1
|
Tenaglia AH, Luján LA, Ríos DN, Molina CR, Midlej V, Iribarren PA, Berazategui MA, Torri A, Saura A, Peralta DO, Rodríguez-Walker M, Fernández EA, Petiti JP, Serradell MC, Gargantini PR, Sparwasser T, Alvarez VE, de Souza W, Luján HD. Antibodies to variable surface antigens induce antigenic variation in the intestinal parasite Giardia lamblia. Nat Commun 2023; 14:2537. [PMID: 37137944 PMCID: PMC10156722 DOI: 10.1038/s41467-023-38317-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2023] [Accepted: 04/25/2023] [Indexed: 05/05/2023] Open
Abstract
The genomes of most protozoa encode families of variant surface antigens. In some parasitic microorganisms, it has been demonstrated that mutually exclusive changes in the expression of these antigens allow parasites to evade the host's immune response. It is widely assumed that antigenic variation in protozoan parasites is accomplished by the spontaneous appearance within the population of cells expressing antigenic variants that escape antibody-mediated cytotoxicity. Here we show, both in vitro and in animal infections, that antibodies to Variant-specific Surface Proteins (VSPs) of the intestinal parasite Giardia lamblia are not cytotoxic, inducing instead VSP clustering into liquid-ordered phase membrane microdomains that trigger a massive release of microvesicles carrying the original VSP and switch in expression to different VSPs by a calcium-dependent mechanism. This novel mechanism of surface antigen clearance throughout its release into microvesicles coupled to the stochastic induction of new phenotypic variants not only changes current paradigms of antigenic switching but also provides a new framework for understanding the course of protozoan infections as a host/parasite adaptive process.
Collapse
Affiliation(s)
- Albano H Tenaglia
- Centro de Investigación y Desarrollo en Inmunología y Enfermedades Infecciosas (CIDIE), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)/Universidad Católica de Córdoba (UCC), X5016HDK, Córdoba, Argentina
- Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC), CONICET, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Lucas A Luján
- Centro de Investigación y Desarrollo en Inmunología y Enfermedades Infecciosas (CIDIE), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)/Universidad Católica de Córdoba (UCC), X5016HDK, Córdoba, Argentina
| | - Diego N Ríos
- Centro de Investigación y Desarrollo en Inmunología y Enfermedades Infecciosas (CIDIE), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)/Universidad Católica de Córdoba (UCC), X5016HDK, Córdoba, Argentina
- Clínica Universitaria Reina Fabiola, Universidad Católica de Córdoba, Córdoba, Argentina
| | - Cecilia R Molina
- Centro de Investigación y Desarrollo en Inmunología y Enfermedades Infecciosas (CIDIE), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)/Universidad Católica de Córdoba (UCC), X5016HDK, Córdoba, Argentina
| | - Victor Midlej
- Instituto de Biofísica Carlos Chagas Filho and Centro Nacional de Biologia Estrutural e Bioimagem (CENABIO), Universidade Federal do Rio de Janeiro (UFRJ), 21941-170, Rio de Janeiro, Brazil
- Instituto Oswaldo Cruz, Fundação Oswaldo Cruz (FIOCRUZ), 21040-900, Rio de Janeiro, Brazil
| | - Paula A Iribarren
- Instituto de Investigaciones Biotecnológicas (IIBIO), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)/Universidad Nacional de General San Martín (UNSAM), B1650HMP, Buenos Aires, Argentina
| | - María A Berazategui
- Instituto de Investigaciones Biotecnológicas (IIBIO), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)/Universidad Nacional de General San Martín (UNSAM), B1650HMP, Buenos Aires, Argentina
- Department of Life Sciences, Sir Alexander Fleming Building, Imperial College London, London, UK
| | - Alessandro Torri
- Centro de Investigación y Desarrollo en Inmunología y Enfermedades Infecciosas (CIDIE), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)/Universidad Católica de Córdoba (UCC), X5016HDK, Córdoba, Argentina
- Viruses and RNA Interference Unit, CNRS Unité Mixte de Recherche, Institut Pasteur, Paris, France
| | - Alicia Saura
- Centro de Investigación y Desarrollo en Inmunología y Enfermedades Infecciosas (CIDIE), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)/Universidad Católica de Córdoba (UCC), X5016HDK, Córdoba, Argentina
- Cátedra de Química Biológica, Facultad de Ciencias de la Salud, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Damián O Peralta
- Centro de Investigación y Desarrollo en Inmunología y Enfermedades Infecciosas (CIDIE), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)/Universidad Católica de Córdoba (UCC), X5016HDK, Córdoba, Argentina
| | - Macarena Rodríguez-Walker
- Centro de Investigación y Desarrollo en Inmunología y Enfermedades Infecciosas (CIDIE), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)/Universidad Católica de Córdoba (UCC), X5016HDK, Córdoba, Argentina
| | - Elmer A Fernández
- Centro de Investigación y Desarrollo en Inmunología y Enfermedades Infecciosas (CIDIE), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)/Universidad Católica de Córdoba (UCC), X5016HDK, Córdoba, Argentina
- Fundación para el progreso de la Medicina, Córdoba, Argentina
| | - Juan P Petiti
- Instituto de Investigaciones en Ciencias de la Salud (INICSA), Centro de Microscopía Electrónica, Facultad de Ciencias Médicas. CONICET/Universidad Nacional de Córdoba, X5016HUA, Córdoba, Argentina
| | - Marianela C Serradell
- Centro de Investigación y Desarrollo en Inmunología y Enfermedades Infecciosas (CIDIE), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)/Universidad Católica de Córdoba (UCC), X5016HDK, Córdoba, Argentina
- Laboratorio de Parasitología y Micología, Departamento de Bioquímica Clínica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, X5016HUA, Córdoba, Argentina
| | - Pablo R Gargantini
- Centro de Investigación y Desarrollo en Inmunología y Enfermedades Infecciosas (CIDIE), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)/Universidad Católica de Córdoba (UCC), X5016HDK, Córdoba, Argentina
| | - Tim Sparwasser
- Institute of Medical Microbiology and Hygiene, University Medical Center of the Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Vanina E Alvarez
- Instituto de Investigaciones Biotecnológicas (IIBIO), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)/Universidad Nacional de General San Martín (UNSAM), B1650HMP, Buenos Aires, Argentina
| | - Wanderley de Souza
- Instituto de Biofísica Carlos Chagas Filho and Centro Nacional de Biologia Estrutural e Bioimagem (CENABIO), Universidade Federal do Rio de Janeiro (UFRJ), 21941-170, Rio de Janeiro, Brazil
| | - Hugo D Luján
- Centro de Investigación y Desarrollo en Inmunología y Enfermedades Infecciosas (CIDIE), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)/Universidad Católica de Córdoba (UCC), X5016HDK, Córdoba, Argentina.
