Biology subjects

Fontaine, A.

Publications and source records attributed to Fontaine, A..

At least 19 recordsLinked to original sources

bioRxiv2026

Salmonid science on the move: Twenty years of research through the lens of early career researchers

Salmonids are among the most studied fish species worldwide, owing to their wide geographic distribution, diversity of life-history strategies, ecological and socioeconomic importance, and vulnerability to global change. In this review, we take advantage of two decades of the International Workshop of PhDs and Post-doctoral Fellows on Anadromous Salmonids (NoWPaS) conference series to track the evolution of salmonid science through the lens of early-career researchers (ECRs). From all abstracts presented at NoWPaS meetings between 2005 and 2025, we extracted structured qualitative and quantitative information to characterize major trends and shifts in the field. Our results show a strong research bias toward Atlantic salmon and brown trout, concentrated in Europe and Atlantic Canada, and a persistent mismatch between the life stages and habitats studied. In particular, the marine phase remains understudied in comparison to fresh and coastal waters. Over the study period, salmonid research shifted markedly from hydro-geomorphological and habitat-based approaches toward genetic and genomic methods, alongside the rise of advanced telemetry methods for reconstructing individual life histories. Research orientation, measured as a gradient from fundamental to applied research, was on average intermediate but varied among countries and disciplines, with the UK and Norway showing shifts to more applied research, as well as the discipline of Ecology becoming more applied. Additionally, we identified a significant increase in Climate change and Aquaculture as research drivers, with some drivers well-represented in some species (e.g., Hydropower and dams for landlocked Atlantic salmon and Climate change for Arctic char). These trends should be interpreted in context of the composition of the NoWPaS network: participation is primarily ECRs in the Northern Hemisphere, with research from Asia, South America, and western North America largely absent from this synthesis. Despite this lens, our analysis identifies clear knowledge gaps, particularly around marine life stages and species other than Atlantic salmon and brown trout, and highlights opportunities for broadening taxonomic, geographic, and life-history coverage in future salmonid research. We also present a roadmap, identifying combinations of life stages, disciplines and taxa which have been under-represented and constitute potential knowledge gaps, while also flagging those combinations that have already been well studied. Overall, we advocate for a continued shift toward integrative and holistic approaches, bridging distinct research disciplines, to better understand, manage, and conserve salmonids under increasingly uncertain future environmental conditions.

ecology↗

bioRxiv2026

Adeno-associated virus serotype tropism and transduction in murine dorsal root ganglia following direct injection.

The peripheral nervous system (PNS) is highly heterogeneous, comprised of diverse subclasses of motor and sensory neurons. Optogenetics offers a high-resolution approach for interrogating neural circuits; however, optogenetic proteins must be selectively delivered to defined neuronal circuits in order to elucidate circuit-specific functional mechanisms. Adeno-associated viral vectors (AAVs) are widely used to deliver transgenes to the nervous system due to their relative safety and strong transgene expression. Multiple AAV serotypes are in common use, each capable of preferentially transducing distinct tissues and neuronal populations. However, characterization of the transduction behavior of these serotypes in the PNS, particularly in the dorsal root ganglia (DRG) and sensory nervous system (SNS), remain limited. This study evaluated the transduction efficiency of AAV8, AAV9, AAV2re, and PHP.S following direct intraganglionic injection into the DRG. AAV8, AAV9, and PHP.S exhibited comparable transduction efficiencies, whereas AAV2re transduced more than twofold fewer neurons. Despite similar overall efficiencies between AAV8, AAV9, and PHP.S, the neuronal volume distributions of transduced neurons were serotype-dependent. These results demonstrate that AAV serotype selection influences both the extent and size of transduced DRG neurons, indicating that serotype selection should be considered carefully when designing experiments that target peripheral sensory circuits.

neuroscience↗

bioRxiv2026

Dlx5/6 regulate perineuronal net-synapse coupling and stabilize adult cortical Parvalbumin neurons networks

