Schistosoma mansoni mucin gene (SmPoMuc) expression: epigenetic control to shape adaptation to a new host

Immuno-molecular profile for Biomphalaria glabrata/Schistosoma mansoni interaction

The complex innate immune defense of Biomphalaria glabrata, the intermediate host of Schistosoma mansoni, governs the successful development of the intramolluscan stages of the parasite. The interaction between the snail and the parasite involves a complex immune molecular crosstalk between several parasite antigens and the snail immune recognition receptors, evoking different signals and effector molecules. This work seeks to discuss the immune-related molecules that influence compatibility in Biomphalaria glabrata/Schistosoma mansoni interaction and the differential expression of these molecules between resistant and susceptible snails. It also includes the current understanding of the immune molecular determinants that govern the compatibility in sympatric and allopatric interactions, and the expression of these molecules after immune priming and the secondary immune response. Herein, the differences in the immune-related molecules in the interaction of other Biomphalaria species with Schistosoma mansoni compared to the Biomphalaria glabrata model snail are highlighted. Understanding the diverse immune molecular determinants in the snail/schistosome interaction can lead to alternative control strategies for schistosomiasis.

How much epigenetics and quantitative trait loci (QTL) mapping tell us about parasitism maintenance and resistance/susceptibility to hosts

Interactions between the environment, parasites, vectors, and/or intermediate hosts are complex and involve several factors that define the success or failure of an infection. Among these interactions that can affect infections by a parasite, it is possible to highlight the genetic and epigenetic mechanisms in hosts and parasites. The interaction between genetics, epigenetics, infection, and the host's internal and external environment is decisive and dictates the outcome of a parasitic infection and the resistance, susceptibility, and transmission of this parasite. Epigenetic changes become important mediators in the regulation of gene expression, allowing the evasion of the parasite to immune host barriers, its transmission to new hosts, and the end of its development cycle. Epigenetics is a new frontier in the understanding of the interaction mechanisms between parasite and host that, along with information from the gene regions associated with complex phenotypic variations, the Quantitative Trait Loci, brings new possibilities to investigate more modern and efficient approaches to the treatment, control, and eradication of parasitic diseases. In this brief review, a general overview of the use of epigenetic information and mapping of Quantitative Trait Loci was summarized, both in genes of parasites and hosts, for understanding the mechanisms of resistance and/or susceptibility in parasitic relationships; also, the main search platforms were quantitatively compared, aiming to facilitate access data produced over a period of twenty years.

Epigenetic Markers Associated with Schistosomiasis

It is important to consider the use of the epigenome as source of complementary data for genome knowledge, which is suitable for the diagnosis of schistosomiasis. Usually, a laboratory diagnosis of schistosomiasis is performed by means of 1. Egg detection in the stool or urine by microscopy remains with limited sensitivity; 2. Immunological screening, in which positivity persists after treatment, and 3. Molecular appraisals prevail over the disadvantages of the currently used methods. In this sense, molecular methodologies are being developed based on epigenetic biomarkers, aiming to improve the diagnosis of the disease and clinical treatment as early as possible to prevent the occurrence of serious liver damage.

Immune Evasion Strategies of Schistosomes

Human schistosomes combat the unique immune systems of two vastly different hosts during their indirect life cycles. In gastropod molluscs, they face a potent innate immune response composed of variable immune recognition molecules and highly phagocytic hemocytes. In humans, a wide variety of innate and adaptive immune processes exist in proximity to these parasites throughout their lifespan. To survive and thrive as the second most common parasitic disease in humans, schistosomes have evolved many techniques to avoid and combat these targeted host responses. Among these techniques are molecular mimicry of host antigens, the utilization of an immune resistant outer tegument, the secretion of several potent proteases, and targeted release of specific immunomodulatory factors affecting immune cell functions. This review seeks to describe these key immune evasion mechanisms, among others, which schistosomes use to survive in both of their hosts. After diving into foundational observational studies of the processes mediating the establishment of schistosome infections, more recent transcriptomic and proteomic studies revealing crucial components of the host/parasite molecular interface are discussed. In order to combat this debilitating and lethal disease, a comprehensive understanding of schistosome immune evasion strategies is necessary for the development of novel therapeutics and treatment plans, necessitating the discussion of the numerous ways in which these parasitic flatworms overcome the immune responses of both hosts.