| |
Collapse
|
2
|
Van Houten J. A Review for the Special Issue on Paramecium as a Modern Model Organism. Microorganisms 2023; 11:microorganisms11040937. [PMID: 37110360 PMCID: PMC10143506 DOI: 10.3390/microorganisms11040937] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Revised: 03/28/2023] [Accepted: 03/29/2023] [Indexed: 04/07/2023] Open
Abstract
This review provides background and perspective for the articles contributing to the Special Issue of MDPI Micro-organisms on Paramecium as a Modern Model Organism. The six articles cover a variety of topics, each taking advantage of an important aspect of Paramecium biology: peripheral surface proteins that are developmentally regulated, endosymbiont algae and bacteria, ion channel regulation by calmodulin, regulation of cell mating reactivity and senescence, and the introns that dwell in the large genome. Each article highlights a significant aspect of Paramecium and its versatility.
Collapse
Affiliation(s)
- Judith Van Houten
- Department of Biology, University of Vermont, Burlington, VT 05405, USA
| |
Collapse
|
3
|
Pirritano M, Yakovleva Y, Potekhin A, Simon M. Species-Specific Duplication of Surface Antigen Genes in Paramecium. Microorganisms 2022; 10:microorganisms10122378. [PMID: 36557632 PMCID: PMC9788069 DOI: 10.3390/microorganisms10122378] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2022] [Revised: 11/21/2022] [Accepted: 11/22/2022] [Indexed: 12/05/2022] Open
Abstract
Paramecium is a free-living ciliate that undergoes antigenic variation and still the functions of these variable surface antigen coats in this non-pathogenic ciliate remain elusive. Only a few surface antigen genes have been described, mainly in the two model species P. tetraurelia strain 51 and P. primaurelia strain 156. Given the lack of suitable sequence data to allow for phylogenetics and deeper sequence comparisons, we screened the genomes of six different Paramecium species for serotype genes and isolated 548 candidates. Our approach identified the subfamilies of the isogenes of individual serotypes that were mostly represented by intrachromosomal gene duplicates. These showed different duplication levels, and chromosome synteny suggested rather young duplication events after the emergence of the P. aurelia species complex, indicating a rapid evolution of surface antigen genes. We were able to identify the different subfamilies of the surface antigen genes with internal tandem repeats, which showed consensus motifs across species. The individual isogene families showed additional consensus motifs, indicating that the selection pressure holds individual amino acids constant in these repeats. This may be a hint of the receptor function of these antigens rather than a presentation of random epitopes, generating the variability of these surface molecules.
Collapse
Affiliation(s)
- Marcello Pirritano
- Molecular Cell Biology and Microbiology, School of Mathematics and Natural Sciences, University of Wuppertal, 42119 Wuppertal, Germany
| | - Yulia Yakovleva
- Molecular Cell Biology and Microbiology, School of Mathematics and Natural Sciences, University of Wuppertal, 42119 Wuppertal, Germany
| | - Alexey Potekhin
- Laboratory of Cellular and Molecular Protistology, Zoological Institute of Russian Academy of Sciences, 190121 Saint Petersburg, Russia
- Research Department for Limnology, University of Innsbruck, 5310 Mondsee, Austria
| | - Martin Simon
- Molecular Cell Biology and Microbiology, School of Mathematics and Natural Sciences, University of Wuppertal, 42119 Wuppertal, Germany
- Correspondence:
| |
Collapse
|
4
|
Plattner H. Ciliate Research. From Myth to Trendsetting Science. J Eukaryot Microbiol 2022; 69:e12926. [PMID: 35608570 DOI: 10.1111/jeu.12926] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2022] [Revised: 05/18/2022] [Accepted: 05/18/2022] [Indexed: 11/28/2022]
Abstract
This special issue of the Journal of Eukaryotic Microbiology (JEM) summarizes achievements obtained by generations of researchers with ciliates in widely different disciplines. In fact, ciliates range among the first cells seen under the microscope centuries ago. Their beauty made them an object of scientia amabilis and their manifold reactions made them attractive for college experiments and finally challenged causal analyses at the cellular level. Some of this work was honored by a Nobel Prize. Some observations yielded a baseline for additional novel discoveries, occasionally facilitated by specific properties of some ciliates. This also offers some advantage in the exploration of closely related parasites (malaria). Articles contributed here by colleagues from all over the world encompass a broad spectrum of ciliate life, from genetics to evolution, from molecular cell biology to ecology, from intercellular signaling to epigenetics etc. This introductory chapter, largely based on my personal perception, aims at integrating work presented in this special issue of JEM into a broader historical context up to current research.
