Evidence for Specific Genotype-Dependent Immune Priming in the Lophotrochozoan Biomphalaria glabrata Snail.

International audienceHistorically, the prevailing view in the field of invertebrate immunity was that invertebrates that do not possess acquired adaptive immunity rely on innate mechanisms with low specificity and no memory. Several recent studies have shaken this paradigm and suggested that the immune defenses of invertebrates are more complex and specific than previously thought. Mounting evidence has shown that at least some invertebrates (mainly Ecdysozoa) show high levels of specificity in their immune responses to different pathogens, and that subsequent reexposure may result in enhanced protection (recently called 'immune priming'). Here, we investigated immune priming in the Lophotrochozoan snail species Biomphalaria glabrata, following infection by the trematode pathogen Schistosoma mansoni. We confirmed that snails were protected against a secondary homologous infection whatever the host strain. We then investigated how immune priming occurs and the level of specificity of B. glabrata immune priming. In this report we confirmed that immune priming exists and we identified a genotype-dependent immune priming in the fresh-water snail B. glabrata

A Shift from Cellular to Humoral Responses Contributes to Innate Immune Memory in the Vector Snail Biomphalaria glabrata

International audienceDiscoveries made over the past ten years have provided evidence that invertebrate anti-parasitic responses may be primed in a sustainable manner, leading to the failure of a secondary encounter with the same pathogen. This phenomenon called " immune priming " or "innate immune memory" was mainly phenomenological. The demonstration of this process remains to be obtained and the underlying mechanisms remain to be discovered and exhaustively tested with rigorous functional and molecular methods, to eliminate all alternative explanations. In order to achieve this ambitious aim, the present study focuses on the Lophotrochozoan snail, Biomphalaria glabrata, in which innate immune memory was recently reported. We provide herein the first evidence that a shift from a cellular immune response (encapsulation) to a humoral immune response (biomphalysin) occurs during the development of innate memory. The molecular characterisation of this process in Biompha-laria/Schistosoma system was undertaken to reconcile mechanisms with phenomena

Hyperdiverse Gene Cluster in Snail Host Conveys Resistance to Human Schistosome Parasites

Schistosomiasis, a neglected global pandemic, may be curtailed by blocking transmission of the parasite via its intermediate hosts, aquatic snails. Elucidating the genetic basis of snail-schistosome interaction is a key to this strategy. Here we map a natural parasite-resistance polymorphism from a Caribbean population of the snail Biomphalaria glabrata. In independent experimental evolution lines, RAD genotyping shows that the same genomic region responds to selection for resistance to the parasite Schistosoma mansoni. A dominant allele in this region conveys an 8-fold decrease in the odds of infection. Fine-mapping and RNA-Seq characterization reveal a 25%) haplotypes across the GRC, a significantly non-neutral pattern, suggests that balancing selection maintains diversity at the GRC. Thus, the GRC resembles immune gene complexes seen in other taxa and is likely involved in parasite recognition. The GRC is a potential target for controlling transmission of schistosomiasis, including via genetic manipulation of snails

Les Schistosomes et leurs hôtes : apport des marqueurs moléculaires à la connaissance de leur phylogéographie, épidémiologie et écologie

In the past few years, the development of molecular systematic methods in phylogenetic studies has considerably increased our knowledge of the historical biogeography of schistosomes (Trematoda : Schistosomatidae) and some of their intermediate snail hosts across the continents. Concomitantly, at a more restricted geographic scale, host and parasite population structures have been characterized, using neutral molecular markers, providing an improved understanding of coevolutionary dynamics between hosts and parasites and their epidemiological implications. Finally, at a microspatial scale, analyses of the genotypic composition of parasite infrapopulation, within both definitive and intermediate hosts, have provided useful information on transmission and recruitment processes in the field. Based on recent published studies, we will review (i) phylogeographical hypotheses for the origin and radiation of Schistosoma in Asia, India, Africa, and South America, (ii) new Schistosoma species recently described, (iii) coevolutionary processes acting in fragmented population, (iv) local patterns by which hosts may acquire schistosome infection and factors which are likely to enhance diversity, providing opportunities for parasite adaptation to host and/or environmental change

Chronobiology of trematode cercarial emergence: from data recovery to epidemiological, ecological and evolutionary implications

International audienceOne major challenge for parasites with complex cycles consists to succeed in the transmission from one host to the next host. To maximize the probability of encountering the right host, numerous trematode species have selected various emergence rhythms occurring during the escape of the short-lived cercariae from the mollusc host. Cercarial shedding patterns are beautiful examples of adaptation of the parasite for a successful rendezvous with its subsequent host. In this review, after an analysis of the technical and statistical aspects specific to such studies, we compile the knowledge and unresolved issues we have about the synchronization of these rhythms, their genetic support and the role of the host physiology or activity. We are also interested on how cercarial rhythmicity influences cercarial densities in waters of transmission sites and then the risk of host infection in case of schistosomiasis. Ecological significance of the inter- and intra-specific diversity of these rhythms is emphasized as well as the evolutionary implication of new chronotypes resulting from the capture of new host species and promoting reproductive isolation and alloxenic speciation. Currently, genome sequence data now available for some trematodes such as the schistosomes provide an unprecedented resource for new research approaches that should contribute identification of the genes and mechanisms involved in determining the cercarial shedding rhythms observe

RECHERCHES EXPÉRIMENTALESSUR L'ÉVOLUTION LARVAIREDE SKRJABING YL US NASICOLA(NEMATODA : METASTRONGYLOIDEA)CHEZ DEUX MOLLUSQUES TERRESTRES

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RECHERCHES EXPÉRIMENTALESSUR L'ÉVOLUTION LARVAIREDE SKRJABING YL US NASICOLA(NEMATODA : METASTRONGYLOIDEA)CHEZ DEUX MOLLUSQUES TERRESTRES

International audienc

Les Schistosomes et leurs hôtes : apport des marqueurs moléculaires à la connaissance de leur phylogéographie, épidémiologie et écologie

In the past few years, the development of molecular systematic methods in phylogenetic studies has considerably increased our knowledge of the historical biogeography of schistosomes (Trematoda : Schistosomatidae) and some of their intermediate snail hosts across the continents. Concomitantly, at a more restricted geographic scale, host and parasite population structures have been characterized, using neutral molecular markers, providing an improved understanding of coevolutionary dynamics between hosts and parasites and their epidemiological implications. Finally, at a microspatial scale, analyses of the genotypic composition of parasite infrapopulation, within both definitive and intermediate hosts, have provided useful information on transmission and recruitment processes in the field. Based on recent published studies, we will review (i) phylogeographical hypotheses for the origin and radiation of Schistosoma in Asia, India, Africa, and South America, (ii) new Schistosoma species recently described, (iii) coevolutionary processes acting in fragmented population, (iv) local patterns by which hosts may acquire schistosome infection and factors which are likely to enhance diversity, providing opportunities for parasite adaptation to host and/or environmental change

PARABASCUS LEPIDOTUS LOOSS, 1907(TREMADOTA, LECITHODENDRIIDAE) :UN EXEMPLE DE PARASITE TRANSFUGE

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