Influenza

Influenza Edwin D. Kilbourne, M.D. DistingUished Service Professor Mount Sinai School of Medicine of the City University of New York New York, New York

Plenum Medical Book Company • New York and London

Library of Congress Cataloging in Publication Data

Kilbourne, Edwin D. (Edwin Dennis), 1920-Influenza.

Includes bibliographies and index. I. Influenza. 2. Influenza viruses.

oviridae . WC SIS K483i) l. Title. [DNLM: I. Influenza. 2. Orthomyx-

RC150.K6 1987 616.2 '03 ISBN 978-1-4684-5241-9 ISBN 978-1-4684-5239-6 (eBook)

© 1987 Edwin D. Kilbourne, M.D.

Plenum Medical Book Company is an imprint of Plenum Publishing Corporation 233 Spring Street, New York, N.Y. 10013

All rights reserved

87-2510

No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, microfilming, recording, or otherwise, without written permission from the Publisher

Softcover reprint of the hardcover 1st edition 1987

DOI 10.1007/978-1-4684-5239-6

This book is d~dicated to the memory of Frank L. Horsfall, Jr., mentor and friend, in whose laboratory at the Rockefeller Institute for Medical Research I first met the virus of influenza and learned the methods of quantitative biology.

Preface

My lifetime encompasses the postwar subsidence in the early 1920s of the greatest influenza pandemic in history, direct encounters with FM1 virus at Fort Mon­mouth in 1947, the care of influenza patients in the 1950s, the pursuit of the in­fluenza virus through the modern pandemics of 1957 and 1968, and a present in which the genes of the virus have dissembled in the DNA of vaccinia virus and Escherichia coli through the wand of "high tech."

If my corpus could be fossilized for archival and archaeological purposes, it would be found to contain immune cells branded with the imprint of the "swine" influenza virus of post-1918 and brain cells no less imprinted with memories of the abortive return of its descendant during America's bicentennial. But before that unlikely event, I wanted to try to make some sense out of this baffling dis­ease and its viruses-expecting no definitive revelations but hoping for a sharper definition of problems. Hence this book.

It is an audacious act in these days of specialization to essay a book such as this singlehandedly, but I have done so for selfish reasons. I wanted to reexam­ine old questions about the nature of influenza and its epidemics in the light of the dazzling advances in molecular biology of the past few years. No virus has been better studied, but few diseases are less well understood. The influenza vi­rus glycoproteins have become models for biologists interested in membrance as­sembly and function; knowledge of their tertiary (and even quaternary) structure surpasses that available for most other proteins. The rapidly mutating RNAs of influenza virus have captured the interest and fired the imagination of evolutio·n­ary geneticists. Cellular immunologists have discovered this enveloped virus and, in collaboration with molecular geneticists, have studied the recognition of sin­gle viral proteins introduced by cloning vectors.

I marvel, properly, at all this activity and applaud it, but the physician in me asks, what about influenza? What about the disease? At this time, after a profes­sionallifetime of laboratory investigations and 2 years of intensive scholarship, I cannot tell you why people get sick with influenza or how they do. How this elegantly characterized virus causes aches and pains and fever is simply not un­derstood. Nor do we fully comprehend viral virulence or the genesis of pan­demics. But we shall. The only prophecy that I dare to make is that we are on the threshold of deep insights into pathogenesis that will come from the conver­gence of presently parallel studies of the molecules of both virus and host. I hope

vii

viii PREFACE

that this book can expedite this convergence by illuminating gray areas and draw­ing attention to studies outside the mainstream of virology.

One day we shall "see influenza plain."

