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Mondal A, Sánchez C HM, Marshall JM. MGDrivE 3: A decoupled vector-human framework for epidemiological simulation of mosquito genetic control tools and their surveillance. PLoS Comput Biol 2024; 20:e1012133. [PMID: 38805562 DOI: 10.1371/journal.pcbi.1012133] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2023] [Accepted: 05/03/2024] [Indexed: 05/30/2024] Open
Abstract
Novel mosquito genetic control tools, such as CRISPR-based gene drives, hold great promise in reducing the global burden of vector-borne diseases. As these technologies advance through the research and development pipeline, there is a growing need for modeling frameworks incorporating increasing levels of entomological and epidemiological detail in order to address questions regarding logistics and biosafety. Epidemiological predictions are becoming increasingly relevant to the development of target product profiles and the design of field trials and interventions, while entomological surveillance is becoming increasingly important to regulation and biosafety. We present MGDrivE 3 (Mosquito Gene Drive Explorer 3), a new version of a previously-developed framework, MGDrivE 2, that investigates the spatial population dynamics of mosquito genetic control systems and their epidemiological implications. The new framework incorporates three major developments: i) a decoupled sampling algorithm allowing the vector portion of the MGDrivE framework to be paired with a more detailed epidemiological framework, ii) a version of the Imperial College London malaria transmission model, which incorporates age structure, various forms of immunity, and human and vector interventions, and iii) a surveillance module that tracks mosquitoes captured by traps throughout the simulation. Example MGDrivE 3 simulations are presented demonstrating the application of the framework to a CRISPR-based homing gene drive linked to dual disease-refractory genes and their potential to interrupt local malaria transmission. Simulations are also presented demonstrating surveillance of such a system by a network of mosquito traps. MGDrivE 3 is freely available as an open-source R package on CRAN (https://cran.r-project.org/package=MGDrivE2) (version 2.1.0), and extensive examples and vignettes are provided. We intend the software to aid in understanding of human health impacts and biosafety of mosquito genetic control tools, and continue to iterate per feedback from the genetic control community.
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Affiliation(s)
- Agastya Mondal
- Divisions of Epidemiology and Biostatistics, School of Public Health, University of California, Berkeley, California, United States of America
| | - Héctor M Sánchez C
- Divisions of Epidemiology and Biostatistics, School of Public Health, University of California, Berkeley, California, United States of America
| | - John M Marshall
- Divisions of Epidemiology and Biostatistics, School of Public Health, University of California, Berkeley, California, United States of America
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Kefi M, Cardoso-Jaime V, Saab SA, Dimopoulos G. Curing mosquitoes with genetic approaches for malaria control. Trends Parasitol 2024:S1471-4922(24)00092-8. [PMID: 38760256 DOI: 10.1016/j.pt.2024.04.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2024] [Revised: 04/15/2024] [Accepted: 04/15/2024] [Indexed: 05/19/2024]
Abstract
Malaria remains a persistent global public health challenge because of the limitations of current prevention tools. The use of transgenic mosquitoes incapable of transmitting malaria, in conjunction with existing methods, holds promise for achieving elimination of malaria and preventing its reintroduction. In this context, population modification involves the spread of engineered genetic elements through mosquito populations that render them incapable of malaria transmission. Significant progress has been made in this field over the past decade in revealing promising targets, optimizing genetic tools, and facilitating the transition from the laboratory to successful field deployments, which are subject to regulatory scrutiny. This review summarizes recent advances and ongoing challenges in 'curing' Anopheles vectors of the malaria parasite.
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Affiliation(s)
- Mary Kefi
- Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, USA
| | - Victor Cardoso-Jaime
- Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, USA
| | - Sally A Saab
- Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, USA
| | - George Dimopoulos
- Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, USA.
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3
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Harris KD, Greenbaum G. Rescue by gene swamping as a gene drive deployment strategy. Cell Rep 2023; 42:113499. [PMID: 38039130 DOI: 10.1016/j.celrep.2023.113499] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Revised: 10/05/2023] [Accepted: 11/13/2023] [Indexed: 12/03/2023] Open
Abstract
Gene drives are genetic constructs that can spread deleterious alleles with potential application to population suppression of harmful species. As gene drives can potentially spill over to other populations or species, control measures and fail-safe strategies must be considered. Gene drives can generate a rapid change in the population's genetic composition, leading to substantial demographic decline, processes that are expected to occur at a similar timescale during gene drive spread. We developed a gene drive model that combines evolutionary and demographic dynamics in a two-population setting. The model demonstrates how feedback between these dynamics generates additional outcomes to those generated by the evolutionary dynamics alone. We identify an outcome of particular interest where short-term suppression of the target population is followed by gene swamping and loss of the gene drive. This outcome can prevent spillover and is robust to the evolution of resistance, suggesting it may be suitable as a fail-safe strategy for gene drive deployment.
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Affiliation(s)
- Keith D Harris
- Department of Ecology, Evolution and Behavior, The Hebrew University of Jerusalem, Jerusalem 91904, Israel.
| | - Gili Greenbaum
- Department of Ecology, Evolution and Behavior, The Hebrew University of Jerusalem, Jerusalem 91904, Israel.
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Finda MF, Juma EO, Kahamba NF, Mthawanji RS, Sambo M, Emidi B, Wiener S, O'Brochta D, Santos M, James S, Okumu FO. Perspectives of African stakeholders on gene drives for malaria control and elimination: a multi-country survey. Malar J 2023; 22:384. [PMID: 38129897 PMCID: PMC10740233 DOI: 10.1186/s12936-023-04787-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2023] [Accepted: 11/09/2023] [Indexed: 12/23/2023] Open
Abstract
BACKGROUND Gene drive modified mosquitoes (GDMMs) have the potential to address Africa's persistent malaria problem, but are still in early stages of development and testing. Continuous engagement of African stakeholders is crucial for successful evaluation and implementation of these technologies. The aim of this multi-country study was, therefore, to explore the insights and recommendations of key stakeholders across Africa on the potential of GDMMs for malaria control and elimination in the continent. METHODS A concurrent mixed-methods study design was used, involving a structured survey administered to 180 stakeholders in 25 countries in sub-Saharan Africa, followed by 18 in-depth discussions with selected groups and individuals. Stakeholders were drawn from academia, research and regulatory institutions, government ministries of health and environment, media and advocacy groups. Thematic content analysis was used to identify key topics from the in-depth discussions, and descriptive analysis was done to summarize information from the survey data. RESULTS Despite high levels of awareness of GDMMs among the stakeholders (76.7%), there was a relatively low-level of understanding of their key attributes and potential for malaria control (28.3%). When more information about GDMMs was provided to the stakeholders, they readily discussed their insights and concerns, and offered several recommendations to ensure successful research and implementation of the technology. These included: (i) increasing relevant technical expertise within Africa, (ii) generating local evidence on safety, applicability, and effectiveness of GDMMs, and (iii) developing country-specific regulations for safe and effective governance of GDMMs. A majority of the respondents (92.9%) stated that they would support field trials or implementation of GDMMs in their respective countries. This study also identified significant misconceptions regarding the phase of GDMM testing in Africa, as several participants incorrectly asserted that GDMMs were already present in Africa, either within laboratories or released into the field. CONCLUSION Incorporating views and recommendations of African stakeholders in the ongoing research and development of GDMMs is crucial for instilling stakeholder confidence on their potential application. These findings will enable improved planning for GDMMs in Africa as well as improved target product profiles for the technologies to maximize their potential for solving Africa's enduring malaria challenge.
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Affiliation(s)
- Marceline F Finda
- Environmental Health and Ecological Sciences, Ifakara Health Institute, PO Box 53, Ifakara, Tanzania.
| | - Elijah O Juma
- Pan-African Mosquito Control Association (PAMCA), Off Mbagathi Road, PO Box 44455-00100, Nairobi, Kenya
| | - Najat F Kahamba
- Environmental Health and Ecological Sciences, Ifakara Health Institute, PO Box 53, Ifakara, Tanzania
| | - Rhosheen S Mthawanji
- Malawi Liverpool Wellcome Trust Clinical Research Programme, Blantyre 3, PO Box 30096, Chichiri, Malawi
| | - Maganga Sambo
- Environmental Health and Ecological Sciences, Ifakara Health Institute, PO Box 53, Ifakara, Tanzania
| | - Basiliana Emidi
- National Institute for Medical Research, PO Box 1462, Mwanza, Tanzania
| | - Susan Wiener
- Foundation for the National Institutes of Health, 11400 Rockville Pike, Suite 600, North Bethesda, MD, 20852, USA
| | - David O'Brochta
- Foundation for the National Institutes of Health, 11400 Rockville Pike, Suite 600, North Bethesda, MD, 20852, USA
| | - Michael Santos
- Foundation for the National Institutes of Health, 11400 Rockville Pike, Suite 600, North Bethesda, MD, 20852, USA
| | - Stephanie James
- Foundation for the National Institutes of Health, 11400 Rockville Pike, Suite 600, North Bethesda, MD, 20852, USA
| | - Fredros O Okumu
- Environmental Health and Ecological Sciences, Ifakara Health Institute, PO Box 53, Ifakara, Tanzania
- School of Life Science and Bioengineering, The Nelson Mandela African Institution of Science and Technology, P. O. Box 447, Arusha, Tanzania
- School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow, G128QQ, UK
- School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, 1 Smuts Avenue, Braamofontein, 2000, South Africa
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Raban R, Marshall JM, Hay BA, Akbari OS. Manipulating the Destiny of Wild Populations Using CRISPR. Annu Rev Genet 2023; 57:361-390. [PMID: 37722684 PMCID: PMC11064769 DOI: 10.1146/annurev-genet-031623-105059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/20/2023]
Abstract
Genetic biocontrol aims to suppress or modify populations of species to protect public health, agriculture, and biodiversity. Advancements in genome engineering technologies have fueled a surge in research in this field, with one gene editing technology, CRISPR, leading the charge. This review focuses on the current state of CRISPR technologies for genetic biocontrol of pests and highlights the progress and ongoing challenges of using these approaches.
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Affiliation(s)
- Robyn Raban
- Department of Cell and Developmental Biology, School of Biological Sciences, University of California, San Diego, La Jolla, California, USA;
| | - John M Marshall
- Divisions of Epidemiology and Biostatistics, School of Public Health, University of California, Berkeley, California, USA
| | - Bruce A Hay
- Division of Biology and Biological Engineering (BBE), California Institute of Technology, Pasadena, California, USA
| | - Omar S Akbari
- Department of Cell and Developmental Biology, School of Biological Sciences, University of California, San Diego, La Jolla, California, USA;
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Kormos A, Dimopoulos G, Bier E, Lanzaro GC, Marshall JM, James AA. Conceptual risk assessment of mosquito population modification gene-drive systems to control malaria transmission: preliminary hazards list workshops. Front Bioeng Biotechnol 2023; 11:1261123. [PMID: 37965050 PMCID: PMC10641379 DOI: 10.3389/fbioe.2023.1261123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2023] [Accepted: 10/09/2023] [Indexed: 11/16/2023] Open
Abstract
The field-testing and eventual adoption of genetically-engineered mosquitoes (GEMs) to control vector-borne pathogen transmission will require them meeting safety criteria specified by regulatory authorities in regions where the technology is being considered for use and other locales that might be impacted. Preliminary risk considerations by researchers and developers may be useful for planning the baseline data collection and field research used to address the anticipated safety concerns. Part of this process is to identify potential hazards (defined as the inherent ability of an entity to cause harm) and their harms, and then chart the pathways to harm and evaluate their probability as part of a risk assessment. The University of California Malaria Initiative (UCMI) participated in a series of workshops held to identify potential hazards specific to mosquito population modification strains carrying gene-drive systems coupled to anti-parasite effector genes and their use in a hypothetical island field trial. The hazards identified were placed within the broader context of previous efforts discussed in the scientific literature. Five risk areas were considered i) pathogens, infections and diseases, and the impacts of GEMs on human and animal health, ii) invasiveness and persistence of GEMs, and interactions of GEMs with target organisms, iii) interactions of GEMs with non-target organisms including horizontal gene transfer, iv) impacts of techniques used for the management of GEMs and v) evolutionary and stability considerations. A preliminary hazards list (PHL) was developed and is made available here. This PHL is useful for internal project risk evaluation and is available to regulators at prospective field sites. UCMI project scientists affirm that the subsequent processes associated with the comprehensive risk assessment for the application of this technology should be driven by the stakeholders at the proposed field site and areas that could be affected by this intervention strategy.
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Affiliation(s)
- Ana Kormos
- Vector Genetics Laboratory, University of California, Davis, Davis, CA, United States
| | - George Dimopoulos
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, Malaria Research Institute, Johns Hopkins University, Baltimore, MD, United States
| | - Ethan Bier
- Department of Cell and Developmental Biology, University of California, San Diego, San Diego, CA, United States
| | - Gregory C. Lanzaro
- Vector Genetics Laboratory, University of California, Davis, Davis, CA, United States
| | - John M. Marshall
- Divisions of Epidemiology and Biostatistics, School of Public Health, University of California, Berkeley, Berkeley, CA, United States
| | - Anthony A. James
- Departments of Microbiology and Molecular Genetics and Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA, United States
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Bennett JB, Wu SL, Chennuri PR, Myles KM, Ndeffo-Mbah ML. Expansions to the MGDrivE suite for simulating the efficacy of novel gene-drive constructs in the control of mosquito-borne diseases. BMC Res Notes 2023; 16:258. [PMID: 37798614 PMCID: PMC10557238 DOI: 10.1186/s13104-023-06533-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2023] [Accepted: 09/25/2023] [Indexed: 10/07/2023] Open
Abstract
OBJECTIVE The MGDrivE (MGDrivE 1 and MGDrivE 2) modeling framework provides a flexible and expansive environment for testing the efficacy of novel gene-drive constructs for the control of mosquito-borne diseases. However, the existing model framework did not previously support several features necessary to simulate some types of intervention strategies. Namely, current MGDrivE versions do not permit modeling of small molecule inducible systems for controlling gene expression in gene drive designs or the inheritance patterns of self-eliminating gene drive mechanisms. RESULTS Here, we demonstrate a new MGDrivE 2 module that permits the simulation of gene drive strategies incorporating small molecule-inducible systems and self-eliminating gene drive mechanisms. Additionally, we also implemented novel sparsity-aware sampling algorithms for improved computational efficiency in MGDrivE 2 and supplied an analysis and plotting function applicable to the outputs of MGDrivE 1 and MGDrivE 2.