Collapse
|
5
|
Karunanithi S, Oruganti V, Marker S, Rodriguez-Viana AM, Drews F, Pirritano M, Nordström K, Simon M, Schulz MH. Exogenous RNAi mechanisms contribute to transcriptome adaptation by phased siRNA clusters in Paramecium. Nucleic Acids Res 2019; 47:8036-8049. [PMID: 31251800 PMCID: PMC6735861 DOI: 10.1093/nar/gkz553] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2018] [Revised: 06/06/2019] [Accepted: 06/19/2019] [Indexed: 01/26/2023] Open
Abstract
Extensive research has characterized distinct exogenous RNAi pathways interfering in gene expression during vegetative growth of the unicellular model ciliate Paramecium. However, role of RNAi in endogenous transcriptome regulation, and environmental adaptation is unknown. Here, we describe the first genome-wide profiling of endogenous sRNAs in context of different transcriptomic states (serotypes). We developed a pipeline to identify, and characterize 2602 siRNA producing clusters (SRCs). Our data show no evidence that SRCs produce miRNAs, and in contrast to other species, no preference for strand specificity of siRNAs. Interestingly, most SRCs overlap coding genes and a separate group show siRNA phasing along the entire open reading frame, suggesting that the mRNA transcript serves as a source for siRNAs. Integrative analysis of siRNA abundance and gene expression levels revealed surprisingly that mRNA and siRNA show negative as well as positive associations. Two RNA-dependent RNA Polymerase mutants, RDR1 and RDR2, show a drastic loss of siRNAs especially in phased SRCs accompanied with increased mRNA levels. Importantly, most SRCs depend on both RDRs, reminiscent to primary siRNAs in the RNAi against exogenous RNA, indicating mechanistic overlaps between exogenous and endogenous RNAi contributing to flexible transcriptome adaptation.
Collapse
Affiliation(s)
- Sivarajan Karunanithi
- Cluster of Excellence, Multimodal Computing and Interaction, Saarland University and Department for Computational Biology and Applied Algorithmics, Max Planck Institute for Informatics, Saarland Informatics Campus, 66123 Saarbrücken, Germany.,Graduate School of Computer Science, Saarland Informatics Campus, 66123 Saarbrücken, Germany.,Institute for Cardiovascular Regeneration, Goethe-University Hospital, 60590 Frankfurt, Germany
| | - Vidya Oruganti
- Cluster of Excellence, Multimodal Computing and Interaction, Saarland University and Department for Computational Biology and Applied Algorithmics, Max Planck Institute for Informatics, Saarland Informatics Campus, 66123 Saarbrücken, Germany
| | - Simone Marker
- Molecular Cell Dynamics, Centre for Human and Molecular Biology, Saarland University, 66123 Saarbrücken, Germany
| | - Angela M Rodriguez-Viana
- Molecular Cell Dynamics, Centre for Human and Molecular Biology, Saarland University, 66123 Saarbrücken, Germany
| | - Franziska Drews
- Molecular Cell Dynamics, Centre for Human and Molecular Biology, Saarland University, 66123 Saarbrücken, Germany.,Molecular Cell Biology and Microbiology, Wuppertal University, 42097 Wuppertal, Germany
| | - Marcello Pirritano
- Molecular Cell Dynamics, Centre for Human and Molecular Biology, Saarland University, 66123 Saarbrücken, Germany.,Molecular Cell Biology and Microbiology, Wuppertal University, 42097 Wuppertal, Germany
| | - Karl Nordström
- Genetics/Epigenetics, Centre for Human and Molecular Biology, Saarland University, 66123 Saarbrücken, Germany
| | - Martin Simon
- Molecular Cell Dynamics, Centre for Human and Molecular Biology, Saarland University, 66123 Saarbrücken, Germany.,Molecular Cell Biology and Microbiology, Wuppertal University, 42097 Wuppertal, Germany
| | - Marcel H Schulz
- Cluster of Excellence, Multimodal Computing and Interaction, Saarland University and Department for Computational Biology and Applied Algorithmics, Max Planck Institute for Informatics, Saarland Informatics Campus, 66123 Saarbrücken, Germany.,Institute for Cardiovascular Regeneration, Goethe-University Hospital, 60590 Frankfurt, Germany
| |
Collapse
|
6
|
Faso C, Hehl AB. A cytonaut's guide to protein trafficking in Giardia lamblia. ADVANCES IN PARASITOLOGY 2019; 106:105-127. [PMID: 31630756 DOI: 10.1016/bs.apar.2019.08.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Over the past years, the subcellular organization of the Excavata member Giardia lamblia (syn. duodenalis, intestinalis) has been investigated in considerable detail. There are several reasons for this endeavour which go beyond this parasite's medical importance and are mostly concerned with its reduced subcellular complexity and debated evolutionary status. One may say that simplification has emerged as a paradigm for the evolution of Giardia's subcellular architecture. However, a complete appreciation of the evolutionary and ecological significance of this phenomenon is far from complete. In this chapter, we present and discuss the most recent data on the main trafficking pathways in G. lamblia which include endo- and exo-cytosis, organellar import and function. We provide perspectives on open questions concerning organelle replication and inheritance and include a technical outlook on methods and approaches to genetic manipulations in G. lamblia. A better understanding of G. lamblia subcellular organization at the morphological and molecular level complements any effort aimed at elucidating this parasitic species' evolutionary status and could provide us with the basis for novel strategies to interfere with parasite transmission and/or pathogenesis.
