Intro

Question 1

Definitions!

Answer 1

-virology = study of viruses & viral disease
-virologist = someone who studies viruses
-virion = complete virus particle (RNA or DNA) + protein coat w external envelope (external infective form)
-virus = infectious agent: virion or inactivated virus particle or virtual nucleic acid & protein in infected cell (broad)
-viroid = infectious particle smaller than viruses, agent of plant disease, small circular RNA (lack protein coat) NOT A VIRUS

Question 2

Describe why veterinary virology is important.

Answer 2

-high rates of mortality & morbidity
-financial loss
-zoonosis

Question 3

Describe virus.

Answer 3

-non living
-nucleic acid genome (DNA or RNA) surrounded by protein coat (sometimes lipid envelope)
-no cell organelles
-cant make energy or proteins by themself
-obligate intracellular parasites
-no genetic capability to multiply by division
-reproduction via assembly line

Question 4

Describe Edward Jenner.

Answer 4

-inoculated cowpox matter into boy -> became immune to small pox
-vacca = cow
-vaccine invented

Question 5

Describe Louis Pasteur.

Answer 5

-injected dried potassium hydroxide treated infected rabbit brain material into boys bitten by rabid dogs & both recovered

Question 6

Describe the Chamberland filter.

Answer 6

-filter has pores smaller than bacteria
-pioneered discovery of viruses
-used in famous tobacco mosaic virus experiment

Question 7

Describe Dmitri Ivanoski.

Answer 7

Question 8

Describe Friedrich Loeffler & Paul Frisch.

Answer 8

-passed first animal virus thru similar filter
-discovered the cause of foot & mouth disease virus

Question 9

Describe Walter Reed.

Answer 9

-discovered yellow fever is transmitted thru mosquitos

Question 10

Describe Peyton Rous.

Answer 10

-discovery of oncogenic viruses
-isolated first tumor causing animal virus
-‘rous sarcoma virus’

Question 11

Describe Ernst Ruska & Max Knoll.

Answer 11

-invention of electron microscope

Question 12

Describe the fowl pox virus.

Answer 12

-1st virus to successfully propagated in embryo aged hen egg

Question 13

Describe tissue culture.

Answer 13

1. Sanford = culture of isolated mammalian cells
2. Enders = growth of poliovirus in cell culture
3. Dulbecco & Vogt = plaque assay for first animal virus polio virus

Question 14

Describe rinderpest.

Answer 14

-only animal disease declared globally eradicated

Question 15

Describe the Baltimore Classification system.

Answer 15

-old system (not used anymore)
-based on viral genome

Question 16

Describe ICTV.

Answer 16

-international committee on taxonomy of viruses
-currently used to classify viruses
-charged by international union of microbio societies w task of developing, refining, & maintaining universal virus taxonomy
-considers:
>nature of virus genome & virus genetic diversity
>virus replication strategy
>virus morphology

Question 17

Describe the smallest VS the largest virus.

Answer 17

1. Smallest
   -porcine circovrius type 1
2. Largest
   -pox virus in animals, humans, birds

Question 18

Describe pleomorphism.

Answer 18

-ability of virus to alter shape or size

Question 19

Describe the common methods used to determine the morphology of viruses.

Answer 19

1. electron microscope (EM)
2. cryo-electron microscope (cryo-EM)
3. x ray crystallographic method
4. Nuclear magnetic resonance (NMR)

Question 20

Describe the morphology of viruses.

Answer 20

-capsid = protein shell of virus that encases viral nucleic acid or genome
>made up of capsomeres
—basic subunit protein in the capsid of a virus
>most viruses have one capsid expect reoviruses (double layered capsid)

Question 21

Describe nucleocapsid.

Answer 21

Capsid + Virus Nucleic acid (DNA or RNA)/Genome

Question 22

Describe helical symmetry.

Answer 22

-in all animal viruses the helical nucleocapid is enclosed within lipoprotein envelope
-naked helical nucleocapsids common in plant viruses like tobacco mosaic virus

Question 23

Describe cubic/icosahedral symmetry.

