Biomphalaria snails are instrumental in transmission of the human blood fluke Schistosoma mansoni. With the World Health Organization's goal to eliminate schistosomiasis as a global health problem by 2025, there is now renewed emphasis on snail control. Here, we characterize the genome of Biomphalaria glabrata, a lophotrochozoan protostome, and provide timely and important information on snail biology. We describe aspects of phero-perception, stress responses, immune function and regulation of gene expression that support the persistence of B. glabrata in the field and may define this species as a suitable snail host for S. mansoni. We identify several potential targets for developing novel control measures aimed at reducing snail-mediated transmission of schistosomiasis.

Leishmaniasis is a protozoan parasitic disease that affects 12 million people worldwide. The first line choice for the treatment of this disease is antimonial drugs. In the endemic regions, resistance to this class of drugs is a major impediment to treatment. Microbes often become resistant to drugs by mutation or down-regulation of uptake systems, but the uptake system for the antimonial drugs in Leishmania is unknown. In other organisms, aquaglyceroporins have been shown to facilitate uptake of trivalent metalloids. In this study, we report the identification and characterization of aquaglyceroporins from Leishmania major (LmAQP1) and Leishmania tarentolae (LtAQP1), respectively. These Leishmania proteins have the conserved signature motifs of aquaglyceroporins. Transfection of LmAQP1 into three species of Leishmania, L. tarentolae, Leishmania infantum, and L. major, produced hypersensitivity to both As(III) and Sb(III) in all three strains. Increased production of LmAQP1 was detected by immunoblotting. Drug-resistant parasites with various mutations leading to resistance mechanisms became hypersensitive to both metalloids after expression of LmAQP1. Increased rates of uptake of As(III) or Sb(III) correlated with metalloid sensitivity of the wild type and drug-resistant transfectants. Transfection of LmAQP1 in a Pentostam-resistant field isolate also sensitized the parasite in the macrophage-associated amastigote form. One allele of LmAQP1 was disrupted in L. major, and the resulting cells became 10-fold more resistant to Sb(III). This is the first report of the uptake of a metalloid drug by an aquaglyceroporin in Leishmania, suggesting a strategy to reverse resistance in the field.

For many decades, invertebrate immunity was believed to be non-adaptive, poorly specific, relying exclusively on sometimes multiple but germ-line encoded innate receptors and effectors. But recent studies performed in different invertebrate species have shaken this paradigm by providing evidence for various types of somatic adaptations at the level of putative immune receptors leading to an enlarged repertoire of recognition molecules. Fibrinogen Related Proteins (FREPs) from the mollusc Biomphalaria glabrata are an example of these putative immune receptors. They are known to be involved in reactions against trematode parasites. Following not yet well understood somatic mechanisms, the FREP repertoire varies considerably from one snail to another, showing a trend towards an individualization of the putative immune repertoire almost comparable to that described from vertebrate adaptive immune system. Nevertheless, their antigenic targets remain unknown. In this study, we show that a specific set of these highly variable FREPs from B. glabrata forms complexes with similarly highly polymorphic and individually variable mucin molecules from its specific trematode parasite S. mansoni (Schistosoma mansoni Polymorphic Mucins: SmPoMucs). This is the first evidence of the interaction between diversified immune receptors and antigenic variant in an invertebrate host/pathogen model. The same order of magnitude in the diversity of the parasite epitopes and the one of the FREP suggests co-evolutionary dynamics between host and parasite regarding this set of determinants that could explain population features like the compatibility polymorphism observed in B. glabrata/S. mansoni interaction. In addition, we identified a third partner associated with the FREPs/SmPoMucs in the immune complex: a Thioester containing Protein (TEP) belonging to a molecular category that plays a role in phagocytosis or encapsulation following recognition. The presence of this last partner in this immune complex argues in favor of the involvement of the formed complex in parasite recognition and elimination from the host.

