One-step RT-qPCR assay for ZIKV RNA detection in Aedes aegypti samples: A protocol to study infection & gene expression during ZIKV infection

Abstract

Background: Zika virus (ZIKV) is transmitted to humans during the bite of an infected mosquito. In a scenario of globalization and climate change, the frequency of outbreaks has and will increase in areas with competent vectors, revealing a need for continuous improvement of ZIKV detection tools in vector populations. A simple, rapid and sensitive assay for viral detection is qRT-PCR, yet oligos optimized for ZIKV detection in mammalian cells and samples have repeatedly shown high background when used on mosquito RNA. In this work we present a one-step qRT-PCR protocol that allows for the detection of ZIKV in mosquitoes and for the evaluation of gene expression from the same mosquito sample and RNA. This assay is a less expensive qRT-PCR approach than that most frequently used in the literature and has a much lower background, allowing for confident detection. Methods: Our new oligo design to detect ZIKV RNA included in silico analysis of both viral and mosquito ( Ae. aegypti and Ae. albopictus )genomes, targeting sequences conserved between Asian and African ZIKV lineages, but not matching Aedes genomes. This assay will allow researchers to avoid nonspecific amplification in insect samples due to viral integration into the mosquito genome, a phenomenon known to happen in wild and colonized populations of mosquitoes. Standard curves constructed with in vitro transcribed ZIKV RNA were used to optimize the sensitivity, efficiency and reproducibility of the assay. Results: Finally, the assay was used with success to detect both ZIKV RNA in infected mosquitoes and to detect expression of the Defensin A gene, an antimicrobial peptide (AMP) involved in Aedes aegypti immune response to virus infection. Conclusions: The experimental approach to detect ZIKV RNA in Aedes aegypti presented here has demonstrated to be specific, sensitive and reliable, and additionally it allows for the analysis of mosquito gene expression during ZIKV infection.