Textbook of Medical Virology (eBook)

Erik Lycke, ERLING NORRBY (Herausgeber)

eBook Download: PDF | EPUB

2014 | 1. Auflage
384 Seiten
Elsevier Science (Verlag)
978-1-4831-9194-2 (ISBN)

Infos

Textbook of Medical Virology presents a critical review of general principles in the field of medical virology. It discusses the description and molecular structures of virus. It addresses the morphology and classifications of viruses. It also demonstrates the principal aspects of virus particle structure. Some of the topics covered in the book are the symmetrical arrangements of viruses; introduction to different families of animal viruses; biochemistry of virus particles; the immunological properties and biological activities of viral gene products; description of enzymatic activities of viruses; and haemagglutination, cell fusion, and haemolysis of viruses. The description and characteristics of viral antigens are covered. The identification and propagation of viruses in tissue and cell cultures are discussed. An in-depth analysis of the principles of virus replication is provided. A study of the morphogenesis of virions is also presented. A chapter is devoted to virus-induced changes of cell structures and functions. The book can provide useful information to virologists, microbiologists, students, and researchers.

Inhalt

Front Cover 1
Textbook of Medical Virology 4
Copyright Page 5
Table of Contents 10
Preface 6
List of contributors 8
Chapter 1. Viruses - a unique kind of infectious agent 16
Bibliography 18
Chapter 2. The morphology of virus particles. 
19 
Infectious nucleic acid 19
Principal aspects of virus particle structure 19
Live or dead 
20 
Structural proteins - symmetry arrangements 20
The virus envelope 23
Classification of viruses 24
Introduction to different families of animal viruses 27
Bibliography 31
Chapter 3. The biochemistry of virus particles 32
Virus-DNA 32
Virus-RNA 35
Virus proteins 38
Additional components in virions 42
Bibliography 42
Chapter 4. Viral gene products their immunological
43 
Viral antigens 43
Haemagglutination 47
Cell fusion and haemolysis 50
Enzymatic activities of viral gene products 51
Bibliography 52
Chapter 5. Cultivation of viruses 53
Identification and propagation of viruses in tissue and cell cultures 53
Identification and propagation of viruses in embryonated hen's eggs 57
Identification and cultivation of viruses in experimental animals 58
Bibliography 59
Chapter 6. General views on virus replication 60
Morphological methods for analysis of virus replication 60
Molecular methods for characterization of virus replication 61
Quantitative determination of virus infectivity 61
Quantitative determination of other biological properties of viral 
63 
The different phases of virus replication 63
Bibliography 65
Chapter 7. Attachment of viruses to cell receptors and 
66 
Virus and receptors 67
Penetration 68
Bibliography 71
Chapter 8. Replication, transcription and translation of 
72 
Classes of RNA viruses 72
Reoviruses 74
Picornaviruses 75
Togaviruses 78
Rhabdoviruses and paramyxoviruses 79
Orthomyxoviruses 81
Retroviruses 83
Bibliography 86
Chapter 9. Replication, transcription and translation of 
87 
Parvoviruses 87
Papovaviruses 89
Adenoviruses 91
Herpesviruses 94
Poxviruses 96
Bibliography 98
Chapter 10. The morphogenesis of virions 99
The maturation and release of non-enveloped viruses 99
The morphogenesis of enveloped viruses 99
Bibliography 107
Chapter 11. Virus-induced changes of cell structures and 
108 
Cytopathic changes 108
Inclusions in virus-infected cells 112
The effect of integration of viral antigens in cellular membranes 113
Effects of viruses on functions of highly specialized cells 113
Chromosomal changes 115
Virus-induced cell transformation 115
Interferon 119
Bibliography 119
Chapter 12. Virus genetics 120
Mutations 120
Recombination 123
Phenotypic mixing and complementation 124
Bibliography 126
Chapter 13. General aspects of pathogenesis of virus 
127 
Modes of transmission of virus diseases 129
The importance of cellular and viral receptor functions 131
The spread of virus infections within the body 132
The importance of barrier systems in limiting the spread of the 
134 
Influence of immune reactions on the pathogenesis 135
Influence of constitution, age, sex and genetic bacliground 137
Bibliography 139
Chapter 14. Pathogenesis of acute virus infections 140
Respiratory infections 140
Infections of visceral organs 141
