Volatile allosteric antagonists of mosquito odorant receptors inhibit human-host attraction

Abstract

Odorant-dependent behaviors in insects are triggered by the binding of odorant ligands to the variable subunits of heteromeric olfactory receptors. Previous studies have shown, however, that specific odor binding to ORco, the common subunit of odorant receptor heteromers, may allosterically alter olfactory receptor function and profoundly affect subsequent behavioral responses. Using an insect cell–based screening platform, we identified and characterized several antagonists of the odorant receptor coreceptor of the African malaria vector Anopheles gambiae (AgamORco) in a small collection of natural volatile organic compounds. Because some of the identified antagonists were previously shown to strongly repel Anopheles and Culex mosquitoes, we examined the bioactivities of the identified antagonists against Aedes , the third major genus of the Culicidae family. The tested antagonists inhibited the function of Ae. aegypti ORco ex vivo and repelled adult Asian tiger mosquitoes ( Ae. albopictus ). Binary mixtures of specific antagonists elicited higher repellency than single antagonists, and binding competition assays suggested that this enhanced repellence is due to antagonist interaction with distinct ORco sites. Our results also suggest that the enhanced mosquito repellency by antagonist mixtures is due to additive rather than synergistic effects of the specific antagonist combinations on ORco function. Taken together, these findings provide novel insights concerning the molecular aspects of odorant receptor function. Moreover, our results demonstrate that a simple screening assay may be used for the identification of allosteric modifiers of olfactory-driven behaviors capable of providing enhanced personal protection against multiple mosquito-borne infectious diseases.

Quality Control Methods for Aedes albopictus Sterile Male Transportation

“…Egg batches were collected daily and kept sealed in the laboratory of the Benaki Phytopathological Institute (BPI) (Kifissia, Greece) or transported to the laboratory of Agricultural Zoology at the University of Thessaly (UTH) (Volos, Greece, driving distance 3 h from BPI). Before trials, eggs were submerged in stale tap mineral water for hatching and rearing [37,[40][41][42]. The flight ability tests were conducted at BPI, whilst for the survival and mating performance tests (effect of mating, food and water stress on male survival and male mating performance) eggs (in oviposition substrates) were transported to UTH and reared there to serve as the respective controls in various tests.…”

Drosophila olfaction: past, present and future

“…Moreover, from information within at least the public domain, very few receptors have been subject to screens for artificial agonists or antagonists (e.g. [290][291][292][293]), although complementary chemoinformatic approaches to identify novel chemical modulators of receptors in silico show promise [294][295][296]. Some of these chemicals induce behaviours in laboratory-based assays [291][292][293][294]297], but there is little evidence of successful field trials.…”

“…[290][291][292][293]), although complementary chemoinformatic approaches to identify novel chemical modulators of receptors in silico show promise [294][295][296]. Some of these chemicals induce behaviours in laboratory-based assays [291][292][293][294]297], but there is little evidence of successful field trials.…”

A Combined Computational Methodology for the Discovery of Hit Compounds with Putative Insect Repellency Properties

“…Mosquito adults were obtained from a laboratory colony of Aedes albopictus which was maintained at 25 � 2 °C, 80 % relative humidity, and photoperiod of 16 : 8-h light/dark (L/D). [59]…”

“…A repellence bioassay based on human landing counts was used to evaluate the repellent effect of the selected compounds. [59,61] The total exposure time was 5 minutes, DEET (as a positive control) and untreated hand (as a control) were also included. Icaridin was not tested at all doses since in the highest one (200 μg/cm 2 ) the repellency index (RI) was lower than 95 %.…”