Overexpression of Two Members of D7 Salivary Genes Family is Associated with Pyrethroid Resistance in the Malaria Vector Anopheles Funestus s.s. but Not in Anopheles Gambiae in Cameroon.

Emmanuel Elanga-Ndille,Magellan Tchouakui,Helen Irving,Lynda Nouage,Cyrille Ndo,Daniel Nguete Nguiffo,Parfait Awono-Ambene,Billy Tene-Fossog,Charles S Wondji,Tatiane Assatse,Achille Binyang

doi:10.3390/genes10030211

Abstract

D7 family proteins are among the most expressed salivary proteins in mosquitoes. They facilitate blood meal intake of the mosquito by scavenging host amines that induce vasoconstriction, platelet aggregation and pain. Despite this important role, little information is available on the impact of insecticide resistance on the regulation of D7 proteins and consequently on the blood feeding success. In this study, real-time quantitative polymerase chain reaction (qPCR) analyses were performed to investigate how pyrethroid resistance could influence the expression of genes encoding D7 family proteins in Anopheles gambiae and Anopheles funestus s.s. mosquitoes from Elon in the Central Cameroon. Out of 328 collected mosquitoes, 256 were identified as An. funestus sl and 64 as An. gambiae sl. Within the An. funestus group, An. funestus s.s. was the most abundant species (95.95%) with An. rivulorum, An. parensis and An. rivulorum-like also detected. All An. gambiae s.l mosquitoes were identified as An. gambiae. High levels of pyrethroid resistance were observed in both An. gambiae and An. funestus mosquitoes. RT-qPCR analyses revealed a significant overexpression of two genes encoding D7 proteins, D7r3 and D7r4, in pyrethroids resistant An. funestus. However, no association was observed between the polymorphism of these genes and their overexpression. In contrast, overall D7 salivary genes were under-expressed in pyrethroid resistant An. gambiae. This study provides preliminary evidences that pyrethroid resistance could influence blood meal intake through over-expression of D7 proteins although future studies will help establishing potential impact on vectorial capacity.

Highlights

In the early 2000s, thanks to the Abuja Declaration and the achievement of the MillenniumDevelopment Goals, immense efforts have been made to control malaria, with the goal to eliminate its transmission worldwide
After assessing insecticide susceptibility in malaria vectors in Elon, we compared the expression of D7 family genes in the salivary gland of pyrethroid resistant and susceptible An. gambiae and An. funestus s.s. mosquitoes
We found that An. gambiae and An. funestus s.s. are both multiple resistant to almost all the insecticides currently used in public health

Summary

Introduction

Development Goals, immense efforts have been made to control malaria, with the goal to eliminate its transmission worldwide These efforts have led to a significant and substantial progress in reducing malaria morbidity and mortality, despite the slight upward trend observed between the years 2016 and 2017 [1]. This remarkable reduction of malaria burden is strongly associated with an increased coverage of people at risk with insecticide-treated bed nets (ITNs), long-lasting insecticidal nets (LLINs) and to a lesser extent indoor residual spraying (IRS) with insecticides [2]. Blood meal intake has been shown to be influenced by specific salivary proteins including the D7 proteins family [3,4]

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Conclusion