Aedes aegypti Mosquitoes Detect Acidic Volatiles Found in Human Odor Using the IR8a Pathway

Abstract

Graphical Abstract Highlights d Ae. aegypti Ir8a mutant mosquitoes cannot sense lactic acid, a human sweat component d Attraction to humans and human odor is reduced in Ir8a mutant mosquitoes d Ae. aegypti IR8a pathway responds to human-odor cues during blood feeding d The Ir8a mutant host-seeking defect cannot be rescued by other olfactory receptors SUMMARY Mosquitoes use olfaction as a primary means of detecting their hosts. Previously, the functional ablation of a family of Aedes aegypti olfactory receptors, the odorant receptors (ORs), was not sufficient to reduce host seeking in the presence of carbon dioxide (CO 2 ).This suggests the olfactory receptors that remain, such as the ionotropic receptors (IRs), could play a significant role in host detection. To test this, we disrupted the Ir8a co-receptor in Ae. aegypti using CRISPR/Cas9. We found that Ir8a mutant female mosquitoes are not attracted to lactic acid, a behaviorally active component of human sweat, and they lack odor-evoked responses to acidic volatiles. The loss of Ir8a reduces mosquito attraction to humans and their odor. We show that the CO 2 -detection pathway is necessary but not sufficient for IR8a to detect human odor. Our study reveals that the IR8a pathway is crucial for an anthropophilic vector mosquito to effectively seek hosts.

Acid-Sensing Ion Channels Mediate Type III Adenylyl Cyclase-Independent Acid-Sensing of Mouse Olfactory Sensory Neurons

“…Due to increasing CO2 emission and exacerbated air pollution, humans and wild animals are more frequently exposed to acidic environments. Through affecting the olfactory system, acids disturb the ecosystem and interfere with the survival behaviors of wild animals by impeding their ability to sense predator or food odorants [1][2][3]. Recent studies have shown that acid-sensing in insects is mediated by IR8a and IR64a, two ionotropic receptors [2,17].…”

“…Through affecting the olfactory system, acids disturb the ecosystem and interfere with the survival behaviors of wild animals by impeding their ability to sense predator or food odorants [1][2][3]. Recent studies have shown that acid-sensing in insects is mediated by IR8a and IR64a, two ionotropic receptors [2,17]. Yet, it is unknown how acidic volatiles and protons activate OSNs of mammals and influence their olfactory communication.…”

“…Recently, two ionotropic receptors (IR), IR8a and IR64a, have been identified in the insect olfactory system [2,17], and they directly mediate the acid-sensing of mosquitoes and Drosophila.…”

Cas9-mediated gene-editing in the malaria mosquito Anopheles stephensi by ReMOT Control

“…To solve the growing problem of mosquito-borne disease, we need improved and more efficient gene editing methods. CRISPR/Cas9-based targeted disruption of genes in mosquito vectors of human pathogens is a powerful method to uncover underlying aspects of mosquito pathogen transmission biology that can be targeted for basic biological understanding and for mosquito control efforts [1][2][3][4][5] .…”

Identification of human skin bacteria attractive to the Asian Tiger mosquito

“…A recent study conducted on Ae. aegypti mosquitoes evidenced that IR8a pathway is required for sensing human-borne acidic volatiles (Raji et al, 2019). To a lesser extent, other skin VOCs such as 1-octen-3-ol, acetone and ammonia can also attract mosquitoes (Majeed et al, 2016;Raji and DeGennaro, 2017).…”