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Affiliation(s)
| | - Sean L Wu
- Institute for Health Metrics and Evaluation, University of Washington, Seattle, WA, 98121, USA
| | - Pratima R Chennuri
- Department of Entomology, Texas A & M University, College Station, TX, 77843, USA
- Future Fields, Edmonton, AB, T5H 0L5, Canada
| | - Kevin M Myles
- Department of Entomology, Texas A & M University, College Station, TX, 77843, USA
| | - Martial L Ndeffo-Mbah
- Department of Integrative Biosciences, Texas A&M University, College Station, TX, 77843, USA.
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Pescod P, Bevivino G, Anthousi A, Shelton R, Shepherd J, Lombardo F, Nolan T. Measuring the Impact of Genetic Heterogeneity and Chromosomal Inversions on the Efficacy of CRISPR-Cas9 Gene Drives in Different Strains of Anopheles gambiae. CRISPR J 2023; 6:419-429. [PMID: 37702604 DOI: 10.1089/crispr.2023.0029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/14/2023] Open
Abstract
The human malaria vector Anopheles gambiae is becoming increasingly resistant to insecticides, spurring the development of genetic control strategies. CRISPR-Cas9 gene drives can modify a population by creating double-stranded breaks at highly specific targets, triggering copying of the gene drive into the cut site ("homing"), ensuring its inheritance. The DNA repair mechanism responsible requires homology between the donor and recipient chromosomes, presenting challenges for the invasion of laboratory-developed gene drives into wild populations of target species An. gambiae species complex, which show high levels of genome variation. Two gene drives (vas2-5958 and zpg-7280) were introduced into three An. gambiae strains collected across Africa with 5.3-6.6% variation around the target sites, and the effect of this variation on homing was measured. Gene drive homing across different karyotypes of the 2La chromosomal inversion was also assessed. No decrease in gene drive homing was seen despite target site heterology, demonstrating the applicability of gene drives to wild populations.
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Affiliation(s)
- Poppy Pescod
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom; Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, Greece
| | - Giulia Bevivino
- Division of Parasitology, Department of Public Health and Infectious Diseases, University of Rome "la Sapienza," Rome, Italy; Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, Greece
| | - Amalia Anthousi
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom; Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, Greece
- Department of Biology, University of Crete, Heraklion, Crete, Greece; and Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, Greece
- Department of Insects and Vector Borne Diseases, Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, Greece
| | - Ruth Shelton
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom; Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, Greece
| | - Josephine Shepherd
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom; Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, Greece
| | - Fabrizio Lombardo
- Division of Parasitology, Department of Public Health and Infectious Diseases, University of Rome "la Sapienza," Rome, Italy; Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, Greece
| | - Tony Nolan
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom; Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, Greece
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Mondal A, C. HMS, Marshall JM. MGDrivE 3: A decoupled vector-human framework for epidemiological simulation of mosquito genetic control tools and their surveillance. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.09.556958. [PMID: 37745458 PMCID: PMC10515759 DOI: 10.1101/2023.09.09.556958] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/26/2023]
Abstract
Novel mosquito genetic control tools, such as CRISPR-based gene drives, hold great promise in reducing the global burden of vector-borne diseases. As these technologies advance through the research and development pipeline, there is a growing need for modeling frameworks incorporating increasing levels of entomological and epidemiological detail in order to address questions regarding logistics and biosafety. Epidemiological predictions are becoming increasingly relevant to the development of target product profiles and the design of field trials and interventions, while entomological surveillance is becoming increasingly important to regulation and biosafety. We present MGDrivE 3 (Mosquito Gene Drive Explorer 3), a new version of a previously-developed framework, MGDrivE 2, that investigates the spatial population dynamics of mosquito genetic control systems and their epidemiological implications. The new framework incorporates three major developments: i) a decoupled sampling algorithm allowing the vector portion of the MGDrivE framework to be paired with a more detailed epidemiological framework, ii) a version of the Imperial College London malaria transmission model, which incorporates age structure, various forms of immunity, and human and vector interventions, and iii) a surveillance module that tracks mosquitoes captured by traps throughout the simulation. Example MGDrivE 3 simulations are presented demonstrating the application of the framework to a CRISPR-based homing gene drive linked to dual disease-refractory genes and their potential to interrupt local malaria transmission. Simulations are also presented demonstrating surveillance of such a system by a network of mosquito traps. MGDrivE 3 is freely available as an open-source R package on CRAN (https://cran.r-project.org/package=MGDrivE2) (version 2.1.0), and extensive examples and vignettes are provided. We intend the software to aid in understanding of human health impacts and biosafety of mosquito genetic control tools, and continue to iterate per feedback from the genetic control community.
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Affiliation(s)
- Agastya Mondal
- Divisions of Epidemiology and Biostatistics, School of Public Health, University of California, Berkeley, CA, 94720, USA
| | - Héctor M. Sánchez C.
- Divisions of Epidemiology and Biostatistics, School of Public Health, University of California, Berkeley, CA, 94720, USA
| | - John M. Marshall
- Divisions of Epidemiology and Biostatistics, School of Public Health, University of California, Berkeley, CA, 94720, USA
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Carballar-Lejarazú R, Dong Y, Pham TB, Tushar T, Corder RM, Mondal A, Sánchez C. HM, Lee HF, Marshall JM, Dimopoulos G, James AA. Dual effector population modification gene-drive strains of the African malaria mosquitoes, Anopheles gambiae and Anopheles coluzzii. Proc Natl Acad Sci U S A 2023; 120:e2221118120. [PMID: 37428915 PMCID: PMC10629562 DOI: 10.1073/pnas.2221118120] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Accepted: 06/05/2023] [Indexed: 07/12/2023] Open
Abstract
Proposed genetic approaches for reducing human malaria include population modification, which introduces genes into vector mosquitoes to reduce or prevent parasite transmission. We demonstrate the potential of Cas9/guide RNA (gRNA)-based gene-drive systems linked to dual antiparasite effector genes to spread rapidly through mosquito populations. Two strains have an autonomous gene-drive system coupled to dual anti-Plasmodium falciparum effector genes comprising single-chain variable fragment monoclonal antibodies targeting parasite ookinetes and sporozoites in the African malaria mosquitoes Anopheles gambiae (AgTP13) and Anopheles coluzzii (AcTP13). The gene-drive systems achieved full introduction within 3 to 6 mo after release in small cage trials. Life-table analyses revealed no fitness loads affecting AcTP13 gene-drive dynamics but AgTP13 males were less competitive than wild types. The effector molecules reduced significantly both parasite prevalence and infection intensities. These data supported transmission modeling of conceptual field releases in an island setting that shows meaningful epidemiological impacts at different sporozoite threshold levels (2.5 to 10 k) for human infection by reducing malaria incidence in optimal simulations by 50 to 90% within as few as 1 to 2 mo after a series of releases, and by ≥90% within 3 mo. Modeling outcomes for low sporozoite thresholds are sensitive to gene-drive system fitness loads, gametocytemia infection intensities during parasite challenges, and the formation of potentially drive-resistant genome target sites, extending the predicted times to achieve reduced incidence. TP13-based strains could be effective for malaria control strategies following validation of sporozoite transmission threshold numbers and testing field-derived parasite strains. These or similar strains are viable candidates for future field trials in a malaria-endemic region.
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Affiliation(s)
| | - Yuemei Dong
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, Malaria Research Institute, Johns Hopkins University, Baltimore, MD21205
| | - Thai Binh Pham
- Department of Microbiology & Molecular Genetics, University of California, Irvine, CA92697-4025
| | - Taylor Tushar
- Department of Microbiology & Molecular Genetics, University of California, Irvine, CA92697-4025
| | - Rodrigo M. Corder
- Divisions of Epidemiology and Biostatistics, School of Public Health, University of California, Berkeley, CA94720
| | - Agastya Mondal
- Divisions of Epidemiology and Biostatistics, School of Public Health, University of California, Berkeley, CA94720
| | - Héctor M. Sánchez C.
- Divisions of Epidemiology and Biostatistics, School of Public Health, University of California, Berkeley, CA94720
| | - Hsu-Feng Lee
- Department of Microbiology & Molecular Genetics, University of California, Irvine, CA92697-4025
| | - John M. Marshall
- Divisions of Epidemiology and Biostatistics, School of Public Health, University of California, Berkeley, CA94720
| | - George Dimopoulos
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, Malaria Research Institute, Johns Hopkins University, Baltimore, MD21205
| | - Anthony A. James
- Department of Microbiology & Molecular Genetics, University of California, Irvine, CA92697-4025
- Department of Molecular Biology & Biochemistry, University of California, Irvine, CA92697-3900
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11
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James SL, Quemada H, Benedict MQ, Dass B. Requirements for market entry of gene drive-modified mosquitoes for control of vector-borne diseases: analogies to other biologic and biotechnology products. Front Bioeng Biotechnol 2023; 11:1205865. [PMID: 37362219 PMCID: PMC10285705 DOI: 10.3389/fbioe.2023.1205865] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2023] [Accepted: 05/25/2023] [Indexed: 06/28/2023] Open
Abstract
Gene drive-modified mosquitoes (GDMMs) are proposed as new tools for control and elimination of malaria and other mosquito-borne diseases, and promising results have been observed from testing conducted in containment. Although still at an early stage of development, it is important to begin now to consider approval procedures and market entry strategies for the eventual implementation of GDMMs in the context of disease control programs, as these could impact future research plans. It is expected that, as for other types of new products, those seeking to bring GDMMs to market will be required to provide sufficient information to allow the regulator(s) to determine whether the product is safe and effective for its proposed use. There already has been much emphasis on developing requirements for the biosafety components of the "safe and effective" benchmark, largely concerned with their regulation as genetically modified organisms. Other potential approval requirements have received little attention, however. Although GDMMs are expected to be implemented primarily in the context of public health programs, any regulatory analogies to other public health products, such as pharmaceuticals, vaccines, or chemical pesticides, must take into account the characteristics of live mosquito products. Typical manufacturing standards related to product identity, potency or quality will need to be adapted to GDMMs. Valuable lessons can be drawn from the regulatory approval processes for other whole organism and genetically modified (GM) organism products. Supply chain requirements, such as scale of production, location and design of production facilities, and methods of distribution and delivery, will be dependent upon the characteristics of the particular GDMM product, the conditions of use, and the region to be served. Plans for fulfilling supply chain needs can build upon experience in the development of other live insect products for use in public health and agriculture. Implementation of GDMMs would benefit from additional research on enabling technologies for long-term storage of mosquito life stages, efficient mass production, and area-wide delivery of GDMMs. Early consideration of these practical requirements for market entry will help to mitigate downstream delays in the development of these promising new technologies.
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Affiliation(s)
- Stephanie L. James
- GeneConvene Global Collaborative, Foundation for the NIH, Bethesda, MD, United States
| | | | | | - Brinda Dass
- GeneConvene Global Collaborative, Foundation for the NIH, Bethesda, MD, United States
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12
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James S, Santos M. The Promise and Challenge of Genetic Biocontrol Approaches for Malaria Elimination. Trop Med Infect Dis 2023; 8:201. [PMID: 37104327 PMCID: PMC10140850 DOI: 10.3390/tropicalmed8040201] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2023] [Revised: 03/15/2023] [Accepted: 03/23/2023] [Indexed: 04/03/2023] Open
Abstract
Malaria remains an ongoing public health challenge, with over 600,000 deaths in 2021, of which approximately 96% occurred in Africa. Despite concerted efforts, the goal of global malaria elimination has stalled in recent years. This has resulted in widespread calls for new control methods. Genetic biocontrol approaches, including those focused on gene-drive-modified mosquitoes (GDMMs), aim to prevent malaria transmission by either reducing the population size of malaria-transmitting mosquitoes or making the mosquitoes less competent to transmit the malaria parasite. The development of both strategies has advanced considerably in recent years, with successful field trials of several biocontrol methods employing live mosquito products and demonstration of the efficacy of GDMMs in insectary-based studies. Live mosquito biocontrol products aim to achieve area-wide control with characteristics that differ substantially from current insecticide-based vector control methods, resulting in some different considerations for approval and implementation. The successful field application of current biocontrol technologies against other pests provides evidence for the promise of these approaches and insights into the development pathway for new malaria control agents. The status of technical development as well as current thinking on the implementation requirements for genetic biocontrol approaches are reviewed, and remaining challenges for public health application in malaria prevention are discussed.
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Affiliation(s)
- Stephanie James
- Foundation for the National Institutes of Health, North Bethesda, MD 20852, USA
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13
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Conway MJ, Haslitt DP, Swarts BM. Targeting Aedes aegypti Metabolism with Next-Generation Insecticides. Viruses 2023; 15:469. [PMID: 36851683 PMCID: PMC9964334 DOI: 10.3390/v15020469] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2023] [Revised: 02/03/2023] [Accepted: 02/06/2023] [Indexed: 02/11/2023] Open
Abstract
Aedes aegypti is the primary vector of dengue virus (DENV), zika virus (ZIKV), and other emerging infectious diseases of concern. A key disease mitigation strategy is vector control, which relies heavily on the use of insecticides. The development of insecticide resistance poses a major threat to public health worldwide. Unfortunately, there is a limited number of chemical compounds available for vector control, and these chemicals can have off-target effects that harm invertebrate and vertebrate species. Fundamental basic science research is needed to identify novel molecular targets that can be exploited for vector control. Next-generation insecticides will have unique mechanisms of action that can be used in combination to limit selection of insecticide resistance. Further, molecular targets will be species-specific and limit off-target effects. Studies have shown that mosquitoes rely on key nutrients during multiple life cycle stages. Targeting metabolic pathways is a promising direction that can deprive mosquitoes of nutrition and interfere with development. Metabolic pathways are also important for the virus life cycle. Here, we review studies that reveal the importance of dietary and stored nutrients during mosquito development and infection and suggest strategies to identify next-generation insecticides with a focus on trehalase inhibitors.
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Affiliation(s)
- Michael J. Conway
- Foundational Sciences, Central Michigan University College of Medicine, Mount Pleasant, MI 48859, USA
| | - Douglas P. Haslitt
- Foundational Sciences, Central Michigan University College of Medicine, Mount Pleasant, MI 48859, USA
| | - Benjamin M. Swarts
- Department of Chemistry and Biochemistry, Central Michigan University, Mount Pleasant, MI 48859, USA
- Biochemistry, Cell, and Molecular Biology Graduate Programs, Central Michigan University, Mount Pleasant, MI 48859, USA
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14
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Gene drive in species complexes: defining target organisms. Trends Biotechnol 2023; 41:154-164. [PMID: 35868886 DOI: 10.1016/j.tibtech.2022.06.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Revised: 06/17/2022] [Accepted: 06/27/2022] [Indexed: 01/24/2023]
Abstract
Engineered gene drives, which bias their own inheritance to increase in frequency in target populations, are being developed to control mosquito malaria vectors. Such mosquitoes can belong to complexes of both vector and nonvector species that can produce fertile interspecific hybrids, making vertical gene drive transfer (VGDT) to sibling species biologically plausible. While VGDT to other vectors could positively impact human health protection goals, VGDT to nonvectors might challenge biodiversity ones. Therefore, environmental risk assessment of gene drive use in species complexes invites more nuanced considerations of target organisms and nontarget organisms than for transgenes not intended to increase in frequency in target populations. Incorporating the concept of target species complexes offers more flexibility when assessing potential impacts from VGDT.
