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IMED2001 > Introduction to viruses > Flashcards

Introduction to viruses Flashcards

1
Q

What was the first virus identified?

A

Yellow fever virus

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2
Q

When was small pox introduced?

A

16th century to distinguish from great pox aka syphilis

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3
Q

What causes smallpox?

A

variola virus

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4
Q

What kind of virus is variola virus?

A

A poxvirus

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5
Q

What is so significant about smallpox?

A

It was the first disease successfully eradicated by vaccination

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6
Q

How many people did Spanish Flu kill?

A

> 50 million people

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7
Q

Why is it difficult to control pandemic influenza?

A

New strains continuously emerging

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8
Q

What cancer was HIV associated with?

A

Kaposi’s sarcoma

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9
Q

Are new emergences of viruses rare events?

A

No, new viruses emerge regularly

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10
Q

What is MERS?

A

Middle East Respiratory Syndrome, a new coronavirus disease that emerged in 2012 and by 2015 it had disseminated to 27 different countries

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11
Q

How fatal is MERS?

A

Fatal in 50% of infected

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12
Q

What was the origin of MERS?

A

Camel to human transmission

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13
Q

What is the host range of viruses determined by?

A

Virus requirements for attachment to host cell

Availability of host cell factors required by virus to replicate

Ability of virus to evade host defences

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14
Q

Can viruses cross species barriers?

A

Yes and they frequently do

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15
Q

How does mode of infection determine clinical outcome?

A

The cells which can be infected will determine what is damaged. (Eg. HIV attaches to CD4 so it can only infect CD4 T cells)

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16
Q

How does influenza virus A infect people?

A

It attaches to sialic acid on epithelial cells

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17
Q

What is the structure of a virus?

A

3 main parts:

Nucleic acid (DNA or RNA)

Protein coat (capsid)

Lipid membrane (envelope)

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18
Q

Are all viruses enveloped?

A

No

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19
Q

What is a virion?

A

A single virus particle

Infectious and fully developed

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20
Q

What type of structures can the viral nucleic acids be?

A

DNA or RNA

Single or double stranded

Linear or circular

Can be segmented

Size ranges from a few thousand nt to 250k or more

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21
Q

How many nts can giant viruses have?

A

1m+

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22
Q

What are some examples of giant viruses?

A

Mimivirus

Pandoravirus

23
Q

What is a capsid?

A

A protein coat that surrounds the nucleic acid

24
Q

What is the capsid used for?

A

It is a vehicle for transport and proteiction

25
Q

What makes up most of the mass of the virus?

A

The capsid

26
Q

What is a capsid made up of?

A

Repeated subunits called capsomeres.

27
Q

What are capsomeres made up of?

A

Single or several protein types. Arrangement is characteristic for the particular virus

28
Q

What are the types of viral morphologies that are possible?

A

Helical viruses

Icosahedral viruses

Complex

29
Q

What are helical viruses like structurally?

A

Rigid or flexible

Nucleic acid within hollow cylindrical, helical capsid

Spiral arrangement of capsomers around nucleic acid

30
Q

What are some examples of helical viruses?

A

Ebola

Influenza

31
Q

When was helical symmetry of viruses first described?

A

1955 by Fraenkal, Conrat and Williams

32
Q

How are icosahedral viruses formed?

A

Capsomers assemble into 20 equilateral triangular faces

33
Q

What can regular complex viruses look like?

A

Capsids can have both helical and icosahedral symmetry.

Additional structures can also be present such as the capsid (polyhedral) and the sheath (helical)

Think of bacteriophages to understand this better

34
Q

What can irregular complex viruses look like?

A

Non-symmetrical capsid structure (eg pox viruses)

They lack clearly identifiable capsids

Several coats can be present around the nucleic acids

35
Q

What can envelope of virus be used for?

A

To group viruses

36
Q

What are viral envelopes made of?

A

Outer lipid membrane derived from host membrane and contains viral proteins.

37
Q

What does the viral envelope do?

A

Mediates viral attachment to host cells for cell entry

38
Q

What structures do enveloped viruses usually have?

A

Helical or icosahedral

39
Q

How are viruses seen?

A

EM

40
Q

How small are viruses?

A

100 times smaller than a single bacterial cell

41
Q

What did mimivirus resemble when it was first discovered?

A

Gram positive bacteria residing within amoeba

42
Q

How does sputnik replicate itself if it cannot replicate in acanthamoeba by itself?

A

It uses the machinery of another virus called mamvirus to replicate itself.

43
Q

What are the ways viruses are classified?

A

Orders (-virales)

Families (-viridae)

Genera (-virus)

Species

44
Q

How are viruses grouped into families?

A

Morphology

Nucleic acid type (RNA or DNA)

Strategy of replication

45
Q

What are the criteria for grouping viruses into genera?

A

Primary criteria:

Significant differences in genome sequence

Minor difference in genome structure

Type species: virus which has all the properties characteristic of a certain genus

46
Q

What are the criteria for grouping viruses into a certain species?

A

Separate species associated with serological differences, genomic differences, and structural + physical properties.

47
Q

What is a species when talking about viruses?

A

Defined as class of viruses with many properties that constitutes a replicating lineage and occupies a particular ecological niche

48
Q

How are new species of virus created?

A

Variant species arise as a result of minor mutations in genome

49
Q

How are species subgrouped?

A

Subtypes

Clades

Strains

Variants

Quasispecies

50
Q

What are prions?

A

Non-viral proteins that cause disease. (eg spongiform encephalopathy)

51
Q

What diseases are caused by prions?

A

Chronic wasting disease in deer

Mad cow disease

Cruetzfeldt-Jakob disease in humans (vCJD)

Kuru - first identifiable spongiform encephalopathy

52
Q

Where are prions typically located?

A

In nervous tissue

53
Q

What do prions do?

A

Convert glycoprotein PrP(c) to PrP(Sc) [misfolds the protein]

54
Q

How is mad cow disease transmissible?

A

Surgical instruments

Orally: via consumption of infected meat/nervous tissue

IMED2001 (44 decks)

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