Biology subjects

Failloux, A.-B.

Publications and source records attributed to Failloux, A.-B..

6 recordsLinked to original sources

bioRxiv2023

Assessing vector competence of mosquitoes from northeastern France to West Nile virus and Usutu virus

West Nile virus (WNV) and Usutu virus (USUV) are two arthropod-borne viruses that circulate in mainland France. Assessing vector competence has only been conducted so far with mosquitoes from southern France while an increasingly active circulation of WNV and USUV has been reported in the last years. The main vectors are mosquitoes of the Culex genus and the common mosquito Culex pipiens. Here, we measure the vector competence of five mosquito species (Aedes rusticus, Aedes albopictus, Anopheles plumbeus, Culex pipiens and Culiseta longiareolata) present in northeastern France. Field-collected populations were exposed to artificial infectious blood meal containing WNV or USUV and examined at different days post-infection. We show that (i) Cx. pipiens transmitted WNV and USUV, (ii) Ae. rusticus only WNV, and (iii) unexpectedly, Ae. albopictus transmitted both WNV and USUV. Less surprising, An. plumbeus was not competent for both viruses. Combined with data on distribution and population dynamics, these assessments of vector competence will help in developing a risk map and implementing appropriate prevention and control measures. Author summaryWest Nile virus (WNV) and Usutu virus (USUV) are on the rise in Europe and in France. WNV is reported in France as early as the 1960s in the Camargue and USUV more recently, in 2015 in eastern France. The re-emergence of WNV infections in the Camargue is associated with an expansion towards the North which is also favorable to maintain a viral transmission cycle. USUV frequently co-circulates with WNV sharing the same mosquito vectors. Culex pipiens, able to feed on birds and humans, is considered to be the main vector in France. Our study is the first to investigate the vector competence to WNV and USUV of five different mosquito species collected in northeastern France. We ascertain that French Cx. pipiens mosquitoes are competent to both WNV and USUV. More surprisingly, the mosquito Aedes albopictus from northeastern France was able to transmit WNV and USUV. Based on our result, we propose that surveillance of mosquitoes combined with viral detections must be implemented in northeastern France to allow early viral detection and timely intervention to prevent outbreaks of these two neurological diseases.

microbiology↗

bioRxiv2022

Rasputin/G3BP mediates o-nyong-nyong virus subversion of antiviral immunity in Anopheles coluzzii

The G3BP proteins in vertebrates and Aedes mosquito ortholog, Rasputin, are essential for alphavirus infection, but the underlying mechanism of Rasputin/G3BP proviral activity is poorly understood. It has been suggested that G3BP could influence host immune signaling, but this has not been functionally demonstrated. Here, we find that depletion of Rasputin activity in Anopheles mosquitoes, the primary vectors of the alphavirus onyong-nyong (ONNV), provokes dysregulation of the antiviral Imd, JAK/STAT and RNAi pathways, indicating that Rasputin is required for expression of normal basal immunity in uninfected mosquitoes. Depletion of Rasputin during ONNV bloodmeal infection causes increased transcript abundance of genes in the Imd pathway including positive regulator Rel2, and decreases ONNV infection in mosquitoes. Loss of Rasputin is complemented by co-depletion of Imd pathway positive regulator, Rel2, which restores normal ONNV infection levels. Thus, the presence of Rasputin is required for ONNV inhibition of Imd activity, and viral inhibition of Imd explains much of the Rasputin proviral activity. The viral non-structural protein 3 (nsP3) binds to Rasputin and alters the profile of cellular proteins binding to Rasputin. In the presence of nsP3, 48 Rasputin-binding proteins are unchanged but seven binding proteins are excluded and eight new proteins bind Rasputin. The Rasputin binding partners altered by nsP3 are candidate factors for ONNV immune manipulation and subversion through Rasputin. Overall, these results are consistent with and strongly suggest a mechanism in which ONNV, probably nsP3, co-opts the normal Rasputin function assuring basal cellular immune activity in order to inhibit antiviral immunity and promote infection. These observations may be generalizable for Rasputin function during alphavirus infection of other mosquitoes, as well as for G3BP function in the mammalian host, and could offer a target for vector-based control of arbovirus transmission.

microbiology↗

bioRxiv2020

Experimental adaptation of dengue virus 1 to Aedes albopictus mosquitoes by in vivo selection

In most of the world, Dengue virus (DENV) is mainly transmitted by the mosquito Aedes aegypti while in Europe, Aedes albopictus is responsible for human DENV cases since 2010. Identifying mutations that make DENV more competent for transmission by Ae. albopictus will help to predict emergence of epidemic strains. Ten serial passages in vivo in Ae. albopictus led to select DENV-1 strains with greater infectivity for this vector in vivo and in cultured mosquito cells. These changes were mediated by multiple adaptive mutations in the virus genome, including a mutation at position 10,418 in the DENV 3UTR within an RNA stem-loop structure involved in subgenomic flavivirus RNA (sfRNA) production. Using reverse genetics, we showed that the 10,418 mutation alone does not confer a detectable increase in transmission efficiency in vivo. These results reveal the complex adaptive landscape of DENV transmission by mosquitoes and emphasize the role of epistasis in shaping evolutionary trajectories of DENV variants.