The transcriptional mechanisms that maintain adult Parvalbumin (PV) interneuron function and cortical network stability remain poorly understood. We previously showed that the inactivation in GABAergic neurons of Dlx5/6, coding for transcription factors, disrupts social interaction and reduces PV interneuron density in the prefrontal cortex. Here, combining transcriptional and histological analyses with ex vivo electrophysiological and in vivo electroencephalographical (EEG) recordings, we show that Dlx5/6 regulate a molecular program controlling perineuronal net (PNN) homeostasis in the adult cortex. Dlx5/6 inactivation dysregulated the expression of multiple PNN-associated genes and induced region-specific remodelling of PNN mesh architecture in the prefrontal and somatosensory cortices. These structural changes were accompanied by alterations in excitatory and inhibitory synaptic organization and by a disrupted coupling between local PNN structure and synaptic properties. Ex vivo electrophysiological recordings revealed that fast-spiking interneurons displayed altered intrinsic properties and reduced excitatory synaptic drive in a region-specific manner, while EEG recordings during social interaction showed impaired recruitment of prefrontal gamma oscillations. Together, these findings identify Dlx5/6 as regulators of adult PV interneuron stability, linking extracellular matrix homeostasis to synaptic organization and cortical network dynamics. More broadly, it provides a new mechanistic framework connecting Dlx5/6 function to PV-related pathological phenotypes, including neuropsychiatric disorders. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=89 SRC="FIGDIR/small/740286v1_ufig1.gif" ALT="Figure 1"> View larger version (31K): org.highwire.dtl.DTLVardef@147c75dorg.highwire.dtl.DTLVardef@171e7d9org.highwire.dtl.DTLVardef@12c5c67org.highwire.dtl.DTLVardef@166790d_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2026

Multi-site temporal control of optogenetic stimulation enhances firing frequencies in peripheral nerves

We find that multi-site temporal control of optogenetic photostimulation in peripheral nerves can enhance firing rates by overcoming the intrinsic limitation of opsin photophysics. The benefits of multi-site optogenetic stimulation were demonstrated with three approaches: (1) in silico modeling, (2) ex vivo in the sciatic nerve, and (3) in vivo in the vagus nerve. An in silico model of multi-site optogenetic stimulation was developed in two Hodgkin and Huxley type neuron models, that supported our hypothesis. The ex vivo sciatic nerve showed an increase in firing frequency that is physiologically relevant for functional control. The technique was then applied in vivo for optogenetic vagus nerve stimulation resulting in significant changes in heart rate compared with standard methods of single-site stimulation. Improving the control of optogenetically induced neural firing will have broad impacts for future developments in optical nerve interfaces and brain-machine interfaces.

neuroscience↗

bioRxiv2026

Early-warning surveillance of West Nile and Usutu viruses in water and mosquito excreta using digital PCR

1.West Nile virus (WNV) and Usutu virus (USUV) are mosquito-borne pathogens maintained in bird-mosquito cycles and increasingly cause human and equine disease in temperate regions. As most infections are asymptomatic, surveillance based on clinical and veterinary reports provides delayed signals for vector control and equine vaccination strategies. We implemented, in 2024 and 2025, an operational environmental surveillance strategy combining molecular xenomonitoring of adult mosquito excreta with water sampling from wetlands and mosquito breeding sites, coupled to a standardized multiplex reverse transcription digital PCR workflow. Viral detection was performed using a multiplex digital PCR assay with characterized limits of blank, detection, and quantification, and low-level positives were confirmed by Sanger sequencing. This multi-matrix approach detected WNV RNA in southern France as early as 1 July 2024, 40 days before the first human case and 67 days before the first equine alert, and on 9 April 2025, a full 19 weeks ahead of the first human case that year. USUV RNA was similarly detected from 5 July 2024 and 22 April 2025, providing actionable early warnings to guide targeted vector control and preparedness. Across both years, WNV and USUV were detected 29 and 8 times among 396 samples in 2024, and 90 and 14 times among 815 samples in 2025, revealing previously unrecognized, cryptic virus circulation. These results demonstrate that integrating environmental surveillance provides a sensitive, proactive framework for the early detection of emerging Culex-borne arboviruses, offering precious lead time for public one-health strategies.