Physiology and immunity of the invasive giant African snail, Achatina (Lissachatina) fulica, intermediate host of Angiostrongylus cantonensis

As one of the most successful invasive land snail species, Achatina (Lissachatina) fulica Bowdich, 1822 has achieved wide global distribution, particularly in (sub)tropical regions, with further dispersal likely due to climate change. This species of giant African snails (up to 17 cm shell length) is a pest that has extensive negative impact on agriculture and can serve as vector for several parasites, including Angiostrongylus cantonensis, a nematode parasite that causes (human) eosinophilic meningitis, an emergent disease. Investigation showed that A. cantonensis infection negatively impacts the metabolism of A. fulica by depleting polysaccharide stores of the intermediate host, compromising the energy balance of the snail. A review of the literature indicates that A. fulica possesses potent innate type immune defenses to counter infection, including phagocytic hemocytes capable of deploying reactive oxygen species and lectins for non-self recognition, a serine protease-dependent coagulation response (not observed in other taxa of gastropods), as well as antimicrobial proteins including achacin, an antimicrobial protein. A recent chromosome level genome assembly will facilitate progressively detailed characterization of these immune features of A. fulica. We strongly encourage further immunological studies of A. fulica, ranging from organismal level to molecular biology to gain better understanding of the A. fulica internal defense response to nematode pathogens like A. cantonensis and the contribution of immune function to the invasiveness of (snail) species. Characterization of immunity of A. fulica, representing the understudied Stylommatophora (panpulmonate landsnails) will also broaden the comparative immunology of Gastropoda.

The antischistosomal potential of GSK-J4, an H3K27 demethylase inhibitor: insights from molecular modeling, transcriptomics and in vitro assays

Background

Schistosomiasis chemotherapy is largely based on praziquantel (PZQ). Although PZQ is very safe and tolerable, it does not prevent reinfection and emerging resistance is a primary concern. Recent studies have shown that the targeting of epigenetic machinery in Schistosoma mansoni may result in severe alterations in parasite development, leading to death. This new route for drug discovery in schistosomiasis has focused on classes of histone deacetylases (HDACs) and histone acetyltransferases (HATs) as epigenetic drug targets. Schistosoma histone demethylases also seem to be important in the transition of cercariae into schistosomula, as well as sexual differentiation in adult worms.

Methods

The Target-Pathogen database and molecular docking assays were used to prioritize the druggability of S. mansoni histone demethylases. The transcription profile of Smp_03400 was re-analyzed using available databases. The effect of GSK-J4 inhibitor in schistosomula and adult worms’ motility/viability/oviposition was assessed by in vitro assays. Ultrastructural analysis was performed on adult worms exposed to GSK-J4 by scanning electron microscopy, while internal structures and muscle fiber integrity was investigated by confocal microscopy after Langeronʼs carmine or phalloidin staining.

Results

The present evaluation of the potential druggability of 14 annotated S. mansoni demethylase enzymes identified the S. mansoni ortholog of human KDM6A/UTX (Smp_034000) as the most suitable druggable target. In silico analysis and molecular modeling indicated the potential for cofactor displacement by the chemical probe GSK-J4. Our re-analysis of transcriptomic data revealed that Smp_034000 expression peaks at 24 h in newly transformed schistosomula and 5-week-old adult worms. Moreover, this gene was highly expressed in the testes of mature male worms compared to the rest of the parasite body. In in vitro schistosome cultures, treatment with GSK-J4 produced striking effects on schistosomula mortality and adult worm motility and mortality, as well as egg oviposition, in a dose- and time-dependent manner. Unexpectedly, western blot assays did not demonstrate overall modulation of H3K27me3 levels in response to GSK-J4. Confocal and scanning electron microscopy revealed the loss of original features in muscle fibers and alterations in cell-cell contact following GSK-J4 treatment.

Conclusions

GSK-J4 presents promising potential for antischistosomal control; however, the underlying mechanisms warrant further investigation.