Collapse
Affiliation(s)
- Carmen Faso
- Laboratory of Molecular Parasitology, Institute of Parasitology, University of Zurich (ZH), Zürich, Switzerland
| | - Adrian B Hehl
- Laboratory of Molecular Parasitology, Institute of Parasitology, University of Zurich (ZH), Zürich, Switzerland.
| |
Collapse
|
7
|
The remembrance of the things past: Conserved signalling pathways link protozoa to mammalian nervous system. Cell Calcium 2018; 73:25-39. [DOI: 10.1016/j.ceca.2018.04.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Revised: 04/01/2018] [Accepted: 04/01/2018] [Indexed: 12/13/2022]
|
8
|
Doerder FP. Barcodes Reveal 48 New Species of Tetrahymena
, Dexiostoma
, and Glaucoma
: Phylogeny, Ecology, and Biogeography of New and Established Species. J Eukaryot Microbiol 2018; 66:182-208. [DOI: 10.1111/jeu.12642] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2018] [Revised: 04/30/2018] [Accepted: 05/21/2018] [Indexed: 11/28/2022]
Affiliation(s)
- F. Paul Doerder
- Department of Biological, Geological and Environmental Sciences; Cleveland State University; 2121 Euclid Avenue Cleveland Ohio 44115
| |
Collapse
|
9
|
Charlesworth D, Barton NH, Charlesworth B. The sources of adaptive variation. Proc Biol Sci 2017; 284:rspb.2016.2864. [PMID: 28566483 DOI: 10.1098/rspb.2016.2864] [Citation(s) in RCA: 102] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2017] [Accepted: 05/04/2017] [Indexed: 12/16/2022] Open
Abstract
The role of natural selection in the evolution of adaptive phenotypes has undergone constant probing by evolutionary biologists, employing both theoretical and empirical approaches. As Darwin noted, natural selection can act together with other processes, including random changes in the frequencies of phenotypic differences that are not under strong selection, and changes in the environment, which may reflect evolutionary changes in the organisms themselves. As understanding of genetics developed after 1900, the new genetic discoveries were incorporated into evolutionary biology. The resulting general principles were summarized by Julian Huxley in his 1942 book Evolution: the modern synthesis Here, we examine how recent advances in genetics, developmental biology and molecular biology, including epigenetics, relate to today's understanding of the evolution of adaptations. We illustrate how careful genetic studies have repeatedly shown that apparently puzzling results in a wide diversity of organisms involve processes that are consistent with neo-Darwinism. They do not support important roles in adaptation for processes such as directed mutation or the inheritance of acquired characters, and therefore no radical revision of our understanding of the mechanism of adaptive evolution is needed.
Collapse
Affiliation(s)
- Deborah Charlesworth
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Charlotte Auerbach Road, Edinburgh EH9 3FL, UK
| | - Nicholas H Barton
- Institute of Science and Technology Austria, Klosterneuburg 3400, Austria
| | - Brian Charlesworth
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Charlotte Auerbach Road, Edinburgh EH9 3FL, UK
| |
Collapse
|
10
|
Plattner H. Evolutionary Cell Biology of Proteins from Protists to Humans and Plants. J Eukaryot Microbiol 2017; 65:255-289. [PMID: 28719054 DOI: 10.1111/jeu.12449] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2017] [Revised: 07/04/2017] [Accepted: 07/07/2017] [Indexed: 01/10/2023]
Abstract
During evolution, the cell as a fine-tuned machine had to undergo permanent adjustments to match changes in its environment, while "closed for repair work" was not possible. Evolution from protists (protozoa and unicellular algae) to multicellular organisms may have occurred in basically two lineages, Unikonta and Bikonta, culminating in mammals and angiosperms (flowering plants), respectively. Unicellular models for unikont evolution are myxamoebae (Dictyostelium) and increasingly also choanoflagellates, whereas for bikonts, ciliates are preferred models. Information accumulating from combined molecular database search and experimental verification allows new insights into evolutionary diversification and maintenance of genes/proteins from protozoa on, eventually with orthologs in bacteria. However, proteins have rarely been followed up systematically for maintenance or change of function or intracellular localization, acquirement of new domains, partial deletion (e.g. of subunits), and refunctionalization, etc. These aspects are discussed in this review, envisaging "evolutionary cell biology." Protozoan heritage is found for most important cellular structures and functions up to humans and flowering plants. Examples discussed include refunctionalization of voltage-dependent Ca2+ channels in cilia and replacement by other types during evolution. Altogether components serving Ca2+ signaling are very flexible throughout evolution, calmodulin being a most conservative example, in contrast to calcineurin whose catalytic subunit is lost in plants, whereas both subunits are maintained up to mammals for complex functions (immune defense and learning). Domain structure of R-type SNAREs differs in mono- and bikonta, as do Ca2+ -dependent protein kinases. Unprecedented selective expansion of the subunit a which connects multimeric base piece and head parts (V0, V1) of H+ -ATPase/pump may well reflect the intriguing vesicle trafficking system in ciliates, specifically in Paramecium. One of the most flexible proteins is centrin when its intracellular localization and function throughout evolution is traced. There are many more examples documenting evolutionary flexibility of translation products depending on requirements and potential for implantation within the actual cellular context at different levels of evolution. From estimates of gene and protein numbers per organism, it appears that much of the basic inventory of protozoan precursors could be transmitted to highest eukaryotic levels, with some losses and also with important additional "inventions."