ecology↗

bioRxiv2024

Pleiotropic function of Dlx5/6 in coordinating the development of mammalian vocal and auditory organs

Acoustic communication, essential for mammalian social interactions, involves both effector (vocal) and receptor (auditory) organs that present a wide variety of morphologies between species. The molecular mechanisms supporting the harmonious diversification of effector and receptor systems along with the evolution of species-specific acoustic communication are still poorly understood. It is conceivable that common genetic pathways determine the parallel morphogenesis of vocal and auditory systems. Here, we investigated this question by generating mutant mice with targeted invalidation of Dlx5/6 genes in the otic placode and cephalic neural crest cells, contributing to the formation of the ear and vocal tract components. We show that Dlx5/6 inactivation provokes simultaneous defects of the outer, middle and inner ear and of the jaw, pharynx and larynx musculoskeletal systems. Our findings support the notion that Dlx5/6 genes played a pleiotropic role in the co-adaptation of vocal and auditory systems in mammals.

developmental biology↗

bioRxiv2024

Genomic surveillance reveals that the dengue 2 virus lineage responsible for the 2023-2024 epidemic in the French Caribbean Islands is resistant to Mosnodenvir

Dengue fever is the most important arbovirosis for public health, with more than 5 million cases worldwide in 2023. Mosnodenvir is the first anti-dengue compound with very high preclinical pan-serotype activity, currently undergoing phase 2 clinical evaluation. Here, by analyzing dengue virus (DENV) genomes from the ongoing epidemic in the French Caribbean Islands, we show that they all exhibit mutation NS4B:V91A, previously associated with strong resistance to mosnodenvir in vitro. Using antiviral activity tests on clinical and reverse-genetic strains, we confirm a 600-fold decrease in mosnodenvir sensitivity. Finally, combining phylogenetic analysis and experimental testing for resistance, we find that the V91A resistance mutation likely emerged multiple times over the last 30 years in DENV-2 and DENV-3. These results call for increased genomic surveillance, in particular to track lineages with resistance mutations. These efforts should allow to better assess the activity profile of DENV treatments in development against circulating strains.

microbiology↗

bioRxiv2024

Molecular Xenomonitoring (MX) allows real-time surveillance of West Nile and Usutu virus in mosquito populations.