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15
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Garrood WT, Cuber P, Willis K, Bernardini F, Page NM, Haghighat-Khah RE. Driving down malaria transmission with engineered gene drives. Front Genet 2022; 13:891218. [PMID: 36338968 PMCID: PMC9627344 DOI: 10.3389/fgene.2022.891218] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Accepted: 09/13/2022] [Indexed: 11/26/2022] Open
Abstract
The last century has witnessed the introduction, establishment and expansion of mosquito-borne diseases into diverse new geographic ranges. Malaria is transmitted by female Anopheles mosquitoes. Despite making great strides over the past few decades in reducing the burden of malaria, transmission is now on the rise again, in part owing to the emergence of mosquito resistance to insecticides, antimalarial drug resistance and, more recently, the challenges of the COVID-19 pandemic, which resulted in the reduced implementation efficiency of various control programs. The utility of genetically engineered gene drive mosquitoes as tools to decrease the burden of malaria by controlling the disease-transmitting mosquitoes is being evaluated. To date, there has been remarkable progress in the development of CRISPR/Cas9-based homing endonuclease designs in malaria mosquitoes due to successful proof-of-principle and multigenerational experiments. In this review, we examine the lessons learnt from the development of current CRISPR/Cas9-based homing endonuclease gene drives, providing a framework for the development of gene drive systems for the targeted control of wild malaria-transmitting mosquito populations that overcome challenges such as with evolving drive-resistance. We also discuss the additional substantial works required to progress the development of gene drive systems from scientific discovery to further study and subsequent field application in endemic settings.
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Affiliation(s)
- William T. Garrood
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Piotr Cuber
- Department of Molecular Biology, Core Research Laboratories, Natural History Museum, London, United Kingdom
| | - Katie Willis
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Federica Bernardini
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Nicole M. Page
- Department of Life Sciences, Imperial College London, London, United Kingdom
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16
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Common LK, Kleindorfer S, Colombelli-Négrel D, Dudaniec RY. Genetics reveals shifts in reproductive behaviour of the invasive bird parasite Philornis downsi collected from Darwin’s finch nests. Biol Invasions 2022. [DOI: 10.1007/s10530-022-02935-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
AbstractDue to novel or dynamic fluctuations in environmental conditions and resources, host and parasite relationships can be subject to diverse selection pressures that may lead to significant changes during and after invasion of a parasite. Genomic analyses are useful for elucidating evolutionary processes in invasive parasites following their arrival to a new area and host. Philornis downsi (Diptera: Muscidae), the avian vampire fly, was introduced to the Galápagos Islands circa 1964 and has since spread across the archipelago, feeding on the blood of developing nestlings of endemic land birds. Since its discovery, there have been significant changes to the dynamics of P. downsi and its novel hosts, such as shifting mortality rates and changing oviposition behaviour, however no temporal genetic studies have been conducted. We collected P. downsi from nests and traps from a single island population over a 14-year period, and genotyped flies at 469 single nucleotide polymorphisms (SNPs) using restriction-site associated DNA sequencing (RADSeq). Despite significant genetic differentiation (FST) between years, there was no evidence for genetic clustering within or across four sampling years between 2006 and 2020, suggesting a lack of population isolation. Sibship reconstructions from P. downsi collected from 10 Darwin’s finch nests sampled in 2020 showed evidence for shifts in reproductive behaviour compared to a similar genetic analysis conducted in 2004–2006. Compared with this previous study, females mated with fewer males, individual females oviposited fewer offspring per nest, but more unique females oviposited per nest. These findings are important to consider within reproductive control techniques, and have fitness implications for both parasite evolution and host fitness.
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17
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Vásquez VN, Reddy MR, Marshall JM. Environmentally appropriate vector control is facilitated by standard metrics for simulation-based evaluation. FRONTIERS IN TROPICAL DISEASES 2022. [DOI: 10.3389/fitd.2022.953212] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
As anthropogenic factors contribute to the introduction and expansion of new and established vector species, the geographic incidence of mosquito-borne disease is shifting. Computer simulations, informed by field data where possible, facilitate the cost-effective evaluation of available public health interventions and are a powerful tool for informing appropriate policy action. However, a variety of measurements are used in such assessments; this can complicate direct comparisons across both vector control technologies and the models used to simulate them. The expansion of biocontrol to include genetically engineered organisms is now prompting additional metrics with no analogy to traditional measurement approaches. We propose Standard Entomological Metrics (SEMs) to facilitate the model-based appraisal of both existing and novel intervention tools and define two examples: Suppression Efficacy Score and Time to Reduction Target. We formulate twelve synthetic case studies featuring two vector control technologies over three years of observed daily temperature in Cairns, Australia. After calculating Suppression Efficacy Score and Time to Reduction Target results, we apply these example outcomes to a discussion of health policy decision-making using SEMs. We submit that SEMs such as Suppression Efficacy Score and Time to Reduction Target facilitate the wholistic and environmentally appropriate simulation-based evaluation of intervention programs and invite the community to further discussion on this topic.
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18
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Gantz VM, Bier E. Active genetics comes alive: Exploring the broad applications of CRISPR-based selfish genetic elements (or gene-drives): Exploring the broad applications of CRISPR-based selfish genetic elements (or gene-drives). Bioessays 2022; 44:e2100279. [PMID: 35686327 PMCID: PMC9397133 DOI: 10.1002/bies.202100279] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Revised: 05/06/2022] [Accepted: 05/10/2022] [Indexed: 11/11/2022]
Abstract
Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-based "active genetic" elements developed in 2015 bypassed the fundamental rules of traditional genetics. Inherited in a super-Mendelian fashion, such selfish genetic entities offered a variety of potential applications including: gene-drives to disseminate gene cassettes carrying desired traits throughout insect populations to control disease vectors or pest species, allelic drives biasing inheritance of preferred allelic variants, neutralizing genetic elements to delete and replace or to halt the spread of gene-drives, split-drives with the core constituent Cas9 endonuclease and guide RNA (gRNA) components inserted at separate genomic locations to accelerate assembly of complex arrays of genetic traits or to gain genetic entry into novel organisms (vertebrates, plants, bacteria), and interhomolog based copying systems in somatic cells to develop tools for treating inherited or infectious diseases. Here, we summarize the substantial advances that have been made on all of these fronts and look forward to the next phase of this rapidly expanding and impactful field.
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Affiliation(s)
- Valentino M Gantz
- Department of Cell and Developmental Biology, University of California, La Jolla, California, USA
| | - Ethan Bier
- Department of Cell and Developmental Biology, University of California, La Jolla, California, USA
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19
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Leung S, Windbichler N, Wenger EA, Bever CA, Selvaraj P. Population replacement gene drive characteristics for malaria elimination in a range of seasonal transmission settings: a modelling study. Malar J 2022; 21:226. [PMID: 35883100 PMCID: PMC9327287 DOI: 10.1186/s12936-022-04242-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Accepted: 07/11/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Gene drives are a genetic engineering method where a suite of genes is inherited at higher than Mendelian rates and has been proposed as a promising new vector control strategy to reinvigorate the fight against malaria in sub-Saharan Africa. METHODS Using an agent-based model of malaria transmission with vector genetics, the impacts of releasing population-replacement gene drive mosquitoes on malaria transmission are examined and the population replacement gene drive system parameters required to achieve local elimination within a spatially-resolved, seasonal Sahelian setting are quantified. The performance of two different gene drive systems-"classic" and "integral"-are evaluated. Various transmission regimes (low, moderate, and high-corresponding to annual entomological inoculation rates of 10, 30, and 80 infectious bites per person) and other simultaneous interventions, including deployment of insecticide-treated nets (ITNs) and passive healthcare-seeking, are also simulated. RESULTS Local elimination probabilities decreased with pre-existing population target site resistance frequency, increased with transmission-blocking effectiveness of the introduced antiparasitic gene and drive efficiency, and were context dependent with respect to fitness costs associated with the introduced gene. Of the four parameters, transmission-blocking effectiveness may be the most important to focus on for improvements to future gene drive strains because a single release of classic gene drive mosquitoes is likely to locally eliminate malaria in low to moderate transmission settings only when transmission-blocking effectiveness is very high (above ~ 80-90%). However, simultaneously deploying ITNs and releasing integral rather than classic gene drive mosquitoes significantly boosts elimination probabilities, such that elimination remains highly likely in low to moderate transmission regimes down to transmission-blocking effectiveness values as low as ~ 50% and in high transmission regimes with transmission-blocking effectiveness values above ~ 80-90%. CONCLUSION A single release of currently achievable population replacement gene drive mosquitoes, in combination with traditional forms of vector control, can likely locally eliminate malaria in low to moderate transmission regimes within the Sahel. In a high transmission regime, higher levels of transmission-blocking effectiveness than are currently available may be required.
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Affiliation(s)
- Shirley Leung
- Institute for Disease Modeling, Bill & Melinda Gates Foundation, Seattle, WA, USA
| | - Nikolai Windbichler
- Department of Life Sciences, Imperial College London, South Kensington, London, UK
| | - Edward A Wenger
- Institute for Disease Modeling, Bill & Melinda Gates Foundation, Seattle, WA, USA
| | - Caitlin A Bever
- Institute for Disease Modeling, Bill & Melinda Gates Foundation, Seattle, WA, USA
| | - Prashanth Selvaraj
- Institute for Disease Modeling, Bill & Melinda Gates Foundation, Seattle, WA, USA.
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20
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Larval mosquito management and risk to aquatic ecosystems: A comparative approach including current tactics and gene-drive Anopheles techniques. Transgenic Res 2022; 31:489-504. [PMID: 35798930 PMCID: PMC9489571 DOI: 10.1007/s11248-022-00315-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Accepted: 06/13/2022] [Indexed: 11/23/2022]
Abstract
Genetic engineering of mosquitoes represents a promising tactic for reducing human suffering from malaria. Gene-drive techniques being developed that suppress or modify populations of Anopheles gambiae have the potential to be used with, or even possibly obviate, microbial and synthetic insecticides. However, these techniques are new and therefore there is attendant concern and uncertainty from regulators, policymakers, and the public about their environmental risks. Therefore, there is a need to assist decision-makers and public health stewards by assessing the risks associated with these newer mosquito management tactics so the risks can be compared as a basis for informed decision making. Previously, the effect of gene-drive mosquitoes on water quality in Africa was identified as a concern by stakeholders. Here, we use a comparative risk assessment approach for the effect of gene-drive mosquitoes on water quality in Africa. We compare the use of existing larvicides and the proposed genetic techniques in aquatic environments. Based on our analysis, we conclude that the tactic of gene-drive Anopheles for malaria management is unlikely to result in risks to aquatic environments that exceed current tactics for larval mosquitoes. As such, these new techniques would likely comply with currently recommended safety standards.
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21
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Beeton NJ, Wilkins A, Ickowicz A, Hayes KR, Hosack GR. Spatial modelling for population replacement of mosquito vectors at continental scale. PLoS Comput Biol 2022; 18:e1009526. [PMID: 35648783 PMCID: PMC9191746 DOI: 10.1371/journal.pcbi.1009526] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Revised: 06/13/2022] [Accepted: 04/22/2022] [Indexed: 11/24/2022] Open
Abstract
Malaria is one of the deadliest vector-borne diseases in the world. Researchers are developing new genetic and conventional vector control strategies to attempt to limit its burden. Novel control strategies require detailed safety assessment to ensure responsible and successful deployments. Anopheles gambiae sensu stricto (s.s.) and Anopheles coluzzii, two closely related subspecies within the species complex Anopheles gambiae sensu lato (s.l.), are among the dominant malaria vectors in sub-Saharan Africa. These two subspecies readily hybridise and compete in the wild and are also known to have distinct niches, each with spatially and temporally varying carrying capacities driven by precipitation and land use factors. We model the spread and persistence of a population-modifying gene drive system in these subspecies across sub-Saharan Africa by simulating introductions of genetically modified mosquitoes across the African mainland and its offshore islands. We explore transmission of the gene drive between the two subspecies that arise from different hybridisation mechanisms, the effects of both local dispersal and potential wind-aided migration to the spread, and the development of resistance to the gene drive. Given the best current available knowledge on the subspecies’ life histories, we find that an introduced gene drive system with typical characteristics can plausibly spread from even distant offshore islands to the African mainland with the aid of wind-driven migration, with resistance beginning to take over within a decade. Our model accounts for regional to continental scale mechanisms, and demonstrates a range of realistic dynamics including the effect of prevailing wind on spread and spatio-temporally varying carrying capacities for subspecies. As a result, it is well-placed to answer future questions relating to mosquito gene drives as important life history parameters become better understood. Conventional control methods have dramatically reduced malaria, but it still kills over 300,000 children in Africa each year, and this number could increase as their effectiveness wanes. Novel control methods using gene drives rapidly reduce or modify malaria vector populations in laboratory settings, and hence are now being considered for field applications. We use modelling to assess how a gene drive might spread and persist in the malaria-carrying subspecies Anopheles gambiae sensu stricto (s.s.) and Anopheles coluzzii. These two subspecies interbreed and compete, so we model how these interactions affect the spread of the drive at a continental scale. In scenarios that allow mosquitoes to travel on prevailing wind currents, we find that a gene drive can potentially spread across national borders—and jump from offshore islands to the African mainland—but spread is eventually arrested when the drive allele is ousted by a resistant allele. As we learn more about the population dynamics of both genetically modified and wild mosquitoes, and as gene drive systems are further developed to allow local containment and evade resistance, our model will be able to answer more detailed questions about how they can be applied in the field effectively and safely.
