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1.
Cureus ; 15(10): e46955, 2023 Oct.
Article in English | MEDLINE | ID: mdl-38022295

ABSTRACT

Cardiac lipomas are benign primary cardiac tumors that are most often asymptomatic and diagnosed incidentally. Cardiac magnetic resonance imaging (MRI) is the imaging modality of choice when aiming to characterize these tumors. A minority of cardiac lipomas are intramyocardial, which, when combined with the much more common post-infarction fatty metaplasia, makes diagnosing these lipomas very challenging. We review a case of intramyocardial lipoma in the distal interventricular septum that was initially detected on a low-dose computed tomography for lung cancer screening and the subsequent findings on cardiac MRI that made the diagnosis. Additionally, this case also helps to support the conservative management of intramyocardial lipomas that are more distal in the left ventricle and subsequently at lower risk for conduction arrhythmias.

2.
PLoS One ; 18(2): e0278466, 2023.
Article in English | MEDLINE | ID: mdl-36812214

ABSTRACT

There have been over 621 million cases of COVID-19 worldwide with over 6.5 million deaths. Despite the high secondary attack rate of COVID-19 in shared households, some exposed individuals do not contract the virus. In addition, little is known about whether the occurrence of COVID-19 resistance differs among people by health characteristics as stored in the electronic health records (EHR). In this retrospective analysis, we develop a statistical model to predict COVID-19 resistance in 8,536 individuals with prior COVID-19 exposure using demographics, diagnostic codes, outpatient medication orders, and count of Elixhauser comorbidities in EHR data from the COVID-19 Precision Medicine Platform Registry. Cluster analyses identified 5 patterns of diagnostic codes that distinguished resistant from non-resistant patients in our study population. In addition, our models showed modest performance in predicting COVID-19 resistance (best performing model AUROC = 0.61). Monte Carlo simulations conducted indicated that the AUROC results are statistically significant (p < 0.001) for the testing set. We hope to validate the features found to be associated with resistance/non-resistance through more advanced association studies.


Subject(s)
COVID-19 , Humans , SARS-CoV-2 , Retrospective Studies , Machine Learning , Electronic Health Records
3.
Front Bioeng Biotechnol ; 10: 975786, 2022.
Article in English | MEDLINE | ID: mdl-36394032

ABSTRACT

For more than 60 years, efforts to develop mating-based mosquito control technologies have largely failed to produce solutions that are both effective and scalable, keeping them out of reach of most governments and communities in disease-impacted regions globally. High pest suppression levels in trials have yet to fully translate into broad and effective Aedes aegypti control solutions. Two primary challenges to date-the need for complex sex-sorting to prevent female releases, and cumbersome processes for rearing and releasing male adult mosquitoes-present significant barriers for existing methods. As the host range of Aedes aegypti continues to advance into new geographies due to increasing globalisation and climate change, traditional chemical-based approaches are under mounting pressure from both more stringent regulatory processes and the ongoing development of insecticide resistance. It is no exaggeration to state that new tools, which are equal parts effective and scalable, are needed now more than ever. This paper describes the development and field evaluation of a new self-sexing strain of Aedes aegypti that has been designed to combine targeted vector suppression, operational simplicity, and cost-effectiveness for use in disease-prone regions. This conditional, self-limiting trait uses the sex-determination gene doublesex linked to the tetracycline-off genetic switch to cause complete female lethality in early larval development. With no female progeny survival, sex sorting is no longer required, eliminating the need for large-scale mosquito production facilities or physical sex-separation. In deployment operations, this translates to the ability to generate multiple generations of suppression for each mosquito released, while being entirely self-limiting. To evaluate these potential benefits, a field trial was carried out in densely-populated urban, dengue-prone neighbourhoods in Brazil, wherein the strain was able to suppress wild mosquito populations by up to 96%, demonstrating the utility of this self-sexing approach for biological vector control. In doing so, it has shown that such strains offer the critical components necessary to make these tools highly accessible, and thus they harbour the potential to transition mating-based approaches to effective and sustainable vector control tools that are within reach of governments and at-risk communities who may have only limited resources.