BackgroundWest Nile (WNV) and Usutu (USUV) virus are vector-borne flaviviruses causing neuroinvasive infections in both humans and animals. Entomological surveillance is a method of choice for identifying virus circulation ahead of the first human and animal cases, but performing molecular screening of vectors is expensive, and time-consuming. MethodsWe implemented the MX (Molecular Xenomonitoring) strategy for the detection of WNV and USUV circulation in mosquito populations in rural and urban areas in Nouvelle-Aquitaine region (France) between July and August 2023, using modified BG Sentinel traps. We first performed molecular screening and sequencing on excreta from trapped mosquitoes before confirming the results by detecting, sequencing and isolating viruses from individual mosquitoes. FindingsWe identified WNV and USUV-infected mosquitoes in 3 different areas, concurrently with the first human cases reported in the region. Trapped mosquito excreta revealed substantial virus co-circulation (75% of traps had PCR+ excreta for at least one of both viruses). Cx. pipiens was the most common species infected by both WNV and USUV. Genomic data from excreta and mosquitoes showed the circulation of WNV lineage 2 and USUV lineage Africa 3, both phylogenetically close to strains that circulated in Europe in recent years. Four WNV and 3 USUV strains were isolated from trapped mosquitoes. InterpretationMX strategy is easy and rapid to implement on the field, and has proven its effectiveness in detecting WNV and USUV circulation in local mosquito populations. FundingThis study received funding from the Direction Generale de lArmement (PDH 2 NBC-5-B-2212) and ARBOGEN (funded by MSDAVENIR). Research in contextO_ST_ABSEvidence before this studyC_ST_ABSWNV and USUV circulate through complex transmission cycles involving mosquitoes as vectors, birds as amplifying hosts and several mammal species as dead-end hosts. Transmission to humans primarily occurs through mosquito bites for both viruses. Notably, WNV can also be transmitted through blood donations and organ transplants. It is estimated that a significant proportion of both WNV and USUV infections in vertebrate hosts remain unreported due to their predominantly asymptomatic nature or nonspecific clinical presentation. Nevertheless, neuroinvasive and potentially fatal disease can occur, in particular among vulnerable populations such as elderly and immunocompromised patients. In France, after its first detection in 2015, USUV has been sporadically found in eastern and southern departments, with confirmed infections in birds, mosquitoes and mammals, and few human cases described. WNV has recently caused annual outbreaks of varying intensities involving humans, equids and avifauna in French departments mainly located in the Mediterranean area. Because of low viral loads and/or brief viremia, diagnosis of both pathogens is often based on serological evidence, and few genomic data are available on strains having circulated in France. Entomological surveillance can be used as an early warning method for WNV and USUV surveillance, but is costly to implement as it requires the collection of large numbers of mosquitoes to detect virus circulation when infection rates in mosquito populations are low. Therefore, viral surveillance in France still heavily relies on human and animal surveillance, i.e. late indicators of viral circulation. Added value of this studyThis study describes the implementation of the MX (Molecular Xenomonitoring) strategy for the effective surveillance of WNV and USUV circulation within mosquito populations. MX uses of modified BG Sentinels that allow (i) trapped mosquitoes to survive for several days and (ii) corresponding mosquito excreta to be collected and preserved on filter paper. MX has demonstrated many advantages over traditional entomological surveillance. Firstly, screening excreta collectively deposited by a community of trapped mosquitoes for the presence of viruses in the first instance is time and cost efficient, as one sample is tested for viral RNA, regardless of the number and species diversity in the trap. Second, filter papers with mosquito excreta can be transported from the field to the laboratory at room temperature by regular postal mail, bringing real-time detection within reach. WNV and USUV RNA have been detected and sequenced directly from the mosquito excreta shortly after collection. Thirdly, MX adapters increase the longevity of trapped mosquitoes, thereby allowing extension of the time between trap collections and increasing the likelihood of virus shedding by infected mosquitoes. Fourthly, this approach is easy to implement in the field and requires neither a strong entomological background nor specific technical skills. All these aspects make the MX strategy a powerful, non-invasive and cost-effective tool for real-time monitoring of enzootic WNV and USUV circulation. Authors should describe here how their findings add value to the existing evidence.WNV was never detected on the Atlantic seaboard of France until October 2022. Molecular evidence of WNV circulation was obtained in 3 symptomatic horses in the Nouvelle Aquitaine region in October 2022, concomitantly with an USUV human case with no recent travel history outside the region. This was a harbinger of an increase in cases over the next year. In 2023, MX succeeded in detecting the enzootic co-circulation of WNV and USUV in rural and urban areas of Nouvelle Aquitaine, simultaneously with the first cases of WNV detected by human and animal surveillance and the first human case of USUV diagnosed in the end of July 2023. Genomic and phylogenetic information was obtained directly from trapped mosquito excreta, before information derived from animal or human surveillance. Mosquitoes from traps with PCR-positive excreta were analysed individually, which allowed to calculate infection rates in mosquitoes. WNV and USUV were isolated from single Cx. pipiens mosquitoes. Cx. pipiens was the species most commonly found positive for either viruses although WNV was also detected in Ochlerotatus and Aedes mosquitoes, including one tiger mosquito (Ae. albopictus) in the urban environment. We argue that the MX approach is a major asset in the early warning detection of WNV and USUV circulation to alert health policy makers and take suitable control measures.

molecular biology↗

bioRxiv2024

Sand flies and Toscana virus: intra-vector infection dynamics and impact on Phlebotomus perniciosus life-history traits

