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Biology 512 - General Virology

10:00 -10:50 am, MWF

2023 Haworth Hall

Instructors: Dr. Constance HallbergDr. David Davido

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Virology - the study of viruses

- structure of viruses

- virus replication

- virus - host interaction

- evolution of viruses- virus epidemiology

- diseases caused by viruses

Includes:

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Viruses infect almost all organisms

- Bacteria

- Algae- Plants

- Fungi

- Insects- Other Invertebrates

- Vertebrates

Including:

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Discovery of viruses

1892: First observation of a filterable infectious agent

tobacco mosaic virus (TMV)

1898: First description of a filterable animal infectious agentfoot and mouth disease virus (FMDV)

1901: First identification of a human virusyellow fever (YF) virus

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Viruses in human history

1580-1350 B.C.

withered leg

poliovirus

Striped tulips

appeared in 1576

tulip mosaic virus

Was Alexander theGreat killed by

West Nile virus?

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New viruses emerge in addition to those already known

- influenza virus

- respiratory syncytial virus

- dengue virus- West Nile virus

- measles

Previously known: Recently emerged:

- HIV

- Nipah virus

- Ebola virus- Sin Nombre virus

- SARS coronavirus

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Viruses are important tools in molecular and cellular biology

- cellular oncogenes first discovered due to their presence

in retroviruses that could transform cells (1966, F. Rous)

Nobel Prizes involving virology:

- use of restriction enzymes and recombinant DNAtechnology using SV40 virus (1978; D. Nathans, P. Berg)

- discovery of reverse transcriptase from retroviruses(1975; D. Baltimore, H. Temin)

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What is a virus?

- an infectious, obligate, intracellular parasite

- viral genome is comprised of DNA or RNA

- viral genome is replicated within a host cell and viral

components are synthesized by cellular machinery

- a virion, or infectious virus particle, is assembled from

newly synthesized viral proteins and viral genome

- progeny virions transmit the viral genome to new host

cells to initiate the next infectious cycle

Properties of viruses:

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Major components of a virion

1. viral genome

comprised of DNA or RNA

2. capsid or nucleocapsid

capsid: protein shell surrounding the viralgenome in a virus particle

nucleocapsid: a nucleic acid - protein assembly

packaged within the virion3. envelope - host cell derived lipid bilayer containing

viral glycoproteins

the outer layer of many virus particles

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Classification of viruses

- virion size

- virion shape

- capsid symmetry

- presence or absence of an envelope

examples: Fig. 2.1

1. Virion morphology:

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Virion morphology

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Classification of viruses

- RNA: single or double stranded

segmented or non-segmented

positive or negative sense

RNA-dependent RNA replication

- DNA: single or double strandedDNA-dependent DNA replication

- viruses that encode reverse transcriptase

RNA or DNA

2. Genome structure:

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Classification of viruses

- replication strategy

genome type

host involvement

- host range

plant viruses

insect virusesviruses of vertebrates

- mode of transmission

arboviruses

3. Biologic properties:

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ICTV classification

Order ....virales

Example Mononegavirales

viruses with a single piece of negative sense RNA as a genome

Family ....viridae

Fundamental unit of virus taxonomy

Table 1.2 lists majorvirus families

Subfamily ....virinae

Genus ....virus

International Committee on Taxonomy of Viruses

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ICTV classification

Example:

Family: Herpesviridae

Subfamily:Alphaherpesvirinae

Genus: Simplexvirus (HSV-1)

causative agent of cold sores

Varicellovirus (VZV)causative agent of chickenpox and

shingles