Intro to Virology

Question 1

What is a virus?

Answer 1

Entities whose genomes are elements of nucleic acid that replicate using cellular machinery. They are the smallest infective agents and are metabolically inert.

Question 2

What are the components of a intact viral particle?

Answer 2

1) Nucleic acid genome
- ds/ssDNA or ss/ds/segmented RNA
- can be linear or circular

2) Capsid
- protein coat made of capsomeres
- antigenic

3) Envelope
- not in all viruses
- lipid membrane w inner protein later and protruding glycoprotein spikes
- ether sensitive

Question 3

What are the 5 steps of the viral replication cycle?

Answer 3

1) Attachment/adsorption
2) Penetration/entry
3) Uncoating
4) Replication
5) Assembly, maturation and release

Question 4

How does the replication of DNA viruses different from that of RNA viruses?

Answer 4

DNA viruses have their DNA transcribed
- initially for viral genome replication
- later for structural proteins

RNA viruses either
1) +ve ssRNA: behaves like mRNA → directly translated
2) -ve ssRNA: needs to be transcribed to mRNA (+ve strand) → translated
3) Retroviruses: need RNA-dependent DNA pol → RNA into DNA → integrate into host genome

Question 5

What are the cellular effects of viruses?

Answer 5

1) Cytopathic effect (cell death)
2) Latency (quiescent infection w/o effect)
3) Cellular transformation (malignancy)

Question 6

What are some ways you can get rid of viruses?

Answer 6

1) Heat
2) Cold
3) UV
4) Drying
5) Ether and Chloroform (for enveloped)
6) REDOX agents
7) Disinfectants

Question 7

How would you transport px samples for testing?

Answer 7

Use Viral Transport Medium except blood (heparinised), CSF and stools (collect plain)

Question 8

Which form of T cells are activated in viral MHC 1 activation?

Answer 8

CD8+ Tc cells

Question 9

What antigen-presentation pathway is relevant to viral infections?

Answer 9

MHC I

Question 10

How do you interpret a viral serology?

Answer 10

IgM: recent infection
IgG: past infection