Toscana virus (TOSV) is a leading cause of summer viral meningitis in central Italy and south of France, and can cause severe neurological cases. Within the Mediterranean basin, it is transmitted by hematophagous sand flies belonging to the Phlebotomus genus. Despite the identification of the primary TOSV vectors, the viruss developmental cycle in vector species remains largely unknown. Limited research has been conducted on transmission dynamics and the vectorial competence and capacity of the principal TOSV vector, Phlebotomus perniciosus. In this context, we investigated the intra-vector TOSV infection dynamics in Ph. perniciosus, as well as its impact on the vectors life history traits. Female sand flies were experimentally infected with TOSV though an artificial blood meal. Systemic dissemination of the virus was observed approximately three days post-infection, potentially resulting in a shorter extrinsic incubation period. Moreover, the study revealed a longer hatching time for eggs laid by infected females. This research not only confirmed the vector competence of Ph. perniciosus but also provided the first insight into TOSVs developmental cycle and its impact on the vector. These findings prompt further exploration of TOSV transmission dynamics, raise new hypotheses on the virus transmission and highlight the importance of follow-up studies. Author summaryToscana virus (TOSV) is a reemerging sandfly-borne virus causing neuroinvasive infections in humans. This virus is endemic in the Mediterranean basin, with a potential risk of introduction in northern Europe and Asia. Despite decades of research, few studies have focused on the development cycle of TOSV in sand flies and the dynamics of transmission. Here, we provide a comprehensive study of the intra-vector dynamics of TOSV infection and its impact on both vector biology and transmission. Through experimental infections of the major vector Phlebotomus perniciosus, we not only confirmed vector competence but also provided the first insight into the TOSV developmental cycle in the vector by estimating the extrinsic incubation period at six days. Our study reveals an impact of TOSV infection on vector hatching time leading to a delayed emergence of infected sand flies, with a potential impact on transmission. Our findings encourage further exploration of transmission dynamics, raise new hypotheses on alternative transmission pathways, and emphasize the importance of follow-up studies.

microbiology↗

bioRxiv2024

Vascular damage and excessive proliferation compromise liver function after extended hepatectomy in mice

Surgical resection remains the gold standard for liver tumor treatment, yet the emergence of post-operative liver failure, known as the small for size syndrome (SFSS), poses a substantial challenge. The activation of hypoxia sensors in a SFSS liver remnant initiated early angiogenesis, improving vascular architecture, safeguarding against liver failure and reducing mortality. The study aimed to elucidate vascular remodeling mechanisms in SFSS, its impact on hepatocyte function and subsequent liver failure. Mice underwent extended partial hepatectomy to induce SFSS, a subset were exposed to hypoxia immediately after surgery. Hypoxia bolstered post- hepatectomy survival rates. Early proliferation of liver sinusoidal cells coupled with augmented recruitment of endothelial progenitor cells (EPC) via the VEGF/SDF-1 pathway resulted in heightened vascular density, improved lobular perfusion, and limited hemorrhagic events in the regenerating liver under hypoxia. The administration of G-CSF mimicked the effects of hypoxia on vascular remodeling and EPC recruitment, though it failed to rescue survival. Compared to normoxia, hypoxia restrained hepatocyte proliferation yet improved the function of the regenerating remnant, favoring functional preservation in the liver remnant. Injection of AAV8- TBG-HNF4 virus for hepatocyte-specific overexpression of HNF4, the master regulator of hepatocyte function, enforced functionality in proliferating hepatocytes. The combination, only, of HNF4 overexpression and G-CSF treatment rescued survival post-SFSS-setting hepatectomy. In summary, SFSS arises due to imbalance and desynchronized interplay between functional regeneration and vascular restructuring. To enhance survival following SFSS-hepatectomy, a two- pronged strategy is essential, addressing the preservation of function in the proliferating parenchymal cells alongside the simultaneous mitigation of vascular harm. One Sentence SummaryCombined treatment with G-CSF and HNF4 overexpression rescues vascular damage and function to improve survival after extended hepatectomy in mice.

cell biology↗

bioRxiv2023

Multiplexed amplicon sequencing reveals the heterogeneous spatial distribution of pyrethroid resistance mutations in Aedes albopictus mosquito populations in Southern France.

