Yeast interfering RNA larvicides targeting neural genes induce high rates of Anopheles larval mortality

Abstract

BackgroundAlthough larviciding can reduce the number of outdoor biting malaria vector mosquitoes, which may help to prevent residual malaria transmission, the current larvicide repertoire is faced with great challenges to sustainability. The identification of new effective, economical, and biorational larvicides could facilitate maintenance and expansion of the practice of larviciding in integrated malaria vector mosquito control programmes. Interfering RNA molecules represent a novel class of larvicides with untapped potential for sustainable mosquito control. This investigation tested the hypothesis that short interfering RNA molecules can be used as mosquito larvicides.ResultsA small interfering RNA (siRNA) screen for larval lethal genes identified siRNAs corresponding to the Anopheles gambiae suppressor of actin (Sac1), leukocyte receptor complex member (lrc), and offtrack (otk) genes. Saccharomyces cerevisiae (baker’s yeast) was engineered to produce short hairpin RNAs (shRNAs) for silencing of these genes. Feeding larvae with the engineered yeasts resulted in silenced target gene expression, a severe loss of neural synapses in the larval brain, and high levels of larval mortality. The larvicidal activities of yeast interfering RNA larvicides were retained following heat inactivation and drying of the yeast into user-friendly tablet formulations that induced up to 100% larval mortality in laboratory trials.ConclusionsReady-to-use dried inactivated yeast interfering RNA larvicide tablets may someday be an effective and inexpensive addition to malaria mosquito control programmes and a valuable, biorational tool for addressing residual malaria transmission.Electronic supplementary materialThe online version of this article (10.1186/s12936-017-2112-5) contains supplementary material, which is available to authorized users.

Mosquito control practices and perceptions: An analysis of economic stakeholders during the Zika epidemic in Belize, Central America

“…Recent advances in the use of transgenic release strategies for vector control have highlighted the critical importance of effective community engagement prior to the use of new mosquito control technologies, particularly when genetically modified organisms (GMOs) are being considered [ 18 , 24 – 27 ]. Others and we have proposed the use of larvicidal genetically modified microbes that express interfering RNA [ 16 , 17 , 28 , 29 ] and recognize the importance of engaging the communities in which such interventions could potentially be used. To this end, the survey of economic stakeholders included two questions regarding the potential use of GMO larvicides, assuming that they were demonstrated to be both safe and effective.…”

“…= 16). Of the respondents willing to try a GMO larvicide, they were most willing to use genetically modified bacteria (60%, Table 6 ), a technique which has demonstrated promise in laboratory studies [ 16 , 17 , 29 ]. 54% expressed willingness to use genetically modified algae ( Table 6 ), which has also been tested in laboratory studies [ 30 ].…”

“…We recently developed interfering RNA larvicides that kill up to 100% of mosquito larvae in laboratory trials [ 16 , 17 ]. We have identified several potential delivery systems for these larvicides [ 16 , 17 ] and are evaluating their efficacy in semi-field trials. The input of intended users is crucial for the ultimate acceptability and practical efficacy of proposed interventions as they are being developed [ 18 ].…”

Opening the toolkit for genetic analysis and control of Anopheles mosquito vectors

“…Although most commonly used in adults, the technique can also be successfully applied to embryos [9] to study developmental gene function and, with some difficulty, to pupae [10]. Larvae do not survive the injection process well, and techniques have been recently modified to silence larval genes by feeding chitosan/dsRNA nanoparticles or bacteria/yeast expressing dsRNAs [11]. Overall, the technique provides rapid assessment of loss of gene function phenotypes, however in anophelines not all genes and/or tissues are targeted efficiently [12] and so care is needed to monitor protein (or mRNA) turnover.…”

“…By targeting vital genes, RNAi may play a role in anopheline and malaria control. Perhaps the closest to translation are RNAi-based larvicides delivered as dried pellets to defined larval breeding sources to provide Anopheles specific killing with limited toxicity to other organisms [11].…”