Biology subjects

Exbrayat, A.

Publications and source records attributed to Exbrayat, A..

4 recordsLinked to original sources

bioRxiv2024

A metagenomics-based survey of the virus diversity in mosquito vectors allows the first detection of Sindbis virus in Burkina Faso

Mosquito-borne viruses represent a threat to human health worldwide. This taxonomically-diverse group includes numerous viruses that recurrently spread into new regions. Thus, periodic surveillance of the arbovirus diversity in a given region can help optimizing the diagnosis of arboviral infections. Nevertheless, such screenings are rarely carried out, especially in low-income countries. Consequently, case investigation is often limited to a fraction of the arbovirus diversity. This situation probably results in undiagnosed cases. Here, we have explored the diversity of mosquito-borne viruses in two regions of Burkina Faso. To this end, we have screened mosquitoes collected along three years in six urban and rural areas using untargeted metagenomics. The analysis focused on two mosquito species, Aedes aegypti and Culex quinquefasciatus, considered among the main vectors of arboviruses worldwide. The screening detected Sindbis virus (SINV, Togaviridae) for the first time in Burkina Faso. This zoonotic arbovirus has spread from Africa into Europe. SINV causes periodic outbreaks in Europe but its distribution and epidemiology in Africa remains largely unstudied. SINV was detected in one of the six areas of the study, and at a single year. Detection was validated with isolation in cell culture. SINV was only detected in Cx. quinquefasciatus, thus extending the list of potential vectors of SINV in nature. SINV infection rate in mosquitoes was similar to those observed in European regions that experience SINV outbreaks. A phylogenetic analysis placed the nearly-full genome within a cluster of Central African strains of lineage I. This cluster is supposedly at the origin of the SINV strains introduced into Europe. Thus, West Africa should also be considered as a potential source of the European SINV strains. Our results call for studies on the prevalence of SINV infections in the region to estimate disease burden and the interest of SINV diagnostic in case investigation. Author summaryMosquito-borne viruses are responsible for millions of cases worldwide every year. Moreover, they have repeatedly shown an ability to spread over large distances. Thus, periodic surveys of the arbovirus diversity in a given region can help to define the diagnostic tests to use during case investigation. However, comprehensive surveys are rarely carried out, especially in low-income countries. Here, the arbovirus diversity was assessed in two main mosquito vectors in Burkina Faso using untargeted metagenomics. This screening identified Sindbis virus (SINV), a zoonotic arbovirus, for the first time in Burkina Faso. Moreover, SINV was found in nature for the first time in Culex quinquefasciatus, a main mosquito vector of several pathogens and with a cosmopolitan distribution. SINV leads to periodic outbreaks mainly in Europe. Despite a likely African origin, its distribution and epidemiology in Africa remains largely unstudied. The SINV sequence from Burkina Faso felt within the cluster of Central African strains thought to be at the origin of the European SINV strains. Thus, our results indicate that West Africa should be considered as another potential source of the SINV introductions in Europe. Further studies are required to characterize SINV epidemiology in Burkina Faso and the West African region.

microbiology↗

bioRxiv2023

Host influence on the eukaryotic virome of sympatric mosquitoes and abundance of diverse viruses with a broad host range.

Mosquitoes harbor a large diversity of eukaryotic viruses. Those viromes probably influence mosquito physiology and the transmission of human pathogens. Nevertheless, their ecology remains largely unstudied. Here, we address two key questions in virome ecology. First, we assessed the influence of mosquito species on virome taxonomic diversity and relative abundance. Contrary to most previous studies, the potential effect of the habitat was explicitly included. Thousands of individuals of Culex poicilipes and Culex tritaeniorhynchus, two vectors of viral diseases, were concomitantly sampled in three habitats over two years. A total of 95 viral taxa from 25 families were identified with meta-transcriptomics, with 75% of taxa shared by both mosquitoes. Viromes significantly differed by mosquito species but not by habitat. Differences were largely due to changes in relative abundance of shared taxa. Then, we studied the diversity of viruses with a broad host range. We searched for viral taxa shared by the two Culex species and Aedes vexans, another disease vector, present in one of the habitats. Twenty-six out of the 163 viral taxa were found in the three mosquitoes. These taxa encompassed 14 families. A database analysis supported broad host ranges for many of those viruses, as well as a widespread geographical distribution. Thus, the viromes of mosquitoes from the same genera mainly differed in the relative abundance of shared taxa, whereas differences in viral diversity dominated between mosquito genera. Whether this new model of virome diversity and structure applies to other mosquito communities remains to be determined.