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Affiliation(s)
- Nicholas J. Beeton
- Data61, CSIRO, 3 Castray Esplanade, Battery Point TAS, Australia
- * E-mail: (NJB); (AW)
| | - Andrew Wilkins
- Mineral Resources, CSIRO, 1 Technology Court, Pullenvale QLD, Australia
- * E-mail: (NJB); (AW)
| | - Adrien Ickowicz
- Data61, CSIRO, 3 Castray Esplanade, Battery Point TAS, Australia
| | - Keith R. Hayes
- Data61, CSIRO, 3 Castray Esplanade, Battery Point TAS, Australia
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22
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Connolly JB, Mumford JD, Glandorf DCM, Hartley S, Lewis OT, Evans SW, Turner G, Beech C, Sykes N, Coulibaly MB, Romeis J, Teem JL, Tonui W, Lovett B, Mankad A, Mnzava A, Fuchs S, Hackett TD, Landis WG, Marshall JM, Aboagye-Antwi F. Recommendations for environmental risk assessment of gene drive applications for malaria vector control. Malar J 2022; 21:152. [PMID: 35614489 PMCID: PMC9131534 DOI: 10.1186/s12936-022-04183-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2022] [Accepted: 05/11/2022] [Indexed: 11/11/2022] Open
Abstract
Building on an exercise that identified potential harms from simulated investigational releases of a population suppression gene drive for malaria vector control, a series of online workshops identified nine recommendations to advance future environmental risk assessment of gene drive applications.
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Affiliation(s)
- John B Connolly
- Department of Life Sciences, Imperial College London, Silwood Park, Sunninghill, Ascot, UK.
| | - John D Mumford
- Centre for Environmental Policy, Imperial College London, Silwood Park, Sunninghill, Ascot, UK
| | | | | | - Owen T Lewis
- Department of Zoology, University of Oxford, Oxford, UK
| | - Sam Weiss Evans
- Program On Science, Technology & Society, John F. Kennedy School of Government, Harvard University, Cambridge, MA, USA
| | - Geoff Turner
- Department of Life Sciences, Imperial College London, Silwood Park, Sunninghill, Ascot, UK
| | | | - Naima Sykes
- Department of Life Sciences, Imperial College London, Silwood Park, Sunninghill, Ascot, UK
| | - Mamadou B Coulibaly
- Malaria Research and Training Center (MRTC), University of Sciences, Techniques and Technologies of Bamako, Bamako, Mali
| | - Jörg Romeis
- Research Division Agroecology and Environment, Agroscope, Zürich, Switzerland
| | - John L Teem
- Genetic Biocontrols LLC, Tallahassee, FL, USA
| | - Willy Tonui
- Environmental Health and Safety (EHS Consultancy) Ltd, Nairobi, Kenya
| | - Brian Lovett
- Division of Plant and Soil Sciences, West Virginia University, Morgantown, USA
| | - Aditi Mankad
- CSIRO Synthetic Biology Future Science Platform, CSIRO Land & Water, Brisbane, Australia
| | - Abraham Mnzava
- African Leaders Malaria Alliance, Dar es Salaam, Tanzania
| | - Silke Fuchs
- Department of Life Sciences, Imperial College London, Silwood Park, Sunninghill, Ascot, UK
| | | | - Wayne G Landis
- Institute of Environmental Toxicology and Chemistry, College of the Environment, Western Washington University, Bellingham, WA, USA
| | - John M Marshall
- Divisions of Biostatistics and Epidemiology, School of Public Health, University of California, Berkeley, USA
| | - Fred Aboagye-Antwi
- Department of Animal Biology and Conservation Sciences, University of Ghana, Legon, Accra, Ghana
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23
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Chae K, Dawson C, Valentin C, Contreras B, Zapletal J, Myles KM, Adelman ZN. Engineering a self-eliminating transgene in the yellow fever mosquito, Aedes aegypti. PNAS NEXUS 2022; 1:pgac037. [PMID: 36713320 PMCID: PMC9802104 DOI: 10.1093/pnasnexus/pgac037] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Accepted: 03/22/2022] [Indexed: 02/01/2023]
Abstract
Promising genetics-based approaches are being developed to reduce or prevent the transmission of mosquito-vectored diseases. Less clear is how such transgenes can be removed from the environment, a concern that is particularly relevant for highly invasive gene drive transgenes. Here, we lay the groundwork for a transgene removal system based on single-strand annealing (SSA), a eukaryotic DNA repair mechanism. An SSA-based rescuer strain (kmoRG ) was engineered to have direct repeat sequences (DRs) in the Aedes aegypti kynurenine 3-monooxygenase (kmo) gene flanking the intervening transgenic cargo genes, DsRED and EGFP. Targeted induction of DNA double-strand breaks (DSBs) in the DsRED transgene successfully triggered complete elimination of the entire cargo from the kmoRG strain, restoring the wild-type kmo gene, and thereby, normal eye pigmentation. Our work establishes the framework for strategies to remove transgene sequences during the evaluation and testing of modified strains for genetics-based mosquito control.
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Affiliation(s)
- Keun Chae
- Department of Entomology, Texas A&M University, College Station, TX 77843, USA
| | - Chanell Dawson
- Department of Entomology, Texas A&M University, College Station, TX 77843, USA
| | - Collin Valentin
- Department of Entomology, Texas A&M University, College Station, TX 77843, USA
| | - Bryan Contreras
- Department of Entomology, Texas A&M University, College Station, TX 77843, USA
| | - Josef Zapletal
- Department of Industrial and Systems Engineering, Texas A&M University, College Station, TX 77843, USA
| | - Kevin M Myles
- Department of Entomology, Texas A&M University, College Station, TX 77843, USA
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24
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Mondal A, Vásquez VN, Marshall JM. Target Product Profiles for Mosquito Gene Drives: Incorporating Insights From Mathematical Models. FRONTIERS IN TROPICAL DISEASES 2022. [DOI: 10.3389/fitd.2022.828876] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Mosquito-borne diseases such as malaria continue to pose a major global health burden, and the impact of currently-available interventions is stagnating. Consequently, there is interest in novel tools to control these diseases, including gene drive-modified mosquitoes. As these tools continue to be refined, decisions on whether to implement them in the field depend on their alignment with target product profiles (TPPs) that define product characteristics required to achieve desired entomological and epidemiological outcomes. TPPs are increasingly being used for malaria and vector control interventions, such as attractive targeted sugar baits and long-acting injectable drugs, as they progress through the development pipeline. For mosquito gene drive products, reliable predictions from mathematical models are an essential part of these analyses, as field releases could potentially be irreversible. Here, we review the prior use of mathematical models in developing TPPs for malaria and vector control tools and discuss lessons from these analyses that may apply to mosquito gene drives. We recommend that, as gene drive technology gets closer to field release, discussions regarding target outcomes engage a wide range of stakeholders and account for settings of interest and vector species present. Given the relatively large number of parameters that describe gene drive products, machine learning approaches may be useful to explore parameter space, and an emphasis on conservative fitness estimates is advisable, given the difficulty of accurately measuring these parameters prior to field studies. Modeling may also help to inform the risk, remediation and cost dimensions of mosquito gene drive TPPs.
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25
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Higgs S. An Introduction to Containment Recommendations for Gene Drive Mosquitoes and the Laboratory Rearing of Genetically Engineered Mosquitoes in Africa. Vector Borne Zoonotic Dis 2022; 22:1-2. [PMID: 34995158 DOI: 10.1089/vbz.2021.0072] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- Stephen Higgs
- Biosecurity Research Institute, Kansas State University, Manhattan, Kansas, USA
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26
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Guissou C, Quinlan MM, Sanou R, Ouédraogo RK, Namountougou M, Diabaté A. Preparing an Insectary in Burkina Faso to Support Research in Genetic Technologies for Malaria Control. Vector Borne Zoonotic Dis 2022; 22:18-28. [PMID: 34995157 PMCID: PMC8787693 DOI: 10.1089/vbz.2021.0041] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
The Institut de Recherche en Sciences de la Santé (IRSS) of Burkina Faso, West Africa, was the first African institution to import transgenic mosquitoes for research purposes. A shift from the culture of mosquito research to regulated biotechnology research and considerable management capacity is needed to set up and run the first insectary for transgenic insects in a country that applied and adapted the existing biosafety framework, first developed for genetically modified (GM) crops, to this new area of research. The additional demands arise from the separate regulatory framework for biotechnology, referencing the Cartagena Protocol on Biosafety, and the novelty of the research strain, making public understanding and acceptance early in the research pathway important. The IRSS team carried out extensive preparations following recommendations for containment of GM arthropods and invested efforts in local community engagement and training with scientific colleagues throughout the region. Record keeping beyond routine practice was established to maintain evidence related to regulatory requirements and risk assumptions. The National Biosafety Agency of Burkina Faso, Agence Nationale de Biosécurité (ANB), granted the permits for import of the self-limiting transgenic mosquito strain, which took place in November 2016, and for conducting studies in the IRSS facility in Bobo-Dioulasso. Compliance with permit terms and conditions of the permits and study protocols continued until the conclusion of studies, when the transgenic colonies were terminated. All this required close coordination between management and the insectary teams, as well as others. This article outlines the experiences of the IRSS to support others undertaking such studies. The IRSS is contributing to the ongoing development of genetic technologies for malaria control, as a partner of Target Malaria. The ultimate objective of the innovation is to reduce malaria transmission by using GM mosquitoes of the same species released to reduce the disease-vectoring native populations of Anopheles gambiae s.l.
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Affiliation(s)
- Charles Guissou
- Institut de Recherche en Sciences de la Santé-Direction Régionale de l''Ouest (IRSS-DRO), Bobo-Dioulasso, Burkina Faso
| | - M Megan Quinlan
- Centre for Environmental Policy, Imperial College London, United Kingdom
| | - Roger Sanou
- Institut de Recherche en Sciences de la Santé-Direction Régionale de l''Ouest (IRSS-DRO), Bobo-Dioulasso, Burkina Faso
| | - Robert K Ouédraogo
- Institut de Recherche en Sciences de la Santé-Direction Régionale de l''Ouest (IRSS-DRO), Bobo-Dioulasso, Burkina Faso
| | - Moussa Namountougou
- Institut de Recherche en Sciences de la Santé-Direction Régionale de l''Ouest (IRSS-DRO), Bobo-Dioulasso, Burkina Faso
| | - Abdoulaye Diabaté
- Institut de Recherche en Sciences de la Santé-Direction Régionale de l''Ouest (IRSS-DRO), Bobo-Dioulasso, Burkina Faso
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Abstract
Gene drives are selfish genetic elements that are transmitted to progeny at super-Mendelian (>50%) frequencies. Recently developed CRISPR-Cas9-based gene-drive systems are highly efficient in laboratory settings, offering the potential to reduce the prevalence of vector-borne diseases, crop pests and non-native invasive species. However, concerns have been raised regarding the potential unintended impacts of gene-drive systems. This Review summarizes the phenomenal progress in this field, focusing on optimal design features for full-drive elements (drives with linked Cas9 and guide RNA components) that either suppress target mosquito populations or modify them to prevent pathogen transmission, allelic drives for updating genetic elements, mitigating strategies including trans-complementing split-drives and genetic neutralizing elements, and the adaptation of drive technology to other organisms. These scientific advances, combined with ethical and social considerations, will facilitate the transparent and responsible advancement of these technologies towards field implementation.
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Affiliation(s)
- Ethan Bier
- Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA, USA.
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Goldsmith CL, Kang KE, Heitman E, Adelman ZN, Buchman LW, Kerns D, Liu X, Medina RF, Vedlitz A. Stakeholder Views on Engagement, Trust, Performance, and Risk Considerations About Use of Gene Drive Technology in Agricultural Pest Management. Health Secur 2021; 20:6-15. [PMID: 34981962 DOI: 10.1089/hs.2021.0101] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Gene drive is an experimental technique that may make it possible to alter the genetic traits of whole populations of a species through the genetic modification of a relatively small number of individuals. This technology is sufficiently new that literature on the understanding and views of stakeholders and the public regarding the use of gene drive organisms in agricultural pest management is just beginning to emerge. Our team conducted a 2-pronged engagement process with Texas gene drive agricultural stakeholders to ascertain their values, beliefs, and preferences about the efficacy, safety, and risk management considerations of gene drive technology as a potential tool for agricultural pest management. We found that a majority of stakeholders support gene drive research and its potential use for managing agricultural pests. Our work with stakeholders confirms both their willingness to be engaged and the importance they place on stakeholder and public engagement regarding these issues, as well as the need to address these issues before use of gene drive as a pest management mechanism will be accepted and trusted.