Edwin D. Kilbourne New York

Acknowledgments

I take pleasure in acknowledging the unfailing generosity of colleagues through­out the world who have shared their research findings with me in advance of pub­lication. They include the following, none of whom should be held responsible for my interpretation of their work:

Gordon L. Ada, Gillian M. Air, Robert B. Belshe, Robert F. Betts, George C. Brownlee, Doris J. Bucher, Robert M. Chanock, Purnell W. Choppin, Mary Lou Clements, Richard W. Compans, Robert B. Couch, Nigel J. Dimmock, Walter R. Dowdle, R. Gordon Douglas, Jr., Bernard C. Easterday, Francis A. Ennis, John P. Fox, Walter Gerhard, Mary Jane Gething, Paul W. Glezen, R. Edgar Hope­Simpson, Alan P. Kendal, Hans-Dieter Klenk, Robert M. Krug, Robert A. Lamb, William Graeme Laver, Hunein F. Maassab, Koichiro Maeno, Gordon Meikle­john, Brian R. Murphy, Debi P. Nayak, Michael B. A. Oldstone, Peter Palese, James C. Paulson, Marcel Pons, Carol S. Reiss, Rudolf Rott, Christoph Scholtis­sek, Jerome L. Schulman, Irene T. Schulze, John J. Skehel, Masahiro Veda, Colin Ward, Robert G. Webster, D. C. Wiley, Peter F. Wright, Nicholas G. Wrigley, and V. M. Zhdanov.

I am deeply indebted to Marilyn Tartaglia for her dedicated and tireless ef­forts in the preparation of the major portion of this manuscript and to Valerie M. Josephson, whose editorial skills facilitated its completion.

E.D.K.

ix

Contents

I. INTRODUCTION

1. History of Influenza

Introduction ................................................ 3 The Credibility of Historical Evidence .......................... 3 Prehistory: The Origin of Influenza. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Influenza Prior to 1889 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Influenza 1889-1933: Seroarcheology and the Recycling of Antigens 5 Influenza Post-1933 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Early History Revisited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 The Pandemics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Pandemics Defined. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 The Modern Pandemics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Influenza 1918 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Influenza 1946-47 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Influenza 1957 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Influenza 1968 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Influenza Post-1968: Major Antigenic Changes in the Virus Are

Not Necessarily Followed by Pandemics. . . . . . . . . . . . . . . . . . . 19 Influenza 1976: The First Epidemic of Swine Influenza Virus

Infection in Man . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Influenza 1977. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

II. THE INFLUENZA VIRUSES

2. Taxonomy and Comparative Virology of the Influenza Viruses

Introduction ................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Taxonomy of Influenza Viruses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 Relation of Influenza Viruses to Other Enveloped Viruses with RNA

Genomes ........ '" .. . ...... .. .... .... .... . . .... ... ..... . 28 Influenza Viruses as Segmented Genome Viruses . . . . . . . . . . . . . . . . . 30 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

xi

xii CONTENTS

3. Viral Structure and Composition

Introduction ................................................ 33 Size and Morphology of Influenza Virus Particles . . . . . . . . . . . . . . . . . 33

The Viral Envelope. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 Internal Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

Structure of the Envelope Glycoproteins. . . . . . . . . . . . . . . . . . . . . . . . . 45 Hemagglutinin Structure ................................ ,... 45 Neuraminidase Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 Carbohydrate. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 Lipid. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 RNA..................................................... 50

Structural Differences among Influenza. A, B, and C Viruses. . . . . . . 51 Tick-Borne Viruses Structurally Similar to Orthomyxoviruses . . . . . . . 52 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

4. Replication of Influenza Viruses

Replication Systems and Viral Quantitation . . . . . . . . . . . . . . . . . . . . . . 57 Viral Genes and Gene Products Involved in Virus Replication:

Coding Assignments of Influenza Virus Genes. . . . . . . . . . . . . . . . . . 58 Stages of Infection and Replication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

Viral Attachment to Host Cells: Adsorption .................... 59 Viral Entry. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

Proteolytic Activation of the HA and Virus-Cell Fusion .. . . . . . . 61 Virus-Cell Fusion ........................................ 62 Cell Entry and Uncoating through Endocytosis. . . . . . . . . . . . . . . . 62

