Chemical antagonistic effects on the human odor-evoked responses of yellow fever mosquito, Aedes aegypti

Many chemical compounds that repel biting insects such as mosquitoes have been tested to assess their potential contribution to public health and determine their suitability as effective alternatives to insecticides in managing insect pests. Based on our previous research findings of several terpenoid compounds, including alpha-terpinene and citronellal, that elicited inhibitory neuronal responses in the olfactory sensilla of Aedes aegypti, we proposed that chemical repellents exhibiting inhibitory effects (inhibitory chemical repellents) may interact with human odorants in the peripheral olfactory system of mosquitoes, resulting in the interruption of the mosquitoes' olfactory recognition of human hosts. In the current study, we examined three potential human-odor-sensitive odorant receptors, AaOR13, AaOR15, and AaOR55 in female Aedes aegypti (Ae. aegypti), functionally characterized their responses to certain human odorants from the categories of aldehydes, aromatics, and alcohols that may act as cues indicating the presence of human hosts, investigated the interference of inhibitory terpenoids identified in our previous study against AaORs' response to human odorants, and determined the effect of these inhibitory terpenoids on the detection of human odorants in the olfactory sensory neurons (OSN) of Ae. aegypti antennae. The results of these investigations demonstrate the potency of two inhibitory terpenoids, alpha-terpinene and citronellal, in disrupting the human-odor recognition at the cellular and molecular level, which may ultimately impair mosquito host-seeking capacity and thus prove useful for efforts to protect humans from mosquito-biting behavior and, hence, mosquito-borne disease infections.