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Virology RUSVM > Block 1 > Flashcards

Block 1 Flashcards

1
Q

Define virology

A

Virology: The study of viruses and viral diseases

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2
Q

Define virus

A

Virus: broad term to describe any aspect of the infectious agent and includes:
i. The infectious (viron) or inactivated virus particle
ii. Viral nucleic acid
iii. Protein in the infected cell

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3
Q

Define Virion

A

Virion: A complete/mature virus particle that consists of an RNA or DNA core
sometimes with external envelopes and that is the extracellular infective form of a virus

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4
Q

Define Viroid

A

Viroid: An infectious particle smaller than any of the know viruses, an agent of certain plant diseases
i. This particle only consists of extremely small circular RNA molecules,
lacking the protein coat/capsid of a virus

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5
Q

What is the importance of veterinary virology (3 examples)

A

a. Viruses cause high rates of mortality and morbidity in animals and birds
b. Viral diseases in animals and birds cause financial loss to livestock and poultry
industries
c. Some viruses are zoonotic

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6
Q

viruses are Non living entities
That Contain nucleic acid genome (DNA or RNA) surrounded by a protein coat (and
sometimes an envelope). All viruses are obligate intracellular parasites. What does this mean for the virus when outside and inside the cell?

A

i. Outside the cell, viruses are inert or dormant particles
ii. Inside the cell, viruses hijack and utilize the host cell’s machinery to
produce its proteins and nucleic acids for the next generation of virus

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7
Q

Viruses do not have what, make what, or can reproduce how?

A

i. Have standard cellular organelles
ii. Make energy or proteins by themselves
iii. Have the genetic ability to multiply by division
1. Viruses reproduce like an assembly line where various parts of the
virus come together from different parts of the host cell to form
new virus particles

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8
Q

What is the smallest virus?

A

Porcine circovirus type 1

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9
Q

What is the largest virus?

A

Poxvirus (200nm diameter & 300 nm in length) → humans,
animals and birds

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10
Q

What is pleomorphism?

A

the ability of some viruses to alter their shape and size

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11
Q

What is Electron microscopy?

A

Biological materials have little inherent contrast → need to be stained
Requires negative staining with electron dense material (Uranyl acetate, Phosphotungstate)

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12
Q

What is Cryo-Electron Microscopy (Cryo-EM)?

A

Allows observation of specimens in their natural environment (not stained or fixed) at cryogenic temperatures

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13
Q

What is X-Ray Crystallographic Method?

A

Virus particles are crystallized and then are reflected with heat from x-rays

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14
Q

What is Nuclear Magnetic Resonance (NMR)?

A

Very high quality images

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15
Q

Explain the capsid of a virus

A

a. Capsid = protein shell of a virus that encases/envelopes the viral nucleic acid or
genome
b. Made up of capsomeres
i. Capsomere = basic subunit protein in the capsid of a virus
c. Most viruses have 1 capsid (except reoviruses which have double layered capsids)
d. Nucleocapsid = Capsid + Virus Nucleic Acid (DNA or RNA)/Genome

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16
Q

What is the function of a capsid? (8)

A

i. Protects viral nucleic acids from enzymes, chemicals, environment
ii. Structural symmetry of the virus
iii. Attachment of the virus specific receptors on the susceptible host cell
iv. Interaction with host cell membranes to form the envelope
v. Uncoating of the genome in the host cell
vi. Transport of the viral genome to the appropriate site
vii. Facilitates specific recognition and packaging of the nucleic acid genome
viii. Contain antigenic sites → determine antigenicity of the virus

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17
Q

What is helical symmetry? Animal and plant viruses

A

i. Animal viruses→ Helical nucleocapsid is enclosed within a lipoprotein envelope
ii. Plant viruses → Naked helical nucleocapsids → no envelope (ex: tobacco mosaic virus)

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18
Q

Cubic/Icosahedral Symmetry
Have 2 types of capsomers: pentagonal and hexagonal. Explain

A
  1. Pentagonal → make up vertices (corners/pentons)
    a. There are always 12 pentons
  2. Hexagonal → make up facets (hexons)
    a. # of hexons varies with the virus groups
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19
Q

What is the T-Number?

A

Triangulation Number (T-Number)
1. Describes the relation between the number of pentagons and hexagons of the icosahedron
a. T = h^2 + h*k + k^2
b. H and k are the distances between the successive pentagons on the virus surface for each axis
2. Examples:
a. Parvovirus: T=1
i. Simplest icosahedron
ii. Capsid consists of 60 copies of CP protein
b. Reoviridae

i. Outer capsid: T=13 icosahedral symmetry
ii. Inner capsid: T=2 icosahedral symmetry
3. Naked icosahedral vs. enveloped icosahedral

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20
Q

What is complex symmetry?

A

i. Virions are composed of several parts each with separate shapes and symmetries
ii. Ex: pox viruses, bacterial viruses

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21
Q

What is the envelope of a virus?

A

a. A lipid bilayer with embedded proteins
i. Formed from the cellular membrane of a host cell
ii. Maintained only in aqueous or moist environments
b. Inactivated by the the dissolution of lipid membrane with lipid solvents such as:
i. Ether
ii. Chloroform
iii. Sodium deoxycholate, detergents, etc.
c. Enveloped viruses are easier to sterilize than non-enveloped viruses & cannot survive for long periods in the environment

22
Q

What are 3 functions of the envelope of a virus?

A

i. Facilitate virus entry into host cells
ii. Help the virus adapt fast and evade the host immune system
iii. Can cause persistent infections

23
Q

How is the envelope formed?

A

Formed by budding of viral nucleocapsid through a cellular membrane
(like cytoplasmic, golgi, or nucleus membranes)

24
Q

There are two types of proteins that make the envelope of a virus. What are they?