Collapse
Affiliation(s)
- Helmut Plattner
- Department of Biology, University of Konstanz, P. O. Box M625, Konstanz, 78457, Germany
| |
Collapse
|
11
|
Pilling OA, Rogers AJ, Gulla-Devaney B, Katz LA. Insights into transgenerational epigenetics from studies of ciliates. Eur J Protistol 2017; 61:366-375. [PMID: 28689743 DOI: 10.1016/j.ejop.2017.05.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Revised: 05/06/2017] [Accepted: 05/09/2017] [Indexed: 12/23/2022]
Abstract
Epigenetics, a term with many meanings, can be broadly defined as the study of dynamic states of the genome. Ciliates, a clade of unicellular eukaryotes, can teach us about the intersection of epigenetics and evolution due to the advantages of working with cultivable ciliate lineages, plus their tendency to express extreme phenotypes such as heritable doublet morphology. Moreover, ciliates provide a powerful model for studying epigenetics given the presence of dimorphic nuclei - a somatic macronucleus and germline micronucleus - within each cell. Here, we exemplify the power of studying ciliates to learn about epigenetic phenomena. We highlight "classical" examples from morphology and physiology including cortical inheritance, mating type determination, and serotype expression. In addition, we detail molecular studies of epigenetic phenomena, including: DNA elimination; alternative processing and unscrambling; and copy number determination. Based on the implications of these studies, we discuss epigenetics as a possible functional mechanism for rapid speciation in ciliates.
Collapse
Affiliation(s)
- Olivia A Pilling
- Department of Biological Sciences, Smith College, Northampton, MA 01063, USA
| | - Anna J Rogers
- Department of Biological Sciences, Smith College, Northampton, MA 01063, USA
| | | | - Laura A Katz
- Department of Biological Sciences, Smith College, Northampton, MA 01063, USA; Program in Organismic and Evolutionary Biology, University of Massachusetts, Amherst, MA 01003, USA.
| |
Collapse
|
12
|
Staudt E, Ramasamy P, Plattner H, Simon M. Differential subcellular distribution of four phospholipase C isoforms and secretion of GPI-PLC activity. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:3157-3168. [PMID: 27693913 DOI: 10.1016/j.bbamem.2016.09.022] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Revised: 09/04/2016] [Accepted: 09/27/2016] [Indexed: 12/11/2022]
Abstract
Phospholipase C (PLC) is an important enzyme of signal transduction pathways by generation of second messengers from membrane lipids. PLCs are also indicated to cleave glycosylphosphatidylinositol (GPI)-anchors of surface proteins thus releasing these into the environment. However, it remains unknown whether this enzymatic activity on the surface is due to distinct PLC isoforms in higher eukaryotes. Ciliates have, in contrast to other unicellular eukaryotes, multiple PLC isoforms as mammals do. Thus, Paramecium represents a perfect model to study subcellular distribution and potential surface activity of PLC isoforms. We have identified distinct subcellular localizations of four PLC isoforms indicating functional specialization. The association with different calcium release channels (CRCs) argues for distinct subcellular functions. They may serve as PI-PLCs in microdomains for local second messenger responses rather than free floating IP3. In addition, all isoforms can be found on the cell surface and they are found together with GPI-cleaved surface proteins in salt/ethanol washes of cells. We can moreover show them in medium supernatants of living cells where they have access to GPI-anchored surface proteins. Among the isoforms we cannot assign GPI-PLC activity to specific PLC isoforms; rather each PLC is potentially responsible for the release of GPI-anchored proteins from the surface.
Collapse
Affiliation(s)
- Emanuel Staudt
- Saarland University, Molecular Cell Dynamics, Centre for Human and Molecular Biology, Campus A2 4, 66123 Saarbrücken, Germany; University of Kaiserslautern, Department of Biology, Erwin-Schrödinger Straße, Building Nr. 14, 67663 Kaiserslautern, Germany
| | - Pathmanaban Ramasamy
- Saarland University, Molecular Cell Dynamics, Centre for Human and Molecular Biology, Campus A2 4, 66123 Saarbrücken, Germany
| | - Helmut Plattner
- University of Konstanz, Senior Research Group for Cell Biology and Ultrastructure Research, Department of Biology, 78457 Konstanz, Germany
| | - Martin Simon
- Saarland University, Molecular Cell Dynamics, Centre for Human and Molecular Biology, Campus A2 4, 66123 Saarbrücken, Germany.
| |
Collapse
|
13
|
Plattner H. Signalling in ciliates: long- and short-range signals and molecular determinants for cellular dynamics. Biol Rev Camb Philos Soc 2015; 92:60-107. [PMID: 26487631 DOI: 10.1111/brv.12218] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2015] [Revised: 07/28/2015] [Accepted: 08/21/2015] [Indexed: 12/30/2022]
Abstract
In ciliates, unicellular representatives of the bikont branch of evolution, inter- and intracellular signalling pathways have been analysed mainly in Paramecium tetraurelia, Paramecium multimicronucleatum and Tetrahymena thermophila and in part also in Euplotes raikovi. Electrophysiology of ciliary activity in Paramecium spp. is a most successful example. Established signalling mechanisms include plasmalemmal ion channels, recently established intracellular Ca2+ -release channels, as well as signalling by cyclic nucleotides and Ca2+ . Ca2+ -binding proteins (calmodulin, centrin) and Ca2+ -activated enzymes (kinases, phosphatases) are involved. Many organelles are endowed with specific molecules cooperating in signalling for intracellular transport and targeted delivery. Among them are recently specified soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs), monomeric GTPases, H+ -ATPase/pump, actin, etc. Little specification is available for some key signal transducers including mechanosensitive Ca2+ -channels, exocyst complexes and Ca2+ -sensor proteins for vesicle-vesicle/membrane interactions. The existence of heterotrimeric G-proteins and of G-protein-coupled receptors is still under considerable debate. Serine/threonine kinases dominate by far over tyrosine kinases (some predicted by phosphoproteomic analyses). Besides short-range signalling, long-range signalling also exists, e.g. as firmly installed microtubular transport rails within epigenetically determined patterns, thus facilitating targeted vesicle delivery. By envisaging widely different phenomena of signalling and subcellular dynamics, it will be shown (i) that important pathways of signalling and cellular dynamics are established already in ciliates, (ii) that some mechanisms diverge from higher eukaryotes and (iii) that considerable uncertainties still exist about some essential aspects of signalling.
