homogenate have been used successfully, their respective transfection efficiencies (rates of establishing stable germ line infections) have not been directly compared. Transfection efficiency may be affected by variation in Wolbachia quantity or quality within the donor embryos and/or the buffer types used in embryo homogenization. Here we have compared Wolbachia bacteria that originate from different embryonic regions for their competencies in establishing stable germ line infections. The following three buffers were compared for their abilities to maintain an appropriate in vitro environment for Wolbachia during homogenization and injection: phosphate-buffered saline, Drosophila Ringer's buffer, and a sucrose-phosphate-glutamate solution (SPG buffer). The results demonstrate that Wolbachia bacteria from both anterior and posterior embryo cytoplasms are competent for establishing infection, although differing survivorships of injected hosts were observed. Buffer comparison shows that embryos homogenized in SPG buffer yielded the highest transfection success. No difference was observed in transfection efficiencies when the posterior cytoplasm transfer and SPG-homogenized embryo techniques were compared. We discuss the results in relation to intra- and interspecific Wolbachia transfection and the future adaptation of the microinjection technique for additional insects.
Generation of a Novel Wolbachia Infection in Aedes Albopictus (Asian Tiger Mosquito) Via Embryonic Microinjection
Insect Biochemistry and Molecular Biology. Aug, 2005 | Pubmed ID: 15944085
Genetic strategies that reduce or block pathogen transmission by mosquitoes are being investigated as a means to augment current control measures. Strategies of vector suppression and replacement are based upon intracellular Wolbachia bacteria, which occur naturally in many insect populations. Maternally inherited Wolbachia have evolved diverse mechanisms to manipulate host insect reproduction and promote infection invasion. One mechanism is cytoplasmic incompatibility (CI) through which Wolbachia promotes infection spread by effectively sterilizing uninfected females. In a prior field test, releases of Wolbachia-infected males were used to suppress a field population of Culex pipiens. An additional strategy would employ Wolbachia as a vehicle to drive desired transgenes into vector populations (population replacement). Wolbachia-based population suppression and population replacement strategies require an ability to generate artificial Wolbachia associations in mosquitoes. Here, we demonstrate a technique for transferring Wolbachia (transfection) in a medically important mosquito species: Aedes albopictus (Asian tiger mosquito). Microinjection was used to transfer embryo cytoplasm from a double-infected Ae. albopictus line into an aposymbiotic line. The resulting mosquito line is single-infected with the wAlbB Wolbachia type. The artificially generated infection type is not known to occur naturally and displays a new CI crossing type and the first known example of bidirectional CI in Aedes mosquitoes. We discuss the results in relation to applied mosquito control strategies and the evolution of Wolbachia infections in Ae. albopictus.
Science (New York, N.Y.). Oct, 2005 | Pubmed ID: 16224027
A proposed strategy to aid in controlling the growing burden of vector-borne disease is population replacement, in which a natural vector population is replaced by a population with a reduced capacity for disease transmission. An important component of such a strategy is the drive system, which serves to spread a desired genotype into the targeted field population. Endosymbiotic Wolbachia bacteria are potential transgene drivers, but infections do not naturally occur in some important mosquito vectors, notably Aedes aegypti. In this work, stable infections of wAlbB Wolbachia were established in A. aegypti and caused high rates of cytoplasmic incompatibility (that is, elimination of egg hatch). Laboratory cage tests demonstrated the ability of wAlbB to spread into an A. aegypti population after seeding of an uninfected population with infected females, reaching infection fixation within seven generations.