Transcription and Replication of Influenza Virus RNA. . . . . . . . . . . 62 Primary Transcription. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 Secondary Transcription and RNA Replication. . . . . . . . . . . . . . . . 67

Synthesis of Viral Proteins. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 The P Proteins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 NP..................................................... 68 The N on structural Proteins ................................ 70 Hemagglutinin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 Neuraminidase. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

Viral Maturation and Assembly .............................. 71 Virus Budding and Release .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

Abortive and Inefficient Virus Replication. . . . . . . . . . . . . . . . . . . . . . . 74 Anomalous Viral Replication and the Formation of Defective Virus. . 76 Interference. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

5. Cytopathogenesis and Cytopathology of Influenza Virus Infection of Cells in Culture

Introduction ................................................ 89 Primary Intrinsic Cytotoxicity of Influenza Viruses. . . . . . . . . . . . . . . . 89

CONTENTS xiii

Effects in Intact Animals 89 In Vitro Effects of Influenza Viruses on Polymorphonuclear

Leukocytes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90 Viral Effects on Other Blood Leukocytes. . . . . . . . . . . . . . . . . . . . . . . 91 Viral Effects on Other Cells ................................. 94

Cell Systems Supportive of Productive Replication and Plaque Formation by Influenza Viruses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94

Cytopathic Effects of Influenza Viruses in Specialized Cells ..... 95 The Nature of Influenza Virus Cytopathic Effects. . . . . . . . . . . . . . 95

Cytopathology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 Nuclear and Cytoplasmic Inclusions ...................... 99 The Kinetics of CPE: Influenza Virus Plaque Formation in Cell

Cultures as a Model of Microinfection . . . . . . . . . . . . . . . . . . . . . . . 99 The Possible Role of Lysosomal Enzymes in Influenza Virus CPE 105 The Molecular Basis of CPE . . . . . . . . . . . . . . . . . 106

References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

6. Influenza Virus Genetics, Viral Adaptation, and Evolution

Introduction ................................................ 111 The Nature of the Viral Genome . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 111 Genetic Systems ............................................ .

Viral Heterogeneity ........................................ . Host Cell Heterogeneity .................................... .

Viral Mutation and Mutants .................................. .

113 114 114 115

Mutation Frequency. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 115 Frequency of Influenza Virus Antigenic Variation. . . . . . . . . . . . . .. 115 Molecular Basis of Influenza Virus Mutations .................. 116 Laboratory-Derived Mutants and Their Contribution to Genetic

Analysis of Influenza Viruses. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 116 Phenotypic Markers ...................................... 116 Operational Mutants: Conditional Lethal Mutants Used in

Definitive Genetic Studies of Influenza Viruses. . . . . . . . . . . . .. 117 Temperature-Sensitive (ts) Mutants . . . . . . . . . . . . . . . . . . . . . . .. 117 Host Range (hr) Mutants. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 118 Temperature-Dependent Host Range (td-hr) Mutants. . . . . . . .. 118 Drug-Resistant Mutants. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 118

Viral Variation .................. . . . . . . . . . . . . . . . . . . . . . . . . 119 Antigenic Variants ......................................... 119

Sites of Antigenic Variation: The HA Polypeptide. . . . . . . . . . . . .. 119 The Molecular Basis of HA Antigenic Variation. . . . . . . . . . . . . .. 121 Antigenic Variation in the NA . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 121 Antigenic Variation in Other Viral Proteins. . . . . . . . . . . . . . . . . .. 121

Biologically Selected (Nonimmunoselected) Variants. . . . . . . . . . . .. 122 Nonimmunoselected HA Variants. . . . . . . . . . . . . . . . . . . . . . . . . .. 122

