New technologies to study helminth development and host-parasite interactions

How parasites develop and survive, and how they stimulate or modulate host immune responses are important in understanding disease pathology and for the design of new control strategies. Microarray analysis and bulk RNA sequencing have provided a wealth of data on gene expression as parasites develop through different life-cycle stages and on host cell responses to infection. These techniques have enabled gene expression in the whole organism or host tissue to be detailed, but do not take account of the heterogeneity between cells of different types or developmental stages, nor the spatial organisation of these cells. Single-cell RNA-seq (scRNA-seq) adds a new dimension to studying parasite biology and host immunity by enabling gene profiling at the individual cell level. Here we review the application of scRNA-seq to establish gene expression cell atlases for multicellular helminths and to explore the expansion and molecular profile of individual host cell types involved in parasite immunity and tissue repair. Studying host-parasite interactions in vivo is challenging and we conclude this review by briefly discussing the applications of organoids (stem-cell derived mini-tissues) to examine host-parasite interactions at the local level, and as a potential system to study parasite development in vitro. Organoid technology and its applications have developed rapidly, and the elegant studies performed to date support the use of organoids as an alternative in vitro system for research on helminth parasites.     

Diversity in parasitic helminths of Australasian marsupials and monotremes: a molecular perspective

Marsupials and monotremes are a prominent part of the mammalian fauna in Australia, and harbour an extremely diverse and highly distinctive array of helminth parasites. Their study has been relatively neglected, likely because they have no direct, adverse socioeconomic impact. As the body plans of helminths generally are very simple and morphological characterisation likely underestimates true diversity, molecular tools have been employed to assess genetic diversity. Using biochemical and/or molecular methods, recent studies show extensive diversity in helminths of marsupials, with cryptic species being commonly encountered. The purpose of this article is to review current knowledge about the diversity of parasitic helminths of marsupials and monotremes, to raise questions as to whether current molecular data can be used to estimate diversity, what mechanisms lead to such diversity, to critically appraise the molecular tools that have been employed thus far to explore diversity and to discuss the directions which might be taken in the future employing improved techniques.     

A host-independent role for Fasciola hepatica transforming growth factor-like molecule in parasite development

The trematode parasite Fasciola hepatica causes chronic infection in hosts, enabled by an immunosuppressed environment. Both host and parasite factors are known to contribute to this suggesting that avoidance of immunopathology is beneficial to both parties. We have previously characterised a parasite transforming growth factor (TGF)-like molecule, FhTLM, that interacts with host macrophages to prevent antibody-dependent cell cytotoxicity (ADCC). FhTLM is one of many described helminth TGF homologues and multiple helminths are now known to utilise host immune responses as developmental cues. To test whether, or how, F. hepatica uses FhTLM to manipulate host immunity, we initially examined its effects on the CD4 T-cell phenotype. Despite inducing IL-10, there was no induction of FoxP3 within the CD4 T-cell compartment. In addition to inducing IL-10, a wide range of chemokines were elicited from both CD4 T-cells and macrophages. However, no growth or survival advantage was conferred on F. hepatica in our co-culture system when CD4 T-cells, macrophages, or eosinophils were tested. Finally, using RNA interference we were able to verify a host-independent role for FhTLM in parasite growth. Despite the similarities of FhTLM with other described helminth TGF homologues, here we demonstrate species-specific divergence.     

Molecular crosstalk in host-parasite relationships: schistosome- and leech-host interactions

The host-parasite relationship is based on subtle interplay between parasite survival strategies and host defense mechanisms. In this context, parasites often use the same or similar immune signaling molecules and/or molecular mimicry to escape host immunosurveillance. Both processes represent an adaptive strategy to ensure host immunocompatibility. This bidirectional communication between parasites and their hosts includes the renin-angiotensin, opioid and opiate systems. Here, Michel Salzet, André Capron and George Stefano review recent work on the interaction of common signaling mechanisms in schistosomes, leeches and their host.     

