Lecture 16: Virology Flashcards by Amelia Humphrey

What is a virus

A package of genetic information (can be DNA or RNA) protected by a protein shell for delivery into a host cell to be expressed and replicated

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Who intially described virus

Eward Jenner in 1798

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What are the four characteristics which differentiate viruses from other micro-organisms

nucleic acid (either have DNA or RNA) not both
Lack of nuclear membrane and external cell wall
Very small genomes, so only codes for a very small number of proteins
Do not possess intracellular systems (like ribosomes), they are obligate intracellular parasites, meaning that they depend on a host cell and use their machinery to replicate

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What is the largest bacterial cell

smallpox virus (200 nm x 300 nm), need an electron microscope to see

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What does the tobacco mosaic virus infect

plants

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When were smallpox pustules found

found on 3000 year old mummy of Pharaoh Ramses

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What virus was found in 1400 BC

Paralytic poliomyelitis which causes leg deformities

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What viral diseases were found over the past 1000 years

Smallpox and measlses

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What viral diseases were found over the past 100 years

Spanish Influenza, HIV

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What viral disease made human life expectancy decrease

Spanish influenza

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What viral diseases were found over the past 10 years

West Nile, SARS, MERS, Avian Flu, HINI pandemic flu, Ebola, SARS-CoV2

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How are viruses named/classified

Usually based on data available at the time of discovery

Based on;
Disease
Cyto-pathology (what they cause)
Site of isolation
Places or people that discovered them
Biochemical features

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What viruses were named based on the disease they are associated with

HIV, Measles

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What viruses were named based on their cyto-pathology they cause

Cytomegalovirus

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What viruses were named based on their site of isolation

Adenovirus, Enterovirus, Phinovirus

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What viruses were named based on the people or places that discovered them

Epstein-Barr virus, West Nile Fever

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What viruses were named based on biochemical features

Retrovirus

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What is viral classification is based upon

Size and shape

Enveloped or naked

Nucleic acid compostion (RNA or DNA)

Genome organization

Antigenic differences (Ex. H1N1)

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What are capsomere

Smallest protein subunit of the capsid

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What is a capsid

Capsomers assemble to form viral capsid - surrounds the viral genome

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Nucleocapsid

Capsid + genomic nucleic acids (DNA or RNA) virus found within

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What is the typically shape of a capsid

symmetrical

What type of virus has a cubic/icosehedral shape

Herpes virus

Probs the most common type of shape

What virus has a helical shape

influenza virus

What is a complex virus

doesn't fit into the other two shapes ex., Pox virus

What are surface structures in viruses

Surface projections and glycoproteins bind host receptors to allow entry

What is the envelope of virus

lipid layer surrounding some viruses, it is derived from the host cell membrane

Is a virus with or without an envelope easier to kill

Enveloped virus is easier to kill, because the virus needs the envelope to survive

A ______ virus is stable in the environment

Non-enveloped virus

A ____ virus is labile in the environment

Enveloped virus

What does it mean if the virus is stable

Resist desiccation, acids, detergents or heat Ex. Viruses usually infect the gastrointestinal tract (norovirus and hepatitis A) Transmitted easily via hands and fomites

What does it mean if the virus is labile

damaged by drying (dies very quickly), acid, detergents or heat (herpes viruses, HIV, HCV, HBV, influenza) Must stay moist - transmitted in droplet or body fluids Do not usually infect the gastroinesteinal tract, usually blood-borne or respiratory

What is the composition of RNA viruses

RNA single stranded - positive polarity - negative polarity (need ti reversily translate to mRNA) RNA double stranded one segmented

What is the composition of DNA viruses

Single stranded or double stranded

What viruses are acquired via direct personal contact

Herpes viruses: skin -> skin HIV: need exposure to blood Influenza: close association likely not from a formit

What viruses are acquired via airborne spread

Chickenpox, measles

What viruses are acquired via fomites

enteroviruses, noroviruses

What viruses are acquired via vectors

West Nile from a misquoto

What viruses are acquired via vertical transmission

mom --> fetus HIV, Herpes simplex, cytomegalovirus, rubella (german measles)

What viruses are acquired via enteral

(food/waterborne) Hepatitis A, gastroenteritis viruses

What are the steps of the virus life cycle at the cellular level

1. attachment 2. penetration 3. uncoating 4. transcription 5. translation 6. genome replication 7. assembly 8. release

What are the steps of infection at an organism level

This is the host interaction 1. Entry into host 2. Primary replication 3. Spread 4. Cell and tissue tropism 5. Secondary replication 6. Cell injury or persistence 7. Host immune response

What are the consequences of virus-cell interactions

Viral proliferation and cell lysis Latent infection (non replicating virus) Persistent infection (ongoing viral replication, few or no symptoms) ocogenesis (cellular proferation) No apparent disease

What viruses can result in Viral proliferation and cell lysis

cold sores (HSV), gential herpes (H1S1 or HSV2), chickenpox

What viruses can result in latent infection (non replicating virus)

Herpes viruses, human papilloma viruses

what viruses can result in persistent infection (ongoing viral replication, few or no symptoms)

Hepatitis C and B, HIV Tissue injury may be induced by the virus or an immune response to th eviral infection

what virus can result in oncogenesis

human papilloma virus, EMV

What virus has no apparent disease

Hepatitis G

What are the different ways of diagnosing viral infections

Clinical faetures Laboratory diagnosis: - Detection of viral antigens in tissues/in serum Antibody testing through virus isolation - rising IgG, IgM, very high titer IgG , any IgG) DNA or RNA amplification: in tissue sections, from tissues, in serum and fluids

What is a syndromic approach

when viruses can be found in multiple places ex. herpes

What are prions

"proteninceous infectious partciles" An infectious agent composed of protein

What are characteritics of prions

a prion dose not self replicate, it induces existing protein to take on the "rogue" form Very highly resistant (exterme temperatures, both dry and wet as well as radition) Causes severe neurological diseases in host of mammalian species

What are examples of the spongifoem encephalopathies in the human form

Human forms from prions are Creutzfeldt-Jacob Disease (takes decades to become disease) New varient of the disease can come on within 5 years Kuru (neurological disease caused from eating brains

What are examples of the spongifoem encephalopathies in the animal form

Bovine Spongiform Encephalopathy, AKA: Mad Cow Disease Can potentially be transmitted to humans