The risk of mosquito-borne diseases transmission is moving fast toward temperate climates with the colonization and proliferation of the Asian tiger mosquito vector Aedes albopictus and the rapid and mass transport of passengers returning from tropical regions where the viruses are endemic. The prevention of major Aedes-borne viruses heavily relies on the use of insecticides for vector control, mainly pyrethroids In Europe. High-throughput molecular assays can provide a cost-effective surrogate to phenotypic insecticide resistance assays when mutations have been previously linked to a resistance phenotype. Here, we screened for the spatial distribution of kdr mutations at a large scale using a two-step approach based on multiplexed amplicon sequencing and an unprecedented collection of field-derived mosquitoes in South of France. We identified the presence of the V1016G allele in 14 sites. The V1016G allele was predominantly found in South-East France close to the Italian border with two additional isolated sites close to Bordeaux and Marmande. All mosquitoes were heterozygous for this mutation and should not be phenotypically resistant to pyrethroid insecticide. Four other mutations were identified in our targeted genomic sequence: I1532T, M1006L, M1586L, M995L. Sequencing a section of maternally inherited mitochondrial genome confirmed that the spread of Ae. albopictus in France originated from founders with haplogroup A1. These findings contribute to the broader understanding of resistance dynamics in Europe and can inform targeted approaches to mitigate the impact of resistance on vector control.

genetics↗

bioRxiv2022

Combining two Genetic Sexing Strains allows sorting of non-transgenic males for Aedes genetic control

Chemical control of disease vectoring mosquitoes Aedes albopictus and Aedes aegypti is costly, unsustainable, and increasingly ineffective due to the spread of insecticide resistance. The Sterile Insect Technique is a valuable alternative but is limited by the slow, error-prone, and wasteful sex-separation requirement. Here, we present four Genetic Sexing Strains (two for each Aedes species) based on fluorescence markers linked to the m and M sex loci, allowing for the isolation of transgenic males. Furthermore, we demonstrate how combining these sexing strains enables the production of non-transgenic males. Scaling-up would allow the sorting of 100,000 first instar male larvae in under 1.5 hours with an estimated 0.01-0.1% female contamination. Cost-efficiency analyses revealed that using these strains could result in important savings while setting up and running a mass-rearing facility. Altogether, these Genetic Sexing Strains should enable a major upscaling in control programmes against these important vectors. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=136 SRC="FIGDIR/small/483912v2_ufig1.gif" ALT="Figure 1"> View larger version (42K): org.highwire.dtl.DTLVardef@761545org.highwire.dtl.DTLVardef@6e80f2org.highwire.dtl.DTLVardef@d3911dorg.highwire.dtl.DTLVardef@1dc19ce_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗

bioRxiv2022

Relevance study of vector competence and insecticide resistance in Aedes aegypti laboratory lines