4.
PLoS Negl Trop Dis ; 16(5): e0010315, 2022 05.
Article in English | MEDLINE | ID: mdl-35576193

ABSTRACT

Establishment of novel mosquito control technologies such as the use of genetically engineered insects typically involves phased testing to generate robust data-sets that support its safe and effective use as a vector control tool. In this study, we demonstrate the ability of the transgenic self-limiting OX513A Aedes aegypti strain to suppress a wild type Ae. aegypti population in an outdoor containment facility in India. OX513A is a genetically engineered Ae. aegypti strain with a repressible dominant self-limiting gene. When male adult OX513A mate with wild female adults, a single copy of the self-limiting gene is inherited by all the progeny, leading to death of >95% of progeny during larval/pupal development. A wild-type population of Ae. aegypti was established and stabilized during a 14 week period in five paired field cage units, each consisting of control and treatment cages, followed by weekly releases of OX513A male adults to suppress the target population. The successive introductions of OX513A male adults led to a consistent decline in wild type numbers eventually resulting in the elimination of Ae. aegypti from all treated cages within 10 to 15 weeks of release. This study demonstrates that Ae. aegypti elimination may be a realistic and achievable target in relatively isolated environments.


Subject(s)
Aedes , Yellow Fever , Aedes/genetics , Animals , Female , Male , Mosquito Control , Mosquito Vectors/genetics , Pest Control, Biological/methods
5.
Respir Med Case Rep ; 26: 321-325, 2019.
Article in English | MEDLINE | ID: mdl-30937281

ABSTRACT

Pulmonary vein stenosis (PVS) is a serious complication of radiofrequency ablation (RFA) for the treatment of atrial fibrillation. The prevalence of this complication was reported to be as high as 42% in 1999 when RFA was first implemented [1]. However, with improvements in operator technique including wide area circumferential ablation, antral isolation, and the use of intracardiac ultrasound, the incidence of symptomatic severe PVS following RFA ranges from 0% to 2.1% while the incidence of symptomatic pulmonary vein occlusion (PVO) following RFA was found to be 0.67% [2-8]. Despite a decrease in the incidence of clinically significant PVS following RFA, there have been increased reports of complications associated with PVS to include hemoptysis, scarring, lung infarction, and intraparenchymal hemorrhage [9]. Studies have shown that PVS is often misdiagnosed as pneumonia, pulmonary embolism, and lung cancer and as a result, patients are often subjected to unnecessary diagnostic procedures [2,10]. The current first line treatment for this condition is percutaneous balloon angioplasty with stenting; however, there are studies that have shown that there is a relatively high rate of restenosis despite optimal medical therapy [2-3,10,11]. Three case reports have described the use of lobectomy to treat patients with persistent respiratory symptoms in the setting of severe PVO with good outcomes [12-14]. We present a case of iatrogenic PVO and ipsilateral severe PVS following RFA who underwent attempted lobectomy for persistent exertional dyspnea and persistent hypoperfusion of the left upper lung lobe despite percutaneous intervention and six months of optimal medical therapy. The lobectomy was aborted due to the presence of a significant fibrothorax, and the patient continues to have significant exercise limitation despite participation in pulmonary rehabilitation.

6.
Curr Protoc Chem Biol ; 10(2): e39, 2018 06.
Article in English | MEDLINE | ID: mdl-29927113

ABSTRACT

Antibodies are useful tools for detecting individual proteins in complex samples and for learning about their location, amount, binding partners, and function in cells. Unfortunately, generating antibodies is time consuming and laborious, and their affinity and/or specificity is often limited. This protocol offers a fast and inexpensive alternative to generate antibody surrogates through phage display of a library of fibronectin type III (FN3) monobody variants and affinity selection for binders. © 2018 by John Wiley & Sons, Inc.