Proceedings. Biological Sciences / The Royal Society. Jun, 2006 | Pubmed ID: 16777718
Intracellular Wolbachia bacteria are obligate, maternally inherited endosymbionts found frequently in insects and other invertebrates. The evolutionary success of Wolbachia is due in part to an ability to manipulate reproduction. In mosquitoes and many other insects, Wolbachia causes a form of sterility known as cytoplasmic incompatibility (CI). Wolbachia-induced CI has attracted interest as a potential agent for affecting medically important disease vectors. However, application of the approach has been restricted by an absence of appropriate, naturally occurring Wolbachia infections. Here, we report the interspecific transfer of Wolbachia infection into a medically important mosquito. Using embryonic microinjection, Wolbachia is transferred from Drosophila simulans into the invasive pest and disease vector: Aedes albopictus (Asian tiger mosquito). The resulting infection is stably maintained and displays a unique pattern of bidirectional CI in crosses with naturally infected mosquitoes. Laboratory population cage experiments examine a strategy in which releases of Wolbachia-infected males are used to suppress mosquito egg hatch. We discuss the results in relation to developing appropriate Wolbachia-infected mosquito strains for population replacement and population suppression strategies.
PLoS Pathogens. Jun, 2006 | Pubmed ID: 16789837
Transmission of malaria is dependent on the successful completion of the Plasmodium lifecycle in the Anopheles vector. Major obstacles are encountered in the midgut tissue, where most parasites are killed by the mosquito's immune system. In the present study, DNA microarray analyses have been used to compare Anopheles gambiae responses to invasion of the midgut epithelium by the ookinete stage of the human pathogen Plasmodium falciparum and the rodent experimental model pathogen P. berghei. Invasion by P. berghei had a more profound impact on the mosquito transcriptome, including a variety of functional gene classes, while P. falciparum elicited a broader immune response at the gene transcript level. Ingestion of human malaria-infected blood lacking invasive ookinetes also induced a variety of immune genes, including several anti-Plasmodium factors. Twelve selected genes were assessed for effect on infection with both parasite species and bacteria using RNAi gene silencing assays, and seven of these genes were found to influence mosquito resistance to both parasite species. An MD2-like receptor, AgMDL1, and an immunolectin, FBN39, showed specificity in regulating only resistance to P. falciparum, while the antimicrobial peptide gambicin and a novel putative short secreted peptide, IRSP5, were more specific for defense against the rodent parasite P. berghei. While all the genes that affected Plasmodium development also influenced mosquito resistance to bacterial infection, four of the antimicrobial genes had no effect on Plasmodium development. Our study shows that the impact of P. falciparum and P. berghei infection on A. gambiae biology at the gene transcript level is quite diverse, and the defense against the two Plasmodium species is mediated by antimicrobial factors with both universal and Plasmodium-species specific activities. Furthermore, our data indicate that the mosquito is capable of sensing infected blood constituents in the absence of invading ookinetes, thereby inducing anti-Plasmodium immune responses.
Science (New York, N.Y.). Jun, 2007 | Pubmed ID: 17510324
We present a draft sequence of the genome of Aedes aegypti, the primary vector for yellow fever and dengue fever, which at approximately 1376 million base pairs is about 5 times the size of the genome of the malaria vector Anopheles gambiae. Nearly 50% of the Ae. aegypti genome consists of transposable elements. These contribute to a factor of approximately 4 to 6 increase in average gene length and in sizes of intergenic regions relative to An. gambiae and Drosophila melanogaster. Nonetheless, chromosomal synteny is generally maintained among all three insects, although conservation of orthologous gene order is higher (by a factor of approximately 2) between the mosquito species than between either of them and the fruit fly. An increase in genes encoding odorant binding, cytochrome P450, and cuticle domains relative to An. gambiae suggests that members of these protein families underpin some of the biological differences between the two mosquito species.
Science (New York, N.Y.). Jun, 2007 | Pubmed ID: 17588928
Mosquitoes are vectors of parasitic and viral diseases of immense importance for public health. The acquisition of the genome sequence of the yellow fever and Dengue vector, Aedes aegypti (Aa), has enabled a comparative phylogenomic analysis of the insect immune repertoire: in Aa, the malaria vector Anopheles gambiae (Ag), and the fruit fly Drosophila melanogaster (Dm). Analysis of immune signaling pathways and response modules reveals both conservative and rapidly evolving features associated with different functional gene categories and particular aspects of immune reactions. These dynamics reflect in part continuous readjustment between accommodation and rejection of pathogens and suggest how innate immunity may have evolved.