Collapse
Affiliation(s)
- Helmut Plattner
- Department of Biology, University of Konstanz, PO Box M625, 78457, Konstanz, Germany
| |
Collapse
|
14
|
Cheaib M, Dehghani Amirabad A, Nordström KJV, Schulz MH, Simon M. Epigenetic regulation of serotype expression antagonizes transcriptome dynamics in Paramecium tetraurelia. DNA Res 2015; 22:293-305. [PMID: 26231545 PMCID: PMC4535620 DOI: 10.1093/dnares/dsv014] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2015] [Accepted: 06/28/2015] [Indexed: 12/31/2022] Open
Abstract
Phenotypic variation of a single genotype is achieved by alterations in gene expression patterns. Regulation of such alterations depends on their time scale, where short-time adaptations differ from permanently established gene expression patterns maintained by epigenetic mechanisms. In the ciliate Paramecium, serotypes were described for an epigenetically controlled gene expression pattern of an individual multigene family. Paradoxically, individual serotypes can be triggered in Paramecium by alternating environments but are then stabilized by epigenetic mechanisms, thus raising the question to which extend their expression follows environmental stimuli. To characterize environmental adaptation in the context of epigenetically controlled serotype expression, we used RNA-seq to characterize transcriptomes of serotype pure cultures. The resulting vegetative transcriptome resource is first analysed for genes involved in the adaptive response to the altered environment. Secondly, we identified groups of genes that do not follow the adaptive response but show co-regulation with the epigenetically controlled serotype system, suggesting that their gene expression pattern becomes manifested by similar mechanisms. In our experimental set-up, serotype expression and the entire group of co-regulated genes were stable among environmental changes and only heat-shock genes altered expression of these gene groups. The data suggest that the maintenance of these gene expression patterns in a lineage represents epigenetically controlled robustness counteracting short-time adaptation processes.
Collapse
Affiliation(s)
- Miriam Cheaib
- Molecular Cell Dynamics, Centre for Human and Molecular Biology, Saarland University, Saarbrücken 66123, Germany
| | - Azim Dehghani Amirabad
- Molecular Cell Dynamics, Centre for Human and Molecular Biology, Saarland University, Saarbrücken 66123, Germany Cluster of Excellence for Multimodal Computing and Interaction, Saarland University and Max Planck Institute for Informatics, Saarbrücken 66123, Germany
| | - Karl J V Nordström
- Epigenetics Department, Centre for Human and Molecular Biology, Saarland University, Saarbrücken 66123, Germany
| | - Marcel H Schulz
- Cluster of Excellence for Multimodal Computing and Interaction, Saarland University and Max Planck Institute for Informatics, Saarbrücken 66123, Germany
| | - Martin Simon
- Molecular Cell Dynamics, Centre for Human and Molecular Biology, Saarland University, Saarbrücken 66123, Germany
| |
Collapse
|
15
|
Baranasic D, Oppermann T, Cheaib M, Cullum J, Schmidt H, Simon M. Genomic characterization of variable surface antigens reveals a telomere position effect as a prerequisite for RNA interference-mediated silencing in Paramecium tetraurelia. mBio 2014; 5:e01328. [PMID: 25389173 PMCID: PMC4235209 DOI: 10.1128/mbio.01328-14] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2014] [Accepted: 06/24/2014] [Indexed: 12/02/2022] Open
Abstract
UNLABELLED Antigenic or phenotypic variation is a widespread phenomenon of expression of variable surface protein coats on eukaryotic microbes. To clarify the mechanism behind mutually exclusive gene expression, we characterized the genetic properties of the surface antigen multigene family in the ciliate Paramecium tetraurelia and the epigenetic factors controlling expression and silencing. Genome analysis indicated that the multigene family consists of intrachromosomal and subtelomeric genes; both classes apparently derive from different gene duplication events: whole-genome and intrachromosomal duplication. Expression analysis provides evidence for telomere position effects, because only subtelomeric genes follow mutually exclusive transcription. Microarray analysis of cultures deficient in Rdr3, an RNA-dependent RNA polymerase, in comparison to serotype-pure wild-type cultures, shows cotranscription of a subset of subtelomeric genes, indicating that the telomere position effect is due to a selective occurrence of Rdr3-mediated silencing in subtelomeric regions. We present a model of surface antigen evolution by intrachromosomal gene duplication involving the maintenance of positive selection of structurally relevant regions. Further analysis of chromosome heterogeneity shows that alternative telomere addition regions clearly affect transcription of closely related genes. Consequently, chromosome fragmentation appears to be of crucial importance for surface antigen expression and evolution. Our data suggest that RNAi-mediated control of this genetic network by trans-acting RNAs allows rapid epigenetic adaptation by phenotypic variation in combination with long-term genetic adaptation by Darwinian evolution of antigen genes. IMPORTANCE Alternating surface protein structures have been described for almost all eukaryotic microbes, and a broad variety of functions have been described, such as virulence factors, adhesion molecules, and molecular camouflage. Mechanisms controlling gene expression of variable surface proteins therefore represent a powerful tool for rapid phenotypic variation across kingdoms in pathogenic as well as free-living eukaryotic microbes. However, the epigenetic mechanisms controlling synchronous expression and silencing of individual genes are hardly understood. Using the ciliate Paramecium tetraurelia as a (epi)genetic model, we showed that a subtelomeric gene position effect is associated with the selective occurrence of RNAi-mediated silencing of silent surface protein genes, suggesting small interfering RNA (siRNA)-mediated epigenetic cross talks between silent and active surface antigen genes. Our integrated genomic and molecular approach discloses the correlation between gene position effects and siRNA-mediated trans-silencing, thus providing two new parameters for regulation of mutually exclusive gene expression and the genomic organization of variant gene families.