Infections of the skin and mucous membranes 143
Infections of the nervous system 146
Bibliography 149
Chapter 15. The pathogenesis of congenital infections 150
Different ways by which a virus may cause fetal damage 151
Spread of virus in congenital infections 152
Direct effects of fetal infections 153
Indirect fetal-damaging effects in connection with infections of 
157 
Bibliography 158
Chapter 16. The pathogenesis of persistent infections 159
Chronic subclinical infections with immune pathological reactions 161
Latent infections 163
Slow virus infections caused by conventional viruses 166
Bibliography 169
Chapter 17. Slow infections caused by non-immunogenic 
170 
Different forms of infectious encephalopathy 170
Biological and physical-chemical properties of atypical infectious 
174 
How do atypical infectious agents spread? 175
Bibliography 177
Chapter 18. Viruses and tumours 178
Tumour viruses in animals 182
Human tumour viruses 189
Human tumour virus candidates 190
Bibliography 192
Chapter 19. Mechanisms of defence against virus infections 193
Non-specific immunity 193
Humoral immunity 195
Cell-mediated immunity 198
Immunopathological effects of virus infections 199
Virus infections in connection with malignant diseases and immune 
202 
Immunological defence against congenital virus infections 202
Bibliography 203
Chapter 20. Laboratory techniques for diagnosis of virus 
204 
Isolation of viruses 204
Direct identification of virus or viral antigens in samples from patients 208
Analysis of antibody response in patients 210
Evaluation of laboratory results 215
Bibliography 216
Chapter 21. The epidemiology of virus diseases 217
Methods of surveillance of the epidemiological occurrence of infectious 
217 
The dissemination mechanisms of virus infections 219
Epidemiological patterns of virus infections 221
Examples of the epidemiology of some virus diseases 221
Bibliography 226
Chapter 22. Inactivation of viral infectivity and disinfection 227
Bibliography 230
Chapter 23. Immune prophylaxis 231
Passive immunization 231
Active immunization 233
Bibliography 244
Chapter 24. Antiviral drugs 245
Mechanisms of action of antiviral drugs 245
Antiviral drugs used for clinical chemotherapy 247
Antiviral drugs with a potential clinical usefulness 250
Interferon 251
Bibliography 256
Chapter 25. Picornaviruses 257
Properties of picornaviruses 258
Enteroviruses 258
Rhinoviruses 263
Bibliography 265
Chapter 26. Togaviruses 266
Alphaviruses 268
Flaviviruses 268
Rubellavirus (Rubivirus) 271
Bibliography 276
Chapter 27. Orthomyxoviruses (influenza viruses) 277
Properties of the virus 277
Clinical features 279
Pathogenesis 280
Epidemiology 283
Laboratory diagnosis 284
Prophylaxis 285
Bibliography 286
Chapter 28. Paramyxoviruses 287
Parainfluenza virus 288
Mumps virus 291
Measles virus 294
Respiratory syncytial (RS) virus 297
Bibliography 300
Chapter 29. Adenoviruses 301
Properties of the virus 302
Clinical features 304
Epidemiology 306
Prophylaxis 307
Bibliography 307
Chapter 30. Hepatitis viruses 308
Properties of the virus 308
Clinical features 310
Pathogenesis 312
Immunity 313
Laboratory diagnosis 313
Epidemiology 315
Prophylaxis 317
Bibliography 318
Chapter 31. Herpesviruses 319
Properties of the virus 319
Latency and transformation 321
Herpes simplex virus (HSV) 
323 
Varicella-zoster virus (VZV) infections 329
Cytomegalovirus (CMV) infections 331
Epstein-Barr virus (EBV) infections 333
Bibliography 337
Chapter 32. Poxviruses 338
Classification 338
Properties of the virus 339
Variola (smallpox) 340
Smallpox vaccine (vaccinia virus) 340
The WHO smallpox eradication programme 341
Clinical features of variola 341
Laboratory diagnosis 342
Other medically important poxviruses 343
Bibliography 345
Chapter 33. Other viruses 346
Reoviruses 346
Retroviruses 346
Bunyaviruses 347
Arenaviruses 349
Coronaviruses 350
Rhabdoviruses (rabies virus) 351
Marburg/Ebola virus 353
Parvoviruses 354
Papovaviruses 354
Bibliography 355
Chapter 34. Viral syndromes 356
Respiratory tract infections 356
Infections of the pharynx 358
Infections with exanthemas 359
Hepatitis 360
Gastrointestinal infections 360
Urogenital infections 361
Infections of the nervous system 362
Infections of the sensory organs 364
Neonatal infections 365
Bibliography 366
Appendix: Chlamydia 368
Microbiology of chlamydiae 368
Chlamydia psittaci infections 369
Chlamydia trachomatis infections 369
Laboratory diagnosis 371
Susceptibility of chlamydiae to antibiotics 375
Index 376