Answer 23

-2 types of capsomers present in icosahedral capsid
-pentagonal capsomers at vertices (pentons) & the hexagonal capsomers making up the facets (hexons)
-always 12 pentons but # of hexons varies w virus group
-triangulation # (T#) = describes relation between the # of pentagons & hexagons of the icosahedron
FORMULA:
T = h^2 + (h)(k) + k^2
[h&k are the distance between successive pentagons on the virus surface for each axis]

Question 24

Describe complex symmetry.

Answer 24

Pox virus

Question 25

Describe the functions of the viral capsid.

Answer 25

1. Resp for structural symmetry of virus particle 2. Encases & protects viral nucleic acid from enzymes (nucleases), chemicals, & physical conditions (pH & temp) 3. Receptor attachment proteins on viral capsid for attachment of the virus to receptors on host 4. Interaction w host cell membrane to form the envelope 5. Uncoating of the genome in host cell 6. Transport of the viral genome to the appropriate site 6. Packaging of nucleic acid genome 7. Contains antigenic sites & determines antigenicity of virus

Question 26

Describe enveloped viruses.

Answer 26

-envelope = lipid bilayer with embedded proteins >acquired by budding of viral nucleocapsid thru cell membrane like cytoplasmic membrane, golgi membrane, or nucleus membrane >2 kinds of viral proteins found in envelope: glycoprotein & matrix protein

Question 27

Describe the virus envelope glycoproteins.

Answer 27

1. External glycoprotein -major antigen of virus -hemagglutination, receptor binding, antigenicity, membrane function 2. Channel proteins -hydrophobic proteins that form protein lined channel thru envelope -alters permeability of membrane -modify internal environment of virus

Question 28

Describe the virus envelope matrix protein.

Answer 28

-link internal nucleocapsid to the lipid membrane envelope -role in virus assembly -stabilization of lipid envelope -recognition site of nucleocapsid at the PM -mediates encapsidation of the RNA-nucleoprotein cores into membrane envelope

Question 29

Describe the lipid bi layer in virus envelope.

Answer 29

-from cell membrane of host like cytoplasmic membrane, nuclear, membrane, ER membrane -in aqueous or moist environment (lipid envelope sensitive to desiccation, heat, alteration of pH) -enveloped virus inactivated by dissolution of lipid membrane with lipid solvents: >ether, chloroform, sodium deoxycholate, detergents *enveloped viruses easy to sterilize than non enveloped viruses & cant survive for longer periods in environment*

Question 30

Describe nucleic acids.

Answer 30

Question 31

Describe the mechanisms of generic diversity of viruses.

Answer 31

1. Antigenic drift = mutations (ex. Point mutation) 2. Antigenic shift = recombination (singe gene seg) -intramolecular recombination involves the exchanged of nucleotide seq between diff but closely related viruses during replication -reassortment most IMP for high genetic diversity in viruses w segmented genome (more than one gene seg)

Question 32

Describe viral enzymes.

Answer 32

1. Retroviral integrate (IN) -enzyme made by retrovirus (HIV) that allows genetic material to be integrated into DNA of infected cell 2. Reverse transcriptase (RT) -enzyme used to gen complementary DNA (cDNA) from a RNA template 3. Nucleic acid polymerase -viral genome replication

Question 33

Describe viral nonstructural proteins.

Answer 33

-proteins play role in infected cell during virus replication or act in regulation of virus replication or virus assembly

Question 34

Describe an incomplete, defective, psuedotype & pseudo virion.

Answer 34

1. Incomplete virion -virus w/o nucleic acid (empty capsid) 2. Defective virion -virus that cant replicate bc its lacks full complement/copy of viral genes -defective viral particles result from mutations or errors in production or assembly of virions 3. Pseudovirion -non viral genome within viral capsid like host nucleic acid instead of viral nucleic acid 4. Psuedotypes -when related viruses infect the same cell -genome of one virus may be enclosed in the heterologous capsid of the second virus