Parasitic Flatworms Molecular Biology, Biochemistry, Immunology and Physiology This page intentionally left blank Parasitic Flatworms Molecular Biology, Biochemistry, Immunology and Physiology Edited by Aaron G. Maule Parasitology Research Group School of Biology and Biochemistry Queen’s University of Belfast Belfast UK and Nikki J. Marks Parasitology Research Group School of Biology and Biochemistry Queen’s University of Belfast Belfast UK CABI is a trading name of CAB International CABI Head Office CABI North American Office Nosworthy Way 875 Massachusetts Avenue Wallingford 7th Floor Oxfordshire OX10 8DE Cambridge, MA 02139 UK USA Tel: +44 (0)1491 832111 Tel: +1 617 395 4056 Fax: +44 (0)1491 833508 Fax: +1 617 354 6875 E-mail: [email protected] E-mail: [email protected] Website: www.cabi.org ©CAB International 2006. All rights reserved. No part of this publication may be reproduced in any form or by any means, electronically, mechanically, by photocopying, recording or otherwise, without the prior permission of the copyright owners. A catalogue record for this book is available from the British Library, London, UK. Library of Congress Cataloging-in-Publication Data Parasitic flatworms : molecular biology, biochemistry, immunology and physiology / edited by Aaron G. Maule and Nikki J. Marks. p. ; cm. Includes bibliographical references and index. ISBN-13: 978-0-85199-027-9 (alk. paper) ISBN-10: 0-85199-027-4 (alk. paper) 1. Platyhelminthes. [DNLM: 1. Platyhelminths. 2. Cestode Infections. QX 350 P224 2005] I. Maule, Aaron G. II. Marks, Nikki J. III. Tittle. QL391.P7P368 2005 616.9'62--dc22 2005016094 ISBN-10: 0-85199-027-4 ISBN-13: 978-0-85199-027-9 Typeset by SPi, Pondicherry, India. Printed and bound in the UK by Biddles Ltd, King’s Lynn. Contents Contributors xv Preface xix Access to Colour Illustrations xx PART I PHYLOGENY, GENETICS AND TRANSCRIPTOMES 1 The Evolution of Parasitism in Flatworms 1 D.T.J. Littlewood Introduction 1 Parasitism in the Platyhelminthes 6 The Origins of Obligate Parasitism – The Appearance of the Neodermata 7 When did the Neodermata appear? 12 The Neodermata – advantages of a new skin 13 The Radiation of the Parasitic Flatworms 15 Radiation of the Monogenea 16 Radiation of the Cestoda 20 Radiation of the Aspidogastrea 23 Radiation of the Digenea 24 Concluding Remarks 27 Acknowledgements 30 References 31 2 Genomes and Genomics of Parasitic Flatworms 37 D.A. Johnston Introduction 38 Genome Features 40 Genome size 40 Genome composition 42 DNA methylation 42 Repeat sequences 43 Integration of host DNA sequences 46 v vi Contents Genome instability 47 Gene processing 48 Karyotype Features 50 Chromosome number 50 Ploidy 50 Sex chromosomes 52 Recombination frequency 53 Telomeres 54 Mitochondrial Genomes 54 General characteristics 54 Gene order 58 Genetic code 59 Maternal inheritance 61 Flatworm Genomics 64 Rationale 64 Gene discovery and transcriptome analysis 64 Physical mapping 66 Chromosome mapping 66 Genome sequencing 67 Concluding Remarks 67 Acknowledgements 68 References 68 3 Genetic Discrimination of Echinococcus Species and Strains 81 D.P. McManus Introduction 81 Genetic Variation in Echinococcus 82 Identification of Echinococcus Isolates Using Molecular Genetic Techniques 84 RFLP/RAPD analysis 84 PCR-amplified DNA sequences 84 Mutation scanning methods 85 Microsatellite markers 85 Molecular Identification of E. granulosus Strains 85 Sheep–dog (Genotype 1) and horse–dog (Genotype 4 – E. equinus) strains 85 Cattle–dog strain (Genotype 5 – E. ortleppi)87 Camel–dog strain (Genotype 6) 89 Pig–dog strains (Genotypes 7 and 9) 89 Cervid strains (Genotypes 8 and 10) 89 Detection of Echinococcus Nucleic Acids in Clinical Samples 90 DNA Detection of Infection in Definitive and Intermediate Hosts 90 Concluding Remarks 91 Acknowledgements 92 References 92 4 Ribosomal DNA Variation in Parasitic Flatworms 96 D. Blair Introduction 96 Nuclear Ribosomal Operons 98 Intergenic spacers 100 Internal transcribed spacers (ITSs) 102 Intra-individual variation and repeat sequences 103 Contents vii Intra- and interspecific variation 107 Functional motifs 108 Secondary structure 108 Small and Large Subunit Genes 109 Mitochondrial Ribosomal Genes 115 Hybrids 116 Concluding Remarks 117 References 117 5 Genetic Studies on Monogeneans with Emphasis on Gyrodactylus 124 ∨ C.O. Cunningham and I. Matejusová Introduction 124 Difficulties in Molecular Studies of Monogenea 125 Molecular Markers for Monogenean Species 126 The rRNA genes and spacers 126 The SSU (18S) rRNA gene 127 The rRNA internal transcribed spacer (ITS) 127 The rRNA intergenic spacer (IGS) 129 Large Subunit (LSU) (28S) rRNA gene 129 Other Regions of the Monogenean Genome 130 Monogenean Species Concept and Species Complexes 130 Molecular Analysis within