microbiology↗

bioRxiv2020

Improved reference genome of the arboviral vector Aedes albopictus

The Asian tiger mosquito Aedes albopictus is globally expanding and has become the main vector for human arboviruses in Europe. Here we present AalbF2, a dramatically improved assembly of the Ae. albopictus genome that has revealed widespread viral insertions, novel microRNAs and piRNA clusters, the sex determining locus, new immunity genes, and has enabled genome-wide studies of geographically diverse Ae. albopictus populations and analyses of the developmental and stage-dependent network of expression data. Additionally, we built the first physical map for this species with 75% of the assembled genome anchored to the chromosomes. These up-to-date resources of the genome provide a foundation to improve understanding of the adaptation potential and the epidemiological relevance of this species and foster the development of innovative control measures. One Sentence SummaryLong-read and Hi-C-based de novo assembly of the arboviral vector Aedes albopictus genome fosters deeper understanding of its biological features.

genomics↗

bioRxiv2019

A new high-throughput tool to screen mosquito-borne viruses in Zika virus endemic/epidemic areas

Mosquitoes are vectors of arboviruses affecting animal and human health. Arboviruses circulate primarily within an enzootic cycle and recurrent spillovers contribute to the emergence of human-adapted viruses able to initiate an urban cycle involving anthropophilic mosquitoes. The increasing volume of travel and trade offers multiple opportunities for arbovirus introduction in new regions. This scenario has been exemplified recently with the Zika pandemic. To incriminate a mosquito as vector of a pathogen, several criteria are required such as the detection of natural infections in mosquitoes. In this study, we used a high-throughput chip based on the BioMarkTM Dynamic arrays system capable of detecting 64 arboviruses in a single experiment. A total of 17,958 mosquitoes collected in Zika-endemic/epidemic countries (Brazil, French Guiana, Guadeloupe, Suriname, Senegal, and Cambodia) were analyzed. Here we show that this new tool can detect endemic and epidemic viruses in different mosquito species in an epidemic context. Thus, this fast and low-cost method can be suggested as a novel epidemiological surveillance tool to identify circulating arboviruses.

molecular biology↗

bioRxiv2019

Polymorphism analyses and protein modelling inform on functional specialization of Piwi clade genes in the arboviral vector Aedes albopictus

Current knowledge of the piRNA pathway is based mainly on studies on the model organism Drosophila melanogaster, where three proteins of the Piwi subclade of the Argonaute family interact with PIWI-interacting RNAs to silence transposable elements in gonadal tissues. In mosquito species that transmit epidemic arboviruses such as the Dengue and Chikungunya viruses, Piwi clade genes underwent expansion, are also expressed in the soma, and code for proteins that may elicit antiviral functions and crosstalk with other proteins of recognized antiviral mechanisms. These observations underline the importance of expanding our knowledge of the piRNA pathway beyond D. melanogaster.\n\nHere we focus on the emerging arboviral vector Aedes albopictus and we couple traditional approaches of expression and adaptive evolution analyses with most current computational predictions of protein structure to study evolutionary divergence among Piwi clade proteins. Superposition of protein homology models indicate high structure similarity among all Piwi proteins, with high levels of amino acid conservation in the inner regions devoted to RNA binding. On the contrary, solvent-exposed surfaces showed low conservation, with several sites under positive selection. Expression profiles of Piwi transcripts during mosquito development and after infection with the Dengue 1 virus showed a concerted elicitation of all Piwi transcripts during viral dissemination, while the maintenance of infection primarily relied on the expression of Piwi5. In contrast, establishment of persistent infection by the Chikungunya virus is accompanied by an increased expression of all Piwi genes, particularly Piwi4 and, again, Piwi5. Overall these results are consistent with functional specialization and a general antiviral role for Piwi5. Experimental evidences of sites under positive selection in Piwi1/3, Piwi4 and Piwi6, further provide useful knowledge to design tailored functional experiments.\n\nAuthor summaryArgonautes are ancient proteins involved in many cellular processes, including innate immunity. Early in eukaryote evolution, Argonautes separated into Ago and Piwi clades, which maintain a dynamic evolutionary history with frequent duplications and losses. The use of Drosophila melanogaster as a model organism proved fundamental to understand the function of Argonautes. However, recent studies showed that the patterns and observations made in D. melanogaster, including the number of Argonautes, their expression profile and their function, are a rarity among Dipterans.\n\nIn vectors of epidemic arboviruses such as Dengue and Chikungunya viruses, Piwi genes underwent expansion, are expressed in the soma, and some of them appear to have antiviral functions. Besides being an important basic question, the identification of which (and how) Piwi genes have antiviral functions may be used for the development of novel genetic-based strategies of vector control. Here we coupled population genetics models with computational predictions of protein structure and expression analyses to investigate the evolution and function of Piwi genes of the emerging vector Aedes albopictus. Our data support a general antiviral role for Piwi5. Instead, the detection of complex expression profiles with the presence of sites under positive selection in Piwi1/3, Piwi4 and Piwi6 requires tailored functional experiments to clarify their antiviral role.

evolutionary biology↗