Effects of the Environment on Developmental Plasticity and Infection Success of Schistosoma Parasites - An Epigenetic Perspective

Evidence of how environmental cues affect the phenotypes of, and compatibility between Schistosoma mansoni and their hosts come from studies in environmental parasitology and research on host diet and chemotherapeutic treatment. Schistosomes deal with a multitude of signals from the water environment as well as cues that come from their hosts, particularly in response to molecules that serve to recognize and destroy them, i.e., those molecules that arise from their hosts' immune systems. These interactions shape, not only the parasite's morphology, metabolism and behavior in the short-term, but also their infection success and development into different stage-specific phenotypes later in their life cycle, through the modification of the parasite's inheritance system. Developmental phenotypic plasticity of S. mansoni is based on epigenetic mechanisms which are also sensitive to environmental cues, but are poorly understood. Here, we argue that specific cues from the environment could lead to changes in parasite development and infectivity, and consequently, environmental signals that come from environmental control measures could be used to influence S. mansoni dynamics and transmission. This approach poses a challenge since epigenetic modification can lead to unexpected and undesired outcomes. However, we suggest that a better understanding of how environmental cues are interpreted by epigenome during schistosome development and host interactions could potentially be applied to control parasite's virulence. We review evidence about the role of environmental cues on the phenotype of S. mansoni and the compatibility between this parasite and its intermediate and definitive hosts.

Sympatric versus 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 increase parasite infectivity/virulence (higher compatibility) when infecting hosts from the same location (in sympatry) than from a foreign location (in allopatry). Analysis of geographic variations in compatibility phenotypes is the most common proxy used to infer local adaptation. However, in some cases, allopatric host-parasite systems demonstrate similar or greater compatibility than in sympatry. In such cases, the potential for local adaptation remains unclear. Here, we study the interaction between Schistosoma and its vector snail Biomphalaria in which such discrepancy in local versus foreign compatibility phenotype has been reported. Herein, we aim at bridging this gap of knowledge by comparing life history traits (immune cellular response, host mortality, and parasite growth) and molecular responses in highly compatible sympatric and allopatric Schistosoma/Biomphalaria interactions originating from different geographic localities (Brazil, Venezuela and Burundi). We found that despite displaying similar prevalence phenotypes, sympatric schistosomes triggered a rapid immune suppression (dual-RNAseq analyses) in the snails within 24h post infection, whereas infection by allopatric schistosomes (regardless of the species) was associated with immune cell proliferation and triggered a non-specific generalized immune response after 96h. We observed that, sympatric schistosomes grow more rapidly. Finally, we identify miRNAs differentially expressed by Schistosoma mansoni that target host immune genes and could be responsible for hijacking the host immune response during the sympatric interaction. We show that despite having similar prevalence phenotypes, sympatric and allopatric snail-Schistosoma interactions displayed strong differences in their immunobiological molecular dialogue. Understanding the mechanisms allowing parasites to adapt rapidly and efficiently to new hosts is critical to control disease emergence and risks of Schistosomiasis outbreaks.

Schistosomiasis, the second most widespread human parasitic disease after malaria, is caused by helminth parasites of the genus Schistosoma. More than 200 million people in 74 countries suffer from the pathological, and societal consequences of this disease. To complete its life cycle, the parasite requires an intermediate host, a freshwater snail of the genus Biomphalaria for its transmission. Given the limited options for treating Schistosoma mansoni infections in humans, much research has focused on developing methods to control transmission by its intermediate snail host. Biomphalaria glabrata. Comparative studies have shown that infection of the snail triggers complex cellular and humoral immune responses resulting in significant variations in parasite infectivity and snail susceptibility, known as the so-called polymorphism of compatibility. However, studies have mostly focused on characterizing the immunobiological mechanisms in sympatric interactions. Herein we used a combination of molecular and phenotypic approaches to compare the effect of infection in various sympatric and allopatric evolutionary contexts, allowing us to better understand the mechanisms of host-parasite local adaptation. Learning more about the immunobiological interactions between B. glabrata and S. mansoni could have important socioeconomic and public health impacts by changing the way we attempt to eradicate parasitic diseases and prevent or control schistosomiasis in the field.

