Intro to Viruses

Question 1

Define a virus, and describe three characteristics of viral invasion of host cells/tissues.

Answer 1

Virus = piece of nucleic acid (viral genome) enclosed in protein coat.

• Must invade host cell to replicate
• May have tissue specificity
• Mutations confer zoonotic ability

Question 2

Descbribe the structure of a virus

Answer 2

• Capsid - protein shell made of capsomeres
• Viral enzymes
• Viral genome
• May have envelope, made of host cell lipid bilayer

Question 3

Describe how viral envelops contribute to virulence.

Answer 3

Enveloped viruses express glycoproteins

• Adhesion to host cells

Question 4

List the three basic shapes of viruses

Answer 4

• Polyhedral
• Helical (helical genome)
• Complex

Question 5

Describe acute infection based on replication and detectability, with some examples.

Answer 5

Acute infection = eliminated by immune system.

Incubation periods are short.

Examples: Rhinoviruses (cold), viral meningitis, SARS-CoV-2

Question 6

Describe latent infection based on replication, detectability and give some examples.

Answer 6

Following acute infection, virus is not eliminated.

• Doesn’t replicate
• Isn’t detectable
• May reactivate and cause illness when body is compromised.

Examples: Herpes, Varicella Zoster, Epstein Barr

Question 7

Describe chronic infection based on replication, detectability and give some examples.

Answer 7

• Continues to replicate
• Detectable
• Damage/disease is chronic

Examples: HIV, Hep B and C

Question 8

Describe slow infection based on how it arises (differences between chronic/latent) and what it affects.

Give some examples.

Answer 8

Prolonged incubation, follow by slow disease.

Unlike latent/chronc, may not begin with period of acute infection.

Due to slow disease nature, typically involves CNS

Examples:

• Rabies
• Rubella
• Prion diseases (Cruetzfeldt-Jakob disease)

Question 9

Viruses can be oncogenic. What viruses contribute to hepatocellular carcinoma?

Answer 9

Hep B and C

Question 10

Viruses can be oncogenic. What viruses contribute to cervical and oropharyngeal cancers?

Answer 10

HPV

Question 11

Viruses can be oncogenic. What viruses contribute to Hodgkin and Burkitt’s lymphoma?

Answer 11

Epstein-Barr virus

Question 12

Viruses can be oncogenic. What viruses contribute to Adult T-cell leukaemia/lymphoma?

Answer 12

HTLV-1

Question 13

Viruses can be oncogenic. What viruses contribute to Kaposi’s sarcoma?

Answer 13

Herpes virus 8