title: CYP6 P450 enzymes and ACE-1 duplication produce extreme and multiple insecticide resistance in the malaria mosquito Anopheles gambiae.
abstract: Malaria control relies heavily on pyrethroid insecticides, to which susceptibility is declining in Anopheles mosquitoes. To combat pyrethroid resistance, application of alternative insecticides is advocated for indoor residual spraying (IRS), and carbamates are increasingly important. Emergence of a very strong carbamate resistance phenotype in Anopheles gambiae from Tiassalé, Côte d'Ivoire, West Africa, is therefore a potentially major operational challenge, particularly because these malaria vectors now exhibit resistance to multiple insecticide classes. We investigated the genetic basis of resistance to the most commonly-applied carbamate, bendiocarb, in An. gambiae from Tiassalé. Geographically-replicated whole genome microarray experiments identified elevated P450 enzyme expression as associated with bendiocarb resistance, most notably genes from the CYP6 subfamily. P450s were further implicated in resistance phenotypes by induction of significantly elevated mortality to bendiocarb by the synergist piperonyl butoxide (PBO), which also enhanced the action of pyrethroids and an organophosphate. CYP6P3 and especially CYP6M2 produced bendiocarb resistance via transgenic expression in Drosophila in addition to pyrethroid resistance for both genes, and DDT resistance for CYP6M2 expression. CYP6M2 can thus cause resistance to three distinct classes of insecticide although the biochemical mechanism for carbamates is unclear because, in contrast to CYP6P3, recombinant CYP6M2 did not metabolise bendiocarb in vitro. Strongly bendiocarb resistant mosquitoes also displayed elevated expression of the acetylcholinesterase ACE-1 gene, arising at least in part from gene duplication, which confers a survival advantage to carriers of additional copies of resistant ACE-1 G119S alleles. Our results are alarming for vector-based malaria control. Extreme carbamate resistance in Tiassalé An. gambiae results from coupling of over-expressed target site allelic variants with heightened CYP6 P450 expression, which also provides resistance across contrasting insecticides. Mosquito populations displaying such a diverse basis of extreme and cross-resistance are likely to be unresponsive to standard insecticide resistance management practices.
authors.affiliation: Vector Biology Department, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, United Kingdom; Centre Suisse de Recherches Scientifiques en Côte d'Ivoire, Abidjan, Cote d'Ivoire.
authors.forename: Constant V
authors.initials: CV
authors.lastname: Edi
authors.affiliation: Vector Biology Department, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, United Kingdom; Institut Régional de Santé Publique/Université d 'Abomey-Calavi, Ouidah, Bénin.
authors.forename: Luc
authors.initials: L
authors.lastname: Djogbénou
authors.affiliation: Biology Department, Boston College, Chestnut Hill, Massachusetts, United States of America.
authors.forename: Adam M
authors.initials: AM
authors.lastname: Jenkins
authors.affiliation: Biology Department, Boston College, Chestnut Hill, Massachusetts, United States of America.
authors.forename: Kimberly
authors.initials: K
authors.lastname: Regna
authors.affiliation: Biology Department, Boston College, Chestnut Hill, Massachusetts, United States of America.
authors.forename: Marc A T
authors.initials: MA
authors.lastname: Muskavitch
authors.affiliation: Vector Biology Department, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, United Kingdom.
authors.forename: Rodolphe
authors.initials: R
authors.lastname: Poupardin
authors.affiliation: Vector Biology Department, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, United Kingdom.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Jones
authors.affiliation: Vector Biology Department, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, United Kingdom; Department of Entomology and Wildlife, University of Cape Coast, Cape Coast, Ghana.
authors.forename: John
authors.initials: J
authors.lastname: Essandoh
authors.affiliation: Unité de Recherche en Ecotoxicologie (URET), Faculty of Sciences, Université de Lomé, Lomé, Togo.
authors.forename: Guillaume K
authors.initials: GK
authors.lastname: Kétoh
authors.affiliation: Vector Biology Department, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, United Kingdom.
authors.forename: Mark J I
authors.initials: MJ
authors.lastname: Paine
authors.affiliation: Centre Suisse de Recherches Scientifiques en Côte d'Ivoire, Abidjan, Cote d'Ivoire; Centre for Neglected Tropical Diseases, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, United Kingdom; Université Nangui-Abrogoua, UFR Sciences de la Nature, Abidjan, Côte d'Ivoire.
authors.forename: Benjamin G
authors.initials: BG
authors.lastname: Koudou
authors.affiliation: Vector Biology Department, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, United Kingdom; Malaria Programme, Wellcome Trust Sanger Institute, Hinxton, Cambridge, United Kingdom.
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Donnelly
authors.affiliation: Vector Biology Department, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, United Kingdom.
authors.forename: Hilary
authors.initials: H
authors.lastname: Ranson
authors.affiliation: Vector Biology Department, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, United Kingdom.
authors.forename: David
authors.initials: D
authors.lastname: Weetman
mesh_terms: D000110:Acetylcholinesterase / Q000235:genetics; D000354:Africa, Western; D000818:Animals; D030801:Animals, Genetically Modified / Q000235:genetics; D000852:Anopheles / Q000235:genetics*; D002219:Carbamates / Q000494:pharmacology; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics*; D004330:Drosophila / Q000187:drug effects / Q000235:genetics; D007305:Insecticide Resistance / Q000235:genetics*; D008288:Malaria / Q000235:genetics / Q000635:transmission*; D010641:Phenotype; D048448:Phenylcarbamates / Q000494:pharmacology; D011722:Pyrethrins / Q000494:pharmacology
chemical_list: D002219:Carbamates; D048448:Phenylcarbamates; D011722:Pyrethrins; D003577:Cytochrome P-450 Enzyme System; D000110:Acetylcholinesterase; C007725:bendiocarb