Variants Selected by Replication Characteristics ............. 122 Host-Determined Antigenic Variation .............. . . . . . . .. 123

xiv CONTENTS

HA Glycosylation Mutants .. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 123 Pleiotropism and Covariation ................................ 123 The Genetics of Major Antigenic Change in Influenza A Viruses .. 124

Genetic and Nongenetic Viral Interactions. . . . . . . . . . . . . . . . . . . . . .. 125 Phenotypic Mixing .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 125

Influenza Virus-Influenza Virus Pseudotypes . . . . . . . . . . . . . . . .. 125 Heterologous Pseudotypes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 126

Genetic Reassortment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 126 Complementation-Reassortment . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 128 Multiplicity Reactivation and Gene Rescue. . . . . . . . . . . . . . . . . . . .. 128

Virulence and Attenuation as Genetic Phenomena . . . . . . . . . . . . . . .. 129 Identification of Single Genes Influencing Virulence and

Attenuation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 130 Analysis of Virulence through Genetic Reassortment ............ 130

Cloning and Expression of Influenza Virus Genes: The New Influenza Virus Genetics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 134 Contributions of Gene Cloning. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 134 Gene Expression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 134 Contribution of the Expression of Isolated Viral Genes to the

Understanding of Influenza Virus Infection. . . . . . . . . . . . . . . . . .. 136 Prospects and Potential of Site-Specific Mutagenesis ....... : . . . .. 137

Viral Variation and Attenuation in Nature. . . . . . . . . . . . . . . . . . . . . .. 137 Influenza Viral Adaptation, Genetic Polymorphism, and Evolution .. 137

Viral Adaptation .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 137 Genetic Dimorphism ....................................... 138 Viral Evolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 141

Influenza Virus Evolution is the Study of the Evolution of Genes, Not Viruses ..................................... 141

Evolutionary Potential of Influenza Viruses as Segmented Genome Viruses. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 142

Evolution of the Genes of Influenza Viruses by Sequential Mutations ............................................. 142 Evolution of the HA Gene ............................... 143

Antigenic Drift ....................................... 143 Evolutionary Changes in the HA Affecting Other Than

Antigenic Sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 144 Evolution of Genes for Nonsurface Viral Proteins. . . . . . . . . . .. 144

NS ..................................... " . . . . . . . . . .. 144 Other Genes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 144

References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 145

III. INFLUENZA: INFECTION AND DISEASE

7. Influenza in Man

Clinical Response to Infection ................................. 157 Findings on Physical Examination ............................ 158

CONTENTS xv

Host-Determined Variation in Disease Expression and Severity. . .. 159 Variation in Symptoms Related to Age ........................ 159

Influenza in Children ..................................... 159 Influenza in Infants. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 160 Influenza in the Elderly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 161

Influence of Genetic Factors on the Expression of Disease. . . . . . .. 161 The Influence of Prior Immunizing Experience on the Severity of

Influenza. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 162 Pregnancy ................................................ 162 Underlying Cardiovascular Disease ........................... 163 Bronchopulmonary Disease ................................ " 164 Other Underlying Diseases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 164 Virus-Determined Variation in Disease Expression and Severity. .. 164

Clinical Responses to Infection with Influenza A, B, and C Viruses Compared. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 164 Influenza B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 164 Influenza C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 165

Variation in Disease Severity Related to Viral Strain or Subtype 167 Unusual Manifestations of Influenza Virus Infection .............. 168

Primary Viral Pneumonia. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 168 Myopathy and Nephropathy ............................... 168

Acute Transient Crural Myopathy in Children. . . . . . . . . . . . . .. 169 Acute Myopathy with Rhabdomyolysis and Myoglobinuria

with Associated Renal Dysfunction ...................... 170 Myopathy of the Elderly in the Absence of Classical Symptoms

of Influenza. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 170 Comment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 170

Carditis ............................................... " 171 Encephalopathy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 171 Other Neurological Manifestations .............. . . . . . . . . . . .. 174 Miscellaneous. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 174

