Evolution et gestion de la résistance des moustiques aux insecticides – ANR-05-SEST-0035

Mosquitoes represent the major family of vector borne diseases, and their control is presently the main method of preventing diseases they transmit. However, insecticides efficiency is now decreased by the emergence of resistance mechanisms. It is crucial to develop new insecticides and control strategies in order to slow the selection of resistance. The goal of this program is to study the evolution of insecticide resistance in order to understand positive and negative adaptive factors associated with resistance genes in view of efficient control strategies. We focused our project on the study of the resistance linked to acetylcholinesterase (AChE) insensitivity which is the synaptic target of many insecticides used presently. Although Culex pipiens mosquitoes will be the main target of our studies, other diseases vectors such as Anopheles or Aedes, will be considered. The project is organized in three complementary parts: · I/ Identify all acetylcholinesterase mutations conferring resistance in natural populations, measure their impact on mosquito fitness, and understand the constraints responsible for their selection. These investigations will be based on an intensive population sampling in several countries where distinct insensitive AChE were detected. Resistant strains will be fixed and mutations studied for their biochemical and molecular properties. Recombinant mutated AChE produced in vitro will allow to characterize the role of each mutation found. Diagnostic tests for each mutation will be worked out, and used to investigate the evolution of their frequency in natural populations. Resistance levels and adaptive costs of these mutations will be compared, using strains with a same genetic background. · II/ Investigate strategies against resistance, either by designing new insecticide molecules efficient on the resistant target, or by devising reasonably existing molecules. We will attempt to develop new insecticides inhibiting specifically the main AChE resistance form. A random screening of chemicals compounds has already allowed the finding of new promising molecules. Improving their efficiency requires a better understanding of their activity. For this purpose, we plan to resolve the structure AChE from resistant and susceptible C. pipiens mosquitoes, either alone or in combination with the identified inhibitors. This will allow the conception of new compounds specific for the resistant form but with no effect on other ACHE. We will test the efficiency of a strategy (Stable Zone Strategy) designed in the laboratory and applied in the field in Montpellier region. · III/ Study the genetic determinism of acetylcholinesterase resistance in Diptera and other insects. Several AChE mutations linked to resistance were described in several insects. We would carry out investigations in order to understand why resistance evolves differently depending on selected species and on ace gene encoding the synaptic enzyme.