ecology↗

bioRxiv2023

A tale of caution: How endogenous viral elements affect virus discovery in transcriptomic data

Large-scale metagenomic and -transcriptomic studies have revolutionized our understanding of viral diversity and abundance. In contrast, endogenous viral elements (EVEs), remnants of viral sequences integrated into host genomes, have received limited attention in the context of virus discovery, especially in RNA-Seq data. EVEs resemble their original viruses, a challenge that makes distinguishing between active infections and integrated remnants difficult, affecting virus classification and biases downstream analyses. Here, we systematically assess the effects of EVEs on a prototypical virus discovery pipeline, evaluate their impact on data integrity and classification accuracy, and provide some recommendations for better practices. We examined EVEs and exogenous viral sequences linked to Orthomyxoviridae, a diverse family of negative-sense segmented RNA viruses, in 13 genomic and 538 transcriptomic datasets of Culicinae mosquitoes. Our analysis revealed a substantial number of viral sequences in transcriptomic datasets. However, a significant portion appeared not to be exogenous viruses but transcripts derived from EVEs. Distinguishing between transcribed EVEs or exogenous virus sequences was especially difficult in samples with low viral abundance. For example, three transcribed EVEs showed full-length segments, devoid of frameshift and nonsense mutations, exhibiting sufficient mean read depths that qualify them as exogenous virus hits. Mapping reads on a host genome containing EVEs before assembly somewhat alleviated the EVE burden, but it led to a drastic reduction of viral hits and reduced quality of assemblies, especially in regions of the viral genome relatively similar to EVEs. Our study highlights that our knowledge of the genetic diversity of viruses can be altered by the underestimated presence of EVEs in transcriptomic datasets, leading to false positives and altered or missing sequence information. Thus, recognizing and addressing the influence of EVEs in virus discovery pipelines will be key to enhancing our ability to capture the full spectrum of viral diversity.

microbiology↗

bioRxiv2022

Spatial scale influences taxon conservation in the eukaryotic virome of a mosquito

Our knowledge on the diversity of eukaryotic viruses has recently undergone a massive expansion. This diversity could influence host physiology through yet unknown phenomena of potential interest to the fields of health and food production. However, the assembly processes in eukaryotic viromes of terrestrial animals remain elusive. This situation hinders hypothesis-driven tests of virome influence on host physiology. Here, we explore virome assembly at different spatial scales in the eukaryotic virome of the mosquito Culex pipiens. This mosquito is a vector of human pathogens worldwide. Several new aspects of virome assembly were unveiled through a sampling involving five countries in Africa and Europe and large sample sizes. A group of viruses was conserved in C. pipiens populations in all countries. This core group represented a relatively large and diverse fraction of the virome. However, core viruses were not shared by all host individuals in a given country, and their infection rates fluctuated between countries and years. Moreover, the distribution of co-infections in individual mosquitoes suggested random co-occurrence of certain core viruses. We also observed differences in the virome depending on geography, with viromes tending to cluster depending on the continent. Thus, our results unveil that taxon conservation in a eukaryotic virome changes with spatial scale. Thus, predictions on virome assembly seem possible at a large geographical scale in C. pipiens. IMPORTANCEThe study of the eukaryotic virome of mosquitoes is an emerging research field. Beyond its fundamental interest, this field could lead to the development of control tools against the transmission of mosquito-borne human pathogens. However, we yet know little on the assembly patterns in the eukaryotic viromes of mosquitoes, as well as of terrestrial animals in general. This situation hampers the design of hypothesis-driven studies on the influence of the virome on pathogen transmission. Here, we have analyzed virome assembly in the mosquito vector Culex pipiens within and between countries in Africa and Europe. Our results show that integrating contrasted spatial scales allows to identify deterministic patterns in virome assembly. Such patterns can guide future studies of virome influence on mosquito physiology.

ecology↗