Developmental and Comparative Immunology. 2008 | Pubmed ID: 18036658
Immunoglobulin superfamily (IgSF) proteins are known for their ability to specifically recognize and adhere to other molecules, mediating cell-surface reception and pathogen recognition. Mammalian IgSF proteins such as antibodies are among the best characterized molecules of the immune system; in contrast, the involvement of invertebrate IgSF members in immunity has not been broadly studied. Analysis of the predicted Anopheles gambiae transcriptome identified 138 proteins that have at least one immunoglobulin domain. Challenge with Plasmodium, Gram-negative or Gram-positive bacteria resulted in significant regulation of 85 IgSF genes, indicating potential roles for these molecules in infection responses and immunity. Based on sequence and expression data, six infection-responsive with immunoglobulin domain (IRID 1-6) genes were chosen and functionally characterized with regard to their role in innate immunity. Reverse-genetic gene-silencing assays showed IRID3, IRID5 and IRID6 contribute to viability upon bacterial infection while IRID4 and IRID6 are involved in limiting Plasmodium falciparum infection.
Gene Discovery in an Invasive Tephritid Model Pest Species, the Mediterranean Fruit Fly, Ceratitis Capitata
BMC Genomics. 2008 | Pubmed ID: 18500975
The medfly, Ceratitis capitata, is a highly invasive agricultural pest that has become a model insect for the development of biological control programs. Despite research into the behavior and classical and population genetics of this organism, the quantity of sequence data available is limited. We have utilized an expressed sequence tag (EST) approach to obtain detailed information on transcriptome signatures that relate to a variety of physiological systems in the medfly; this information emphasizes on reproduction, sex determination, and chemosensory perception, since the study was based on normalized cDNA libraries from embryos and adult heads.
PLoS Pathogens. Jul, 2008 | Pubmed ID: 18604274
Aedes aegypti, the mosquito vector of dengue viruses, utilizes its innate immune system to ward off a variety of pathogens, some of which can cause disease in humans. To date, the features of insects' innate immune defenses against viruses have mainly been studied in the fruit fly Drosophila melanogaster, which appears to utilize different immune pathways against different types of viruses, in addition to an RNA interference-based defense system. We have used the recently released whole-genome sequence of the Ae. aegypti mosquito, in combination with high-throughput gene expression and RNA interference (RNAi)-based reverse genetic analyses, to characterize its response to dengue virus infection in different body compartments. We have further addressed the impact of the mosquito's endogenous microbial flora on virus infection. Our findings indicate a significant role for the Toll pathway in regulating resistance to dengue virus, as indicated by an infection-responsive regulation and functional assessment of several Toll pathway-associated genes. We have also shown that the mosquito's natural microbiota play a role in modulating the dengue virus infection, possibly through basal-level stimulation of the Toll immune pathway.
Genome-wide Analysis of the Interaction Between the Endosymbiotic Bacterium Wolbachia and Its Drosophila Host
BMC Genomics. 2008 | Pubmed ID: 18171476
Intracellular Wolbachia bacteria are obligate, maternally-inherited, endosymbionts found frequently in insects and other invertebrates. The success of Wolbachia can be attributed in part to an ability to alter host reproduction via mechanisms including cytoplasmic incompatibility (CI), parthenogenesis, feminization and male killing. Despite substantial scientific effort, the molecular mechanisms underlying the Wolbachia/host interaction are unknown.
