Biology subjects

Galinier, R.

Publications and source records attributed to Galinier, R..

4 recordsLinked to original sources

bioRxiv2021

Phylogeography of infectious disease: genetic diversity and connectivity of the Ostreid herpesvirus 1 population in France

The genetic diversity of viral populations is a key driver of the spatial and temporal diffusion of viruses; yet, studying the diversity of whole genomes from natural populations still remains a challenge. Phylodynamic approaches are commonly used for RNA viruses harboring small genomes, but have only rarely been applied to DNA viruses with larger genomes. Here, we used the Pacific Oyster Mortality Syndrome (POMS, a disease that affects oyster farms around the world) as a model to study the genetic diversity of its causative agent, the Ostreid herpesvirus 1 (OsHV-1) in the three main French oyster-farming areas. Using ultra-deep sequencing on individual moribund oysters and an innovative combination of bioinformatics tools, we de novo assembled 21 OsHV-1 new genomes. Combining quantification of major and minor genetic variations, phylogenetic analysis and ancestral state reconstruction of discrete traits approaches; we assessed the connectivity of OsHV-1 viral populations between the three oyster-farming areas. Our results suggest that the Marennes- Oleron Bay represents the main source of OsHV-1 diversity, from where the virus has dispersed to other farming areas, a scenario consistent with current practices of oyster transfers in France. We demonstrate that phylodynamic approaches can be applied to aquatic DNA viruses to determine how epidemiological, immunological, and evolutionary processes act and potentially interact to shape their diversity patterns. ImportancePhylogeography is a field of research that attempts to reconstruct the relationships between individual genotypes within a species and then correlate these genealogical relationships with their geographic and temporal origin. This field of research has become an essential step in the understanding of pandemics, in particular to determine the origin, spread and evolution of a pathogen as currently illustrated in studies on viral pandemics. However, because phylogeographic analyses are based on genome variation, stable genomes yield less information than labile genomes. Accordingly, viruses with double-stranded DNA (dsDNA) genomes generally have lower nucleotide diversity than RNA viruses. In this study, by combining the use of both major and minor genetic variations with phylogeographic analyses of the oyster herpesvirus OsHV-1, we highlight genealogical relationships that are not depicted in phylogenetic trees based on consensus viral genomes only. These data offer a plausible scenario reflecting the origin and spread of OsHV-1 populations between oyster- farming sites.

microbiology↗

bioRxiv2018

Dysbiosis of the Biomphalaria glabrata vector snail microbiota following infection by Schistosoma parasites

Host-associated microbiota cari affect the fitness of its host i {eta} a number of ways, including the modification of host-parasite interactions and thus the outcome of disease. Biomphalaria glabrata is the vector snail of the trematode Schistosoma mansoni, the agent of human schistosomiasis, causing hundreds of thousands of deaths every year. Here, we present the first study of the snail bacterial microbiota in response to Schistosoma infection. To examine the interplay between B. glabrata, S. mansoni and snail microbiota, snails were infected and the microbiota composition was analysed by massive 16S rDNA amplicon sequencing approach. We characterized the Biomphalaria bacterial microbiota at the individual level in both naive and infected snails. Sympatric and allopatric strains of parasites were used for infections and re{-}infections to analyse the modification or dysbiosis of snail microbiota in different host-parasite co-evolutionary contexts. Concomitantly, using RNAseq data, we investigated the link between bacterial microbiota dysbiosis and snail anti-microbial peptide immune response. This work paves the way for a better understanding of snail/schistosome interaction, and would have critical consequences in terms of snail control strategies for fighting schistosomiasis disease in the field.

microbiology↗

bioRxiv2018

Sympatric and allopatric evolutionary contexts shape differential immune response in Biomphalaria / Schistosoma interaction

Selective pressures between hosts and their parasites can result in reciprocal evolution or adaptation of specific life history traits. Local adaptation of resident hosts and parasites should lead to host-parasite systems performing better in sympatry when compared to allopatry. Between-population variations in parasite infectivity/virulence and host defence/resistance, referred to as compatibility phenotype, were often the proxy used to analyse sympatric or allopatric adaptation. Nevertheless, some reported cases exist where allopatric host-parasite systems demonstrate compatibility phenotypes similar or greater than the one observed in sympatry. In these cases, the role of local adaptation is worth considering. Here, we study the interaction between Schistosoma and its vector snail Biomphalaria in which such a discrepancy in local versus foreign compatibility phenotype has been observed. Herein, we developed an integrative approach to investigate sympatric and allopatric interaction processes and link the underlying molecular mechanisms to the resulting phenotypes. Using comparative \"omics\" approaches joined to analysis of life history traits (immune cellular response, mortality, prevalence and compatibility) we tried to bridge the gap of knowledge that exists for connecting local adaptation observations to molecular phenotypes in Schistosoma/Biomphalaria interactions.\n\nWe found that despite displaying similar prevalence phenotypes, parasite infection triggered an immune suppression in snails living in sympatry, while it activated an immune response for those living in allopatry. Dual-comparative molecular analyses revealed that parasite infection causes immune suppression in sympatry. miRNAs were used to hijack the hosts immune response, allowing sympatric parasites to initiate their developmental program earlier and more efficiently.\n\nWe show that despite having similar prevalence phenotypes, sympatric and allopatric snail-Schistosoma interactions displayed a strongly different immunobiological molecular dialogue. The ability of allopatric pathogens to adapt rapidly and efficiently to new hosts could have critical consequences on disease emergence and risk of schistosomiasis outbreaks. These observations would have important consequences in term of schistosomiasis disease control.

immunology↗

bioRxiv2018

BgTEP: an antiprotease involved in innate immune sensing in Biomphalaria glabrata

Insect Thioester-containing protein (iTEP) is the most recently defined group among the TEP superfamily. TEPs are key components of the immune system, and iTEPs from flies and mosquitoes were shown to be major immune weapons. Initially characterised from insects, TEP genes homologous to iTEP were further described from several other invertebrates including arthropods, cniderians and mollusks albeit with few functional characterisations. In the freshwater snail Biomphalaria glabrata, a vector of the schistosomiasis disease, the presence of a TEP protein (BgTEP) was previously described in a well-defined immune complex involving snail lectins (FREP) and schistosome parasite mucins (SmPoMuc).\n\nTo investigate the potential role of BgTEP in the immune response of the snail, we first characterised its genomic organisation and its predicted protein structure. A phylogenetic analysis clustered BgTEP in a well-conserved subgroup of mollusk TEP. We then investigated the BgTEP expression profile in different snail tissues, and followed immune challenges using different kinds of intruders during infection kinetics. Results revealed that BgTEP is particularly expressed in hemocytes, the immune-specialised cells in invertebrates, and is secreted into the hemolymph. Transcriptomic results further evidenced an intruder-dependent differential expression pattern of BgTEP whilst interactome experiments showed that BgTEP is capable of binding to the surface of different microbes and parasite either in its full length form or in processed forms.\n\nThrough this work, we report the first characterisation of a snail TEP. Our study also reveals that BgTEP may display an unexpected functional dual-role. In addition to its previously characterised anti-protease activity, we demonstrate that BgTEP can bind to the intruder surface membrane, which supports a likely opsonin role.

immunology↗