Textauszug

2

The morphology of virus particles. Classification of viruses

Erling Norrby

Publisher Summary

This chapter focuses on the studies on morphology of virus particles and their classification. The composition of a conventional virus can be described as follows. Centrally, the particle contains nucleic acid of varying quantity. This nucleic acid is either RNA or DNA but never both kinds simultaneously. Only certain non-enveloped virions can be crystallized. The availability of viral crystals has facilitated three-dimensional analyses by aid of X-ray diffraction. Through earlier studies, it has been possible to shed light upon the interaction between virus nucleic acid and capsid protein. A single-stranded nucleic acid can direct the synthesis of a protein that has a size corresponding to about 1/7 of its molecular weight. Nature generally utilizes symmetrical building principles in the construction of more comprehensive three-dimensional structures. The name of Coronavirus has been given to designate the pattern of the club-like peplomers that radiate from the envelope.

The survival of organic life is dependent on its capacity to replicate genetic material. The most simplified natural form of a viral infectious agent therefore would comprise a limited amount of nucleic acid with capacity to direct its own replication. This form of infectious agent exists in plants but has not been identified so far in other host organisms. It is called viroid. Viroids are composed of a circular form of single-stranded RNA with a molecular weight of about 100000. It is not known how this nucleic acid can be replicated nor has it been clarified how this kind of agent can cause disease in the plants on which it forms a parasite.

Infectious nucleic acid

All known animal, insect and bacterial viruses have an extracellular transport form which includes nucleic acid and a protein shell in which this nucleic acid is enclosed. In some cases the particles also include additional structures. Isolated virus nucleic acid, DNA or RNA, may cause infection and initiate a synthesis of complete virus particles. The nucleic acid is infectious, however, only in cases when the complete virus particle does not contain any enzyme(s) needed to initiate replication (see Chapter 3). Free isolated infectious nucleic acid is an ineffective contagious entity. One single break in the nucleic acid molecule induced by physical or chemical factors will lead to the loss of its infectious capacity. It is therefore of importance to their survival that viral infectious agents have their nucleic acid packed into a protective protein shell during the transport between cells.

Principal aspects of virus particle structure

The composition of a conventional virus can schematically be described as follows. Centrally the particle contains nucleic acid of varying quantity. This nucleic acid is either RNA or DNA, but never both kinds simultaneously. The nucleic acid is surrounded by a protein shell, called capsid (from L. capsa = box). In the case of many viruses the nucleoprotein complex represents the whole virus particle. The virus particle is referred to as the virion. In more complex viruses further (one or more) enclosing structure(s) occur. This component is structurally similar to cellular membranes and is referred to as the envelope. An envelope is composed of proteins specific to the virus and lipids and carbohydrates which are taken preformed from the infected cell. Even the more complex virus particles do not contain organelle structures equivalent to, for example, mitochondria and lysosomes of cells. If strict definitions were applied, a virus should not be called a microorganism. However, for practical reasons, viruses are included in the group of microorganisms.

Virions thus have a relatively simple compostion and, as a consequence, they are small. The largest virions have dimensions of 320 × 270 × 120 nm, a size corresponding to that of certain forms of the smallest bacteria (mycoplasmas), whereas the diameter of the smallest virions is about 20 nm. The difference in volume is 5000-fold. In spite of this variation in dimensions, viruses have common features which motivates their classification as one common category of infectious agent. The limited size of virions allowed a distinction to be made between bacteria and viruses as cellular infectious agents in early studies. Virions were found to be capable of passing through filters which retained bacteria and they were therefore classed as being ultrafiltrable. Furthermore, bacteria were characterized by light microscopy whereas virus particles, because of their limited size, could not be detected. Information about the morphology and dimensions of virions could be clarified firstly through electron-microscopic analysis. Originally it was possible to get only a rough impression of the size and form of virus particles. In 1956 the negative contrast technique for electron microscopy was introduced. Instead of being stained with electron-dense substances, the particles were suspended in a contrast solution. With this technique new possibilities for detailed characterization of virus morphology became available.