Growth factors in skeletal muscle regeneration

Adult skeletal muscles are able to regenerate after injury. This process is due to the activation of quiescent muscle precursor cells, also called satellite cells, which proliferate and differentiate to form new myotubes. In this regeneration process, several growth factors which come from the muscle and/or from the motor nerve and inflammatory cells have been shown to play key roles. However, most of our knowledge comes from in vitro studies, where, during myogenesis, proliferation of satellite cells is regulated by FGFs, TGFβs, PDGF, IGF-I and II, while differentiation appears to be promoted mainly by IGFs. During regeneration in vivo, most of these factors have been shown to operate and interact. Other factors also appear to condition the regeneration process, such as LIF, which acts predominantly as a proliferative factor; and HARP/PTN/HB-GAM and other neurotrophic factors, which may be necessary for the formation of new neuromuscular junctions. TGFβ has a major influence on the reorganisation of the extracellular matrix. This review presents a critical summary of the known effects of growth factors on skeletal muscle regeneration.     

Transforming growth factor-beta and insulin-like signalling pathways in parasitic helminths

The signal transduction pathways involved in regulating developmental arrest in the free-living nematode, Caenorhabditis elegans, are fairly well characterised. However, much less is known about how these processes may influence the developmental timing and maturation in helminth parasites. Here, we provide an overview of two signalling pathways implicated in the regulation of dauer larva formation in C. elegans, the insulin-like signalling pathway and the transforming growth factor-beta pathway, and explore what is known about these signalling pathways in a variety of parasitic helminths. Understanding the differences about how these pathways are affected by environmental cues in free-living versus parasitic species of helminths may provide insights into novel mechanisms for the control or prevention of helminth-induced disease.     

Growth factor receptors in helminth parasites: signalling and host-parasite relationships

Parasitic helminths remain major pathogens of both humans and animals throughout the world. The success of helminth infections depends on the capacity of the parasite to counteract host immune responses but also to exploit host-derived signal molecules for its development. Recent progress has been made in the characterization of growth factor receptors of various nematode and flatworm parasites with the demonstration that transforming growth factor beta (TGF-beta), epidermal growth factor (EGF) and insulin receptor signalling pathways are conserved in helminth parasites and potentially implicated in the host-parasite molecular dialogue and parasite development.     

Relationship between diet and helminths in Gallotia caesaris (Sauria: Lacertidae)

Diet and helminth fauna were analysed in Gallotia caesaris, a small lacertid lizard endemic to El Hierro (Canary Islands, Spain) in order to study the evolutionary and functional relationships between the two traits. This species is omnivorous but consumed a high proportion (82.13%) of plant matter including not only seeds but also leaves and other vegetative parts. Helminth fauna included many helminth species typical of herbivorous reptiles. Both herbivory and helminth presence were higher than expected for a lizard of its size. Comparison with other lacertids suggests that both traits result from an adaptation to insular conditions but that some "evolutionary time" to develop them is needed. Canarian Gallotia lizards, a separate lineage evolving for a long time in insularity, constitutes the most advanced lacertid group in this way. Nevertheless, results for G. caesaris indicate that helminth fauna also changes seasonally tracking variation in diet (and herbivory) throughout the year, which suggests a dynamic interaction between diet and helminth parasites.     

Acute and subacute toxicity of chemotactic conjugates between monoclonal antibody and fMet-Leu-Phe in humans: A phase I clinical trial

Summary Conjugates of the chemotactic peptide fMet-Leu-Phe (fMLP) to IgG retain chemotactic and antigen recognition function in vitro and enhance intra-tumour macrophage numbers in a guinea pig model. We report a study approved by the ethics committee on the acute toxicity of fMLP conjugates in ten consenting cancer patients with metastasizing melanoma and colon cancer. They were given increasing single doses (1–2500 µg) IgG-fMLP made with the anti-melanoma monoclonal antibody (mAb) 9.2.27. Clinical examinations and blood cell counts, urinalysis, electrolytes, and liver and kidney function tests before and after the infusion and weekly thereafter revealed no relevant toxicities. One patient had a herpes zooster exacerbation on day 1, which was judged to be coincidental. Peak post-infusion conjugate serum concentrations fell to unmeasurable levels within a few days. In no case was a human humoral anti-(mouse Ig) immune response detected.This work was supported by grant FOR.254.AK.83 of the Swiss Cancer League.     

