Intro To Virology

Question 1

What is a virus

Answer 1

• Latin : poison
• intracellular, smaller then bacteria (<1um), simple, rely on host for replication (rely on host’s ribosomes)
• VERY FEW can be seen with light microscopy. We don’t know much about them
• we do not know any that carry ribosomes
• do have the ability to evolve

Question 2

History Hallmarks

Answer 2

• Louis Pasteur = father of microbiology, well known for his vaccine work
• Koch and Pasteur proposed “germ theory”
• Koch postulates: framework for investigating disease

Question 3

Koch Postulates

Answer 3

• agent must:
  1) be present in every case of dz
  2) be isolated from host and grow in vitro
  3) dx must be reproduced then pure cultivated agent is introduced into healthy host
  4) same agent must once again be recoverable from newly infected host

Question 4

ICTV nomeclature rules

Answer 4

• order
• family
• subfamily
• genus
• species

Question 5

viral classification

Answer 5

• virion architecture
• viral nucleic acid and replication strategies
• phylogenomics
• antigenic relationships
• biologic characteristics

Question 6

virion architecture

Answer 6

• nucleocapsid size
• nucleocapsid shape
• nucleocapsid symmetry
• enveloped (capsid + nucleic acid enclosed in protein coat) vs naked (glycoprotein studded phospholipid membrane)

Question 7

are enveloped or naked virus more fragile ?

Answer 7

ENVLOPED ! they do not survive well outside host, more susceptible to disinfectants

Question 8

nucleocapsid symmetry

Answer 8

• ->symmetrical
• helical: tubular with subunits
• icosahedral: 20 equilateral triangular faces
• ->non-symmetrical
• complex
• filamentous
• pleomorphic

Question 9

viral nucleic acid and replication strategies

Answer 9

-mRNA is the central molecule for viruses (to make protein) BUT can be single/double stranded DNA/RNA

Question 10

Class I viruses

Answer 10

dsDNA genomes

• papillomaviridae
• adenoviridae
• herpesviridae
• poxyviridae
• asfaviridae

Question 11

Class II viruses

Answer 11

ssDNA genomes

• circoviridae
• parvoviridae

Question 12

Class III viruses

Answer 12

dsRNA genomes

• reoviridae
• birnaviridae

Question 13

Class IV viruses

Answer 13

ssRNA + genomes (already in mRNA)

• picornaviridae
• caliciviridae
• coronaviridae
• areriviridae
• flaviviridae
• togaviridae

Question 14

Class V viruses

Answer 14

ssRNA - genomes

• orthomyxoviridae
• paramyxoviridae
• rhabdoviridae
• filoviridae
• bunyaviridae

Question 15

Class VI and VII viruses

Answer 15

reverse transcriptase

• hepadnaviridae
• retroviridae

Question 16

antigenic relationships (serology)

Answer 16

• relates to Hemagglutinin and Neuraminidase properties of the virus subtype
• H#N# (vaccine only works for that specific subtype of the virus)

Question 17

biologic characteristics

Answer 17

• based on tropism/ mode of transmission (lots of overlap)
  1) enteric
  2) respiratory
  3) arboviruses (natural vectors - mosquitos and ticks)
  4) oncogenic (by close contact, injection, fomites)

Question 18

generalized viral lifecycle

Answer 18

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

Question 19

what does a virus do when its inside the cell

Answer 19

• cause necrosis and apoptosis
• cell transformation
• no discernible effect