Complications of Influenza. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 174 Bacterial Infections. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 174 Noninfectious Pulmonary Complications. . . . . . . . . . . . . . . . . . . . . .. 175 Complications of Viral Infection of the Respiratory Tract Not

Specific for Influenza ..................................... 175 Asthenia and Depression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 175 Effects of Influenza on the Fetus . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 175

Abortions and Stillbirths. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 176 Teratogenic Effects ....................................... 176 Fetally Induced Neoplastic Disease. . . . . . . . . . . . . . . . . . . . . . . . .. 176

Reye's Syndrome .......................................... 176 Pathogenesis and Pathophysiology of Influenza. . . . . . . . . . . . . . . . . .. 178

Sequence of Events. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 179 Implantation of Virus in the Respiratory Tract . . . . . . . . . . . . . . .. 179 Progression of Infection .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 180 Viral Replication, Shedding, and Persistence. . . . . . . . . . . . . . . . .. 180 Contribution of Host Response to Disease. . . . . . . . . . . . . . . . . . .. 181

xvi CONTENTS

Viremia and Infection of Nonrespiratory Organs .............. 182 Pathophysiological Effects of Influenza . . . . . . . . . . . . . . . . . . . . . . .. 182

Effects on Respiratory Function ............................ 182 Effects on Ciliary Function. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 183 In Vivo Effects on Leukocytes. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 183

Polymorphonuclear Leukocytes. . . . . . . . . . . . . . . . . . . . . . . . . .. 183 Lymphocytes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 183 Monocytes and Alveolar Macrophages ..................... 183

Effects on Host Resistance to Bacterial Infections. . . . . . . . . . . . .. 183 Fever. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 184

The Immunologic Response in Influenza ........................ 184 Humoral Antibody Response. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 184

Nature and Kinetics of the Response ........................ 184 The Antigenic Spectrum of Primary Antibody Response in

Influenza. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 186 Antibody Response to NA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 187 Antibody Response to Internal Antigens of the Virus. . . . . . . .. 187

Anamnestic Response in Influenza: "Original Antigenic Sin" . . .. 187 Nonspecific Effects of Influenza Virus on Immune Response. . .. 187

Cell-Mediated Immune Response in Influenza. . . . . . . . . . . . . . . . .. 188 Macrophage Response ..................................... 188 Lymphocyte-Mediated Responses ............. . . . . . . . . . . . . .. 188

Helper T Cells ......................................... 188 Cytotoxic T Lymphocytes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 188

Antibody-Dependent Cell-Mediated Cytotoxicity against Influenza Virus-Infected Cells. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 189

Immunologic Basis of Recovery from Influenza. . . . . . . . . . . . . . . .. 189 The Role of Interferon ................................. . .. 189 The Role of Antibody in Recovery from Influenza. . . . . . . . . . . .. 191 Early Cellular Immune Responses and Recovery. . . . . . . . . . . . .. 191 Other Factors That May Influence Recovery. . . . . . . . . . . . . . . . .. 191

Modulation of the Cellular Immune Response. . . . . . . . . . . . . .. 191 The Importance of an Intact Complement Pathway .......... 192

Immunity to Influenza. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 192 Homologous Immunity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 192 Heterovariant (Intrasubtypic) Immunity ....................... 194 Heterosubtypic Immunity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 194 Serum Antibody as a Marker for Immunity in Influenza ...... . .. 194

The Pathology of Influenza. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 195 Influenza Virus Pneumonia. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 198 Clinical Pathology of Influenza. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 202

Therapy of Influenza . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 202 Specific Chemotherapy: Amantadine .. . . . . . . . . . . . . . . . . . . . . . . .. 202

Mechanism of Action ..................................... 203 Pharmacology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 203 Toxicity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 203 Drug Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 203