Subject(s)
Antibodies, Monoclonal/chemistry , Cell Surface Display Techniques , Fibronectin Type III Domain , Indicators and Reagents/chemical synthesis , Antibodies, Monoclonal/immunology , Antibody Specificity , Fibronectin Type III Domain/immunology , Humans , Indicators and Reagents/chemistry , Peptide Library
7.
Nucleic Acids Res ; 45(18): e158, 2017 Oct 13.
Article in English | MEDLINE | ID: mdl-28985360

ABSTRACT

The 'sandwich' binding format, which uses two reagents that can bind simultaneously to a given analyte, is the gold standard in diagnostics and many biochemical techniques. One of the bottlenecks in creating a sandwich assay is identifying pairs of reagents that bind non-competitively to the target. To bridge this gap, we invented Megaprimer Shuffling for Tandem Affinity Reagents (MegaSTAR) to identify non-competitive binding pairs of recombinant affinity reagents through phage-display. The key innovation in MegaSTAR is the construction of a tandem library, in which two reagents are randomly-displayed on the phage surface. This is accomplished by using a pool of 300-nucleotide long 'megaprimers', which code for previously-selected reagents, to prime second strand synthesis of a single-stranded DNA template and generate millions of pair-wise combinations. The tandem library is then affinity selected to isolate pairs that both reagents contribute to binding the target. As a proof-of-concept, we used MegaSTAR to identify pairs of fibronectin type III monobodies for three human proteins. For each target, we could identify between five and fifteen unique pairs and successfully used a single pair in a sandwich assay. MegaSTAR is a versatile tool for generating sandwich ELISA-grade and bispecific reagents.


Subject(s)
Affinity Labels/metabolism , Cell Surface Display Techniques/methods , Protein Interaction Domains and Motifs , Recombinant Proteins/metabolism , Enzyme-Linked Immunosorbent Assay , Genetic Techniques , High-Throughput Screening Assays/methods , Humans , Peptide Library , Polymerization , Protein Binding , Recombinant Proteins/chemistry
8.
Pest Manag Sci ; 72(3): 618-28, 2016 Mar.
Article in English | MEDLINE | ID: mdl-26374668

ABSTRACT

BACKGROUND: Under permit from the National Biosafety Commission for the use of genetically modified organisms, releases of a genetically engineered self-limiting strain of Aedes aegypti (OX513A) were used to suppress urban pest Ae. aegypti in West Panama. Experimental goals were to assess the effects on a coexisting population of Ae. albopictus and examine operational parameters with relevance to environmental impact. RESULTS: Ae. albopictus populations were shown to be increasing year upon year at each of three study sites, potentially reflecting a broader-scale incursion into the area. Ae. albopictus abundance was unaffected by a sustained reduction in Ae. aegypti by up to 93% through repeated releases of OX513A. Males accounted for 99.99% of released OX513A, resulting in a sustained mating fraction of 75%. Mean mating competitiveness of OX513A was 0.14. The proportion of OX513A in the local environment decreased by 95% within 25 days of the final release. CONCLUSIONS: There was no evidence for species replacement of Ae. aegypti by Ae. albopictus over the course of this study. No unintentional environmental impacts or elevated operational risks were observed. The potential for this emerging technology to mitigate against disease outbreaks before they become established is discussed.


Subject(s)
Aedes , Pest Control, Biological , Aedes/genetics , Animals , Animals, Genetically Modified/genetics , Environment , Female , Male , Panama
9.
Pest Manag Sci ; 72(1): 140-9, 2016 Jan.
Article in English | MEDLINE | ID: mdl-25612154

ABSTRACT

BACKGROUND: We report on the status of imidacloprid and ethiprole resistance in Nilaparvata lugens Stål collected from across South and East Asia over the period 2005-2012. RESULTS: A resistance survey found that field populations had developed up to 220-fold resistance to imidacloprid and 223-fold resistance to ethiprole, and that many of the strains collected showed high levels of resistance to both insecticides. We also found that the cytochrome P450 CYP6ER1 was significantly overexpressed in 12 imidacloprid-resistant populations tested when compared with a laboratory susceptible strain, with fold changes ranging from ten- to 90-fold. In contrast, another cytochrome P450 CYP6AY1, also implicated in imidacloprid resistance, was underexpressed in ten of the populations and only significantly overexpressed (3.5-fold) in a single population from India compared with the same susceptible strain. Further selection of two of the imidacloprid-resistant field strains correlated with an approximate threefold increase in expression of CYP6ER1. CONCLUSIONS: We conclude that overexpression of CYP6ER1 is associated with field-evolved resistance to imidacloprid in brown planthopper populations in five countries in South and East Asia.