Molecular context of Schistosoma mansoni transmission in the molluscan environments: A mini-review

Schistosoma mansoni, being transmitted by some freshwater Biomphalaria snails, is a major causative agent of human schistosomiasis. In the absence of effective vaccine and alternative drug designs to fight against the disease, and with the limitations of molluscicide application, developing more efficient strategies to interrupt the snail-mediated parasite transmission is being emphasized as potentially instrumental in the efforts toward schistosomiasis elimination, hence, necessitating thorough and comprehensive understanding of the fundamental mechanisms involved in the transmission process. Based on the current advances, this paper presents a concise exposition of the cellular, biochemical, genetic and immunological dynamics of the complex and statge-by-stage interactions between the parasite and its vector in their aquatic environment. It also highlights the possible crosstalk between the parasite's intracellular cyclic adenosine monophosphate (cAMP) and p38 mitogen-activated protein kinase (p38 MAPK) during the intramolluscan stage. Undoubtedly, decades of intensive investigation have untangled many S. mansoni-B. glabrata complexities, yet many aspects of the parasite-vector cycle which can help define potential control clues await further elucidation.

Integrated multi-omic analyses in Biomphalaria-Schistosoma dialogue reveal the immunobiological significance of FREP-SmPoMuc interaction

The fresh water snail Biomphalaria glabrata is one of the vectors of the trematode pathogen Schistosoma mansoni, which is one of the agents responsible of human schistosomiasis. In this host-parasite interaction, co-evolutionary dynamic results into an infectivity mosaic known as compatibility polymorphism. Integrative approaches including large scale molecular approaches have been conducted in recent years to improve our understanding of the mechanisms underlying compatibility. This review presents the combination of integrated Multi-Omic approaches leading to the discovery of two repertoires of polymorphic and/or diversified interacting molecules: the parasite antigens S. mansoni polymorphic mucins (SmPoMucs) and the B. glabrata immune receptors fibrinogen-related proteins (FREPs). We argue that their interactions may be major components for defining the compatible/incompatible status of a specific snail/schistosome combination.

A multistrain approach to studying the mechanisms underlying compatibility in the interaction between Biomphalaria glabrata and Schistosoma mansoni

In recent decades, numerous studies have sought to better understand the mechanisms underlying the compatibility between Biomphalaria glabrata and Schistosoma mansoni. The developments of comparative transcriptomics, comparative genomics, interactomics and more targeted approaches have enabled researchers to identify a series of candidate genes. However, no molecular comparative work has yet been performed on multiple populations displaying different levels of compatibility. Here, we seek to fill this gap in the literature. We focused on B. glabrata FREPs and S. mansoni SmPoMucs, which were previously demonstrated to be involved in snail/schistosome compatibility. We studied the expression and polymorphisms of these factors in combinations of snail and schistosome isolates that display different levels of compatibility. We found that the polymorphism and expression levels of FREPs and SmPoMucs could be linked to the compatibility level of S. mansoni. These data and our complementary results obtained by RNA-seq of samples from various snail strains indicate that the mechanism of compatibility is much more complex than previously thought, and that it is likely to be highly variable within and between populations. This complexity must be taken into account if we hope to identify the molecular pathways that are most likely to be good targets for strategies aimed at blocking transmission of the parasite through the snail intermediate host.

Schistosomiasis is the second most widespread human tropical parasitic disease after malaria. It is caused by flatworms of the genus Schistosoma, and poses a considerable threat for human health in numerous Asian, African and South American countries. The World Health Organization has set the goal of eradicating schistosomiasis by 2025. However, no vaccine is available, and we currently have only one drug (praziquantel) that can effectively and efficiently treat the disease. As treatment by mass drug administration would enhance the risk of drug resistance in schistosome parasites, complementary strategies to fight this parasitic disease are urgently needed. Freshwater snails of the Biomphalaria genus act as intermediate hosts in the transmission of the schistosome species. Thus, learning more about the mechanisms of the interaction between these snails and the schistosomes could critically facilitate the identification of potential new candidate molecules that may be targeted to prevent schistosome transmission in the field.