CONTENTS xvii

Ribavirin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 204 Supportive and Physiological Therapy . . . . . . . . . . . . . . . . . . . . . . . .. 204 Management of Influenza Virus Pneumonia. . . . . . . . . . . . . . . . . . .. 204

References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 205

8. The Laboratory Diagnosis of Influenza

Introduction ................................................ 219 Virus Isolation and Identification. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 219

Animal Inoculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 219 Chick Embryos . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 220 Cell Culture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 220

Primary Cell Culture. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 220 Continuous Cell Lines. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 220

Virus Identification. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 221 Direct Demonstration of Influenza Viruses or Viral Proteins in

Patients' Specimens ........................................ 221 Electron Microscopy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 221 Immunofluorescence ....................................... 221 Enzyme Immunoassay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 222

Measurement of Specific Antibody Response. . . . . . . . . . . . . . . . . . . .. 222 Hemagglutination Inhibition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 222 Neutralization ........................ . . . . . . . . . . . . . . . . . . . .. 224 Complement Fixation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 224 Single Radial Hemolysis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 224 Enzyme Immunoassay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 225 Neuraminidase Inhibition ................................... 225

References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 225

9. Animal Influenza: Ecology and Disease

Introduction ................................................ 229 Ecology of Influenza Viruses .................................. 229

Distribution of Influenza A Viruses in Nature ...... . . . . . . . . . . .. 229 Host Range of Influenza Viruses. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 230

Animals in Which Serially Propagated Infections Occur .. . . . . .. 230 Animals Subject to Sporadic Infection ....................... 230 Animals Susceptible to Laboratory Infection . . . . . . . . . . . . . . . . .. 232

Host Specificity of Influenza Viruses . . . . . . . . . . . . . . . . . . . . . . . . .. 232 Interspecific Transmission. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 234

Man to Animals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 235 Animals to Man. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 235

Infection of Animals with Influenza Band C Viruses . . . . . . . . . . .. 235 Disease in Commonly Infected Species. . . . . . . . . . . . . . . . . . . . . . . . .. 236

Influenza in Swine ........................................ , 236 The Viruses ............................................. 236 The Disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 236

xviii CONTENTS

Epizootiology .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 237 Swine Influenza Virus Infection Outside the United States. . . . .. 237

Influenza in Horses ........................................ 238 The Viruses ............................................. 238 Antigenic Variation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 239 The Disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 239 Epizootiology ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 239

Influenza in Domestic Fowl . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 240 Chicken . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 240

The Viruses ............................................. 240 The Disease .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 241 Epizootiology .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 241

Turkey. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 242 The Viruses ............................................. 242 The Disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 242 Epizootiology .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 242

Ducks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . .. 242 The Viruses ............................................. 242 The Disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 242 Epizootiology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 243

Animals Subject to Sporadic Infection. . . . . . . . . . . . . . . . . . . . . . . . . .. 243 Epizootic and Enzootic Influenza in Wild Mammals and Birds. . . . .. 243

Influenza in Migratory and Other Birds. . . . . . . . . . . . . . . . . . . . . . .. 243 Epizootic Influenza in Seals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 244

Influenza in Laboratory Animals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 244 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 245

IV. EPIDEMIOLOGY, SURVEILLANCE, AND CONTROL

10. The EpideIlliology of Influenza

Introduction ................................................ 255 Influenza Surveillance and the Ascertainment of Infection ......... 255

Laboratory Surveillance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 256 Virus Isolation and Identification ........................... 256 Serological Surveillance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 257

Measurements of Morbidity ................................. 258 Direct Methods .......................................... 258 Indirect Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 261

Impact on Mortality Rates. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 261 Influenza as a Burden on the Public Health. . . . . . . . . . . . . . . . . . . . .. 262 Pandemic, Epidemic, and Endemic Disease . . . . . . . . . . . . . . . . . . . . .. 264 Epidemiologic Determinants of Influenza. . . . . . . . . . . . . . . . . . . . . . .. 264