Subject(s)
Hemiptera/drug effects , Imidazoles/pharmacology , Insecticide Resistance , Insecticides/pharmacology , Nitro Compounds/pharmacology , Pyrazoles/pharmacology , Animals , Asia, Southeastern , Cytochrome P-450 Enzyme System/metabolism , Asia, Eastern , Female , Hemiptera/genetics , India , Neonicotinoids
10.
Int J Mol Sci ; 16(10): 23587-603, 2015 Sep 30.
Article in English | MEDLINE | ID: mdl-26437402

ABSTRACT

Often when generating recombinant affinity reagents to a target, one singles out an individual binder, constructs a secondary library of variants, and affinity selects a tighter or more specific binder. To enhance the throughput of this general approach, we have developed a more integrated strategy where the "affinity maturation" step is part of the phage-display pipeline, rather than a follow-on process. In our new schema, we perform two rounds of affinity selection, followed by error-prone PCR on the pools of recovered clones, generation of secondary libraries, and three additional rounds of affinity selection, under conditions of off-rate competition. We demonstrate the utility of this approach by generating low nanomolar fibronectin type III (FN3) monobodies to five human proteins: ubiquitin-conjugating enzyme E2 R1 (CDC34), COP9 signalosome complex subunit 5 (COPS5), mitogen-activated protein kinase kinase 5 (MAP2K5), Splicing factor 3A subunit 1 (SF3A1) and ubiquitin carboxyl-terminal hydrolase 11 (USP11). The affinities of the resulting monobodies are typically in the single-digit nanomolar range. We demonstrate the utility of two binders by pulling down the targets from a spiked lysate of HeLa cells. This integrated approach should be applicable to directed evolution of any phage-displayed affinity reagent scaffold.


Subject(s)
Chromatography, Affinity/methods , Recombinant Proteins/metabolism , Amino Acid Motifs , Amino Acid Sequence , Antibodies/metabolism , Antigens/metabolism , Biotinylation , Calorimetry , Cell Surface Display Techniques , HeLa Cells , Humans , Indicators and Reagents , Kinetics , Molecular Sequence Data , Protein Structure, Secondary
11.
BMC Biol ; 13: 49, 2015 Jul 16.
Article in English | MEDLINE | ID: mdl-26179401

ABSTRACT

BACKGROUND: Development and evaluation of new insect pest management tools is critical for overcoming over-reliance upon, and growing resistance to, synthetic, biological and plant-expressed insecticides. For transgenic crops expressing insecticidal proteins from the bacterium Bacillus thuringiensis ('Bt crops') emergence of resistance is slowed by maintaining a proportion of the crop as non-Bt varieties, which produce pest insects unselected for resistance. While this strategy has been largely successful, multiple cases of Bt resistance have now been reported. One new approach to pest management is the use of genetically engineered insects to suppress populations of their own species. Models suggest that released insects carrying male-selecting (MS) transgenes would be effective agents of direct, species-specific pest management by preventing survival of female progeny, and simultaneously provide an alternative insecticide resistance management strategy by introgression of susceptibility alleles into target populations. We developed a MS strain of the diamondback moth, Plutella xylostella, a serious global pest of crucifers. MS-strain larvae are reared as normal with dietary tetracycline, but, when reared without tetracycline or on host plants, only males will survive to adulthood. We used this strain in glasshouse-cages to study the effect of MS male P. xylostella releases on target pest population size and spread of Bt resistance in these populations. RESULTS: Introductions of MS-engineered P. xylostella males into wild-type populations led to rapid pest population decline, and then elimination. In separate experiments on broccoli plants, relatively low-level releases of MS males in combination with broccoli expressing Cry1Ac (Bt broccoli) suppressed population growth and delayed the spread of Bt resistance. Higher rates of MS male releases in the absence of Bt broccoli were also able to suppress P. xylostella populations, whereas either low-level MS male releases or Bt broccoli alone did not. CONCLUSIONS: These results support theoretical modeling, indicating that MS-engineered insects can provide a powerful pest population suppressing effect, and could effectively augment current Bt resistance management strategies. We conclude that, subject to field confirmation, MS insects offer an effective and versatile control option against P. xylostella and potentially other pests, and may reduce reliance on and protect insecticide-based approaches, including Bt crops.