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Affiliation(s)
- Carol L Goldsmith
- Carol L. Goldsmith, MPA, is Assistant Director and Research Specialist II, Institute for Science, Technology, and Public Policy (ISTPP); Ki Eun Kang, PhD, is a Postdoctoral Research Associate, ISTPP; Zach N. Adelman, PhD, is a Professor, Department of Entomology, Texas A&M AgriLife Research; Leah W. Buchman is a Predoctoral Research Associate, ISTPP, and a Doctoral Candidate, Department of Entomology; David Kerns, PhD, is a Professor, Extension Specialist and Statewide Integrated Pest Management Coordinator, Department of Entomology, Texas A&M AgriLife Research; Xinsheng Liu, PhD, is a Senior Research Scholar and Research Scientist, ISTPP; Raul F. Medina, PhD, is a Professor, Department of Entomology, Texas A&M AgriLife Research; and Arnold Vedlitz, PhD, is Director and Distinguished Research Scholar, ISTPP, and a Professor, Department of Public Service and Administration; all at Texas A&M University, College Station, TX. Elizabeth Heitman, PhD, is a Professor, Program in Ethics in Science and Medicine, Department of Psychiatry, University of Texas Southwestern Medical Center, Dallas, TX
| | - Ki Eun Kang
- Carol L. Goldsmith, MPA, is Assistant Director and Research Specialist II, Institute for Science, Technology, and Public Policy (ISTPP); Ki Eun Kang, PhD, is a Postdoctoral Research Associate, ISTPP; Zach N. Adelman, PhD, is a Professor, Department of Entomology, Texas A&M AgriLife Research; Leah W. Buchman is a Predoctoral Research Associate, ISTPP, and a Doctoral Candidate, Department of Entomology; David Kerns, PhD, is a Professor, Extension Specialist and Statewide Integrated Pest Management Coordinator, Department of Entomology, Texas A&M AgriLife Research; Xinsheng Liu, PhD, is a Senior Research Scholar and Research Scientist, ISTPP; Raul F. Medina, PhD, is a Professor, Department of Entomology, Texas A&M AgriLife Research; and Arnold Vedlitz, PhD, is Director and Distinguished Research Scholar, ISTPP, and a Professor, Department of Public Service and Administration; all at Texas A&M University, College Station, TX. Elizabeth Heitman, PhD, is a Professor, Program in Ethics in Science and Medicine, Department of Psychiatry, University of Texas Southwestern Medical Center, Dallas, TX
| | - Elizabeth Heitman
- Carol L. Goldsmith, MPA, is Assistant Director and Research Specialist II, Institute for Science, Technology, and Public Policy (ISTPP); Ki Eun Kang, PhD, is a Postdoctoral Research Associate, ISTPP; Zach N. Adelman, PhD, is a Professor, Department of Entomology, Texas A&M AgriLife Research; Leah W. Buchman is a Predoctoral Research Associate, ISTPP, and a Doctoral Candidate, Department of Entomology; David Kerns, PhD, is a Professor, Extension Specialist and Statewide Integrated Pest Management Coordinator, Department of Entomology, Texas A&M AgriLife Research; Xinsheng Liu, PhD, is a Senior Research Scholar and Research Scientist, ISTPP; Raul F. Medina, PhD, is a Professor, Department of Entomology, Texas A&M AgriLife Research; and Arnold Vedlitz, PhD, is Director and Distinguished Research Scholar, ISTPP, and a Professor, Department of Public Service and Administration; all at Texas A&M University, College Station, TX. Elizabeth Heitman, PhD, is a Professor, Program in Ethics in Science and Medicine, Department of Psychiatry, University of Texas Southwestern Medical Center, Dallas, TX
| | - Zach N Adelman
- Carol L. Goldsmith, MPA, is Assistant Director and Research Specialist II, Institute for Science, Technology, and Public Policy (ISTPP); Ki Eun Kang, PhD, is a Postdoctoral Research Associate, ISTPP; Zach N. Adelman, PhD, is a Professor, Department of Entomology, Texas A&M AgriLife Research; Leah W. Buchman is a Predoctoral Research Associate, ISTPP, and a Doctoral Candidate, Department of Entomology; David Kerns, PhD, is a Professor, Extension Specialist and Statewide Integrated Pest Management Coordinator, Department of Entomology, Texas A&M AgriLife Research; Xinsheng Liu, PhD, is a Senior Research Scholar and Research Scientist, ISTPP; Raul F. Medina, PhD, is a Professor, Department of Entomology, Texas A&M AgriLife Research; and Arnold Vedlitz, PhD, is Director and Distinguished Research Scholar, ISTPP, and a Professor, Department of Public Service and Administration; all at Texas A&M University, College Station, TX. Elizabeth Heitman, PhD, is a Professor, Program in Ethics in Science and Medicine, Department of Psychiatry, University of Texas Southwestern Medical Center, Dallas, TX
| | - Leah W Buchman
- Carol L. Goldsmith, MPA, is Assistant Director and Research Specialist II, Institute for Science, Technology, and Public Policy (ISTPP); Ki Eun Kang, PhD, is a Postdoctoral Research Associate, ISTPP; Zach N. Adelman, PhD, is a Professor, Department of Entomology, Texas A&M AgriLife Research; Leah W. Buchman is a Predoctoral Research Associate, ISTPP, and a Doctoral Candidate, Department of Entomology; David Kerns, PhD, is a Professor, Extension Specialist and Statewide Integrated Pest Management Coordinator, Department of Entomology, Texas A&M AgriLife Research; Xinsheng Liu, PhD, is a Senior Research Scholar and Research Scientist, ISTPP; Raul F. Medina, PhD, is a Professor, Department of Entomology, Texas A&M AgriLife Research; and Arnold Vedlitz, PhD, is Director and Distinguished Research Scholar, ISTPP, and a Professor, Department of Public Service and Administration; all at Texas A&M University, College Station, TX. Elizabeth Heitman, PhD, is a Professor, Program in Ethics in Science and Medicine, Department of Psychiatry, University of Texas Southwestern Medical Center, Dallas, TX
| | - David Kerns
- Carol L. Goldsmith, MPA, is Assistant Director and Research Specialist II, Institute for Science, Technology, and Public Policy (ISTPP); Ki Eun Kang, PhD, is a Postdoctoral Research Associate, ISTPP; Zach N. Adelman, PhD, is a Professor, Department of Entomology, Texas A&M AgriLife Research; Leah W. Buchman is a Predoctoral Research Associate, ISTPP, and a Doctoral Candidate, Department of Entomology; David Kerns, PhD, is a Professor, Extension Specialist and Statewide Integrated Pest Management Coordinator, Department of Entomology, Texas A&M AgriLife Research; Xinsheng Liu, PhD, is a Senior Research Scholar and Research Scientist, ISTPP; Raul F. Medina, PhD, is a Professor, Department of Entomology, Texas A&M AgriLife Research; and Arnold Vedlitz, PhD, is Director and Distinguished Research Scholar, ISTPP, and a Professor, Department of Public Service and Administration; all at Texas A&M University, College Station, TX. Elizabeth Heitman, PhD, is a Professor, Program in Ethics in Science and Medicine, Department of Psychiatry, University of Texas Southwestern Medical Center, Dallas, TX
| | - Xinsheng Liu
- Carol L. Goldsmith, MPA, is Assistant Director and Research Specialist II, Institute for Science, Technology, and Public Policy (ISTPP); Ki Eun Kang, PhD, is a Postdoctoral Research Associate, ISTPP; Zach N. Adelman, PhD, is a Professor, Department of Entomology, Texas A&M AgriLife Research; Leah W. Buchman is a Predoctoral Research Associate, ISTPP, and a Doctoral Candidate, Department of Entomology; David Kerns, PhD, is a Professor, Extension Specialist and Statewide Integrated Pest Management Coordinator, Department of Entomology, Texas A&M AgriLife Research; Xinsheng Liu, PhD, is a Senior Research Scholar and Research Scientist, ISTPP; Raul F. Medina, PhD, is a Professor, Department of Entomology, Texas A&M AgriLife Research; and Arnold Vedlitz, PhD, is Director and Distinguished Research Scholar, ISTPP, and a Professor, Department of Public Service and Administration; all at Texas A&M University, College Station, TX. Elizabeth Heitman, PhD, is a Professor, Program in Ethics in Science and Medicine, Department of Psychiatry, University of Texas Southwestern Medical Center, Dallas, TX
| | - Raul F Medina
- Carol L. Goldsmith, MPA, is Assistant Director and Research Specialist II, Institute for Science, Technology, and Public Policy (ISTPP); Ki Eun Kang, PhD, is a Postdoctoral Research Associate, ISTPP; Zach N. Adelman, PhD, is a Professor, Department of Entomology, Texas A&M AgriLife Research; Leah W. Buchman is a Predoctoral Research Associate, ISTPP, and a Doctoral Candidate, Department of Entomology; David Kerns, PhD, is a Professor, Extension Specialist and Statewide Integrated Pest Management Coordinator, Department of Entomology, Texas A&M AgriLife Research; Xinsheng Liu, PhD, is a Senior Research Scholar and Research Scientist, ISTPP; Raul F. Medina, PhD, is a Professor, Department of Entomology, Texas A&M AgriLife Research; and Arnold Vedlitz, PhD, is Director and Distinguished Research Scholar, ISTPP, and a Professor, Department of Public Service and Administration; all at Texas A&M University, College Station, TX. Elizabeth Heitman, PhD, is a Professor, Program in Ethics in Science and Medicine, Department of Psychiatry, University of Texas Southwestern Medical Center, Dallas, TX
| | - Arnold Vedlitz
- Carol L. Goldsmith, MPA, is Assistant Director and Research Specialist II, Institute for Science, Technology, and Public Policy (ISTPP); Ki Eun Kang, PhD, is a Postdoctoral Research Associate, ISTPP; Zach N. Adelman, PhD, is a Professor, Department of Entomology, Texas A&M AgriLife Research; Leah W. Buchman is a Predoctoral Research Associate, ISTPP, and a Doctoral Candidate, Department of Entomology; David Kerns, PhD, is a Professor, Extension Specialist and Statewide Integrated Pest Management Coordinator, Department of Entomology, Texas A&M AgriLife Research; Xinsheng Liu, PhD, is a Senior Research Scholar and Research Scientist, ISTPP; Raul F. Medina, PhD, is a Professor, Department of Entomology, Texas A&M AgriLife Research; and Arnold Vedlitz, PhD, is Director and Distinguished Research Scholar, ISTPP, and a Professor, Department of Public Service and Administration; all at Texas A&M University, College Station, TX. Elizabeth Heitman, PhD, is a Professor, Program in Ethics in Science and Medicine, Department of Psychiatry, University of Texas Southwestern Medical Center, Dallas, TX
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Abstract
Gene drives are an emerging technology with tremendous potential to impact public health, agriculture, and conservation. While gene drives can be described simply as selfish genetic elements (natural or engineered) that are inherited at non-Mendelian rates, upon closer inspection, engineered gene drive technology is a complex class of biotechnology that uses a diverse number of genetic features to bias rates of inheritance. As a complex technology, gene drives can be difficult to comprehend, not only for the public and stakeholders, but also to risk assessors, risk managers, and decisionmakers not familiar with gene drive literature. To address this difficulty, we describe a gene drive classification system based on 5 functional characteristics. These characteristics include a gene drive's objective, mechanism, release threshold, range, and persistence. The aggregate of the gene drive's characteristics can be described as the gene drive's architecture. Establishing a classification system to define different gene drive technologies should make them more comprehensible to the public and provide a framework to guide regulatory evaluation and decisionmaking.
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Affiliation(s)
- Justin Overcash
- Justin Overcash, PhD, is an Animal and Plant Health Inspection Service (APHIS) Science Fellow, Biotechnology Regulatory Services, Riverdale, MD
| | - Andrew Golnar
- Andrew Golnar, PhD, is an APHIS Science Fellow, Wildlife Services, Fort Collins, CO
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30
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Tapanelli S, Inghilterra MG, Cai J, Philpott J, Capriotti P, Windbichler N, Christophides GK. Assessment of Plasmodium falciparum Infection and Fitness of Genetically Modified Anopheles gambiae Aimed at Mosquito Population Replacement. FRONTIERS IN TROPICAL DISEASES 2021. [DOI: 10.3389/fitd.2021.806880] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Genetically modified (GM) mosquitoes expressing anti-plasmodial effectors propagating through wild mosquito populations by means of gene drive is a promising tool to support current malaria control strategies. The process of generating GM mosquitoes involves genetic transformation of mosquitoes from a laboratory colony and, often, interbreeding with other GM lines to cross in auxiliary traits. These mosquito colonies and GM lines thus often have different genetic backgrounds and GM lines are invariably highly inbred, which in conjunction with their independent rearing in the laboratory may translate to differences in their susceptibility to malaria parasite infection and life history traits. Here, we show that laboratory Anopheles gambiae colonies and GM lines expressing Cas9 and Cre recombinase vary greatly in their susceptibility to Plasmodium falciparum NF54 infection. Therefore, the choice of mosquitoes to be used as a reference when conducting infection or life history trait assays requires careful consideration. To address these issues, we established an experimental pipeline involving genetic crosses and genotyping of mosquitoes reared in shared containers throughout their lifecycle. We used this protocol to examine whether GM lines expressing the antimicrobial peptide (AMP) Scorpine in the mosquito midgut interfere with parasite infection and mosquito survival. We demonstrate that Scorpine expression in the Peritrophin 1 (Aper1) genomic locus reduces both P. falciparum sporozoite prevalence and mosquito lifespan; both these phenotypes are likely to be associated with the disturbance of the midgut microbiota homeostasis. These data lead us to conclude that the Aper1-Sco GM line could be used in proof-of-concept experiments aimed at mosquito population replacement, although the impact of its reduced fitness on the spread of the transgene through wild populations requires further investigation.
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Tait G, Mermer S, Stockton D, Lee J, Avosani S, Abrieux A, Anfora G, Beers E, Biondi A, Burrack H, Cha D, Chiu JC, Choi MY, Cloonan K, Crava CM, Daane KM, Dalton DT, Diepenbrock L, Fanning P, Ganjisaffar F, Gómez MI, Gut L, Grassi A, Hamby K, Hoelmer KA, Ioriatti C, Isaacs R, Klick J, Kraft L, Loeb G, Rossi-Stacconi MV, Nieri R, Pfab F, Puppato S, Rendon D, Renkema J, Rodriguez-Saona C, Rogers M, Sassù F, Schöneberg T, Scott MJ, Seagraves M, Sial A, Van Timmeren S, Wallingford A, Wang X, Yeh DA, Zalom FG, Walton VM. Drosophila suzukii (Diptera: Drosophilidae): A Decade of Research Towards a Sustainable Integrated Pest Management Program. JOURNAL OF ECONOMIC ENTOMOLOGY 2021; 114:1950-1974. [PMID: 34516634 DOI: 10.1093/jee/toab158] [Citation(s) in RCA: 63] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Indexed: 05/17/2023]
Abstract
Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) also known as spotted-wing drosophila (SWD), is a pest native to Southeast Asia. In the last few decades, the pest has expanded its range to affect all major European and American fruit production regions. SWD is a highly adaptive insect that is able to disperse, survive, and flourish under a range of environmental conditions. Infestation by SWD generates both direct and indirect economic impacts through yield losses, shorter shelf life of infested fruit, and increased production costs. Fresh markets, frozen berries, and fruit export programs have been impacted by the pest due to zero tolerance for fruit infestation. As SWD control programs rely heavily on insecticides, exceedance of maximum residue levels (MRLs) has also resulted in crop rejections. The economic impact of SWD has been particularly severe for organic operations, mainly due to the limited availability of effective insecticides. Integrated pest management (IPM) of SWD could significantly reduce chemical inputs but would require substantial changes to horticultural management practices. This review evaluates the most promising methods studied as part of an IPM strategy against SWD across the world. For each of the considered techniques, the effectiveness, impact, sustainability, and stage of development are discussed.