Viral. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 264 Antigenic Variation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 264

CONTENTS xix

Variation in Other Viral Properties . . . . . . . . . . . . . . . . . . . . . . . . .. 266 Host Factors .............................................. 266

Age. . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 266 Immune Phenotype. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 267 Host Genotype. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 267 Other Host Factors ....................................... 268

Environmental Factors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 268 Season and Climate. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 268 Crowding and Infection Density . . . . . . . . . . . . . . . . . . . . . . . . . . .. 269

Pandemic Influenza. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 270 Pandemics Defined. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 270 Pandemic Determinants. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 271 Pandemicity and the Phenomenon of Viral Disappearance. . . . . . .. 272 Conditions for the Entry of Pandemic Viruses . . . . . . . . . . . . . . . . .. 275

Interpandemic Influenza . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 275 Endemic Influenza. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 277 Epidemiology of Influenza Band C . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 277

Influenza B ............................................... 277 Influenza C ............................................... 278

Experimental and Theoretical Epidemiology of Influenza. . . . . . . . . .. 278 Theoretical Epidemiology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 278 Experimental Epidemiology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 278

Molecular Epidemiology and Epizootiology of Influenza. . . . . . . . . . .. 279 Intraepidemic Viral Heterogeneity . . . . . . . . . . . . . . . . . . . . . . . . . . .. 280 Reassortment of Influenza A H1N1 and H3N2 Viruses in Humans 280 Tracing of an Epidemic (Epizootic) Virus. . . . . . . . . . . . . . . . . . . . . .. 281 Molecular Surveillance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 281 Evidence of Viral Fixation and Reappearance. . . . . . . . . . . . . . . . . .. 281 Implications of Molecular Evolution for Influenza Epidemiology:

The Case of Influenza C Virus ............................. 281 The Limitations and Promise of Molecular Epidemiology. . . . . . . .. 282

References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 282

11. The Control of Influenza

Introduction ................................................ 291 Vaccines: Licensed and Experimental. . . . . . . . . . . . . . . . . . . . . . . . . .. 291

The Immunology of Influenza Vaccination. . . . . . . . . . . . . . . . . . . .. 291 Categorical Problems in the Artificial Presentation of Antigen . .. 293 Kinetics and Duration of Response to Influenza Vaccines. . . . . .. 293 Homologous (Variant-Specific) Immunity. . . . . . . . . . . . . . . . . . . .. 294 Homosubtypic (Heterovariant) Immunity. . . . . . . . . . . . . . . . . . . .. 294 Homotypic (Heterosubtypic) Immunity ...................... 295 Local versus Systemic Immunity. . . . . . . . . . . . . . . . . . . . . . . . . . .. 295 Induction of Cellular Immunity by Vaccines. . . . . . . . . . . . . . . . .. 297 Vaccine-Induced Response to Internal Viral Proteins .......... , 297

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Host Differences in Immunologic Responses to Vaccine. . . . . . .. 298 The Influence of Vaccine Dosage on Response to Inactivated

Influenza Vaccines. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 298 Effects of the Route of Vaccine Administration: Nonreplicating

Antigen Vaccines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 299 The Use of Adjuvants. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 300

Nonreplicating Antigens. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 301 Inactivated Virus. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 301 Subvirion Components: Split and Subunit Vaccines. . . . . . . . . . .. 302 New Approaches to the Formulation of Purified Antigen

Vaccines .............................................. 303 Submolecular Antigens: Oligopeptides. . . . . . . . . . . . . . . . . . . . .. 304 Antigenicity of the HA2 Chain of the HA. . . . . . . . . . . . . . . . . .. 304 Synthetic HA Oligopeptides and Cellular Immunity . . . . . . . . .. 304 Potential Advantages and Problems of Submolecular and

Synthetic Immunogens . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 305 Replicating Antigens. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 305