PLoS Neglected Tropical Diseases. 2009 | Pubmed ID: 19823571
Human lymphatic filariasis is a mosquito-vectored disease caused by the nematode parasites Wuchereria bancrofti, Brugia malayi and Brugia timori. These are relatively large roundworms that can cause considerable damage in compatible mosquito vectors. In order to assess how mosquitoes respond to infection in compatible mosquito-filarial worm associations, microarray analysis was used to evaluate transcriptome changes in Aedes aegypti at various times during B. malayi development. Changes in transcript abundance in response to the different stages of B. malayi infection were diverse. At the early stages of midgut and thoracic muscle cell penetration, a greater number of genes were repressed compared to those that were induced (20 vs. 8). The non-feeding, intracellular first-stage larvae elicited few differences, with 4 transcripts showing an increased and 9 a decreased abundance relative to controls. Several cecropin transcripts increased in abundance after parasites molted to second-stage larvae. However, the greatest number of transcripts changed in abundance after larvae molted to third-stage larvae and migrated to the head and proboscis (120 induced, 38 repressed), including a large number of putative, immunity-related genes (approximately 13% of genes with predicted functions). To test whether the innate immune system of mosquitoes was capable of modulating permissiveness to the parasite, we activated the Toll and Imd pathway controlled rel family transcription factors Rel1 and Rel2 (by RNA interference knockdown of the pathway's negative regulators Cactus and Caspar) during the early stages of infection with B. malayi. The activation of either of these immune signaling pathways, or knockdown of the Toll pathway, did not affect B. malayi in Ae. aegypti. The possibility of LF parasites evading mosquito immune responses during successful development is discussed.
PLoS Pathogens. Apr, 2010 | Pubmed ID: 20368968
Genetic strategies that reduce or block pathogen transmission by mosquitoes have been proposed as a means of augmenting current control measures to reduce the growing burden of vector-borne diseases. The endosymbiotic bacterium Wolbachia has long been promoted as a potential vehicle for introducing disease-resistance genes into mosquitoes, thereby making them refractory to the human pathogens they transmit. Given the large overlap in tissue distribution and intracellular localization between Wolbachia and dengue virus in mosquitoes, we conducted experiments to characterize their interactions. Our results show that Wolbachia inhibits viral replication and dissemination in the main dengue vector, Aedes aegypti. Moreover, the virus transmission potential of Wolbachia-infected Ae. aegypti was significantly diminished when compared to wild-type mosquitoes that did not harbor Wolbachia. At 14 days post-infection, Wolbachia completely blocked dengue transmission in at least 37.5% of Ae. aegypti mosquitoes. We also observed that this Wolbachia-mediated viral interference was associated with an elevated basal immunity and increased longevity in the mosquitoes. These results underscore the potential usefulness of Wolbachia-based control strategies for population replacement.
BMC Genomics. 2010 | Pubmed ID: 20553610
Two fifths of the world's population is at risk from dengue. The absence of effective drugs and vaccines leaves vector control as the primary intervention tool. Understanding dengue virus (DENV) host interactions is essential for the development of novel control strategies. The availability of genome sequences for both human and mosquito host greatly facilitates genome-wide studies of DENV-host interactions.
PLoS Pathogens. Nov, 2011 | Pubmed ID: 22114564
The mosquito immune system is involved in pathogen-elicited defense responses. The NF-κB factors REL1 and REL2 are downstream transcription activators of Toll and IMD immune pathways, respectively. We have used genome-wide microarray analyses to characterize fat-body-specific gene transcript repertoires activated by either REL1 or REL2 in two transgenic strains of the mosquito Aedes aegypti. Vitellogenin gene promoter was used in each transgenic strain to ectopically express either REL1 (REL1+) or REL2 (REL2+) in a sex, tissue, and stage specific manner. There was a significant change in the transcript abundance of 297 (79 up- and 218 down-regulated) and 299 (123 up- and 176 down-regulated) genes in fat bodies of REL1+ and REL2+, respectively. Over half of the induced genes had predicted functions in immunity, and a large group of these was co-regulated by REL1 and REL2. By generating a hybrid transgenic strain, which ectopically expresses both REL1 and REL2, we have shown a synergistic action of these NF-κB factors in activating immune genes. The REL1+ immune transcriptome showed a significant overlap with that of cactus (RNAi)-depleted mosquitoes (50%). In contrast, the REL2+ -regulated transcriptome differed from the relatively small group of gene transcripts regulated by RNAi depletion of a putative inhibitor of the IMD pathway, caspar (35 up- and 140 down-regulated), suggesting that caspar contributes to regulation of a subset of IMD-pathway controlled genes. Infections of the wild type Ae. aegypti with Plasmodium gallinaceum elicited the transcription of a distinct subset of immune genes (76 up- and 25 down-regulated) relative to that observed in REL1+ and REL2+ mosquitoes. Considerable overlap was observed between the fat body transcriptome of Plasmodium-infected mosquitoes and that of mosquitoes with transiently depleted PIAS, an inhibitor of the JAK-STAT pathway. PIAS gene silencing reduced Plasmodium proliferation in Ae. aegypti, indicating the involvement of the JAK-STAT pathway in anti-Plasmodium defense in this infection model.