Monogenean Species 131 Other Genetic Studies in Monogenea 132 Concluding Remarks 133 References 133 6 The Schistosome Transcriptome 138 S. Verjovski-Almeida and R. DeMarco Introduction 138 The Transcriptome Projects 139 Transcriptome Comparisons 139 Evolutionary Implications 141 Novel Transcripts 141 Receptors and Host–Parasite Interaction 142 Immune Evasion 142 Sex Differences 143 Genome Data 143 Novel Drug Targets 143 Vaccines 144 Trans-splicing 145 Retrotransposable Elements 145 Functional Genomics 145 Concluding Remarks 146 References 146 7 Transgenic Flatworms 149 C.G. Grevelding Introduction 149 The Planarian Model 150 Trematodes and Cestodes 151 Transformation Techniques for Schistosomes 153 viii Contents Particle bombardment 153 The PDS-1000/He particle bombardment system 155 Reporter gene activity in bombarded schistosomes 156 Stable Transformation 162 Cestodes, on the Way to Transgenesis 164 Concluding Remarks 165 Acknowledgements 166 References 166 PART II IMMUNOBIOLOGY, HOST–PARASITE INTERACTION AND CONTROL 8 Immunobiology of Schistosomes 174 S.G. Forrester and E.J. Pearce Introduction 174 Host–Parasite Molecular Interactions 175 How Schistosomes Evade the Host Immune System 176 Skin stage parasites 176 Lung stage parasites 178 Adult parasites 178 Host Immune Response to Schistosome Infection (Th1 versus Th2) 179 Potential Players in Th2 Response Induction during a Schistosome Infection 181 Chemotherapy – An Integral Role for the Immune Response 183 Immunotherapy 183 Concluding Remarks 184 Acknowledgements 185 References 185 9 Cestode Infection: Immunological Considerations from Host and Tapeworm Perspectives 193 D.M. McKay and R.A. Webb Introduction 193 Cestode Parasites 194 Immunology – The Basics 195 The Intestine and Immune Responses 197 Create an inhospitable environment 197 Mobilize an active immune response 198 Specifics of the Host Response to Cestode Infection 199 Parenteral infections of cestodes 199 Host response to the oncosphere 199 Resistance to parenteral metacestodes 200 Lumenal Infections: The Immune Response to Hymenolepidid Cestodes 202 Cestode Infections and the Immune Response – Where Do We Go from Here? 203 Evasion and Subversion of the Host Response 204 The Beneficial Tapeworm 204 Concluding Remarks 205 Acknowledgements 206 References 206 10 Signal Transduction at the Host–Parasite Interface 210 T.P.Yoshino, J.J. Vermeire and J.E. Humphries Introduction 210 Tegumental Involvement in Signal Transduction: Perception and Reality 211 Contents ix Elements of Platyhelminth Signal Transduction Systems 213 Molecular and EST data 213 Platyhelminth signalling proteins 214 Platyhelminth Signal Transduction Pathways: Tegument and Beyond 218 Transforming growth factor receptor (TGFR) pathway 218 TGF-β receptor signalling in schistosomes 219 Epidermal growth factor receptor (EGFR) pathway 220 EGFR signalling: roles in the host–parasite relationship 220 G Protein-coupled receptors (GPCRs) 222 GPCRs in parasitic platyhelminths 222 Concluding Remarks 223 Acknowledgements 223 References 224 11 Parasite Effects on the Snail Host Transcriptome 228 M. Knight and N. Raghavan Introduction 228 Effect of Parasite Infection on the Snail Host: Towards a Molecular Understanding 230 Innate immunity 230 Biochemical involvement 231 Parasite-induced changes in gene expression 233 Parasite-induced changes in snail neurobiology 237 Concluding Remarks 238 Acknowledgements 238 References 239 12 Developments in the Chemotherapy of Parasitic Flatworms 243 G.C. Coles Introduction 243 Parasites of Animals 244 Infections of Humans 245 Adult tapeworms 246 Larval tapeworms 246 Taenia solium 246 Echinococcus granulosus 246 Echinococcus multilocularis 247 New Anti-parasitics: Nitazoxanide 247 Mode of Action of Fasciolicides and Cestodicides 247 Resistance 248 Resistance in Fasciola 249 Resistance in monogeneans 249 Resistance in cestodes 249 Detection of resistance 250 Concluding Remarks 250 References 251 13 Drug Resistance in Schistosomes 256 T.A. Day and S. Botros Introduction 256 Schistosomiasis Chemotherapy 257 Impact of Praziquantel 257 Challenges to Detecting and Monitoring Anti-schistosomal Resistance 258 x Contents There is a high background of drug failure 258 Methods for detecting infection are variable 258 Factors other than resistance can produce drug failure 258 It is difficult to substantiate a decreased response in the worms 259 Praziquantel’s mechanism of action is not known 259 Defining resistance 260 Cases of Drug Resistance in Schistosomes 260 Resistance to Hycanthone and Oxamniquine 260 Resistance to Praziquantel 261 Senegal 261 Egypt 262 Concluding Remarks 264 References 265 14 Praziquantel: Mechanism of Action 269 R.M. Greenberg Introduction 269 Praziquantel Mode of Action 270 Voltage-gated Ca2+ Channels