Subject(s)
Animals, Genetically Modified/genetics , Brassica/parasitology , Crops, Agricultural/parasitology , Insecticide Resistance , Moths/genetics , Pest Control, Biological/methods , Transgenes , Animals , Bacillus thuringiensis/genetics , Brassica/genetics , Crops, Agricultural/genetics , Female , Genetic Engineering , Male , Moths/physiology , Plants, Genetically Modified/genetics , Plants, Genetically Modified/parasitology
12.
Pest Manag Sci ; 71(7): 957-65, 2015 Jul.
Article in English | MEDLINE | ID: mdl-25078081

ABSTRACT

BACKGROUND: OX513A is a genetically engineered strain of Aedes aegypti carrying a repressible, dominantly inherited transgene that confers lethality in immature heterozygous progeny. Released male OX513A adults have proven to be effective for the localised suppression of wild Ae. aegypti, highlighting its potential in vector control. Mating and life-table assessments were used to compare OX513A with reared Ae. aegypti strains collected from New Delhi and Aurangabad regions in India. RESULTS: Mating proportions of New Delhi females versus males of OX513A or New Delhi strains were 0.52 and 0.48 respectively, indicating no discrimination by females against either strain, and males of both strains were equally competitive. Developmental time from first instar to adult emergence was significantly longer for OX513A (10.7 ± 0.04 days) than for New Delhi (9.4 ± 0.04 days) and Aurangabad strains (9.1 ± 0.04 days). Differences in mean longevities, female reproductive parameters and population growth parameters between the strains were non-significant. CONCLUSIONS: The laboratory study demonstrates that only minor life-table variations of limited biological relevance exist between OX513A and Indian Ae. aegypti populations, and males had equal potential for mating competitiveness. Thus, results support the OX513A strain as a suitable candidate for continued evaluation towards sustainable management of Ae. aegypti populations in India.


Subject(s)
Aedes/genetics , Aedes/physiology , Animals , Animals, Genetically Modified , Female , Genetic Fitness , Genotype , India , Longevity/genetics , Male , Pest Control, Biological/methods , Reproduction/genetics , Sexual Behavior, Animal
13.
Pest Manag Sci ; 69(2): 149, 2013 Feb.
Article in English | MEDLINE | ID: mdl-23345123
14.
Pest Manag Sci ; 69(7): 809-13, 2013 Jul.
Article in English | MEDLINE | ID: mdl-23203347