Mutants. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 305 Empirically Selected Attenuated Viral Vaccines. . . . . . . . . . . . .. 305 Marker-Selected Mutants ............................... " 305

Host range (hr) mutants. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 305 Temperature-sensitive (ts) mutant vaccines. . . . . . . . . . . . . . .. 306 Cold-adapted (ca) mutants . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 306 Hemagglutinin (HA) inhibitor-resistant mutants . . . . . . . . . . .. 307

Wild-Type (Avian/Human) Influenza Virus Reassortants . . . . . . .. 307 Mutant Reassortants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 307

Wild-Type Laboratory-Adapted hr Mutants ................. 307 Wild-Type-ts Mutant Reassortants ....................... " 307 Wild-Type-ca Mutant Reassortants . . . . . . . . . . . . . . . . . . . . . . .. 307

Reassortant Mutants. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 309 Live Influenza Virus Vaccines: Summary. . . . . . . . . . . . . . . . . . . .. 309 Cloned Influenza Virus HA Gene Replicated and Expressed in

Vaccinia. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 309 Comparison of Replicating versus Nonreplicating Influenza Virus

Antigens in Vaccination ................ . . . . . . . . . . . . . . . . . .. 309 Infection-Permissive Immunization with NA-Specific Vaccine: A

Diphasic Approach to Influenza Immunization . . . . . . . . . . . . . . .. 310 Vaccine Standardization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 310 Complications of Influenza Vaccination ...................... " 312

Intrinsic Viral Cytotoxicity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 313 Nature of Vaccine Reactions ...... . . . . . . . . . . . . . . . . . . . . . . . .. 313

Local Reactions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 313 Systemic Reactions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 313 Hypersensitivity Reactions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 314

Neurological Complications of Influenza Vaccination. . . . . . . . . .. 314 Vasculitis ............................................... 316

CONTENTS xxi

Effects of Influenza Vaccine on Drug Metabolism. . . . . . . . . . . .. 316 Untoward Effects of Live-Virus Vaccines .................... , 316

Chemoprophylaxis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 317 Specific Recommendations for the Control of Influenza by Vaccine

and Chemoprophylaxis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 317 Target Groups for Vaccination ... . . . . . . . . . . . . . . . . . . . . . . . . . . .. 318 Vaccine Recommendations .................................. 319 Antiviral Agent: Amantadine. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 319

Control of Animal Reservoirs of Infection ....................... 319 Sociological and Economic Problems in the Control of Influenza . . .. 321

Implementation of Present Vaccination Policy. . . . . . . . . . . . . . . . .. 321 Vaccine Efficacy in Different Populations .. . . . . . . . . . . . . . . . . .. 321 Strategies for Vaccine Administration. . . . . . . . . . . . . . . . . . . . . . .. 322 The Perennial Problem in Vaccine Supply. . . . . . . . . . . . . . . . . . .. 323

Mass Vaccination against Pandemic Disease: The Swine Influenza Vaccination Program as Paradigm. . . . . . . . . . . . . . . . . . . . . . . . . .. 324 The Influenza Epidemic at Fort Dix, New Jersey in 1976 ...... , 326 Swine Influenza Virus Infection at Fort Dix as a Pandemic

Threat. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 327 New Information. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 327 Unknown at That Time. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 327 Known at That Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 327 Epidemiologic Precedent .. .............................. 327

The National Immunization Program. . . . . . . . . . . . . . . . . . . . . . .. 328 The Decision to Undertake Mass Immunization ............. 328 Implementation of the Program .......................... , 328

The Lessons of 1976 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 331 About Influenza ....................................... , 331 About Mass Immunization: A Retrospective Assessment of the

National Immunization Program. . . . . . . . . . . . . . . . . . . . . . . .. 331 Planning for Future Mass Immunization Programs in Response

to Threats of Pandemic Disease . . . . . . . . . . . . . . . . . . . . . . . . . .. 331 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 332

Index. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 347