Live or dead materia?

During the 1930s it was shown that purified virions of a plant virus could be crystallized. The fact that virus particles were giant molecules with a capacity to crystallize caused extensive discussion about whether a virus should be considered as live or dead materia. The extracellular virus particle which lacks energy-providing systems and has no capacity, or only a limited capacity, for independent metabolism obviously must be considered as a lifeless unit. Since it also lacks capacity for active movement, the transport of virions in time and space from cell to cell is a chance event. If a virion comes into contact with a susceptible cell, however, a sequence of events is initiated which fulfils all definitions of life, i.e. the reproduction of genetic material which is incorporated into new transport particles. The question about live or dead material becomes more complicated when we are dealing with defective viruses which have a capacity to replicate only in cells which concomitantly are infected with another virus (see Chapter 12).

Only certain non-enveloped virions can be crystallized. The availability of viral crystals has facilitated three-dimensional analyses by aid of x-ray diffraction. Through these studies it has been possible to shed light upon the interaction between virus nucleic acid and capsid protein.

Structural proteins – symmetry arrangements

A single-stranded nucleic acid can direct the synthesis of a protein which has a size corresponding to about 1/7 of its molecular weight. This fact caused Watson and Crick, well known for their description of the double helix nature of DNA, to postulate two important principles for the structuring of virus particles. The first principle was that the virus capsid must be built up of repetitive units; the second, that the structure of the capsid should be symmetrical. By use of the two above-mentioned methods of analyses – electron microscopy and x-ray crystallography – and chemical analyses, the correctness of these postulates has been verified. The number and character of the chemical units, structural proteins, which are the building stones in virions, have been described for the majority of animal viruses.

Nature generally utilizes symmetrical building principles in the construction of more comprehensive three-dimensional structures. Hereby, information can be spared since the design of the individual building stones can decide their mutual relationships and therefore allow a spontaneous assembly via crystallization-like processes. It is characteristic of nature that it alternates unique design and symmetrical arrangements on different levels of the organized biological hierarchy in both plants and animals.

The principle of symmetrical constructions is well illustrated by the design of virus particles. Two different forms of symmetry, helical and icosahedral have been used for the construction of virus capsids (Figure 2.1).

Figure 2.1 Schematic description of the structure of a virus with a helical (left part of the picture) or icosahedral (right part of the picture) internal component (nucleocapsid). The particle in the figure is surrounded by an envelope but many viruses lack this structure. A capsid represents the outermost protective structure in such non-enveloped viruses

Helical symmetry

Helical (screw-formed) capsid symmetry is used in the construction of rod-shaped plant virions and bacteriophages and the internal structure of some enveloped animal viruses. Among the rod-shaped viruses tobacco mosaic virus (TMV) has been studied in most detail since it can be obtained in large quantities and crystallized from the juice of leaves from diseased plants. TMV RNA has a molecular weight of 2 million. The nucleic acid winds in a helical form inside a protein helix structure and is thereby protected from external physical and chemical influences.

The protein helix is formed by 2130 units of one single protein with a molecular weight of 18000. The complex of nucleic acid and protein can be dissociated by addition of alkali....

Produkt-Details

• Erscheint lt. Verlag: 28.6.2014
• Sprache: englisch
• Themenwelt: Sachbuch/Ratgeber ► Gesundheit / Leben / Psychologie ► Krankheiten / Heilverfahren
• Themenwelt: Medizin / Pharmazie ► Medizinische Fachgebiete ► Mikrobiologie / Infektologie / Reisemedizin
• Themenwelt: Studium ► Querschnittsbereiche ► Infektiologie / Immunologie
• ISBN-10: 1-4831-9194-X / 148319194X
• ISBN-13: 978-1-4831-9194-2 / 9781483191942