ABSTRACT

BACKGROUND: Insecticides are important tools for managing damaging insect pests. Compounds that are effective against pests such as the whiteflies Bemisia tabaci and Trialeurodes vaporariorum, which show resistance to a range of insecticidal modes of action (MOA), have particular value as components of resistance management programmes. The sulfoximine insecticides are chemically unique as the first to incorporate a sulfoximine functional group. Sulfoxaflor is the first sulfoximine compound under commercial development for the control of sap-feeding insects. Its cross-resistance relationships were investigated by comparing the responses of field-collected strains with those of insecticide-susceptible laboratory strains of B. tabaci and T. vaporariorum. RESULTS: Sulfoxaflor exhibited very low (less than threefold) resistance ratios (RR) when tested against strains of B. tabaci that produced RR of up to 1000-fold to imidacloprid and cross-resistance to other neonicotinoid insecticides. Similarly, sulfoxaflor was not cross-resistant in a strain of B. tabaci exhibiting resistance to a pyrethroid (deltamethrin) and an organophosphate (profenophos). No cross-resistance was observed between sulfoxaflor and imidacloprid in T. vaporariorum. One population of the three field strains tested showed slightly reduced susceptibility to sufloxaflor with an RR of 4.17. By comparison, this same population exhibited an RR of more than 23.8-fold for imidacloprid relative to the susceptible population. CONCLUSION: In spite of sharing a target site with neonicotinoids (the nicotinic acetylcholine receptor), sulfoxaflor was largely unaffected by existing cases of neonicotinoid resistance in B. tabaci and T. vaporariorum. Neonicotinoid resistance mechanisms in these whitefly species are known to be primarily based on enhanced detoxification of insecticide. This lack of cross-resistance indicates that sulfoxaflor is a valuable new tool for the management of sap-feeding pests already resistant to established insecticide groups.


Subject(s)
Hemiptera/drug effects , Imidazoles/pharmacology , Insecticide Resistance , Insecticides/pharmacology , Nitro Compounds/pharmacology , Pyridines/pharmacology , Sulfur Compounds/pharmacology , Animals , Neonicotinoids
15.
Insect Biochem Mol Biol ; 42(7): 506-13, 2012 Jul.
Article in English | MEDLINE | ID: mdl-22504519

ABSTRACT

The tomato leaf miner, Tuta absoluta (Lepidoptera) is a significant pest of tomatoes that has undergone a rapid expansion in its range during the past six years and is now present across Europe, North Africa and parts of Asia. One of the main means of controlling this pest is through the use of chemical insecticides. In the current study insecticide bioassays were used to determine the susceptibility of five T. absoluta strains established from field collections from Europe and Brazil to pyrethroids. High levels of resistance to λ cyhalothrin and tau fluvalinate were observed in all five strains tested. To investigate whether pyrethroid resistance was mediated by mutation of the para-type sodium channel in T. absoluta the IIS4-IIS6 region of the para gene, which contains many of the mutation sites previously shown to confer knock down (kdr)-type resistance to pyrethroids across a range of different arthropod species, was cloned and sequenced. This revealed that three kdr/super-kdr-type mutations (M918T, T929I and L1014F), were present at high frequencies within all five resistant strains at known resistance 'hot-spots'. This is the first description of these mutations together in any insect population. High-throughput DNA-based diagnostic assays were developed and used to assess the prevalence of these mutations in 27 field strains from 12 countries. Overall mutant allele frequencies were high (L1014F 0.98, M918T 0.35, T929I 0.60) and remarkably no individual was observed that did not carry kdr in combination with either M918T or T929I. The presence of these mutations at high frequency in T. absoluta populations across much of its range suggests pyrethroids are likely to be ineffective for control and supports the idea that the rapid expansion of this species over the last six years may be in part mediated by the resistance of this pest to chemical insecticides.


Subject(s)
Insect Proteins/isolation & purification , Insecticide Resistance , Insecticides/pharmacology , Moths/genetics , Nitriles/pharmacology , Pyrethrins/pharmacology , Sodium Channels/isolation & purification , Animals , Brazil , Cloning, Molecular , DNA, Complementary/genetics , DNA, Complementary/metabolism , Europe , Gene Frequency , Insect Proteins/metabolism , Larva/drug effects , Larva/genetics , Molecular Sequence Data , Moths/drug effects , Moths/growth & development , Mutation , Real-Time Polymerase Chain Reaction , Sequence Analysis, DNA , Sodium Channels/metabolism
16.
PLoS One ; 7(2): e31077, 2012.
Article in English | MEDLINE | ID: mdl-22347432