The urban mosquito species Aedes aegypti is the main vector of arboviruses worldwide. Mosquito control with insecticides is the most prevalent method for preventing transmission in the absence of effective vaccines and available treatments; however, the extensive use of insecticides has led to the development of resistance in mosquito populations throughout the world, and the number of epidemics caused by arboviruses has increased. Three mosquito lines with different resistance profiles to deltamethrin were isolated in French Guiana, including one with the I1016 knock-down resistant allele. Significant differences were observed in the cumulative proportion of mosquitoes with a disseminated chikungunya virus infection over time. In addition, certain genes (CYP6BB2, CYP6N12, GST2, trypsin) were variably overexpressed in the midgut at 7 days after an infectious blood meal in these three lines. Therefore, detoxification enzymes and kdr mutations may contribute to an enhanced midgut barrier and reduced dissemination rate. Our work shows that vector competence for chikungunya virus varied between Ae. aegypti laboratory lines with different deltamethrin-resistance profiles. More accurate verification of the functional association between insecticide resistance and vector competence remains to be demonstrated. ImportanceThree Ae. aegypti lines, isolated from the same collection site, underwent different insecticide selection pressures against deltamethrin under laboratory conditions. As a result, they developed different resistant profiles. In this study, when these lines were fed an artificial infectious blood meal containing chikungunya virus, all three lines including the reference strain showed a high infection rate. There was no statistical difference in infection rate found; however, the dissemination rate of the virus from midgut to head were significantly different. A higher resistance level detected by the WHO test was correlated with a lower viral dissemination rate for each strain. This study presented evidence that the insecticide selection pressure or the existence of insecticide resistance could lead to differences in viral dissemination or even transmission in mosquito populations. We hope that our study can give more insights into understanding the roles of mosquito insecticide resistance on viral transmission.

molecular biology↗

bioRxiv2021

Mosquito excreta reveals circulation of West Nile virus and its underlying ecosystem

Emerging and endemic mosquito-borne viruses can be difficult to detect and monitor because they often cause asymptomatic infections in human or vertebrate animals or cause nonspecific febrile illness with a short recovery waiting period. Cases detection in vertebrate hosts can be complemented by entomological surveillance, but this method is not adapted to low infection rates in mosquito populations that typically occur in low or non-endemic areas. We identified West Nile Virus circulation in Camargue, a wetland area in South of France, using a cost effective innovative xenomonitoring method based on the molecular detection of virus in excreta from trapped mosquitoes. We also succeeded at identifying the mosquito community diversity dynamic on several sampling sites, together with the vertebrate hosts on which they fed prior to be captured using amplicon-based metagenomic on mosquito excreta without processing any mosquito. Mosquito excreta-based virus surveillance can be considered as a cost-effective and non-invasive strategy that offers the additional asset to reveal the ecological network underlying arbovirus circulation.

ecology↗

bioRxiv2020

High transmissibility and fetal pathogenicity of recent Zika virus strains from the African lineage

The global emergence of Zika virus (ZIKV) in the last decade revealed the unprecedented ability for a mosquito-borne virus to cause congenital birth defects such as microcephaly. A puzzling aspect of ZIKV emergence is that all human outbreaks and birth defects to date have been exclusively associated with the Asian ZIKV lineage, despite a growing body of laboratory evidence pointing towards higher transmissibility and pathogenicity of the African ZIKV lineage. Whether this apparent paradox reflects the use of relatively old African ZIKV strains in most laboratory studies is unclear. Here, we experimentally compared the transmissibility and pathogenicity of seven low-passage ZIKV strains representing the recently circulating viral genetic diversity. We found that recent African ZIKV strains largely outperformed their Asian counterparts in mosquito transmission kinetics experiments, which translated into a markedly higher epidemic potential in outbreak computer simulations. In addition, African ZIKV strains were significantly more lethal than Asian ZIKV strains in immunocompromised adult mice. Finally, prenatal infection of immunocompetent mouse embryos with an African ZIKV strain resulted in embryonic death whereas it caused microcephaly with Asian ZIKV strains. Together, our results demonstrate the high epidemic potential and pathogenicity of recent ZIKV strains from Africa. Importantly, they also imply that the African ZIKV lineage could more easily go unnoticed by public health surveillance systems than the Asian ZIKV lineage due to its propensity to cause fetal loss rather than birth defects.

microbiology↗

bioRxiv2020

Non-retroviral endogenous viral element limits cognate virus replication in Aedes aegypti ovaries