Collapse
Affiliation(s)
| | - Timo Oppermann
- Department of Biology, University of Kaiserslautern, Kaiserslautern, Germany
| | | | - John Cullum
- Department for Genetics, Faculty of Biology, University of Kaiserslautern, Kaiserslautern, Germany
| | - Helmut Schmidt
- Department of Biology, University of Kaiserslautern, Kaiserslautern, Germany
| | - Martin Simon
- Saarland University, Centre for Human and Molecular Biology, Molecular Cellular Dynamics, Saarbrücken, Germany
| |
Collapse
|
16
|
Ponsuwanna P, Kümpornsin K, Chookajorn T. Genome-wide prediction of the polymorphic Ser gene family in Tetrahymena thermophila based on motif analysis. PLoS One 2014; 9:e105201. [PMID: 25133747 PMCID: PMC4136848 DOI: 10.1371/journal.pone.0105201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2014] [Accepted: 07/21/2014] [Indexed: 11/18/2022] Open
Abstract
Even though antigenic variation is employed among parasitic protozoa for host immune evasion, Tetrahymena thermophila, a free-living ciliate, can also change its surface protein antigens. These cysteine-rich glycosylphosphatidylinositol (GPI)-linked surface proteins are encoded by a family of polymorphic Ser genes. Despite the availability of T. thermophila genome, a comprehensive analysis of the Ser family is limited by its high degree of polymorphism. In order to overcome this problem, a new approach was adopted by searching for Ser candidates with common motif sequences, namely length-specific repetitive cysteine pattern and GPI anchor site. The candidate genes were phylogenetically compared with the previously identified Ser genes and classified into subtypes. Ser candidates were often found to be located as tandem arrays of the same subtypes on several chromosomal scaffolds. Certain Ser candidates located in the same chromosomal arrays were transcriptionally expressed at specific T. thermophila developmental stages. These Ser candidates selected by the motif analysis approach can form the foundation for a systematic identification of the entire Ser gene family, which will contribute to the understanding of their function and the basis of T. thermophila antigenic variation.
Collapse
Affiliation(s)
- Patrath Ponsuwanna
- Department of Biochemistry, Faculty of Science, Mahidol University, Bangkok, Thailand
| | - Krittikorn Kümpornsin
- Department of Biochemistry, Faculty of Science, Mahidol University, Bangkok, Thailand
| | - Thanat Chookajorn
- Center of Excellence in Malaria, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- * E-mail:
| |
Collapse
|
17
|
Simon M, Plattner H. Unicellular Eukaryotes as Models in Cell and Molecular Biology. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2014; 309:141-98. [DOI: 10.1016/b978-0-12-800255-1.00003-x] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
|
18
|
Pardo BG, Millán A, Gómez-Tato A, Fernández C, Bouza C, Alvarez-Dios JA, Cabaleiro S, Lamas J, Leiro JM, Martínez P. Gene expression profiles of spleen, liver, and head kidney in turbot (Scophthalmus maximus) along the infection process with Philasterides dicentrarchi using an immune-enriched oligo-microarray. MARINE BIOTECHNOLOGY (NEW YORK, N.Y.) 2012; 14:570-582. [PMID: 22367415 DOI: 10.1007/s10126-012-9440-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2011] [Accepted: 01/22/2012] [Indexed: 05/31/2023]
Abstract
We evaluated the expression profiles of turbot in spleen, liver, and head kidney across five temporal points of the Philasterides dicentrarchi infection process using an 8x15K Agilent oligo-microarray. The microarray included 2,176 different fivefold replicated gene probes designed from a turbot 3' sequenced EST database. We were able to identify 221 differentially expressed (DE) genes (8.1% of the whole microarray), 113 in spleen, 83 in liver, and 90 in head kidney, in at least 1 of the 5 temporal points sampled for each organ. Most of these genes could be annotated (83.0%) and functionally categorized using GO terms (69.1%) after the additional sequencing of DE genes from the 5' end. Many DE genes were related to innate and acquired immune functions. A high proportion of DE genes were organ-specific (70.6%), although their associated GO functions showed notable similarities in the three organs. The most striking difference in functional distribution was observed between the up- and downregulated gene groups. Upregulated genes were mostly associated to immune functions, while downregulated ones mainly involved metabolism-related genes. Genetic response appeared clustered in a few groups of genes with similar expression profiles along the temporal series. The information obtained will aid to understand the turbot immune response and will specifically be valuable to develop strategies of defense to P. dicentrarchi to achieve more resistant broodstocks for turbot industry.