ABSTRACT

BACKGROUND: The juvenile hormone mimic, pyriproxyfen is a suppressor of insect embryogenesis and development, and is effective at controlling pests such as the greenhouse whitefly Trialeurodes vaporariorum (Westwood) which are resistant to other chemical classes of insecticides. Although there are reports of insects evolving resistance to pyriproxyfen, the underlying resistance mechanism(s) are poorly understood. RESULTS: Bioassays against eggs of a German (TV8) population of T. vaporariorum revealed a moderate level (21-fold) of resistance to pyriproxyfen. This is the first time that pyriproxyfen resistance has been confirmed in this species. Sequential selection of TV8 rapidly generated a strain (TV8pyrsel) displaying a much higher resistance ratio (>4000-fold). The enzyme inhibitor piperonyl butoxide (PBO) suppressed this increased resistance, indicating that it was primarily mediated via metabolic detoxification. Microarray analysis identified a number of significantly over-expressed genes in TV8pyrsel as candidates for a role in resistance including cytochrome-P450 dependent monooxygenases (P450s). Quantitative PCR highlighted a single P450 gene (CYP4G61) that was highly over-expressed (81.7-fold) in TV8pyrsel. CONCLUSION: Over-expression of a single cytochrome P450 gene (CYP4G61) has emerged as a strong candidate for causing the enhanced resistance phenotype. Further work is needed to confirm the role of the encoded P450 enzyme CYP4G61 in detoxifying pyriproxyfen.


Subject(s)
Cytochrome P-450 Enzyme System/genetics , Insecticide Resistance/genetics , Pyridines/pharmacology , Animals , Cytochrome P-450 Enzyme System/physiology , Enzyme Inhibitors/pharmacology , Hemiptera/drug effects , Insecticides/pharmacology , Juvenile Hormones , Piperonyl Butoxide/pharmacology
17.
Pest Manag Sci ; 68(6): 834-8, 2012 Jun.
Article in English | MEDLINE | ID: mdl-22228578

ABSTRACT

BACKGROUND: Trialeurodes vaporariorum Westwood is an important pest of protected crops in temperate regions of the world. Resistance to pyrethroid insecticides is long established in this species, but the molecular basis of the mechanism(s) responsible has not previously been disclosed. RESULTS: Mortality rates of three European strains of T. vaporariorum to the pyrethroid bifenthrin were calculated, and each possessed significant resistance (up to 662-fold) when compared with a susceptible reference strain. Direct sequencing revealed three amino acid substitutions in the para-type voltage-gated sodium channel (the pyrethroid and DDT target site) of bifenthrin-resistant T. vaporariorum at positions previously implicated with pyrethroid or DDT resistance (M918L, L925I and T929I) in other related species. CONCLUSION: This study indicates that resistance to bifenthrin in T. vaporariorum is associated with target-site insensitivity, and that the specific mutations in the sodium channel causing resistance may differ between localities.


Subject(s)
Drug Resistance/genetics , Hemiptera/genetics , Insecticides , Mutation , Pyrethrins , Sodium Channels/genetics , Amino Acid Sequence , Animals , Biological Assay , Female , Male , Molecular Sequence Data , Phenotype , Sequence Analysis, DNA , Sodium Channels/chemistry , Species Specificity
18.
Pest Manag Sci ; 67(8): 891-7, 2011 Aug.
Article in English | MEDLINE | ID: mdl-21432985

ABSTRACT

BACKGROUND: The tomato red spider mite, Tetranychus evansi (Baker and Pritchard), is a serious pest of solanaceous crops in many African countries. In this study an investigation has been conducted to establish whether mutation of the para-type sodium channel underlies pyrethroid resistance in T. evansi strains collected in Southern Malawi. RESULTS: Two T. evansi strains from Malawi showed tolerance to the organophosphate chlorpyrifos and resistance (20-40-fold) to the pyrethroid bifenthrin, but were susceptible to two contemporary acaricides (abamectin and fenpyroximate) in insecticide bioassays. Cloning of a 3.1 kb fragment (domains IIS5 to IVS5) of the T. evansi para gene from pyrethroid-resistant and pyrethroid-susceptible strains revealed a single non-synonymous mutation in the resistant strains that results in an amino acid substitution (M918T) within the domain II region of the channel. Although novel to mites, this mutation confers high levels of resistance to pyrethroids in several insect species where it has always been associated with another mutation (L1014F). This is the first report of the M918T mutation in the absence of L1014F in any arthropod species. Diagnostic tools were developed that allow sensitive detection of this mutation in individual mites. CONCLUSION: This is the first study of pyrethroid resistance in T. evansi and provides contemporary information for resistance management of this pest in Southern Malawi.