VEGF and PlGF: two pleiotropic growth factors with distinct roles in development and homeostasis

Blood vessels are crucial for normal development and growth by providing oxygen and nutrients. As shown by genetic targeting studies in mice, zebrafish and Xenopus blood vessel formation (or angiogenesis) is a multistep process, which is highly dependent on angiogenic growth factors such as VEGF, the founding member of the VEGF family. VEGF binds to the tyrosine kinase receptors VEGFR-1 and VEGFR-2, and loss of VEGF or its receptors results in abnormal angiogenesis and lethality during development. In contrast, PlGF, another member of this family, binds only to VEGFR-1, and appears to be crucial exclusively for pathological angiogenesis in the adult. However, the expression of VEGFR-1 and VEGFR-2 on non-vascular cells suggests additional biological properties for these growth factors. Indeed, the VEGF family and its receptors determine development and homeostasis of many organs, including the respiratory, skeletal, hematopoietic, nervous, renal and reproductive system, independent of their vascular role. These new insights broaden the activity spectrum of these "angiogenic" growth factors, and may have therapeutic implications when using these growth factors for vascular and/or non-vascular purposes.     

Longevity costs of same‐sex interactions: first evidence from a parasitic wasp

Costs of sexual interactions play a key role in life‐history evolution. Although the costs of reproduction have been investigated in both sexes of many insects, the costs of same‐sex interactions have been examined in few species. In parasitic wasps, very little has been reported about the longevity costs of heterosexual interactions, and nothing is known about longevity costs of same‐sex interactions. In this study, the effects of heterosexual and homosexual activities on longevity were evaluated in Psyttalia concolor (Hymenoptera: Braconidae), a synovigenic koinobiont larval‐pupal endoparasitoid of tephritid flies. When compared with individually housed virgin wasps, male longevity was strongly reduced both in males kept with females, and in males kept with other males. When females were kept with males, their longevity was reduced compared with the virgin females and females kept with other females. Overall, the costs of male–female interactions were considerable in both sexes of P. concolor, while same‐sex activities were found to be costly only among males, suggesting that they may have implications for the evolution of the P. concolor mating system.     

Synergistic roles of BMP15 and GDF9 in the development and function of the oocyte-cumulus cell complex in mice: genetic evidence for an oocyte-granulosa cell regulatory loop

Bone morphogenetic protein 15 (BMP15) and growth differentiation factor 9 (GDF9) are oocyte-specific growth factors that appear to play key roles in granulosa cell development and fertility in most mammalian species. We have evaluated the role(s) of these paracrine factors in the development and function of both the cumulus cells and oocytes by assessing cumulus expansion, oocyte maturation, fertilization, and preimplantation embryogenesis in Gdf9+/-Bmp15-/- [hereafter, double mutant (DM)] mice. We found that cumulus expansion, as well as the expression of hyaluronon synthase 2 (Has2) mRNA was impaired in DM oocyte-cumulus cell complexes. This aberrant cumulus expansion was not remedied by coculture with normal wild-type (WT) oocytes, indicating that the development and/or differentiation of cumulus cells in the DM, up to the stage of the preovulatory luteinizing hormone (LH) surge, is impaired. In addition, DM oocytes failed to enable FSH to induce cumulus expansion in WT oocytectomized (OOX) cumulus. Moreover, LH-induced oocyte meiotic resumption was significantly delayed in vivo, and this delayed resumption of meiosis was correlated with the reduced activation of mitogen-activated protein kinase (MAPK) in the cumulus cells, thus suggesting that GDF9 and BMP15 also regulate the function of cumulus cells after the preovulatory LH surge. Although spontaneous in vitro oocyte maturation occurred normally, oocyte fertilization and preimplantation embryogenesis were significantly altered in the DM, suggesting that the full complement of both GDF9 and BMP15 are essential for the development and function of oocytes. Because receptors for GDF9 and BMP15 have not yet been identified in mouse oocytes, the effects of the mutations in the Bmp15 and Gdf9 genes on oocyte development and functions must be produced indirectly by first affecting the granulosa cells and then the oocyte. Therefore, this study provides further evidence for the existence and functioning of an oocyte-granulosa cell regulatory loop.     