The Compatibility Between Biomphalaria glabrata Snails and Schistosoma mansoni: An Increasingly Complex Puzzle

This review reexamines the results obtained in recent decades regarding the compatibility polymorphism between the snail, Biomphalaria glabrata, and the pathogen, Schistosoma mansoni, which is one of the agents responsible for human schistosomiasis. Some results point to the snail's resistance as explaining the incompatibility, while others support a "matching hypothesis" between the snail's immune receptors and the schistosome's antigens. We propose here that the two hypotheses are not exclusive, and that the compatible/incompatible status of a particular host/parasite couple probably reflects the balance of multiple molecular determinants that support one hypothesis or the other. Because these genes are involved in a coevolutionary arms race, we also propose that the underlying mechanisms can vary. Finally, some recent results show that environmental factors could influence compatibility. Together, these results make the compatibility between B. glabrata and S. mansoni an increasingly complex puzzle. We need to develop more integrative approaches in order to find targets that could potentially be manipulated to control the transmission of schistosomiasis.

Epigenetics in Schistosomes: What We Know and What We Need Know

Schistosomes are metazoan parasites and can cause schistosomiasis. Epigenetic modifications include DNA methylation, histone modifications and non-coding RNAs. Some enzymes involved in epigenetic modification and microRNA processes have been developed as drugs to treat the disease. Compared with humans and vertebrates, an in-depth understanding of epigenetic modifications in schistosomes is starting to be realized. DNA methylation, histone modifications and non-coding RNAs play important roles in the development and reproduction of schistosomes and in interactions between the host and schistosomes. Therefore, exploring and investigating the epigenetic modifications in schistosomes will facilitate drug development and therapy for schistosomiasis. Here, we review the role of epigenetic modifications in the development, growth and reproduction of schistosomes, and the interactions between the host and schistosome. We further discuss potential epigenetic targets for drug discovery for the treatment of schistosomiasis.

Epigenetic origin of adaptive phenotypic variants in the human blood fluke Schistosoma mansoni

BACKGROUND

Adaptive evolution is not possible without the generation of phenotypic variants. The origin of these variations has been a central topic in evolutionary biology. Up to now, it was commonly accepted that standing genetic variation is the only cause of phenotypic variants. However, epigenetic information is emerging as a complementary source of heritable phenotypic variation that contributes to evolution. The relative importance of genetics and epigenetics in generating heritable phenotypic variation is nevertheless a matter of debate.

RESULTS

We used a host-parasite system to address this question. The human blood fluke Schistosoma mansoni can adapt rapidly to new intermediate snail hosts. The interaction between parasite and mollusk is characterized by a compatibility polymorphism illustrating the evolutionary dynamics in this system. The principal molecular marker for compatibility (infection success) is the expression pattern of a group of polymorphic mucins (SmPoMuc) in the parasite. We show here that chromatin structure changes as the SmPoMuc promoters are the cause for SmPoMuc transcription polymorphism leading to phenotypic novelty and increase in infection success, i.e., fitness.

CONCLUSION

We establish that epigenetic changes can be the major if not only cause of adaptive phenotypic variants in Schistosoma mansoni, suggesting that epimutations can provide material for adaptive evolution in the absence of genetic variation in other systems. In addition, our results indicate that epidrugs can be used to control parasite development but also parasite evolution.

Polymorphic Mucin-Like Proteins in Schistosoma mansoni, a Variable Antigen and a Key Component of the Compatibility Between the Schistosome and Its Snail Host

The arms race between vertebrate hosts and parasites has led to diversification systems able to generate huge repertoires of immune recognition receptors and antigenic variants. Until recently, the invertebrate immunity was considered to be poorly specific, and consequently, antigenic variability was not expected to be high for their respective parasites. In the present chapter, we show how the study of the interaction between the snail Biomphalaria glabrata and its parasite Schistosome mansoni has shaken this paradigm. We show that the fate of the interaction between the snail and its parasite is at least partly the result of the concordance of highly variable repertoires of immune recognition receptors in the snail and corresponding antigenic variants in the parasite. We call these antigenic variants of the schistosome Schistosoma mansoni polymorphic mucins (SmPoMucs). We show that their high level of diversification is the result of a complex cascade of mechanisms, thus presenting evidence for antigenic variation in a parasite infecting an invertebrate species.