Subject(s)
Insecticides , Pyrethrins , Sodium Channels/genetics , Tetranychidae/genetics , Amino Acid Sequence , Amino Acid Substitution , Animals , Cloning, Molecular , Female , Insecticide Resistance/genetics , Male , Molecular Sequence Data , Point Mutation , Polymerase Chain Reaction , Polymorphism, Restriction Fragment Length , Sequence Analysis, DNA
19.
BMC Genomics ; 12: 56, 2011 Jan 24.
Article in English | MEDLINE | ID: mdl-21261962

ABSTRACT

BACKGROUND: The whitefly Trialeurodes vaporariorum is an economically important crop pest in temperate regions that has developed resistance to most classes of insecticides. However, the molecular mechanisms underlying resistance have not been characterised and, to date, progress has been hampered by a lack of nucleotide sequence data for this species. Here, we use pyrosequencing on the Roche 454-FLX platform to produce a substantial and annotated EST dataset. This 'unigene set' will form a critical reference point for quantitation of over-expressed messages via digital transcriptomics. RESULTS: Pyrosequencing produced around a million sequencing reads that assembled into 54,748 contigs, with an average length of 965 bp, representing a dramatic expansion of existing cDNA sequences available for T. vaporariorum (only 43 entries in GenBank at the time of this publication). BLAST searching of non-redundant databases returned 20,333 significant matches and those gene families potentially encoding gene products involved in insecticide resistance were manually curated and annotated. These include, enzymes potentially involved in the detoxification of xenobiotics and those encoding the targets of the major chemical classes of insecticides. A total of 57 P450s, 17 GSTs and 27 CCEs were identified along with 30 contigs encoding the target proteins of six different insecticide classes. CONCLUSION: Here, we have developed new transcriptomic resources for T. vaporariorum. These include a substantial and annotated EST dataset that will serve the community studying this important crop pest and will elucidate further the molecular mechanisms underlying insecticide resistance.


Subject(s)
Hemiptera/genetics , Insecticides/pharmacology , Animals , Computational Biology , Gene Expression Profiling , Hemiptera/drug effects , Insect Proteins/genetics , Insecticide Resistance/genetics , Phylogeny
20.
J Agric Food Chem ; 59(7): 2950-7, 2011 Apr 13.
Article in English | MEDLINE | ID: mdl-21105655

ABSTRACT

The discovery of sulfoxaflor [N-[methyloxido[1-[6-(trifluoromethyl)-3-pyridinyl]ethyl]-λ(4)-sulfanylidene] cyanamide] resulted from an investigation of the sulfoximine functional group as a novel bioactive scaffold for insecticidal activity and a subsequent extensive structure-activity relationship study. Sulfoxaflor, the first product from this new class (the sulfoximines) of insect control agents, exhibits broad-spectrum efficacy against many sap-feeding insect pests, including aphids, whiteflies, hoppers, and Lygus, with levels of activity that are comparable to those of other classes of insecticides targeting sap-feeding insects, including the neonicotinoids. However, no cross-resistance has been observed between sulfoxaflor and neonicotinoids such as imidacloprid, apparently the result of differences in susceptibility to oxidative metabolism. Available data are consistent with sulfoxaflor acting via the insect nicotinic receptor in a complex manner. These observations reflect the unique structure of the sulfoximines compared with neonicotinoids.


Subject(s)
Insecticides/chemistry , Pyridines/chemistry , Sulfur Compounds/chemistry , Animals , Aphids , Hemiptera , Imidazoles , Insecta , Insecticide Resistance , Neonicotinoids , Nitro Compounds , Receptors, Nicotinic , Structure-Activity Relationship
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