生长因子及其受体在淋巴瘤中异常表达的研究进展

生长因子是一类与受体结合后可以促进细胞增殖和调节细胞多项功能的多肽分子。生长因子及其受体信号通路包括Ras/MAPK、PI3K/AKT和STAT等不仅调控正常细胞的生物学行为,对恶性肿瘤细胞增殖、分化、转化和迁移也具有重要意义。研究发现多种生长因子如VEGF、PDGF和IGF及其受体在多种实体肿瘤如肺癌、乳腺癌、结肠癌中发现有异常表达,在淋巴瘤如DLBCL、PTCL、ML和NL中也存在异常的共同表达,提示在淋巴瘤中可能构成生长因子及其受体的自分泌/旁分泌环路。生长因子及其受体的表达对淋巴瘤患者的预后有一定指导意义,临床研究发现表达生长因子或其受体阳性患者比表达阴性患者有较差的临床预后。这可能与生长因子及其受体对淋巴瘤细胞的增殖、转移和耐药调控有关。目前生长因子及其受体已成为潜在的药物靶点,多种生长因子及其受体抑制剂在开发和临床试验中。本文就近年来生长因子及其受体在淋巴瘤中异常表达研究进展作简要综述。     

Peptidyl-prolyl cis-trans isomerases (immunophilins) and their roles in parasite biochemistry, host-parasite interaction and antiparasitic drug action

Immunophilin is the collective name given to the cyclophilin and FK506-binding protein families. As the name suggests, these include the major binding proteins of certain immunosuppressive drugs: cyclophilins for the cyclic peptide cyclosporin A and FK506-binding proteins for the macrolactones FK506 and rapamycin. Both families, although dissimilar in sequence, possess peptidyl-prolyl cis-trans isomerase activity in vitro and can play roles in protein folding and transport, RNA splicing and the regulation of multi-protein complexes in cells. In addition to enzymic activity, many immunophilins act as molecular chaperones. This property may be conferred by the isomerase domain and/or by additional domains. Recent years have seen a great increase in the number of known immunophilin genes in parasitic protozoa and helminths and in many cases their products have been characterised biochemically and their temporal and spatial expression patterns have been examined. Some of these genes represent novel types: one example is a Toxoplasma gondii gene encoding a protein with both cyclophilin and FK506-binding protein domains. Likely roles in protein folding and oligomerisation, RNA splicing and sexual differentiation have been suggested for parasite immunophilins. In addition, unexpected roles in parasite virulence (Mip FK506-binding protein of Trypanosoma cruzi) and host immuno-modulation (e.g. 18-kDa cyclophilin of T. gondii) have been established. Furthermore, in view of the potent antiparasitic activities of cyclosporins, macrolactones and non-immunosuppressive derivatives of these compounds, immunophilins may mediate drug action and/or may themselves represent potential drug targets. Investigation of the mechanisms of action of these agents may lead to the design of potent and selective antimalarial and other antiparasitic drugs. This review discusses the properties of immunophilins in parasites and the 'animal model'Caenorhabditis elegans and relates these to our understanding of the roles of these proteins in cellular biochemistry, host-parasite interaction and the antiparasitic mechanisms of the drugs that bind to them.     

Neuroblastoma Growth Factors Derived from Neurofibroma (NF1): Participation of Uridine in a Neuroblastoma Growth

Abstract: Human glioma cell extracts were found to elicit a marked growth-promoting activity on human neuroblastoma cells. This activity was also detected in the extracts of neurofibroma type 1 (NF1; von Recklinghausen neurofibromatosis) comprising aberrant Schwann cell growth. The purified substance from the NF1 extracts by HPLC on ODS columns was identical to a pyrimidine nucleoside, uridine, the chemical structure of which was identified by gas chromatography-mass spectrometry. The authentic uridine showed a strong growth-promoting activity on human neuroblastoma cells. Other purine or pyrimidine nucleotides, their derivatives, and ribose sources for their syntheses were employed to test the activity; a purine nucleoside, adenosine, showed a stronger activity than uridine. The current study raises the possibility that human neuroblastoma cells may be affected by dysfunctions of the de novo pathway of both purine and pyrimidine nucleotide biosyntheses.     

Molecular biology of reproduction and development in parasitic nematodes: progress and opportunities

Molecular biological research on the development and reproduction of parasites is of major significance for many fundamental and applied areas of medical and veterinary parasitology. Together with knowledge of parasite biology and epidemiology, the application of molecular tools and technologies provides unique opportunities for elucidating developmental and reproductive processes in helminths. This article focuses specifically on recent progress in studying the molecular mechanisms of development, sexual differentiation and reproduction in parasitic nematodes of socio-economic importance and comparative analyses, where appropriate, with the free-living nematode Caenorhabditis elegans. It also describes the implications of such work for understanding reproduction, tissue migration, hypobiosis, signal transduction and host-parasite interactions at the molecular level, and for seeking new means of parasite intervention.