A

i. Glycoprotein (Two types:
External glycoprotein and Channel proteins
ii. Matrix proteins

25
Q

What is the location and and function of the matrix proteins?

A
  1. Location: Between virus capsid and envelope 2. Functions:
    a. Recognition site of nucleocapsid at the plasma membrane and mediates encapsidation of the RNA-nucleoprotein cores into the membrane envelope
    b. Link the internal nucleocapsid to the lipid membrane envelope
    c. Virus assembly

d. Allow stabilization of the lipid envelope

26
Q

What are 4 functions of External glycoproteins?

A

a. External glycoprotein
i. Usually major antigens of the virus
ii. Functions:
1. Hemagglutination
2. Receptor binding
3. Antigenicity
4. Membrane fusion

27
Q

What are 2 functions of channel proteins?

A

Channel proteins
i. Hydrophobic proteins that form a protein lined channel through the envelope
ii. Function:
1. Alter permeability of the membrane
2. Modify the internal environment of the virus

28
Q

What is antigenic drift?

A

i. Can cause changes in antigenicity or become resistant to drugs
ii. Point mutations (silent, nonsense, missense)

29
Q

What is recombination vs reassortment shift?

A

Recombination
1. Involves the exchange of the nucleotide sequences between different, but close related, viruses during replication
2. Occurs with only one single gene segment

Reassortment
1. Most important mechanism for high genetic diversity in viruses with a segmented genome
2. Only occurs with multiple segments of the genome

30
Q

What are enzyme viral proteins required for? (2)

A
  1. mRNA transcription
  2. Nucleic acid replication
31
Q

What is Retroviral integrase (IN)? Example?

A

Produced by retrovirus that enables its genetic material to be integrated into the DNA of the infected host cell
Ex) HIV

32
Q

What is Reverse transcriptase (RT)?

A

Used to generate complementary DNA from a RNA template

33
Q

What is Nucleic acid polymerases?

A

Viral genome replication

34
Q

What 2 roles do viral nonstructural proteins?

A

i. Play roles within infected host cell during virus replication
ii. Act in regulation of virus replication or virus assembly

35
Q

What is Incomplete virions?

A

Virions without nucleic acid (empty capsid)

36
Q

What is defective virions?

A

i. A virus that cannot replicate because it lacks a full complement/copy of viral genes
ii. Defective viral particles result from mutations or errors in the production or assembly of virions

37
Q

What is Pseudovirion?

A

i. Contains non-viral genome with the viral capsid (such as host nucleic acid instead of viral nucleic acid)

38
Q

What is Pseudotypes?

A

When related viruses infect the same cell, the genome of one virus may be enclosed in the heterologous capsid of the second virus

39
Q

What is Variolation/Inoculation?
How did Edward Jenner invent the first vaccine?
What was Louis pasteur’s contribution to help cure Rabies?

A

i. First method used to immunize an against smallpox
ii. Material taken from a patient in hopes a mild infection would result

Edward jenner → invented vaccination
Inoculated cowpox matter repeatedly into arms of a healthy boy who became immune and did not succumb to smallpox

Louis Pasteur
Injected dried potassium hydroxide treated infected rabbit brain materials to 2 boys bitten by rabid dogs and both recovered

40
Q

What is a chamberland filter and who were some key names who used the filter? (4)

A

i. Filter with pores smaller than bacteria
ii. Dmitri Ivanovski → famous tobacco mosaic virus experiment
iii. Fredirich Loeffler & Paul Frosch → passed 1st animal virus through a filter
and discovered foot-and-mouth disease
iv. Martinus Beijerinck → discovered “viruses” using the chamberland filter

41
Q

What did Walter reed discover?

A

Discovered yellow fever is transmitted through mosquitoes

42
Q

What did Peyton Rous discover?

A

Discovered oncogenic viruses (Rous sarcoma virus)
Isolated the first tumor-causing animal virus

43
Q

What did Russia and Knoll invent?

A

Invented electron microscope to see viruses for the first time

44
Q

What did Woodruff, Goodpasture, and Burnet do?

A

Propagated viruses in eggs

Fowlpox virus → first virus successfully propagated in eggs

45
Q

Sanford, Enders and Dulbecco & Vogt contributed to tissue culture how respectfully?

A

Tissue Culture
i. Sanford → culture of isolated mammalian cells
ii. Enders → growth of Poliovirus in cell culture
iii. Dulbecco & Vogt → plaque assay for first animal virus (poliovirus)

46
Q

Discuss eradication of an infectious disease.
What is rinderpest?

A

a. Eradication involves complete elimination of the pathogen or the disease-causing agent from a defined geographic region
b. Rinderpest = only animal disease declared globally eradicated

47
Q

What is Baltimore Classification system?

A

i. No longer used
ii. Based on viral genome

48
Q

What is International Committee of Taxonomy of Viruses (ICTV) Classification
System?
Purpose?

A

i. The only body charged by the international union of microbiological societies
ii. Purpose: Developing, refining, and maintaining a universal virus taxonomy (classify viruses)

49
Q

International Committee of Taxonomy of Viruses (ICTV) Classification
System considers the following for classification of viruses (3)

A
  1. Nature of virus genome and virus genetic diversity
  2. Virus replication strategies
  3. Virus morphology
50
Q
A
  1. Order (ends with -virales) Herpesvirales
  2. Family (ends with -viridae)

Herpesviridae

  1. Subfamily (ends with -virinae)
    Alphaherpesvirinae
  2. Genus (ends with -virus)
    Simplexvirus
  3. Species
    Herpes simplex virus 1 (HSV-1)

Virology RUSVM (7 decks)

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