Antiviral agents

Question 1

How can virus gain entry into the body?

Answer 1

Inhalation
Ingestion
Inoculation (abrasion/mucous membranes/injections/transplants)
Congenital (mother to foetus)

Question 2

How does the body stop a virus?

Answer 2

Humoral and cell mediated defence mechanisms

Question 3

In what 2 ways do antiviral agents tend to work?

Answer 3

Inhibition of nucleic acid synthesis or inhibitor of viral protein

Question 4

What is the role of cytokines in viral defence systems?

Answer 4

Activation of host cells like lymphocytes - T and B cells and NK cells

Question 5

List 2 ways immune-stimualtion can be achieved?

Answer 5

Administration fo human immune globulin or administration of immune-stimulant drugs

Question 6

Generally, how do nucleoside analogue antivirals work?

Answer 6

Interfere with replication of viral nucleic acid

Question 7

How can nuceloside analogies be made more effective?

Answer 7

Prescribed early in infection

Question 8

Describe how nucleoside analogues such as acyclovir work against viruses?

Answer 8

Phophorylated into active state by viral enzymes
Incorporate into viral DNA
Inhibit viral DNA synthesis

Question 9

How is acyclovir selective to viral cells?

Limitations?

Answer 9

Greater affinity for viral than host enzymes

Still has affinity for host enzymes so dose must eb limited

Question 10

How can aciclovir cause encephalitis?

Answer 10

When given systemically if can cross the blood brain barrier

Question 11

Where is aciclovir excreted?

Answer 11

Kidneys

Question 12

List unwanted side effects of aciclovir?

Answer 12

Nausea and headaches

Transient burning sensation on application

Question 13

How does herpes simplex I present?

Answer 13

Coldsores

Question 14

How does varicella zoster virus present?

Answer 14

Chicken pox and shingles (in dermatomes)

Question 15

Idoxuridine is a thymidine analogue, how does it work and how does it differ from aciclovir?

Answer 15

Phosphorylated in cells and incorporated into cellular and viral DNA
Unlike aciclovir it does not block DNA synthesis
Too toxic for systemic use

Question 16

What kind of anti-viral agent is AZT (zidovudine)?

Answer 16

Nucleoside analogue (thymidine)

Question 17

What virus is AZT effective against?

Answer 17

HIV1

Question 18

Describe mode of action of AZT

Answer 18

Inhibits viral RNDA dependent DNA polymerase, preventing further nucleotides incorporating into growing strand of DNA

Question 19

How can the action of AZT be enhanced?

Answer 19

By aciclovir and interferon

Question 20

What are the unwanted effects of AZT?

Answer 20

Anaemia, granulocytopaenia (low granulocyte count)

Question 21

What kind of antiviral agents are reverse transcriptase inhibitors? How do they work?

Answer 21

Non-nucleoside analogues

Inhibit RNA dependent DNA polymerase

Question 22

What are interferons?

Answer 22

Glycoprotein produced by the body in response to a viral infection and enhance cytotoxic capacity of T lymphocytes

Question 23

Why are prions?

Answer 23

Infective agents contain no genetic material and are pure proteins, they can cause configurational changes in host

Question 24

Can instruments in contact with prions be sterilised?

Answer 24

No