Collapse
Affiliation(s)
- Belén G Pardo
- Departamento de Genética, Facultad de Veterinaria, Universidad de Santiago de Compostela, Campus de Lugo, Lugo, Spain
| | | | | | | | | | | | | | | | | | | |
Collapse
|
19
|
Simon MC, Kusch J. Communicative functions of GPI-anchored surface proteins in unicellular eukaryotes. Crit Rev Microbiol 2012; 39:70-8. [DOI: 10.3109/1040841x.2012.691459] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
|
20
|
Müller A, Klöppel C, Smith-Valentine M, Van Houten J, Simon M. Selective and programmed cleavage of GPI-anchored proteins from the surface membrane by phospholipase C. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1818:117-24. [DOI: 10.1016/j.bbamem.2011.10.009] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2011] [Revised: 10/06/2011] [Accepted: 10/07/2011] [Indexed: 01/22/2023]
|
21
|
Conservation and innovation in Tetrahymena membrane traffic: proteins, lipids, and compartments. Methods Cell Biol 2012; 109:141-75. [PMID: 22444145 DOI: 10.1016/b978-0-12-385967-9.00006-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The past decade has seen a significant expansion in our understanding of membrane traffic in Tetrahymena thermophila, facilitated by the development of new experimental tools and by the availability of the macronuclear genome sequence. Here we review studies on multiple pathways of uptake and secretion, as well as work on metabolism of membrane lipids. We discuss evidence for conservation versus innovation in the mechanisms used in ciliates compared with those in other eukaryotic lineages, and raise the possibility that existing gene expression databases can be exploited to analyze specific pathways of membrane traffic in these cells.
Collapse
|
22
|
Lee EH, Kim KH. Identification of differentially expressed genes in parasitic phase Miamiensis avidus (Ciliophora: Scuticociliatia) using suppression subtractive hybridization. DISEASES OF AQUATIC ORGANISMS 2011; 94:135-142. [PMID: 21648242 DOI: 10.3354/dao02320] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Miamiensis avidus, a causative agent of scuticociliatosis in cultured marine fish, can live not only in seawater as a free-living organism but also in fish as a parasite. In this study, a cDNA library of representative mRNAs more specific to parasitic phase M. avidus was generated using suppression subtractive hybridization (SSH), and 520 clones selected from the SSH library were single-run sequenced. The differential gene expression patterns were confirmed by semi-quantitative reverse-transcription PCR. Of the 510 SSH clones, 21 clones of 6 putative genes did not match sequences in the public database. The expectation values (E-values) of 117 clones encoding 9 putative genes were greater than 1 x 10(-5). The other 372 clones that met the criterion of E value <1 x 10-5 were matched to 26 known sequences in the database. Genes associated with signal transduction, cell proliferation, membrane transportation, protein translocation, and transcription regulation were preferentially expressed in parasitic phase M. avidus. The differential gene expression may be needed for the ciliates to survive in the host fish, and the corresponding proteins might be used as antigen candidates for development of scuticociliatosis vaccines.
Collapse
Affiliation(s)
- Eun Hye Lee
- Department of Aquatic Life Medicine, Pukyong National University, Busan 608-737, South Korea
| | | |
Collapse
|
23
|
Carranza PG, Lujan HD. New insights regarding the biology of Giardia lamblia. Microbes Infect 2010; 12:71-80. [DOI: 10.1016/j.micinf.2009.09.008] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2009] [Accepted: 09/15/2009] [Indexed: 10/20/2022]
|
24
|
|
25
|
Klöppel C, Müller A, Marker S, Simon M. Two isoforms of eukaryotic phospholipase C in Paramecium affecting transport and release of GPI-anchored proteins in vivo. Eur J Cell Biol 2009; 88:577-92. [DOI: 10.1016/j.ejcb.2009.05.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2009] [Revised: 05/06/2009] [Accepted: 05/11/2009] [Indexed: 01/17/2023] Open
|
26
|
Sitjà-Bobadilla A. Living off a fish: a trade-off between parasites and the immune system. FISH & SHELLFISH IMMUNOLOGY 2008; 25:358-372. [PMID: 18722790 DOI: 10.1016/j.fsi.2008.03.018] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2007] [Revised: 03/14/2008] [Accepted: 03/27/2008] [Indexed: 05/26/2023]
Abstract
Research in fish immune system and parasite invasion mechanisms has advanced the knowledge of the mechanisms whereby parasites evade or cope with fish immune response. The main mechanisms of immune evasion employed by fish parasites are reviewed and considered under ten headings. 1) Parasite isolation: parasites develop in immuno-privileged host tissues, such as brain, gonads, or eyes, where host barriers prevent or limit the immune response. 2) Host isolation: the host cellular immune response isolates and encapsulates the parasites in a dormant stage without killing them. 3) Intracellular disguise: typical of intracellular microsporidians, coccidians and some myxosporeans. 4) Parasite migration, behavioural and environmental strategies: parasites migrate to host sites the immune response has not yet reached or where it is not strong enough to kill them, or they accommodate their life cycles to the season or the age in which the host immune system is down-regulated. 5) Antigen-based strategies such as mimicry or masking, variation and sharing of parasite antigens. 6) Anti-immune mechanisms: these allow parasites to resist innate humoral factors, to neutralize host antibodies or to scavenge reactive oxygen species within macrophages. 7) Immunodepression: parasites either suppress the fish immune systems by reducing the proliferative capacity of lymphocytes or the phagocytic activity of macrophages, or they induce apoptosis of host leucocytes. 8) Immunomodulation: parasites secrete or excrete substances which modulate the secretion of host immune factors, such as cytokines, to their own benefit. 9) Fast development: parasites proliferate faster than the ability of the host to mount a defence response. 10) Exploitation of the host immune reaction. Knowledge of the evasion strategies adopted by parasites will help us to understand host-parasite interactions and may therefore help in the discovery of novel immunotherapeutic agents or targeted vaccines, and permit the selection of host-resistant strains.
Collapse
Affiliation(s)
- A Sitjà-Bobadilla
- Instituto de Acuicultura de Torre de la Sal, Consejo Superior de Investigaciones Científicas, Torre de la Sal s/n, 12595 Ribera de Cabanes, Castellón, Spain.
| |
Collapse
|