The effect of permethrin resistance on Aedes aegypti transcriptome following ingestion of Zika virus infected blood

Aedes aegypti (L.) is the primary vector of many emerging arboviruses. Insecticide resistance among mosquito populations is a consequence of the application of insecticides for mosquito control. We used RNA-sequencing to compare transcriptomes between permethrin resistant and susceptible strains of Florida Ae. aegypti in response to Zika virus infection. A total of 2,459 transcripts were expressed at significantly different levels between resistant and susceptible Ae. aegypti. Gene ontology analysis placed these genes into 7 categories of biological processes. The 863 transcripts were expressed at significantly different levels between two strains (up/down regulated) more than 2-fold. Quantitative real-time PCR analysis validated Zika-infected response, and suggested a highly overexpressed P450, with AAEL014617 and AAEL006798 as potential candidates for the molecular mechanism of permethrin resistance in Ae. aegypti. Our findings indicated that most detoxification enzymes and immune system enzymes altered their gene expression between the two strains of Ae. aegypti in response to Zika virus infection. Understanding the interactions of arboviruses with resistant mosquito vectors at the molecular level allows for the possible development of new approaches in mitigating arbovirus transmission. This information sheds light on Zika-induced changes in the insecticide resistance of Ae. aegypti with implications for mosquito control strategies. Ae. aegypti larvae were collected from Key West (24.55°N, 81.78°W), Florida, USA and maintained at the Florida Medical Entomological Laboratory (FMEL) in Vero Beach, FL since 2011. The parental collection of Ae. aegypti from the field was initially tested for permethrin resistance, then subjected to permethrin selection for 15 generations (see below) and again assayed for resistance (referred to as the resistant strain). The Orlando strain of Ae. aegypti was collected from Orlando (28.53°N, 81.37°W), Florida, USA and reared in the Mosquito and Fly Research Unit, Center for Medical, Agricultural and Veterinary Entomology, ARS-USDA in Gainesville, FL since 1952. The Orlando strain is recognized as a permethrin susceptible strain of Ae. Aegypti. Four-day-old female adults were fed defibrinated bovine blood containing either ZIKV (treatment) or blood lacking virus (control). The ZIKV infected and control mosquitoes from two Ae. aegypti strains were harvested for a time course study. Individual mosquitoes were dissected into body and legs and tested to confirm susceptibility to infection and disseminated infection rates, respectively. Ten mosquitoes (12 hours and 7 days post ZIKV infection) were pooled for each sample for RNA sequencing.