Molecular and Cellular Biology of Viruses

Phoebe Lostroh

• Publisher: Garland Science
• Year: 2019
• ISBN:
  9780429664304
• Topic: Biological Sciences
• Subtopic: Microbiology & Molecular Biology
• Edition: 1

Viruses interact with host cells in ways that uniquely reveal a great deal about general aspects of molecular and cellular structure and function. Molecular and Cellular Biology of Viruses leads students on an exploration of viruses by supporting engaging and interactive learning. All the major classes of viruses are covered, with separate chapters for their replication and expression strategies, and chapters for mechanisms such as attachment that are independent of the virus genome type. Specific cases drawn from primary literature foster student engagement. End-of-chapter questions focus on analysis and interpretation with answers being given at the back of the book. Examples come from the most-studied and medically important viruses such as HIV, influenza, and poliovirus. Plant viruses and bacteriophages are also included. There are chapters on the overall effect of viral infection on the host cell. Coverage of the immune system is focused on the interplay between host defenses and viruses, with a separate chapter on medical applications such as anti-viral drugs and vaccine development. The final chapter is on virus diversity andevolution, incorporating contemporary insights from metagenomic research.

Key selling feature:

• Readable but rigorous coverage of the molecular and cellular biology of viruses
• Molecular mechanisms of all major groups, including plant viruses and bacteriophages, illustrated by example
• Host-pathogen interactions at the cellular and molecular level emphasized throughout
• Medical implications and consequences included
• Quality illustrations available to instructors
• Extensive questions and answers for each chapter

The Fundamentals of Molecular and Cellular Virology

Virus	Characteristics
Human immunodeficiency virus (HIV)	Retrovirus responsible for the AIDS pandemic.
Variola	Cause of historical smallpox epidemic; eliminated through the use of vaccinia virus in prophylactic immunization.
Rabies virus	Pasteur intentionally attenuated this virus and subsequently employed the attenuated version for therapeutic immunization.
Bacteriophages	Viruses that infect bacteria and archaea; used as models for discovering the fundamental processes of molecular biology.
Influenza A virus	Cause of annual epidemics; occasional cause of global pandemics with high lethality.

The viruses you will meet in this chapter and the concepts they illustrate

In this book, you will learn how miniscule viruses enter, take over, and kill our cells. A molecular understanding of these processes provides insights into how both viruses and their host cells function at a molecular level. It is an exciting time to study viruses because of the breadth and depth of techniques available to investigate them, and the increasing number of known viruses and viral genome sequences (including those for viruses that have never been cultivated in the laboratory). In addition, there are many practical applications of virology. For example, basic research on the molecular biology of the human immunodeficiency virus (HIV) ultimately led to the first treatments that moved HIV infection away from being a death sentence to a chronic, controllable illness (Figure 1.1). Many applications such as these attract people to the field of virology.

Figure 1.1 HIV. This micrograph shows a single HIV virion exiting its host cell. (Courtesy of NIAID published under CC BY 2.0.)

In this chapter, we examine the origins of virology in order to explain how molecular and cellular virology fit into the broader discipline of virology. Molecular biology is fundamentally concerned with how macromolecules, especially proteins and nucleic acids, function to control the structure and behavior of cells. By extension, molecular and cellular virology studies focus particularly on the interactions among viral proteins, viral nucleic acids, cellular proteins, cellular nucleic acids, and cellular organelles. In Technique Box 1.1, we will see that some of the consequences of viral infection can be observed with a light microscope. After, we consider the characteristics shared by all viruses (Section 1.5). We will then discuss viral diversity (Section 1.6), especially with respect to their genomes and the mechanisms by which they synthesize mRNA (Section 1.7). We will also explain, in Section 1.7, how diverse viruses have been named and classified. We will encounter the general method of propagating viruses in a laboratory setting in Section 1.8. The chapter continues with a consideration of the abundance of viral sequences in the human genome (Section 1.9); indeed, DNA of viral origin is found in almost every known cellular genome, where it contributes to the evolution of organisms, including humans. The chapter concludes with a consideration of how sequences of viral nucleic acids and proteins can be used to generate hypotheses about the evolution, structure, and function of viruses and their component parts.

Our goal in this chapter is to prepare you for the rest of the book. Chapter 2 explains how we will divide the virus replication cycle into several parts. Chapters 3 through 11 will address each of these parts of the cycle in turn, with Chapters 5 through 10 focused on the different Baltimore classes of viruses and how they express and replicate their genomes. In Chapter 12, we will learn how viruses generally interact with host processes such as translation and apoptosis, and in Chapter 13, we will see how viruses can cause integrated and persistent infections that can last for the entire life span of their hosts. In Chapters 14 and 15 we will examine how hosts fight back against viral infections. Chapter 16 is about clinical applications of virology, such as vaccines, gene therapy, and antiviral drugs. Chapter 17 concludes with a discussion of the diversity and evolution of viruses.

1.1Molecular and cellular virology focuses on the molecular interactions that occur when a virus infects a host cell

Molecular and cellular virology investigates the molecular and cellular aspects of virus infection. For example, a typical research project in molecular and cellular virology would be to determine the function of each protein encoded by a viral genome. Another typical project would be to determine the subcellular localization of virus assembly in infected cells and the cellular factors that are required for that subcellular localization. Molecular and cellular virology studies have provided a molecular explanation for why HIV infects cells of the immune system but not other types of cells. Other studies conducted through the lenses of molecular and cellular biology have helped us begin to understand why the closely related severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS) coronaviruses cause similar yet distinct diseases (Figure 1.2).

Figure 1.2 The virus that causes severe acute respiratory syndrome. This scanning electron micrograph shows many of the coronaviruses with a close-up on one of the particles.

Molecular and cellular virology also has practical applications such as the design of antiviral medicines and vaccines (Figure 1.3). Antiviral medications typically interfere with viral enzymes not normally found in human cells, whereas vaccines cause a protective immune response to develop without making the treated person sick. Furthermore, viruses can be genetically engineered to serve as agents of gene therapy, which includes the introduction of a functional gene to reverse the effects of nonfunctional or dysfunctional inherited genes. Although we will not address in detail how translational scientists take findings from basic research and turn them into treatments or vaccines, the book will point out many instances where basic research has been used to better human health.

Figure 1.3 Early vaccination. In this watercolor image from 1802, the person on the left was inoculated with a small amount of smallpox virus; the person on the right was inoculated with cowpox virus instead. The person on the right will become immune to smallpox because of vaccination with the cowpox virus. (Courtesy of Wellcome Library, London. Published under CC BY 4.0.)

1.2The discipline of virology can be traced historically to agricultural and medical science

The meaning of the Latin word virus is poison. The name indicates that viruses were first discovered because of their role in producing disease in agriculturally important plants or animals, such as tobacco or livestock. In the late nineteenth century, European microbiologists invented a filter with pores smaller than the diameter of a bacterium that could remove all bacteria from a liquid suspension (Figure 1.4). Using this device to study tobacco mosaic disease revealed that the infectious agent could not be removed by filtration, and so the infectious substance must be smaller than a bacterium. Soon thereafter, other microbiologists showed that viruses were particles, not liquids, and that a virus also causes the agriculturally important foot-and-mouth disease, which can infect a...