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International audience; Numerous high-resolution crystallographic structures of the acetylcholine binding protein (AChBP), a molluscan cholinergic protein, homologous to the extracellular domain of nicotinic acetylcholine receptors, are available. This offers opportunities to model the interaction between various ligands and the acetylcholine binding site. Herein we present a study of the interplay between ligand binding and motions of the C-loop capping the binding site. Nicotinic agonists and antagonists were docked on AChBP X-ray structures. It is shown that the studied agonists and antagonists can be discriminated according to their higher affinities for structures respectively obtained in the presence of agonists or antagonists, highlighting the fact that AChBP structures retain a pharmacological footprint of the compound used in crystallography experiments. A detailed analysis of the binding site cavities suggests that this property is mainly related to the shape of the cavities.

Allopatric and sympatric infections of Lymnaea neotropica and Lymnaea viatrix var. ventricosa with Argentinean and French isolates of Fasciola hepatica were carried out to determine the capacity of these snails to produce metacercariae and to verify if this capacity changed with snail generation. The same process was also made with a French population of Galba truncatula known to be highly susceptible to French isolates of the parasite. In each lymnaeid species separately considered, the survival rate at day 30 post-exposure and prevalence of F. hepatica infection in the group infected with Argentinean miracidia were significantly greater than those recorded in the corresponding French one. Compared to infected G. truncatula, both South American lymnaeids had longer patent periods and produced a higher number of metacercariae. The highest infections were noted with L. v. ventricosa. In the three snail species, metacercarial production was more important with the Argentinean isolate of miracidia than with the French one. If three successive generations of L. v. ventricosa are exposed to the same French isolate of miracidia, cercarial production significantly increased from parents to the F2 generation, while the other characteristics of infection only showed insignificant variations. L. neotropica and L. v. ventricosa are better intermediate hosts for French F. hepatica than local G. truncatula. The numerical increase of shed cercariae in the F1 and F2 generations of L. v. ventricosa demonstrates a rapid adaptation of this species to the French isolate of the parasite., Facultad de Ciencias Veterinarias, Centro de Diagnóstico e Investigaciones Veterinarias