The yellow fever mosquito, Aedes aegypti, is a vector of viruses transmitted to humans and affecting their health worldwide. Pyrethroids are currently the main class of mosquito adulticides, but mosquito control is increasingly problematic due to field-evolved resistance. Resistance mechanisms often coexist and include point mutations and increased expression of genes encoding detoxification enzymes. Additionally, previous studies support the role of ATP-binding cassette (ABC) transporters in insecticide detoxification in mosquitoes. We formulated two hypotheses regarding the role of ABC transporters in the pyrethroid-resistant Puerto Rico (PR) strain of A. aegypti: 1) in addition to previously described mechanisms, genes encoding ABC transporters are upregulated in PR, thereby increasing their ability to export insecticides out of the nervous system; 2) increased P450 activity can trigger fitness costs and ABC transporter genes could be repressed in compensation. To settle this question, we proposed to investigate expression patterns, toxicity and ATPase activity. Expression levels of 6 ABC transporters previously characterized as differentially expressed in insecticide-challenged mosquitoes, or upregulated in pyrethroid-resistant A. aegypti, were compared between PR and a susceptible strain. We expected consistent expression between sexes and ages, since we previously showed that the LD50 of deltamethrin remained constant between ages, and that both sexes of PR were pyrethroid-resistant. Surprisingly, there was little variation in the expression of the investigated ABC genes between susceptible and resistant strains, but sex and age influenced expression differences, suggesting a different role. Therefore, these genes unlikely confer pyrethroid-resistance in PR. Instead, ABC transporters may be induced after insecticide exposure. To complete our study, bioassays will challenge mosquitoes with deltamethrin, with or without ABC transporter modulators. Increased deltamethrin-induced mortality and ATPase activity changes in presence of these compounds would indicate a contribution of ABC transporters in pyrethroid processing and increase knowledge regarding pyrethroid detoxification and mode of action.

Do ABC transporters contribute to pyrethroid resistance in the Puerto Rico strain of Aedes aegypti?

2019 Fall National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.