ESSENTIALS of

VIROLOGY

S. Ram Reddy Department of Microbiology, Kakatiya University, Warangal (India)

S. M. Reddy Department of Botany, Kakatiya University, Warangal (India)

Published by:

Scientific Publishers (India) 5 A, New Pali Road, P.O. Box 91 Jodhpur 342 001 (India) E-mail: info@scientificpub.com Website: www.scientificpub.com

Branch Office Scientific Publishers (India) 4806/24, Ansari Road, Daryaganj New Delhi - 110 002 (India)

Print: 2012 All rights reserved. No part of this publication or the information contained herein may be reproduced, adapted, abridged, translated, stored in a retrieval system, computer system, photographic or other systems or transmitted in any form or by any means, electronic, mechanical, by photocopying, recording or otherwise, without written prior permission from the author and the publishers. Disclaimer: Whereas every effort has been made to avoid errors and omissions, this publication is being sold on the understanding that neither the author nor the publishers nor the printers would be liable in any manner to any person either for an error or for an omission in this publication, or for any action to be taken on the basis of this work. Any inadvertent discrepancy noted may be brought to the attention of the publishers, for rectifying it in future editions, if published. ISBN: 978-81-7233-473-4 (H.B.) 978-81-7233-494-9 (P.B.) eISBN: 978-93-86347-56-5 © Reddy & Reddy, 2007 Printed in India

PREFACE

Virology, in less than hundred years of organized scientific investig-ations, has grown leaps and bounds and ramified into all the disciplines of biology. New information is pouring in at an accelerated pace. Modern disciplines like molecular biology, biotechnology have enriched themselves borrowing much of information from virology. It has wide applications both in basic and applied sciences. Fortunately, excellent advanced treatises are available on the subject providing the latest information from time-to-time. However, a book that can provide basic and holistic information of all viruses to a beginner is a long-felt need. Through this book we made a humble effort to build a strong conceptual foundation of virology so that interested students can navigate through the advanced treatises.

The subject matter of this book is presented in four parts. Part-I deals with history, principles, and taxonomy of viruses. Part-II deals with the biology of bacteriophages. Different aspects of plant viruses are presented in part-III. Part-IV is devoted to animal and human viruses. Mycoviruses, phycoviruses, subviral agents, viroids and prions are introduced in the last part. Though, a wealth of information is available on the subject, keeping in view the scope of the book, we have restricted subject matter to certain limits. The subject matter has been presented in a lucid style well supported by figures, illustrations, tables and graphs so that it could be used for both teaching and learning.

We hope that the contents of the book fulfill the needs of undergraduate and post-graduate students of all biological disciplines including agriculture, veterinary, pharmacy and medicine. We have taken every possible care to present the subject matter in factual form. Nevertheless, human errors are likely to creep in inadvertently. We look forward to our teacher fraternity to point out such errors and also to give constructive suggestions for the improvement of this look in future.

24th December, 2006 Authors Warangal.

ACKNOWLEDGEMENTS

The publication of a book of this kind requires the help and contributions from many people besides the authors. This venture would not have begun were it not for the initial encouragement we received from Late Prof. M.V. Nayudu, Department of Virology, Sri Venkateswara University, Tirupati (A.P). He was instrumental in inducting us into this subject. We also are thankful to Prof. P. Srinivasulu and Prof. D.V.R. Sai Gopal, Department of Virology, Sri Venkateswara University for his encouragement and critically going through the manuscript and offering many suggestions for the improvement of subject matter.

Our teaching for the last three decades to undergraduate and post-graduate students has widened the horizons and increased the depth of the subject. Classroom teaching, seminars and discussions with students have really made us to realize the necessity to bring out a comprehensive book on this subject. Their response to course curriculum was instrumental in its conversion to a text. Thus our student community deserves a pat of appreciation.

We have consulted a large number of reference books, original research papers and review articles available on the subject and liberally borrowed the subject matter, figures, illustrations etc. We express our indebtedness to the publishers and authors of these sources. The partial financial assistance in the form of publication grant received from University Grants Commission, New Delhi is gratefully acknowledged.

We wish to extend appreciation to our families for their patience and encouragement during the preparation of the book

Finally, but most important, we are thankful to Shri Pawan Kumar, Scientific Publishers (India) Jodhpur, and Shri Rajesh Ojha (DTP type setter) for bringing out this book timely and in an excellent format.

FOREWORD

The science of virology has become more relevant than ever before. Emerging viral diseases are posing new challenges to the scientific knowledge. Crop losses due to viral diseases are spreading and increasing progressively due to rapid movement of plant materials, intensive cultivation of limited varieties and origin of new viruses. However, bacterial viruses, plant viruses like CaMV and geminiviruses as well as animal viruses like SV40, baculoviruses, oncoviruses are increasingly contributing to our understanding of cell biology, molecular biology and serving as tools in biotechnology. Despite its high importance, virology has been given a cursory treatment in the curricula of most of the universities. Consequently, the students are introduced to virology only at advanced level. Certainly there is an urgent need to introduce this subject at the entry level itself. This necessitates availability of the book providing sufficient information of introductory nature.

Though several books are available on plant viruses, there is dearth of the books that can provide holistic information about the viruses to a beginner. The present book “Essentials of Virology”, hopefully, bridges this gap. The book covers the basic information on viruses in a systematic manner providing not only the accumulated information but also the recent developments in the subject Certainly contents of the book would be useful to the students pursuing courses both at undergraduate and postgraduate levels in all biological disciplines.

I congratulate the authors for bringing out of this kind, which I hope would fill long-felt need of both teachers and students.

Dr. S.M. Paul Khurana Vice-Chancellor, R.D. University

Jabalpur - 482 001

CONTENTS

Preface iii

Acknowledgements iv

Foreword v

Part I : Principles of Virology

Chapter 1 History of virology 1

Chapter 2 Origin and evolution of viruses 10

Chapter 3 Morphology and chemical composition 16

Chapter 4 Isolation and cultivation 28

Chapter 5 Purification and characterization 36

Chapter 6 Detection and assay 46

Chapter 7 Taxonomy 56

Part II : Bacteriophages

Chapter 8 Distribution and classification 85

Chapter 9 Replication strategies 93

Chapter 10 Phage-host interactions 125

Chapter 11 Importance and applications 130

viii Essentials of Virology

Part III : Plant Viruses

Chapter 12 Nomenclature and classification 139

Chapter 13 Replication strategies 147

Chapter 14 Virus-host interactions 168

Chapter 15 Transmission 179

Chapter 16 Diagnosis of plant viral diseases 187

Chapter 17 Management of plant viral diseases 200

Part IV : Animal and Human Viruses

Chapter 18 Classification 211

Chapter 19 Replication strategies 220

Chapter 20 Virus-host interactions 241

Chapter 21 Pathogenesis 247

Chapter 22 Diagnosis of animal viral diseases 253

Chapter 23 Oncoviruses 265

Chapter 24 Prevention and control of animal and human viral diseases 271

Part V : Miscellaneous Viruses and Subviral agents

Chapter 25 Phycoviruses 297

Chapter 26 Mycoviruses 301

Chapter 27 Subviral agents 306

Chapter 28 Viroids 313

Chapter 29 Prions 319

Abbreviations 327

Glossary 331

Index 335

PART ONE

PRINCIPLES

OF

VIROLOGY