CMB1003/L13 Viral Transmission & Structure

Question 1

Briefly outline the 6 steps of virus multiplication.

Answer 1

Attachment
Penetration
Uncoating
Biosynthesis
Assembly
Release

Question 2

Describe the attachment phase of virus multiplication using the example of HIV. (4)

Answer 2

Diffusion
Low affinity receptor - heparan sulphate - binding induces conformational change in gp120 to expose:
Primary receptor (CD4 or DC-SIGN on dendritic cells)
Coreceptor(s) - CCR5 or CXCR4

Question 3

What is the function of ICAM-1 receptor and the virus that targets it?

Answer 3

Intracellular adhesion molecule
Rhinovirus

Question 4

What is the function of Acetylcholine receptor and the virus that targets it?

Answer 4

Neuronal signal transducer
Rabies virus

Question 5

What is the function of CDW150 (SLAM) receptor and the virus that targets it?

Answer 5

Lymphocyte activation
Measles virus

Question 6

What is the function of Angiotensin-converting enzyme 2 (ACE2) receptor and the virus that targets it?

Answer 6

Maturation of angiotensin - vasoconstriction and blood pressure
SARS-CoV-2

Question 7

What is the function of CCR5 receptor and the virus that targets it?

Answer 7

Chemokine receptor
HIV

Question 8

Give 2 ways in which internalization of viruses occurs.

Answer 8

Fusion from without
Receptor mediated endocytosis

Question 9

Give an example of a virus that fuses from without.

Answer 9

Pseudorabies virus
HIV

Question 10

Give an example of a virus that uses receptor mediated endocytosis.

Answer 10

Influenza
Poliovirus

Question 11

What enzyme do RNA viruses require?

Answer 11

Own RNA polymerases
(RNA-dependent RNA polymerase)

Question 12

What is the function of the proteins encoded by the virus genome? (3)

Answer 12

Replication of genome
Packaging of genome into virus particles
Alter metabolism of infected cell

Question 13

What is translation of most viral mRNAs dependent on?

Answer 13

5’ terminal cap

Question 14

Why must viruses compete for host cell ribosomes?

Answer 14

They do not have their own ribosomes

Question 15

What binds to the cap and 40S ribosomal subunit?

Answer 15

Eukaryotic initiation factors (eIFs)

Question 16

How is protein synthesis inhibited in virally infected cells? (2)

Answer 16

Directly by virus
Action of interferon

Question 17

What post-translational modifications do viral proteins undergo?

Answer 17

The same as the host cell proteins

Question 18

How do enveloped viruses acquire a membrane and surface glycoproteins?

Answer 18

Budding through plasma membrane or nucleus

Question 19

Give an example of a virus which is released by cell lysis.

Answer 19

Poliovirus

Question 20

Give an example of a virus which is released by budding from plasma membrane, and into lumen of ER.

Answer 20

Membrane - Influenza
ER - Rotavirus

Question 21

Give an example of a virus which is spread from cell to cell via pores, and inducing fusion of membranes.

Answer 21

Pores - herpesvirus
Fusion - RSV

Question 22

What can precede or follow release of a virus?

Answer 22

A maturation step

Question 23

What is viremia?

Answer 23

An increase in the concentration of the virus in your bloodstream or the lymphatic system

Question 24

Describe the M13 filamentous bacteriophage. (4)

Answer 24

Circular ssDNA
Cloning and DNA-sequencing
Released without lysing host cell
‘Budding’

Question 25

Why are bacteriophage important?

Answer 25

Can turn bacteria virulent
Alternative to antibiotics
Recombinant DNA technology