AN ESTERASE-LIKE PROTEIN (ELP) CONFERRED MALATHION AND DELTAMETHRIN RESISTANCE IN THE INDIAN FIELD POPULATION OF ANOPHELES STEPHENSI

Abstract

Intro: Chemical insecticides in the form of IRS (Indoor Residual Sprays) and LLITNs (Long Lasting Insecticide Treated Nets) comprise current malaria vector control strategies. However, their extensive usage has led to the emergence of resistance in Anopheles mosquitoes, warranting continuous monitoring and investigation of the underlying mechanisms of resistance developed by the Anopheles vector. In the present study, we identified a novel An. stephensi esterase-like protein; As-ELP, (XP_035915664.1) through differential proteomic profiling, in deltamethrin-resistant An. stephensi from the Indian field population. Methods: As-ELP protein was identified through differential proteomic profiling in the Indian field collected deltamethrin resistant versus susceptible An. Stephensi. Followed by protein characterization using a bioinformatic and molecular approach. RNAi-mediated gene knockdown demonstrated involvement in conferring insecticide resistance. Findings: As-ELP exhibited esterase-like activity and demonstrated binding affinity with malathion and deltamethrin insecticide molecules. Immunofluorescence assays (IFAs) predominantly demonstrated the localization of As-ELP protein in the brain, ovary, and partially in the midgut & salivary glands. Our transcriptomic analysis revealed differential As-ELP expression in various mosquito tissues and life stages. Interestingly, even a 50-60% As-ELP knockdown in An. stephensi caused > 60% mortality in the test mosquitoes after 1 hr. exposure with deltamethrin and malathion insecticides as compared to GFP control mosquitoes. This indicates that As-ELP knockdown caused the reversal (>50%) of resistant to susceptible phenotypes against deltamethrin and malathion. Additionally, a significant reduction in the esterase-like activity (primary detoxification enzyme for malathion and deltamethrin) in the As-ELP knockdown mosquito compared to GFP control was observed. Conclusion: Altogether, our results conclude that As-ELP is a novel protein with esterase-like activity and is involved in the malathion and deltamethrin resistance in the Indian field population of An. stephensi. This protein could be a potent candidate for supporting the current vector control strategies.