The role of mucins in host-parasite interactions. Part I-protozoan parasites

Parasite-derived mucin-like molecules might be involved in parasite attachment to and invasion of host cells. In addition, parasites might secrete mucin-degrading enzymes, enabling the penetration of protective mucus gels that overlie the mucosal surfaces of their potential hosts. Furthermore, they might generate binding ligands on the membrane-bound mucins of host cells by using specific glycosidases. It is possible that host mucins and mucin-like molecules prevent the establishment of parasites or facilitate parasite expulsion. They might also serve as a source of metabolic energy and adhesion ligands for those parasites adapted to exploit them. Sally Hicks and colleagues here review the biochemical properties of mucins and mucin-like molecules in relation to interactions (established and putative) between protozoan parasites and their hosts.     

The role of mucins in host-parasite interactions: Part II - helminth parasites

Some parasites express mucin-like molecules. These have possible roles in attachment and invasion of host cells and in the avoidance of host immune processes. Enzymes of parasite origin might also facilitate infection, either by degrading host mucus barriers or by generating binding sites on host cells. Host mucins have roles in preventing parasite establishment or in parasite expulsion. They, in turn, might be exploited by parasites, either as sources of fuel or binding sites, or as host-finding targets. Here, we describe the biochemical properties of mucins and mucin-like molecules in relation to interactions (established and putative) between helminth parasites and their hosts.     

Micro-autoradiographic studies on host-parasite interactions

Tritium labeled uredospores of Uromyces phaseoli were produced be feeding the host, Phaseolus vulgaris, with ³H-orotic acid. These spores were allowed to germinate on and to penetrate into a bean leaf. 24 hrs after inoculation, the bean rust had formed the first haustorium. All fungal structures, including the fungus walls, were heavily labeled. No label could be detected in the cells that had come into contact with the hyphae. In the infected host cell, the haustorium was labeled heavily, but the sheath around the haustorium and the host cell remained free of label. These results indicate that no detectable amounts of label leach from the bean rust into the host at this stage of infection although it is known that the rust takes up many metabolites. Since the sheath remains free of label and all fungal structures are evenly labeled, it is concluded that the sheath is formed by the host.     

Variability and its implications for host-parasite interactions

Variability in host-parasite interactions has considerable impact on the ecology and evolution of parasites and on the epidemiology of disease. The nature of the impact depends largely on the level of ecological organization where variability occurs: variability of parasites within their individual hosts, variability of host individuals within populations, or variability of hosts and parasites among populations. In this review, Paul Schmid-Hempel and Jacob Koella give some examples of variability at each of these levels, with particular emphasis on microparasites (defined broadly as viruses, bacteria and protozoa), consider the maintenance of the variability, and describe the implications of variability for the epidemiology of disease and the ecology of host parasite associations. In particular, they describe how variability at each level of ecological organization can affect the perception of AIDS and the evolution of virulence.     

Helminth C-type lectins and host-parasite interactions

C-type lectins (C-TLs) are a family of carbohydrate-binding proteins intimately involved in diverse processes including vertebrate immune cell signalling and trafficking, activation of innate immunity in both vertebrates and invertebrates, and venom-induced haemostasis. Helminth C-TLs sharing sequence and structural similarity with mammalian immune cell lectins have recently been identified from nematode parasites, suggesting clear roles for these proteins at the host-parasite interface, notably in immune evasion. Here, Alex Loukas and Rick Maizels review the status of helminth lectin research and suggest ways in which parasitic worms might utilize C-TLs during their life history.     

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.     

Laboratory models for research in vivo and in vitro on malaria parasites of mammals: Current status

In research aimed at developing strategies for the eradication of human malaria, various species of rodent, avian and non-human primate plasmodia are used as laboratory models. Here Barend Mons and Robert Sinden attempt to summarize the most common laboratory models for mammalian malaria, and to shed some light on their applicability to different aspects of malaria research.     

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.     

Building consensus in neuromesodermal research: Current advances and future biomedical perspectives

The development of the vertebrate body axis relies on the activity of different populations of axial progenitors, including neuromesodermal progenitors. Currently, the term ‘Neuromesodermal progenitors’ is associated with various definitions. Here, we use distinct terminologies to highlight advances in our understanding of this cell type at both the single-cell and population levels. We discuss how these recent insights prompt new opportunities to address a range of biomedical questions spanning cancer metastasis, congenital disorders, cellular metabolism, regenerative medicine, and evolution. Finally, we outline some of the major unanswered questions and propose future directions at the forefront of neuromesodermal research.     

A host-parasite list of the protozoan and helminth parasites of New Guinea animals

Ewers W. H. 1973. A host-parasite list of the protozoan and helminth parasites of New Guinea animals. International Journal for Parasitology, 3: 89–110. This paper provides a hostparasite list for protozoan and helminth parasites recorded from native animals of New Guinea. The synonomy of both hosts and parasites are given together with references to the literature of each species of parasite.     

Ethics and biomedical research

Ethics in biomedical research took off from the 1947 Nuremberg Code to its own right in the wake of the Declaration of Helsinki in 1964. Since then, (inter)national regulations and guidelines providing a framework for clinical studies and protection for study participants have been drafted and implemented, while ethics committees and drug evaluation agencies have sprung up throughout the world. These two developments were crucial in bringing about the protection of rights and safety of the participants and harmonization of the conduct of biomedical research. Ethics committees and drug evaluation agencies deliver ethical and scientific assessments on the quality and safety of the projects submitted to them and issue respectively approvals and authorizations to carry out clinical trials, while ensuring that they comply with regulatory requirements, ethical principles, and scientific guidelines. The advent of biomedical ethics, together with the responsible commitment of clinical investigators and of the pharmaceutical industry, has guaranteed respect for the patient, for whom and with whom research is conducted. Just as importantly, it has also ensured that patients reap the benefit of what is the primary objective of biomedical research: greater life expectancy, well-being, and quality of life.     

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.     

高阶相互作用对宿主-寄生群落动态的影响

物种间相互作用是影响生物群落稳定性和多样性的重要因素。基于Lotka-Volterra竞争模型,通过构建多宿主种群的种内和种间高阶相互作用模型,研究宿主种群的间接竞争效应对寄生群落动态的影响机制。为有效地揭示高阶作用对种群动态的影响,通过对比宿主-寄生群落的现象模型以及机制模型,利用机制模型产生的合理数据集对现象模型中高阶项的参数进行拟合,进而探讨了高阶相互作用在群落动态中的作用。结果显示,完整的高阶相互作用模型在描述多宿主-寄生系统的群落动态中表现最优,而直接相互作用模型对群落动态的描述相对较差,即同时考虑种间和种内的高阶相互作用模型更加符合机制模型所描述的群落动态。此外,种内高阶作用和种间高阶作用产生不对称效应,宿主间的种间高阶作用对群落产生的影响较种内高阶作用更为显著。该研究结果在一定意义上丰富了宿主-寄生生物群落的稳定性研究,为理解物种间相互作用的多样性研究提供了依据。