Viruses and Prions Transes

Flashcards about Viruses and Prions, covering topics such as the history of virology, viral structure, classification, multiplication, and their impact on human health.

Louis Pasteur

French scientist who hypothesized that rabies was caused by a living thing smaller than bacteria and developed the first vaccine for rabies in 1884.

Dimitri Ivanovski and Martinus Beijenrick

Scientists who showed that a disease in tobacco plants was caused by the tobacco mosaic virus, proving that plants can become hosts.

Friedrich Loeffler and Paul Frosch

Scientists who discovered an animal virus that causes foot-and-mouth disease in cattle, proving that viruses can also cause infections in animals.

Virus

Term proposed by Louis Pasteur to denote the special group of infectious agents.

Filterable Virus

Infectious fluids passed through porcelain filters designed to trap bacteria, but the cell-free filtered fluid remained infectious proving that an agent smaller than bacteria was the cause of the disease.

Viruses

A unique group of biological entities known to infect every type of cell and can either be inactive or active.

Unique Properties of Viruses

Infectious particles rather than organisms; active or inactive rather than alive or dead; obligate intracellular parasites.

Properties of Viruses

Not cells; obligate intracellular parasites; inactive outside the host cell and active only inside host cells; have a protein shell surrounding a nucleic acid core.

Viral Size Range

Smaller than the average bacterium and require electron microscopes to detect them.

Capsid

Shell surrounding the nucleic acid in a virus.

Nucleocapsid

Capsid and nucleic acid together.

Envelope

A modified piece of the host cell membrane found in some viruses.

Spikes

Found on both naked and enveloped viruses and allow viruses to dock with their host cells.

Naked Viruses

Viruses that consist only of a nucleocapsid.

Virion

A fully-formed virus that is able to establish infection in a host.

Virome

The totality of all viruses associated in one’s body.

Microbiome

Summation of all microorganisms (unicellular / multicellular) associated with one’s body

Genome

Summation of the genetic material in one’s body.

Capsomeres

Identical protein subunits that spontaneously self-assemble to form the capsid.

Helical Capsids

Capsid type with rod-shaped capsomeres that form a continuous helix around the nucleic acid.

Icosahedral Capsids

Capsid type that form icosahedron, a 3D, 20-sided figure with 12 evenly spaced corners.

Complex Capsids

Capsid type found in bacteriophages that is asymmetrical and may have multiple layers of proteins.

Spikes

Protruding glycoproteins essential for attachment to the host cell, found on the viral envelope.

Genome

The full complement of DNA and RNA carried by a cell or virus.

Positive-sense RNA

Single-stranded RNA genomes ready for immediate translation into proteins.

Negative-sense RNA

RNA genomes that need to be converted into the proper form to be made into proteins.

Polymerases

Synthesize DNA and RNA.

Replicases

Copy RNA.

Reverse Transcriptase

Synthesizes DNA from RNA.

Normal Microbiota

The microorganisms that live inside and on humans.

Adsorption

In the life cycle of animal viruses, this begins when the virus encounters a susceptible host and attaches specifically to receptor sites on the cell membrane.

Adsorb

Attachment of a virus to a host cell.

Host Range

The range of cells a virus can invade; can be restricted, moderately restrictive, or broad.

Endocytosis

Entire virus is engulfed by the cells and enclosed in a vacuole or vesicle.

Uncoating

Enzymes in the vacuole dissolve the envelope and capsid, releasing the virus into the cytoplasm.

Latency

The ability of a virus to remain dormant within the host cell, sometimes establishing lifelong occult infection.

Release of Mature Viruses

Enveloped viruses are liberated by budding or exocytosis.

In vivo methods

Viral cultivation in lab animals or embryonic bird tissues.

In vitro methods

Viral cultivation in cell or tissue culture.

Cell culture / tissue culture

In vitro virus cultivation systems.

Primary cell cultures

Fresh isolated animal tissue is placed in a growth medium.

Continuous cell cultures

Have altered chromosome numbers, grow rapidly, and can be continuously subcultured.

Plaques

Clear, well-defined patches in the cell sheet, macroscopic manifestations of cytopathic effects.

Interferon (IFN)

Naturally occurring human cell product used with some success in preventing and treating viral infections.

Spongiform Encephalopathies

Implicated in chronic, persistent disease in humans and animals, causing brain tissue to resemble a sponge.

Prions

Distinct protein fibrils deposited in brain tissue of affected animals, common feature of spongiform encephalopathies.

Creutzfeldt-Jakob Disease (CJD)

Afflicts the CNS of humans, causes gradual degeneration and death, and is transmissible by an unknown mechanism.

Satellite Viruses

Dependent on other viruses for replication.

Viroids

Virus-like agent that parasitizes plants, composed only of naked RNA strands.

Lysogeny

A process where a bacteriophage infects a bacterium but does not immediately kill it. The viral DNA integrates into the host's chromosome, becoming a prophage.

Bacteriophages

Bacterial viruses.

Penetration

In the life cycle of animal viruses, this involves penetration and releasing of the viral genome into the host cell.