The therapeutic mainstay against the protozoan parasite Leishmania is still based on the antiquated pentavalent antimonials (Sb(V)), but resistance is increasing in several parts of the world. Resistance is now partly understood in laboratory isolates, but our understanding of resistance in field isolates is lagging behind. We describe here a comparative analysis of a genetically related pair of Sb(V)-sensitive and -resistant Leishmania donovani strains isolated from kala-azar patients. The resistant isolate exhibited cross-resistance to other unrelated Leishmania drugs including miltefosine and amphotericin B. A comparative proteomics screen has highlighted a number of proteins differentially expressed suggesting that programmed cell death (PCD) is modified in the resistant parasite. Indeed drug-induced PCD progression was altered in the Sb(V)-resistant strain as determined using early and late markers of apoptosis. Two proteins, the heat shock protein HSP83 and the small kinetoplastid calpain-related protein (SKCRP14.1) were shown to be intimately implicated in the drug-induced PCD phenotype. HSP83 increased drug resistance and reduced drug-mediated PCD activation by interfering with the mitochondrial membrane potential, whereas SKCRP14

Over the last decades, there was increasing evidence for the presence of innate immune memory in living organisms. In this review, we compare the innate immune memory of various organisms with a focus on phylogenetics. We discuss the acquisition and molecular basis of immune memory and we describe the innate immune memory paradigm and its role in host defense during evolution. The molecular characterization of innate immunological memory in diverse organisms and host-parasite systems reconciles mechanisms with phenomena and paves the way to molecular comprehension of innate immune memory. We also revise the traditional classification of innate and adaptive immunity in jawed vertebrates. We emphasize that innate immune responses have the capacity to be "primed" or "trained", thereby exerting a yet unknown type of immunological memory upon re-infection.

SummaryAntimonial-containing drugs are the first line of treatment against the parasite Leishmania . Resistance to antimonials has been correlated to its reduced accumulation. We used a dominant negative functional cloning strategy where a Leishmania mexicana expression cosmid bank was transfected in cells resistant to trivalent antimony (SbIII). Cells were selected for increased sensitivity to SbIII. One cosmid was isolated that could bestow SbIII sensitivity to resistant cells. The gene part of this cosmid that is responsible for increased SbIII sensitivity corresponds to AQP1, an aquaglyceroporin. AQP1 was recently shown to be a route by which SbIII can accumulate in Leishmania cells. Transport studies have shown that the L. mexicana AQP1 can restore SbIII transport in resistant cells. Southern blot analysis indicated that the copy number of neither the AQP1 gene nor the other AQP homologues was changed in antimony-resistant mutants of several Leishmania species. The AQP1 gene sequence was also unchanged in mutants. However, the AQP1 RNA levels were downregulated in several Leishmania promastigote species resistant to antimonials. In general, but not always, the level of AQP1 transcript levels correlated well with the accumulation of SbIII and resistance levels in Leishmania cells. AQP1 thus appears to be a key determinant of antimonials accumulation and susceptibility in Leishmania .

Discoveries made over the past ten years have provided evidence that invertebrate antiparasitic 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 Biomphalaria/Schistosoma system was undertaken to reconcile mechanisms with phenomena, opening the way to a better comprehension of innate immune memory in invertebrates. This prompted us to revisit the artificial dichotomy between innate and memory immunity in invertebrate systems.

Many parasites modify their host behaviour to improve their own transmission and survival, but the proximate mechanisms remain poorly understood. An original model consists of the parasitoid Dinocampus coccinellae and its coccinellid host, Coleomegilla maculata; during the behaviour manipulation, the parasitoid is not in contact with its host anymore. We report herein the discovery and characterization of a new RNA virus of the parasitoid (D. coccinellae paralysis virus, DcPV). Using a combination of RT-qPCR and transmission electron microscopy, we demonstrate that DcPV is stored in the oviduct of parasitoid females, replicates in parasitoid larvae and is transmitted to the host during larval development. Next, DcPV replication in the host's nervous tissue induces a severe neuropathy and antiviral immune response that correlate with the paralytic symptoms characterizing the behaviour manipulation. Remarkably, virus clearance correlates with recovery of normal coccinellid behaviour. These results provide evidence that changes in ladybeetle behaviour most likely result from DcPV replication in the cerebral ganglia rather than by manipulation by the parasitoid. This offers stimulating prospects for research on parasitic manipulation by suggesting for the first time that behaviour manipulation could be symbiont-mediated.