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Affiliation(s)
- Gabriella Tait
- Department of Horticulture, Oregon State University, Corvallis, OR, USA
| | - Serhan Mermer
- Department of Horticulture, Oregon State University, Corvallis, OR, USA
| | - Dara Stockton
- USDA-ARS Daniel K. Inouye U.S. Pacific Basin Agricultural Research Center, Hilo, HI, USA
| | - Jana Lee
- USDA-ARS Horticultural Crops Research Unit, Corvallis, OR, USA
| | - Sabina Avosani
- Department of Civil, Environmental and Mechanical Engineering, University of Trento, Trento, Italy
- Research and Innovation Centre, Fondazione Edmund Mach, San Michele all'Adige, Italy
| | - Antoine Abrieux
- Department of Entomology and Nematology, University of California, Davis, CA, USA
| | - Gianfranco Anfora
- Research and Innovation Centre, Fondazione Edmund Mach, San Michele all'Adige, Italy
- Center Agriculture Food Environment, University of Trento, San Michele all'Adige, Trentino, Italy
| | - Elizabeth Beers
- Tree Fruit Research & Extension Center, Washington State University, Wenatchee, WA, USA
| | - Antonio Biondi
- Department of Agriculture, Food and Environment, University of Catania, Catania, Italy
| | - Hannah Burrack
- Department of Entomology and Plant Pathology, North Carolina State University, Raleigh, NC, USA
| | - Dong Cha
- USDA-ARS Daniel K. Inouye U.S. Pacific Basin Agricultural Research Center, Hilo, HI, USA
| | - Joanna C Chiu
- Department of Entomology and Nematology, University of California, Davis, CA, USA
| | - Man-Yeon Choi
- USDA-ARS Horticultural Crops Research Unit, Corvallis, OR, USA
| | | | - Cristina M Crava
- Institute of Biotechnology and Biomedicine (BIOTECMED), University of Valencia, Valencia, Spain
| | - Kent M Daane
- Kearney Agricultural Research and Education Center, Parlier, CA, USA
- Department of Environmental Science, Policy & Management, University of California Berkeley, Berkeley, CA, USA
| | - Daniel T Dalton
- Faculty of Engineering & IT, Carinthia University of Applied Sciences, 9524, Villach, Austria
| | - Lauren Diepenbrock
- Citrus Research and Education Center, Entomology and Nematology Department, University of Florida, Lake Alfred, FL, USA
| | - Phillip Fanning
- USDA Economic Research Service, Market Trade and Economics Division, Kansas City, MO, USA
| | - Fatemeh Ganjisaffar
- Department of Entomology and Nematology, University of California, Davis, CA, USA
| | - Miguel I Gómez
- Dyson School of Applied Economics and Management, Cornell University, Ithaca, NY, USA
| | - Larry Gut
- Department of Entomology, Michigan State University, East Lansing, MI, USA
| | - Alberto Grassi
- Technology Transfer Center, Fondazione Edmund Mach, San Michele all'Adige, Italy
| | - Kelly Hamby
- Department of Entomology, University of Maryland, College Park, MD, USA
| | - Kim A Hoelmer
- USDA-ARS Beneficial Insects Introduction Research Unit, Newark, DE, USA
| | - Claudio Ioriatti
- Technology Transfer Center, Fondazione Edmund Mach, San Michele all'Adige, Italy
| | - Rufus Isaacs
- Department of Entomology, Michigan State University, East Lansing, MI, USA
| | | | - Laura Kraft
- Department of Entomology and Plant Pathology, North Carolina State University, Raleigh, NC, USA
| | - Gregory Loeb
- Department of Entomology, Cornell AgriTech, Geneva, NY, USA
| | | | - Rachele Nieri
- Department of Civil, Environmental and Mechanical Engineering, University of Trento, Trento, Italy
- Research and Innovation Centre, Fondazione Edmund Mach, San Michele all'Adige, Italy
| | - Ferdinand Pfab
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA, USA
| | - Simone Puppato
- Technology Transfer Center, Fondazione Edmund Mach, San Michele all'Adige, Italy
| | - Dalila Rendon
- Department of Horticulture, Oregon State University, Corvallis, OR, USA
| | - Justin Renkema
- London Research and Development Centre - Vineland Campus, Agriculture and Agri-Food Canada, Vineland, ON, Canada
| | | | - Mary Rogers
- Department of Horticultural Science, University of Minnesota, Saint Paul, MN, USA
| | - Fabiana Sassù
- Department of Forest and Soil Sciences, BOKU, University of Natural Resources and Life Sciences, Vienna, Austria
- Insect Pest Control Section, Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture, Vienna, Austria
| | | | - Maxwell J Scott
- Department of Entomology and Plant Pathology, North Carolina State University, Raleigh, NC, USA
| | | | - Ashfaq Sial
- Department of Entomology, University of Georgia, Athens, GA, USA
| | | | - Anna Wallingford
- Department of Agriculture Nutrition and Food Systems, University of New Hampshire, Durham, NH, USA
| | - Xingeng Wang
- USDA-ARS Beneficial Insects Introduction Research Unit, Newark, DE, USA
| | - D Adeline Yeh
- USDA Economic Research Service, Market Trade and Economics Division, Kansas City, MO, USA
| | - Frank G Zalom
- Department of Entomology and Nematology, University of California, Davis, CA, USA
| | - Vaughn M Walton
- Department of Horticulture, Oregon State University, Corvallis, OR, USA
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Qureshi A, Connolly JB. A systematic review assessing the potential for release of vector species from competition following insecticide-based population suppression of Anopheles species in Africa. Parasit Vectors 2021; 14:462. [PMID: 34496931 PMCID: PMC8425169 DOI: 10.1186/s13071-021-04975-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2021] [Accepted: 08/23/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND While insecticide-based vector control can effectively target vector species in areas of high malaria endemicity, such as Anopheles gambiae in Africa, residual disease transmission can occur. Understanding the potential role of competitive displacement between vector species could inform both current insecticide-based vector control programmes and the development of future complementary interventions. METHODS A systematic review was conducted to identify published studies of insecticide-based vector control of Anopheles species in Africa that reported indices for absolute densities of vector species. After screening against inclusion, exclusion and risk of bias criteria, studies were assigned to three categories based on whether they showed population density changes involving decreases in two or more vector species (D), increases in two or more vector species (I), or increases in one vector species concomitant with decreases in another vector species (ID). Category ID studies could thus provide evidence consistent with the release of vector species from competition following the insecticide-based population suppression of Anopheles species. RESULTS Of 5569 papers identified in searches, 30 were selected for quantitative and qualitative analysis. Nineteen studies were assigned to category D and one to category I. Ten studies categorised as ID provided evidence ranging from weak to persuasive that release from competition could have contributed to changes in species composition. Category ID showed no statistical differences from category D for reductions in malaria transmission and levels of insecticide resistance, but did so for insecticide type, pyrethroids being associated with category ID. A qualitative assessment identified five studies that provided the most convincing evidence that release from competition could have contributed to changes in species composition. CONCLUSIONS This review identified evidence that insecticide-based reductions in the density of Anopheles species in Africa could facilitate the release of other vector species from competition. While it remains uncertain whether this evidence is representative of most entomological sequelae of insecticide-based vector control in the field, five studies provided persuasive evidence that insecticide use could lead, at least under some circumstances, to competitive release of non-targeted vector species. These results should inform current and future integrated vector management approaches to malaria control.
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Affiliation(s)
- Alima Qureshi
- Department of Life Sciences, Imperial College London, Silwood Park Campus, Ascot, SL5 7PY UK
| | - John B. Connolly
- Department of Life Sciences, Imperial College London, Silwood Park Campus, Ascot, SL5 7PY UK
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33
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Adelman ZN, Kojin BB. Malaria-Resistant Mosquitoes (Diptera: Culicidae); The Principle is Proven, But Will the Effectors Be Effective? JOURNAL OF MEDICAL ENTOMOLOGY 2021; 58:1997-2005. [PMID: 34018548 DOI: 10.1093/jme/tjab090] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Indexed: 06/12/2023]
Abstract
Over the last few decades, a substantial number of anti-malarial effector genes have been evaluated for their ability to block parasite infection in the mosquito vector. While many of these approaches have yielded significant effects on either parasite intensity or prevalence of infection, just a few have been able to completely block transmission. Additionally, many approaches, while effective against the parasite, also disrupt or alter important aspects of mosquito physiology, leading to corresponding changes in lifespan, reproduction, and immunity. As the most promising approaches move towards field-based evaluation, questions of effector gene robustness and durability move to the forefront. In this forum piece, we critically evaluate past effector gene approaches with an eye towards developing a deeper pipeline to augment the current best candidates.
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Affiliation(s)
- Zach N Adelman
- Department of Entomology and AgriLife Research, Texas A&M University, College Station, TX, USA
| | - Bianca B Kojin
- Department of Entomology and AgriLife Research, Texas A&M University, College Station, TX, USA
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Legros M, Marshall JM, Macfadyen S, Hayes KR, Sheppard A, Barrett LG. Gene drive strategies of pest control in agricultural systems: Challenges and opportunities. Evol Appl 2021; 14:2162-2178. [PMID: 34603490 PMCID: PMC8477592 DOI: 10.1111/eva.13285] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Revised: 06/24/2021] [Accepted: 07/19/2021] [Indexed: 12/18/2022] Open
Abstract
Recent advances in gene-editing technologies have opened new avenues for genetic pest control strategies, in particular around the use of gene drives to suppress or modify pest populations. Significant uncertainty, however, surrounds the applicability of these strategies to novel target species, their efficacy in natural populations and their eventual safety and acceptability as control methods. In this article, we identify issues associated with the potential use of gene drives in agricultural systems, to control pests and diseases that impose a significant cost to agriculture around the world. We first review the need for innovative approaches and provide an overview of the most relevant biological and ecological traits of agricultural pests that could impact the outcome of gene drive approaches. We then describe the specific challenges associated with using gene drives in agricultural systems, as well as the opportunities that these environments may offer, focusing in particular on the advantages of high-threshold gene drives. Overall, we aim to provide a comprehensive view of the potential opportunities and the remaining uncertainties around the use of gene drives in agricultural systems.
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Affiliation(s)
- Mathieu Legros
- CSIRO Agriculture and FoodCanberraACTAustralia
- CSIRO Synthetic Biology Future Science PlatformCanberraACTAustralia
| | - John M. Marshall
- Divisions of Biostatistics and Epidemiology – School of Public HealthUniversity of CaliforniaBerkeleyCAUSA
| | | | | | | | - Luke G. Barrett
- CSIRO Agriculture and FoodCanberraACTAustralia
- CSIRO Synthetic Biology Future Science PlatformCanberraACTAustralia
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35
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Lanzaro GC, Campos M, Crepeau M, Cornel A, Estrada A, Gripkey H, Haddad Z, Kormos A, Palomares S. Selection of sites for field trials of genetically engineered mosquitoes with gene drive. Evol Appl 2021; 14:2147-2161. [PMID: 34603489 PMCID: PMC8477601 DOI: 10.1111/eva.13283] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Revised: 06/29/2021] [Accepted: 07/06/2021] [Indexed: 12/11/2022] Open
Abstract
Novel malaria control strategies using genetically engineered mosquitoes (GEMs) are on the horizon. Population modification is one approach wherein mosquitoes are engineered with genes rendering them refractory to the malaria parasite, Plasmodium falciparum, coupled with a low-threshold, Cas9-based gene drive. When released into a wild vector population, GEMs preferentially transmit these parasite-blocking genes to their offspring, ultimately modifying a vector population into a nonvector one. Deploying this technology awaits ecologically contained field trial evaluations. Here, we consider a process for site selection, the first critical step in designing a trial. Our goal is to identify a site that maximizes prospects for success, minimizes risk, and serves as a fair, valid, and convincing test of efficacy and impacts of a GEM product intended for large-scale deployment in Africa. We base site selection on geographic, geological, and biological, rather than social or legal, criteria. We recognize the latter as critically important but not as a first step in selecting a site. We propose physical islands as being the best candidates for a GEM field trial and present an evaluation of 22 African islands. We consider geographic and genetic isolation, biological complexity, island size, and topography and identify two island groups that satisfy key criteria for ideal GEM field trial sites.
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Affiliation(s)
- Gregory C. Lanzaro
- Vector Genetics LaboratoryDepartment of Pathology, Microbiology and ImmunologySchool of Veterinary MedicineUniversity of CaliforniaDavisCaliforniaUSA
| | - Melina Campos
- Vector Genetics LaboratoryDepartment of Pathology, Microbiology and ImmunologySchool of Veterinary MedicineUniversity of CaliforniaDavisCaliforniaUSA
| | - Marc Crepeau
- Vector Genetics LaboratoryDepartment of Pathology, Microbiology and ImmunologySchool of Veterinary MedicineUniversity of CaliforniaDavisCaliforniaUSA
| | - Anthony Cornel
- Vector Genetics LaboratoryDepartment of Pathology, Microbiology and ImmunologySchool of Veterinary MedicineUniversity of CaliforniaDavisCaliforniaUSA
| | - Abram Estrada
- Vector Genetics LaboratoryDepartment of Pathology, Microbiology and ImmunologySchool of Veterinary MedicineUniversity of CaliforniaDavisCaliforniaUSA
| | - Hans Gripkey
- Vector Genetics LaboratoryDepartment of Pathology, Microbiology and ImmunologySchool of Veterinary MedicineUniversity of CaliforniaDavisCaliforniaUSA
| | - Ziad Haddad
- California Institute of TechnologyJet Propulsion LaboratoryPasadenaCaliforniaUSA
| | - Ana Kormos
- Vector Genetics LaboratoryDepartment of Pathology, Microbiology and ImmunologySchool of Veterinary MedicineUniversity of CaliforniaDavisCaliforniaUSA
| | - Steven Palomares
- Vector Genetics LaboratoryDepartment of Pathology, Microbiology and ImmunologySchool of Veterinary MedicineUniversity of CaliforniaDavisCaliforniaUSA
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36
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Burgess BT, Irvine RL, Howald GR, Russello MA. The Promise of Genetics and Genomics for Improving Invasive Mammal Management on Islands. Front Ecol Evol 2021. [DOI: 10.3389/fevo.2021.704809] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Invasive species are major contributors to global biodiversity decline. Invasive mammalian species (IMS), in particular, have profound negative effects in island systems that contain disproportionally high levels of species richness and endemism. The eradication and control of IMS have become important conservation tools for managing species invasions on islands, yet these management operations are often subject to failure due to knowledge gaps surrounding species- and system-specific characteristics, including invasion pathways and contemporary migration patterns. Here, we synthesize the literature on ways in which genetic and genomic tools have effectively informed IMS management on islands, specifically associated with the development and modification of biosecurity protocols, and the design and implementation of eradication and control programs. In spite of their demonstrated utility, we then explore the challenges that are preventing genetics and genomics from being implemented more frequently in IMS management operations from both academic and non-academic perspectives, and suggest possible solutions for breaking down these barriers. Finally, we discuss the potential application of genome editing to the future management of invasive species on islands, including the current state of the field and why islands may be effective targets for this emerging technology.