Wolbachia Induces Reactive Oxygen Species (ROS)-dependent Activation of the Toll Pathway to Control Dengue Virus in the Mosquito Aedes Aegypti
Proceedings of the National Academy of Sciences of the United States of America. Jan, 2012 | Pubmed ID: 22123956
Wolbachia are maternally transmitted symbiotic bacteria that can spread within insect populations because of their unique ability to manipulate host reproduction. When introduced to nonnative mosquito hosts, Wolbachia induce resistance to a number of human pathogens, including dengue virus (DENV), Plasmodium, and filarial nematodes, but the molecular mechanism involved is unclear. In this study, we have deciphered how Wolbachia infection affects the Aedes aegypti host in inducing resistance to DENV. The microarray assay indicates that transcripts of genes with functions related to immunity and reduction-oxidation (redox) reactions are up-regulated in Ae. aegypti infected with Wolbachia. Infection with this bacterium leads to induction of oxidative stress and an increased level of reactive oxygen species in its mosquito host. Reactive oxygen species elevation is linked to the activation of the Toll pathway, which is essential in mediating the expression of antioxidants to counterbalance oxidative stress. This immune pathway also is responsible for activation of antimicrobial peptides-defensins and cecropins. We provide evidence that these antimicrobial peptides are involved in inhibition of DENV proliferation in Wolbachia-infected mosquitoes. Utilization of transgenic Ae. aegypti and the RNAi depletion approach has been instrumental in proving the role of defensins and cecropins in the resistance of Wolbachia-infected Ae. aegypti to DENV. These results indicate that a symbiotic bacterium can manipulate the host defense system to facilitate its own persistent infection, resulting in a compromise of the mosquito's ability to host human pathogens. Our discoveries will aid in the development of control strategies for mosquito-transmitted diseases.
Transcriptome Profiling of Sexual Maturation and Mating in the Mediterranean Fruit Fly, Ceratitis Capitata
PloS One. 2012 | Pubmed ID: 22303464
Sexual maturation and mating in insects are generally accompanied by major physiological and behavioural changes. Many of these changes are related to the need to locate a mate and subsequently, in the case of females, to switch from mate searching to oviposition behaviour. The prodigious reproductive capacity of the Mediterranean fruit fly, Ceratitis capitata, is one of the factors that has led to its success as an invasive pest species. To identify the molecular changes related to maturation and mating status in male and female medfly, a microarray-based gene expression approach was used to compare the head transcriptomes of sexually immature, mature virgin, and mated individuals. Attention was focused on the changes in abundance of transcripts related to reproduction, behaviour, sensory perception of chemical stimulus, and immune system processes. Broad transcriptional changes were recorded during female maturation, while post-mating transcriptional changes in females were, by contrast, modest. In male medfly, transcriptional changes were consistent both during maturation and as a consequence of mating. Of particular note was the lack of the mating-induced immune responses that have been recorded for Drosophila melanogaster, that may be due to the different reproductive strategies of these species. This study, in addition to increasing our understanding of the molecular machinery behind maturation and mating in the medfly, has identified important gene targets that might be useful in the future management of this pest.