A mucin-like peptide from Fasciola hepatica induces parasite-specific Th1-type cell immunity

Fasciolosis, caused by the liver fluke Fasciola hepatica, is a major parasitic disease of livestock that causes significant economic losses worldwide. Although drugs are effective against liver flukes, they do not prevent reinfection, and continuous treatment is costly. Moreover, resistant fluke strains are emerging. In this context, vaccination is a good alternative since it provides a cost-effective long-term prevention strategy to control fasciolosis. In this paper, we evaluate the Fhmuc peptide as a potential vaccine against fasciolosis. This peptide derives from a mucin-like protein highly expressed in the infective stage of Fasciola hepatica. Mucin-like molecules expressed by parasites can contribute to several infection processes by protecting the parasite from host proteases and recognition by the immune system. We show that the Fhmuc peptide induces Th1-like immune responses specific for F. hepatica excretion-secretion products (FhESP) with a high production of IFNγ. We also investigated whether this peptide could protect animals from infection, and present preliminary data indicating that animals treated with Fhmuc exhibited reduced liver damage compared to non-immunised animals and that this protection was associated with a recruitment of B and T lymphocytes in the peritoneum, as well as eosinophils and mature dendritic cells. These results suggest that the mucin-like peptide Fhmuc could constitute a potential vaccine candidate against fasciolosis and pave the way towards the development of vaccines against parasites.

Advances in gastropod immunity from the study of the interaction between the snail Biomphalaria glabrata and its parasites: A review of research progress over the last decade

This review summarizes the research progress made over the past decade in the field of gastropod immunity resulting from investigations of the interaction between the snail Biomphalaria glabrata and its trematode parasites. A combination of integrated approaches, including cellular, genetic and comparative molecular and proteomic approaches have revealed novel molecular components involved in mediating Biomphalaria immune responses that provide insights into the nature of host-parasite compatibility and the mechanisms involved in parasite recognition and killing. The current overview emphasizes that the interaction between B. glabrata and its trematode parasites involves a complex molecular crosstalk between numerous antigens, immune receptors, effectors and anti-effector systems that are highly diverse structurally and extremely variable in expression between and within host and parasite populations. Ultimately, integration of these molecular signals will determine the outcome of a specific interaction between a B. glabrata individual and its interacting trematodes. Understanding these complex molecular interactions and identifying key factors that may be targeted to impairment of schistosome development in the snail host is crucial to generating new alternative schistosomiasis control strategies.

Differential spatial repositioning of activated genes in Biomphalaria glabrata snails infected with Schistosoma mansoni

Schistosomiasis is an infectious disease infecting mammals as the definitive host and fresh water snails as the intermediate host. Understanding the molecular and biochemical relationship between the causative schistosome parasite and its hosts will be key to understanding and ultimately treating and/or eradicating the disease. There is increasing evidence that pathogens that have co-evolved with their hosts can manipulate their hosts' behaviour at various levels to augment an infection. Bacteria, for example, can induce beneficial chromatin remodelling of the host genome. We have previously shown in vitro that Biomphalaria glabrata embryonic cells co-cultured with schistosome miracidia display genes changing their nuclear location and becoming up-regulated. This also happens in vivo in live intact snails, where early exposure to miracidia also elicits non-random repositioning of genes. We reveal differences in the nuclear repositioning between the response of parasite susceptible snails as compared to resistant snails and with normal or live, attenuated parasites. Interestingly, the stress response gene heat shock protein (Hsp) 70 is only repositioned and then up-regulated in susceptible snails with the normal parasite. This movement and change in gene expression seems to be controlled by the parasite. Other differences in the behaviour of genes support the view that some genes are responding to tissue damage, for example the ferritin genes move and are up-regulated whether the snails are either susceptible or resistant and upon exposure to either normal or attenuated parasite. This is the first time host genome reorganisation has been seen in a parasitic host and only the second time for any pathogen. We believe that the parasite elicits a spatio-epigenetic reorganisation of the host genome to induce favourable gene expression for itself and this might represent a fundamental mechanism present in the human host infected with schistosome cercariae as well as in other host-pathogen relationships.