Endogenous viral elements (EVEs) are viral sequences integrated in host genomes. A large number of non-retroviral EVEs was recently detected in Aedes mosquito genomes, leading to the hypothesis that mosquito EVEs may control exogenous infections by closely related viruses. Here, we experimentally investigated the role of an EVE naturally found in Aedes aegypti populations and derived from the widespread insect-specific virus, cell-fusing agent virus (CFAV). Using CRISPR/Cas9 genome editing, we created an Ae. aegypti line lacking the CFAV EVE. Absence of the EVE resulted in increased CFAV replication in ovaries, possibly modulating vertical transmission of the virus. Viral replication was controlled by targeting of viral RNA by EVE-derived piRNAs. Our results provide evidence that antiviral piRNAs are produced in the presence of a naturally occurring EVE and its cognate virus, demonstrating a functional link between non-retroviral EVEs and antiviral immunity in a natural insect-virus interaction.

microbiology↗

bioRxiv2019

A mosquito survey along a transect of urbanization in Dschang, West Region of Cameroon, reveals potential risk of arbovirus spillovers

BackgroundWith the advance of globalization and the decline of wild habitats, mosquito-borne viruses are no longer confined to their original sylvatic environments and are emerging or remerging worldwide. However, little is known about the mosquito species implicated in the spillovers of these viruses from their enzootic cycles.\n\nMethodWe conducted an entomological field survey to catalogue the relative abundance of the Culicidae fauna in rural, peri-urban and urban areas in the Dschang locality in West Cameroon. Mosquitoes were collected from March-April and July-August 2019 at both aquatic and adult stages, and identified using stereomicroscopes and morphological identification keys.\n\nResultsA total of 1,401 mosquitoes belonging to 4 genera and 26 species were collected (n=427, 470 and 504 in rural, peri-urban and urban areas respectively). The most abundant species Aedes africanus (45.47%) as well as Culex moucheti (8.92 %) were encountered in peri-urban and rural environments. Species like Culex duttoni (14.49%), Culex quinquefasciatus (2.35%) and Aedes aegypti (1.36%) were solely found in urban area. Aedes albopictus (14.42%), Culex (Culiciomyia) (6.57%), Culex tigripes (1.43%) and Eretmapodites chrysogaster (0.64%) on the other hand were collected in the three study sites. Importantly, all these species have been suspected or incriminated as vectors of many arboviruses.\n\nConclusionThis study identified potential sylvatic, urban and bridge-vectors that can play a role in current or future virus emergence in Cameroon. Further investigations are needed to assess if arboviruses are circulating in these areas and to study the vector role of each mosquito species in arbovirus transmission.

ecology↗

bioRxiv2019

European and tropical Aedes albopictus mosquito populations have similar systemic Zika virus infection dynamics

First isolated from a forest in East Africa in the mid-20th century, Zika virus (ZIKV) has now emerged worldwide in urbanized areas where its mosquito vectors, mainly Aedes aegypti and Ae. albopictus, are present. Europe and French overseas territories in the Indian Ocean have been so far spared despite the presence of Ae. albopictus, the Asian tiger mosquito. However, because they have strong economic and touristic links with regions affected by ZIKV, French territories in the Indian Ocean have a high risk of introduction. Here, we assess the susceptibility of two Ae. albopictus populations from Metropolitan France and the Reunion island (a French oversea territory in the Indian Ocean) for a ZIKV isolate from the Asian genotype at a titer ranging from 3 to 7.5 x 106 focus-forming units per milliliter. High infection rates and unpreceded levels of systemic infection rates were observed in both Metropolitan France and the Reunion island populations, without differences in infection rates or intra-mosquito systemic infection dynamics between the two mosquito populations. Ten and 20-days were needed by the virus to disseminate in 50% and 100% of the exposed mosquitoes respectively. Such slow intra-mosquito viral dynamics, in addition to repeatedly reported high transmission barrier in the literature, can impact ZIKV transmission when potentially vectored by Ae. albopictus. However, because mosquito-borne virus intra-host transmission dynamics can be influenced by numerous factors, including virus dose dynamics inside infectious humans or viral evolution towards shorter extrinsic incubation periods (EIP), our results highlight that Ae. albopictus populations present in Metropolitan France and the French territoires in the Indian Ocean might become potential vector for autochthonous ZIKV transmissions.

microbiology↗