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37
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Bier E, Nizet V. Driving to Safety: CRISPR-Based Genetic Approaches to Reducing Antibiotic Resistance. Trends Genet 2021; 37:745-757. [PMID: 33745750 DOI: 10.1016/j.tig.2021.02.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2020] [Revised: 02/23/2021] [Accepted: 02/23/2021] [Indexed: 02/07/2023]
Abstract
Bacterial resistance to antibiotics has reached critical levels, skyrocketing in hospitals and the environment and posing a major threat to global public health. The complex and challenging problem of reducing antibiotic resistance (AR) requires a network of both societal and science-based solutions to preserve the most lifesaving pharmaceutical intervention known to medicine. In addition to developing new classes of antibiotics, it is essential to safeguard the clinical efficacy of existing drugs. In this review, we examine the potential application of novel CRISPR-based genetic approaches to reducing AR in both environmental and clinical settings and prolonging the utility of vital antibiotics.
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Affiliation(s)
- Ethan Bier
- Tata Institute for Genetics and Society, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0349, USA; Section of Cell and Developmental Biology, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0349, USA.
| | - Victor Nizet
- Tata Institute for Genetics and Society, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0349, USA; Collaborative to Halt Antibiotic-Resistant Microbes, Department of Pediatrics, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0687, USA; Skaggs School of Pharmacy & Pharmaceutical Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0687, USA
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38
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Gene-drive suppression of mosquito populations in large cages as a bridge between lab and field. Nat Commun 2021; 12:4589. [PMID: 34321476 PMCID: PMC8319305 DOI: 10.1038/s41467-021-24790-6] [Citation(s) in RCA: 43] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2021] [Accepted: 07/05/2021] [Indexed: 12/03/2022] Open
Abstract
CRISPR-based gene-drives targeting the gene doublesex in the malaria vector Anopheles gambiae effectively suppressed the reproductive capability of mosquito populations reared in small laboratory cages. To bridge the gap between laboratory and the field, this gene-drive technology must be challenged with vector ecology. Here we report the suppressive activity of the gene-drive in age-structured An. gambiae populations in large indoor cages that permit complex feeding and reproductive behaviours. The gene-drive element spreads rapidly through the populations, fully supresses the population within one year and without selecting for resistance to the gene drive. Approximate Bayesian computation allowed retrospective inference of life-history parameters from the large cages and a more accurate prediction of gene-drive behaviour under more ecologically-relevant settings. Generating data to bridge laboratory and field studies for invasive technologies is challenging. Our study represents a paradigm for the stepwise and sound development of vector control tools based on gene-drive. Experimental analysis of gene drive population dynamics has mostly been limited to small cage trials. Here the authors, to fill the gap between lab based studies and field studies, use large indoor cages and see population suppression without the emergence of resistant alleles
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39
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Devos Y, Mumford JD, Bonsall MB, Glandorf DCM, Quemada HD. Risk management recommendations for environmental releases of gene drive modified insects. Biotechnol Adv 2021; 54:107807. [PMID: 34314837 DOI: 10.1016/j.biotechadv.2021.107807] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2021] [Revised: 07/01/2021] [Accepted: 07/21/2021] [Indexed: 12/18/2022]
Abstract
The ability to engineer gene drives (genetic elements that bias their own inheritance) has sparked enthusiasm and concerns. Engineered gene drives could potentially be used to address long-standing challenges in the control of insect disease vectors, agricultural pests and invasive species, or help to rescue endangered species. However, risk concerns and uncertainty associated with potential environmental release of gene drive modified insects (GDMIs) have led some stakeholders to call for a global moratorium on such releases or the application of other strict precautionary measures to mitigate perceived risk assessment and risk management challenges. Instead, we provide recommendations that may help to improve the relevance of risk assessment and risk management frameworks for environmental releases of GDMIs. These recommendations include: (1) developing additional and more practical risk assessment guidance to ensure appropriate levels of safety; (2) making policy goals and regulatory decision-making criteria operational for use in risk assessment so that what constitutes harm is clearly defined; (3) ensuring a more dynamic interplay between risk assessment and risk management to manage uncertainty through closely interlinked pre-release modelling and post-release monitoring; (4) considering potential risks against potential benefits, and comparing them with those of alternative actions to account for a wider (management) context; and (5) implementing a modular, phased approach to authorisations for incremental acceptance and management of risks and uncertainty. Along with providing stakeholder engagement opportunities in the risk analysis process, the recommendations proposed may enable risk managers to make choices that are more proportionate and adaptive to potential risks, uncertainty and benefits of GDMI applications, and socially robust.
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Affiliation(s)
- Yann Devos
- Scientific Committee and Emerging Risk (SCER) Unit, European Food Safety Authority (EFSA), Parma, Italy.
| | - John D Mumford
- Centre for Environmental Policy, Imperial College London, Ascot, United Kingdom
| | | | - Debora C M Glandorf
- National Institute for Public Health and the Environment (RIVM), Bilthoven, the Netherlands
| | - Hector D Quemada
- Department of Biological Sciences, Western Michigan University, Kalamazoo, MI, United States
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40
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Devos Y, Mumford JD, Bonsall MB, Camargo AM, Firbank LG, Glandorf DCM, Nogué F, Paraskevopoulos K, Wimmer EA. Potential use of gene drive modified insects against disease vectors, agricultural pests and invasive species poses new challenges for risk assessment. Crit Rev Biotechnol 2021; 42:254-270. [PMID: 34167401 DOI: 10.1080/07388551.2021.1933891] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Potential future application of engineered gene drives (GDs), which bias their own inheritance and can spread genetic modifications in wild target populations, has sparked both enthusiasm and concern. Engineered GDs in insects could potentially be used to address long-standing challenges in control of disease vectors, agricultural pests and invasive species, or help to rescue endangered species, and thus provide important public benefits. However, there are concerns that the deliberate environmental release of GD modified insects may pose different or new harms to animal and human health and the wider environment, and raise novel challenges for risk assessment. Risk assessors, risk managers, developers, potential applicants and other stakeholders at many levels are currently discussing whether there is a need to develop new or additional risk assessment guidance for the environmental release of GD modified organisms, including insects. Developing new or additional guidance that is useful and practical is a challenge, especially at an international level, as risk assessors, risk managers and many other stakeholders have different, often contrasting, opinions and perspectives toward the environmental release of GD modified organisms, and on the adequacy of current risk assessment frameworks for such organisms. Here, we offer recommendations to overcome some of the challenges associated with the potential future development of new or additional risk assessment guidance for GD modified insects and provide considerations on areas where further risk assessment guidance may be required.
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Affiliation(s)
- Yann Devos
- GMO Unit, European Food Safety Authority (EFSA), Parma, Italy
| | - John D Mumford
- Centre for Environmental Policy, Imperial College London, Ascot, UK
| | | | - Ana M Camargo
- GMO Unit, European Food Safety Authority (EFSA), Parma, Italy
| | | | - Debora C M Glandorf
- National Institute for Public Health and the Environment (RIVM), Bilthoven, The Netherlands
| | - Fabien Nogué
- Institut Jean-Pierre Bourgin, INRAE, AgroParisTech, Université Paris-Saclay, Versailles, France
| | | | - Ernst A Wimmer
- Johann Friedrich Blumenbach Institute of Zoology and Anthropology, GZMB, Georg August University, Göttingen, Germany
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41
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Wu SL, Bennett JB, Sánchez C. HM, Dolgert AJ, León TM, Marshall JM. MGDrivE 2: A simulation framework for gene drive systems incorporating seasonality and epidemiological dynamics. PLoS Comput Biol 2021; 17:e1009030. [PMID: 34019537 PMCID: PMC8186770 DOI: 10.1371/journal.pcbi.1009030] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Revised: 06/08/2021] [Accepted: 05/02/2021] [Indexed: 12/30/2022] Open
Abstract
Interest in gene drive technology has continued to grow as promising new drive systems have been developed in the lab and discussions are moving towards implementing field trials. The prospect of field trials requires models that incorporate a significant degree of ecological detail, including parameters that change over time in response to environmental data such as temperature and rainfall, leading to seasonal patterns in mosquito population density. Epidemiological outcomes are also of growing importance, as: i) the suitability of a gene drive construct for release will depend on its expected impact on disease transmission, and ii) initial field trials are expected to have a measured entomological outcome and a modeled epidemiological outcome. We present MGDrivE 2 (Mosquito Gene Drive Explorer 2): a significant development from the MGDrivE 1 simulation framework that investigates the population dynamics of a variety of gene drive architectures and their spread through spatially-explicit mosquito populations. Key strengths and fundamental improvements of the MGDrivE 2 framework are: i) the ability of parameters to vary with time and induce seasonal population dynamics, ii) an epidemiological module accommodating reciprocal pathogen transmission between humans and mosquitoes, and iii) an implementation framework based on stochastic Petri nets that enables efficient model formulation and flexible implementation. Example MGDrivE 2 simulations are presented to demonstrate the application of the framework to a CRISPR-based split gene drive system intended to drive a disease-refractory gene into a population in a confinable and reversible manner, incorporating time-varying temperature and rainfall data. The simulations also evaluate impact on human disease incidence and prevalence. Further documentation and use examples are provided in vignettes at the project’s CRAN repository. MGDrivE 2 is freely available as an open-source R package on CRAN (https://CRAN.R-project.org/package=MGDrivE2). We intend the package to provide a flexible tool capable of modeling gene drive constructs as they move closer to field application and to infer their expected impact on disease transmission. Malaria, dengue and other mosquito-borne diseases continue to pose a major global health burden through much of the world. Currently available tools, such as insecticides and antimalarial drugs, are not expected to be sufficient to eliminate these diseases from highly-endemic areas, hence there is interest in novel strategies including genetics-based approaches. In recent years, the advent of CRISPR-based gene-editing has greatly expanded the range of genetic control tools available, and MGDrivE 1 (Mosquito Gene Drive Explorer 1) was proposed to simulate the dynamics of these systems through spatially-structured mosquito populations. As the technology has advanced and potential field trials are being discussed, models are now needed that incorporate additional details, such as life history parameters that respond to daily and seasonal environmental fluctuations, and transmission of pathogens between mosquito and vertebrate hosts. Here, we present MGDrivE 2, a gene drive simulation framework that significantly improves upon MGDrivE 1 by addressing these modeling needs. MGDrivE 2 has also been reformulated as a stochastic Petri net, enabling model specification to be decoupled from simulation, making it easier to adapt the model for application to other insect and mammalian species.
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Affiliation(s)
- Sean L. Wu
- Divisions of Epidemiology and Biostatistics, School of Public Health, University of California, Berkeley, California, United States of America
- * E-mail: (SLW); (JMM)
| | - Jared B. Bennett
- Biophysics Graduate Group, Division of Biological Sciences, College of Letters and Science, University of California, Berkeley, California, United States of America
| | - Héctor M. Sánchez C.
- Divisions of Epidemiology and Biostatistics, School of Public Health, University of California, Berkeley, California, United States of America
| | - Andrew J. Dolgert
- Institute for Health Metrics and Evaluation, Seattle, Washington, United States of America
| | - Tomás M. León
- Divisions of Epidemiology and Biostatistics, School of Public Health, University of California, Berkeley, California, United States of America
| | - John M. Marshall
- Divisions of Epidemiology and Biostatistics, School of Public Health, University of California, Berkeley, California, United States of America
- Innovative Genomics Institute, University of California, Berkeley, California, United States of America
- * E-mail: (SLW); (JMM)
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42
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Connolly JB, Mumford JD, Fuchs S, Turner G, Beech C, North AR, Burt A. Systematic identification of plausible pathways to potential harm via problem formulation for investigational releases of a population suppression gene drive to control the human malaria vector Anopheles gambiae in West Africa. Malar J 2021; 20:170. [PMID: 33781254 PMCID: PMC8006393 DOI: 10.1186/s12936-021-03674-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2020] [Revised: 02/24/2021] [Accepted: 02/25/2021] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND Population suppression gene drive has been proposed as a strategy for malaria vector control. A CRISPR-Cas9-based transgene homing at the doublesex locus (dsxFCRISPRh) has recently been shown to increase rapidly in frequency in, and suppress, caged laboratory populations of the malaria mosquito vector Anopheles gambiae. Here, problem formulation, an initial step in environmental risk assessment (ERA), was performed for simulated field releases of the dsxFCRISPRh transgene in West Africa. METHODS Building on consultative workshops in Africa that previously identified relevant environmental and health protection goals for ERA of gene drive in malaria vector control, 8 potentially harmful effects from these simulated releases were identified. These were stratified into 46 plausible pathways describing the causal chain of events that would be required for potential harms to occur. Risk hypotheses to interrogate critical steps in each pathway, and an analysis plan involving experiments, modelling and literature review to test each of those risk hypotheses, were developed. RESULTS Most potential harms involved increased human (n = 13) or animal (n = 13) disease transmission, emphasizing the importance to subsequent stages of ERA of data on vectorial capacity comparing transgenics to non-transgenics. Although some of the pathways (n = 14) were based on known anatomical alterations in dsxFCRISPRh homozygotes, many could also be applicable to field releases of a range of other transgenic strains of mosquito (n = 18). In addition to population suppression of target organisms being an accepted outcome for existing vector control programmes, these investigations also revealed that the efficacy of population suppression caused by the dsxFCRISPRh transgene should itself directly affect most pathways (n = 35). CONCLUSIONS Modelling will play an essential role in subsequent stages of ERA by clarifying the dynamics of this relationship between population suppression and reduction in exposure to specific potential harms. This analysis represents a comprehensive identification of plausible pathways to potential harm using problem formulation for a specific gene drive transgene and organism, and a transparent communication tool that could inform future regulatory studies, guide subsequent stages of ERA, and stimulate further, broader engagement on the use of population suppression gene drive to control malaria vectors in West Africa.
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Affiliation(s)
- John B Connolly
- Department of Life Sciences, Imperial College London, London, UK.
| | - John D Mumford
- Centre for Environmental Policy, Imperial College London, London, UK
| | - Silke Fuchs
- Department of Life Sciences, Imperial College London, London, UK
| | - Geoff Turner
- Department of Life Sciences, Imperial College London, London, UK
| | | | - Ace R North
- Department of Zoology, University of Oxford, Oxford, UK
| | - Austin Burt
- Department of Life Sciences, Imperial College London, London, UK
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43
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Hosack GR, Ickowicz A, Hayes KR. Quantifying the risk of vector-borne disease transmission attributable to genetically modified vectors. ROYAL SOCIETY OPEN SCIENCE 2021; 8:201525. [PMID: 33959322 PMCID: PMC8074930 DOI: 10.1098/rsos.201525] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Accepted: 02/11/2021] [Indexed: 06/12/2023]
Abstract
The relative risk of disease transmission caused by the potential release of transgenic vectors, such as through sterile insect technique or gene drive systems, is assessed with comparison with wild-type vectors. The probabilistic risk framework is demonstrated with an assessment of the relative risk of lymphatic filariasis, malaria and o'nyong'nyong arbovirus transmission by mosquito vectors to human hosts given a released transgenic strain of Anopheles coluzzii carrying a dominant sterile male gene construct. Harm is quantified by a logarithmic loss function that depends on the causal risk ratio, which is a quotient of basic reproduction numbers derived from mathematical models of disease transmission. The basic reproduction numbers are predicted to depend on the number of generations in an insectary colony and the number of backcrosses between the transgenic and wild-type lineages. Analogous causal risk ratios for short-term exposure to a single cohort release are also derived. These causal risk ratios were parametrized by probabilistic elicitations, and updated with experimental data for adult vector mortality. For the wild-type, high numbers of insectary generations were predicted to reduce the number of infectious human cases compared with uncolonized wild-type. Transgenic strains were predicted to produce fewer infectious cases compared with the uncolonized wild-type.