Bilharzia is a parasitic disease endemic in many parts of the world. The schistosoma parasite that causes Bilharzia infects humans but uses a fresh water snail as a secondary host. These two organisms have co-evolved together, and as such the parasite will have mechanisms to overcome the host defences. Understanding this delicately balanced relationship is fundamental to controlling or eradicating the disease. We have studied how this parasite can influence how the DNA within the snail behaves. We have shown snail genes have specific locations within the cell nuclei. Further, we have revealed that specific snail genes related to a schistosome infection change to a new non-random nuclear location as they are turned on or up-regulated. We have snail strains that are susceptible or resistant to the infection of parasites and we can also take live parasites and make them unable to complete an infection by irradiating them. In this unique study, we have shown a gene that is involved in stress pathways moves to a new nuclear location and becomes turned on, but only in susceptible snails, infected with fully functional parasite. Our data suggest that this gene is regulated by the parasite, which has control over the host's DNA, so that the gene is moved to an area where it can be actively expressed. We have uncovered a novel mechanism whereby the spatial organization of a host organism is interfered with by a pathogen. This type of control is probably found in other host-pathogen relationships.

Epigenetic control of gene function in schistosomes: a source of therapeutic targets?

The discovery of the epigenetic regulation of gene expression has revolutionized both our understanding of how genomes function and approaches to the therapy of numerous pathologies. Schistosomes are metazoan parasites and as such utilize most, if not all the epigenetic mechanisms in play in their vertebrate hosts: histone variants, histone tail modifications, non-coding RNA and, perhaps, DNA methylation. Moreover, we are acquiring an increasing understanding of the ways in which these mechanisms come into play during the complex schistosome developmental program. In turn, interest in the actors involved in epigenetic mechanisms, particularly the enzymes that carry out epigenetic modifications of histones or nucleic acid, as therapeutic targets has been stimulated by the finding that their inhibitors exert profound effects, not only on survival, but also on the reproductive function of Schistosoma mansoni. Here, we review our current knowledge, and what we can infer, about the role of epigenetic mechanisms in schistosome development, differentiation and survival. We will consider which epigenetic actors can be targeted for drug discovery and what strategies can be employed to develop potent, selective inhibitors as drugs to cure schistosomiasis.

No more non-model species: the promise of next generation sequencing for comparative immunology

Next generation sequencing (NGS) allows for the rapid, comprehensive and cost effective analysis of entire genomes and transcriptomes. NGS provides approaches for immune response gene discovery, profiling gene expression over the course of parasitosis, studying mechanisms of diversification of immune receptors and investigating the role of epigenetic mechanisms in regulating immune gene expression and/or diversification. NGS will allow meaningful comparisons to be made between organisms from different taxa in an effort to understand the selection of diverse strategies for host defence under different environmental pathogen pressures. At the same time, it will reveal the shared and unique components of the immunological toolkit and basic functional aspects that are essential for immune defence throughout the living world. In this review, we argue that NGS will revolutionize our understanding of immune responses throughout the animal kingdom because the depth of information it provides will circumvent the need to concentrate on a few "model" species.

Elucidating the molecular bases of epigenetic inheritance in non-model invertebrates: the case of the root-knot nematode Meloidogyne incognita

Root-knot nematodes of the genus Meloidogyne are biotrophic plant parasites that exhibit different life cycles and reproduction modes, ranging from classical amphimixis to obligatory mitotic parthenogenesis (apomixis), depending on the species. Meloidogyne incognita, an apomictic species, exhibits a worldwide distribution and a wide host range affecting more than 3000 plant species. Furthermore, evidences suggest that apomixis does not prevent M. incognita from adapting to its environment in contrast to what is expected from mitotic parthenogenesis that should theoretically produce clonal progenies. This raises questions about mechanisms of genome plasticity leading to genetic variation and adaptive evolution in apomictic animals. We reasoned that epigenetic mechanisms might in part be responsible for the generation of phenotypic variants that provide potential for rapid adaptation. We established therefore a pipeline to investigate the principal carriers of epigenetic information, DNA methylation and post-translational histone modifications. Even if M. incognita possesses the epigenetic machinery i.e., chromatin modifying enzymes, 5-methyl-cytosine and 5-hydroxy-methyl-cytosine content is absent or very weak. In contrast, we demonstrated that the canonical histone modifications are present and chromatin shows typical nucleosome structure. This work is the first characterization of carriers of epigenetic information in M. incognita and constitutes a preamble to further investigate if M. incognita development and its adaptation to plant hosts are under epigenetic control. Our pipeline should allow performing similar types of studies in any non-model organism.