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Affiliation(s)
- Geoffrey R. Hosack
- Commonwealth Scientific and Industrial Research Organisation, Data61, Hobart, Tasmania, Australia
| | - Adrien Ickowicz
- Commonwealth Scientific and Industrial Research Organisation, Data61, Hobart, Tasmania, Australia
| | - Keith R. Hayes
- Commonwealth Scientific and Industrial Research Organisation, Data61, Hobart, Tasmania, Australia
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44
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Nolan T. Control of malaria-transmitting mosquitoes using gene drives. Philos Trans R Soc Lond B Biol Sci 2021; 376:20190803. [PMID: 33357060 PMCID: PMC7776936 DOI: 10.1098/rstb.2019.0803] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/26/2020] [Indexed: 01/13/2023] Open
Abstract
Gene drives are selfish genetic elements that can be re-designed to invade a population and they hold tremendous potential for the control of mosquitoes that transmit disease. Much progress has been made recently in demonstrating proof of principle for gene drives able to suppress populations of malarial mosquitoes, or to make them refractory to the Plasmodium parasites they transmit. This has been achieved using CRISPR-based gene drives. In this article, I will discuss the relative merits of this type of gene drive, as well as barriers to its technical development and to its deployment in the field as malaria control. This article is part of the theme issue 'Novel control strategies for mosquito-borne diseases'.
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Affiliation(s)
- Tony Nolan
- Vector Biology, Liverpool School of Tropical Medicine, Liverpool, UK
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45
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Devos Y, Bonsall MB, Firbank LG, Mumford J, Nogué F, Wimmer EA. Gene Drive-Modified Organisms: Developing Practical Risk Assessment Guidance. Trends Biotechnol 2020; 39:853-856. [PMID: 33342557 DOI: 10.1016/j.tibtech.2020.11.015] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Revised: 11/24/2020] [Accepted: 11/25/2020] [Indexed: 12/23/2022]
Abstract
Risk assessors, risk managers, developers, potential applicants, and other stakeholders at many levels discuss the need for new or further risk assessment guidance for deliberate environmental releases of gene drive-modified organisms. However, preparing useful and practical guidance entails challenges, to which we offer recommendations based on our experience drafting guidance.
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Affiliation(s)
- Yann Devos
- GMO Unit, European Food Safety Authority (EFSA), Parma, Italy.
| | | | | | - John Mumford
- Centre for Environmental Policy, Imperial College London, Ascot, UK
| | - Fabien Nogué
- Institut Jean-Pierre Bourgin, INRAE, AgroParisTech, Université Paris-Saclay, Versailles, France
| | - Ernst A Wimmer
- Johann Friedrich Blumenbach Institute of Zoology and Anthropology, GZMB, Georg August University, Göttingen, Germany
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46
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Adolfi A, Gantz VM, Jasinskiene N, Lee HF, Hwang K, Terradas G, Bulger EA, Ramaiah A, Bennett JB, Emerson JJ, Marshall JM, Bier E, James AA. Efficient population modification gene-drive rescue system in the malaria mosquito Anopheles stephensi. Nat Commun 2020; 11:5553. [PMID: 33144570 PMCID: PMC7609566 DOI: 10.1038/s41467-020-19426-0] [Citation(s) in RCA: 80] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Accepted: 10/13/2020] [Indexed: 12/27/2022] Open
Abstract
Cas9/gRNA-mediated gene-drive systems have advanced development of genetic technologies for controlling vector-borne pathogen transmission. These technologies include population suppression approaches, genetic analogs of insecticidal techniques that reduce the number of insect vectors, and population modification (replacement/alteration) approaches, which interfere with competence to transmit pathogens. Here, we develop a recoded gene-drive rescue system for population modification of the malaria vector, Anopheles stephensi, that relieves the load in females caused by integration of the drive into the kynurenine hydroxylase gene by rescuing its function. Non-functional resistant alleles are eliminated via a dominantly-acting maternal effect combined with slower-acting standard negative selection, and rare functional resistant alleles do not prevent drive invasion. Small cage trials show that single releases of gene-drive males robustly result in efficient population modification with ≥95% of mosquitoes carrying the drive within 5-11 generations over a range of initial release ratios.
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Affiliation(s)
- Adriana Adolfi
- Department of Microbiology & Molecular Genetics, University of California, Irvine, CA, 92697-3900, USA
- Liverpool School of Tropical Medicine, Vector Biology Department, L3 5QA, Liverpool, UK
| | - Valentino M Gantz
- Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA, 92093-0349, USA
| | - Nijole Jasinskiene
- Department of Microbiology & Molecular Genetics, University of California, Irvine, CA, 92697-3900, USA
| | - Hsu-Feng Lee
- Department of Microbiology & Molecular Genetics, University of California, Irvine, CA, 92697-3900, USA
| | - Kristy Hwang
- Department of Microbiology & Molecular Genetics, University of California, Irvine, CA, 92697-3900, USA
| | - Gerard Terradas
- Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA, 92093-0349, USA
- Tata Institute for Genetics and Society (TIGS)-UCSD, La Jolla, CA, 92093-0335, USA
| | - Emily A Bulger
- Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA, 92093-0349, USA
- Tata Institute for Genetics and Society (TIGS)-UCSD, La Jolla, CA, 92093-0335, USA
- Developmental and Stem Cell Biology Graduate Program, University of California, San Francisco, CA, 94158, USA
- The Gladstone Institutes, San Francisco, CA, 94158, USA
| | - Arunachalam Ramaiah
- Department of Ecology and Evolutionary Biology, University of California, Irvine, CA, 92697-2525, USA
- Tata Institute for Genetics and Society (TIGS)-India, Bangalore, KA, 560065, India
| | - Jared B Bennett
- Biophysics Graduate Group, Division of Biological Sciences, College of Letters and Science, University of California, Berkeley, CA, 94720, USA
| | - J J Emerson
- Department of Ecology and Evolutionary Biology, University of California, Irvine, CA, 92697-2525, USA
| | - John M Marshall
- Division of Epidemiology & Biostatistics, School of Public Health, University of California, Berkeley, CA, 94720, USA
- Innovative Genomics Institute, Berkeley, CA, 94720, USA
| | - Ethan Bier
- Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA, 92093-0349, USA
- Tata Institute for Genetics and Society (TIGS)-UCSD, La Jolla, CA, 92093-0335, USA
| | - Anthony A James
- Department of Microbiology & Molecular Genetics, University of California, Irvine, CA, 92697-3900, USA.
- Department of Molecular Biology & Biochemistry, University of California, Irvine, CA, 92697-4025, USA.
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Naegeli H, Bresson J, Dalmay T, Dewhurst IC, Epstein MM, Guerche P, Hejatko J, Moreno FJ, Mullins E, Nogué F, Rostoks N, Sánchez Serrano JJ, Savoini G, Veromann E, Veronesi F, Bonsall MB, Mumford J, Wimmer EA, Devos Y, Paraskevopoulos K, Firbank LG. Adequacy and sufficiency evaluation of existing EFSA guidelines for the molecular characterisation, environmental risk assessment and post-market environmental monitoring of genetically modified insects containing engineered gene drives. EFSA J 2020; 18:e06297. [PMID: 33209154 PMCID: PMC7658669 DOI: 10.2903/j.efsa.2020.6297] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Advances in molecular and synthetic biology are enabling the engineering of gene drives in insects for disease vector/pest control. Engineered gene drives (that bias their own inheritance) can be designed either to suppress interbreeding target populations or modify them with a new genotype. Depending on the engineered gene drive system, theoretically, a genetic modification of interest could spread through target populations and persist indefinitely, or be restricted in its spread or persistence. While research on engineered gene drives and their applications in insects is advancing at a fast pace, it will take several years for technological developments to move to practical applications for deliberate release into the environment. Some gene drive modified insects (GDMIs) have been tested experimentally in the laboratory, but none has been assessed in small-scale confined field trials or in open release trials as yet. There is concern that the deliberate release of GDMIs in the environment may have possible irreversible and unintended consequences. As a proactive measure, the European Food Safety Authority (EFSA) has been requested by the European Commission to review whether its previously published guidelines for the risk assessment of genetically modified animals (EFSA, 2012 and 2013), including insects (GMIs), are adequate and sufficient for GDMIs, primarily disease vectors, agricultural pests and invasive species, for deliberate release into the environment. Under this mandate, EFSA was not requested to develop risk assessment guidelines for GDMIs. In this Scientific Opinion, the Panel on Genetically Modified Organisms (GMO) concludes that EFSA's guidelines are adequate, but insufficient for the molecular characterisation (MC), environmental risk assessment (ERA) and post-market environmental monitoring (PMEM) of GDMIs. While the MC,ERA and PMEM of GDMIs can build on the existing risk assessment framework for GMIs that do not contain engineered gene drives, there are specific areas where further guidance is needed for GDMIs.
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48
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Li J, Aidlin Harari O, Doss A, Walling LL, Atkinson PW, Morin S, Tabashnik BE. Can CRISPR gene drive work in pest and beneficial haplodiploid species? Evol Appl 2020; 13:2392-2403. [PMID: 33005229 PMCID: PMC7513724 DOI: 10.1111/eva.13032] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Revised: 05/05/2020] [Accepted: 05/07/2020] [Indexed: 02/06/2023] Open
Abstract
Gene drives based on CRISPR/Cas9 have the potential to reduce the enormous harm inflicted by crop pests and insect vectors of human disease, as well as to bolster valued species. In contrast with extensive empirical and theoretical studies in diploid organisms, little is known about CRISPR gene drive in haplodiploids, despite their immense global impacts as pollinators, pests, natural enemies of pests, and invasive species in native habitats. Here, we analyze mathematical models demonstrating that, in principle, CRISPR homing gene drive can work in haplodiploids, as well as at sex-linked loci in diploids. However, relative to diploids, conditions favoring the spread of alleles deleterious to haplodiploid pests by CRISPR gene drive are narrower, the spread is slower, and resistance to the drive evolves faster. By contrast, the spread of alleles that impose little fitness cost or boost fitness was not greatly hindered in haplodiploids relative to diploids. Therefore, altering traits to minimize damage caused by harmful haplodiploids, such as interfering with transmission of plant pathogens, may be more likely to succeed than control efforts based on introducing traits that reduce pest fitness. Enhancing fitness of beneficial haplodiploids with CRISPR gene drive is also promising.
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Affiliation(s)
- Jun Li
- Department of StatisticsUniversity of CaliforniaRiversideCAUSA
| | | | | | - Linda L. Walling
- Department of Botany and Plant SciencesUniversity of CaliforniaRiversideCAUSA
| | | | - Shai Morin
- Department of EntomologyHebrew University of JerusalemRehovotIsrael
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49
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Golnar AJ, Ruell E, Lloyd AL, Pepin KM. Embracing Dynamic Models for Gene Drive Management. Trends Biotechnol 2020; 39:211-214. [PMID: 33010965 DOI: 10.1016/j.tibtech.2020.08.011] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Revised: 08/25/2020] [Accepted: 08/27/2020] [Indexed: 12/29/2022]
Abstract
Robust methods of predicting how gene drive systems will interact with ecosystems is essential for safe deployment of gene drive technology. We describe how quantitative tools can reduce risk uncertainty, streamline empirical research, guide risk management, and promote cross-sector collaboration throughout the process of gene drive technology development and implementation.
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Affiliation(s)
- Andrew J Golnar
- National Wildlife Research Center, United States Department of Agriculture, Animal and Plant Health Inspection Service, Wildlife Services, 4101 Laporte Ave., Fort Collins, CO 80521, USA.
| | - Emily Ruell
- National Wildlife Research Center, United States Department of Agriculture, Animal and Plant Health Inspection Service, Wildlife Services, 4101 Laporte Ave., Fort Collins, CO 80521, USA
| | - Alun L Lloyd
- Biomathematics Graduate Program and Department of Mathematics, North Carolina State University, Raleigh, NC 27695, USA
| | - Kim M Pepin
- National Wildlife Research Center, United States Department of Agriculture, Animal and Plant Health Inspection Service, Wildlife Services, 4101 Laporte Ave., Fort Collins, CO 80521, USA
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50
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Next-generation gene drive for population modification of the malaria vector mosquito, Anopheles gambiae. Proc Natl Acad Sci U S A 2020; 117:22805-22814. [PMID: 32839345 PMCID: PMC7502704 DOI: 10.1073/pnas.2010214117] [Citation(s) in RCA: 103] [Impact Index Per Article: 25.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Genetic systems for controlling transmission of vector-borne diseases are moving from discovery-stage demonstrations of proofs-of-principle to the next phases of development. A successful transition requires meeting safety and efficacy criteria defined in target product profiles. We show here that the Cas9/guide RNA-based gene-drive components of a genetically-engineered malaria mosquito vector, Anopheles gambiae, achieve key target product profile requirements for efficacy and performance. This system is designed to achieve mosquito population modification when coupled with genes encoding antiparasite effector molecules and result in stable and sustainable blocking of malaria parasite transmission. A Cas9/guide RNA-based gene drive strain, AgNosCd-1, was developed to deliver antiparasite effector molecules to the malaria vector mosquito, Anopheles gambiae. The drive system targets the cardinal gene ortholog producing a red-eye phenotype. Drive can achieve 98 to 100% in both sexes and full introduction was observed in small cage trials within 6 to 10 generations following a single release of gene-drive males. No genetic load resulting from the integrated transgenes impaired drive performance in the trials. Potential drive-resistant target-site alleles arise at a frequency <0.1, and five of the most prevalent polymorphisms in the guide RNA target site in collections of colonized and wild-derived African mosquitoes do not prevent cleavage in vitro by the Cas9/guide RNA complex. Only one predicted off-target site is cleavable in vitro, with negligible deletions observed in vivo. AgNosCd-1 meets key performance criteria of a target product profile and can be a valuable component of a field-ready strain for mosquito population modification to control malaria transmission.
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