Antiviral agents Flashcards
How can virus gain entry into the body?
Inhalation
Ingestion
Inoculation (abrasion/mucous membranes/injections/transplants)
Congenital (mother to foetus)
How does the body stop a virus?
Humoral and cell mediated defence mechanisms
In what 2 ways do antiviral agents tend to work?
Inhibition of nucleic acid synthesis or inhibitor of viral protein
What is the role of cytokines in viral defence systems?
Activation of host cells like lymphocytes - T and B cells and NK cells
List 2 ways immune-stimualtion can be achieved?
Administration fo human immune globulin or administration of immune-stimulant drugs
Generally, how do nucleoside analogue antivirals work?
Interfere with replication of viral nucleic acid
How can nuceloside analogies be made more effective?
Prescribed early in infection
Describe how nucleoside analogues such as acyclovir work against viruses?
Phophorylated into active state by viral enzymes
Incorporate into viral DNA
Inhibit viral DNA synthesis
How is acyclovir selective to viral cells?
Limitations?
Greater affinity for viral than host enzymes
Still has affinity for host enzymes so dose must eb limited
How can aciclovir cause encephalitis?
When given systemically if can cross the blood brain barrier
Where is aciclovir excreted?
Kidneys
List unwanted side effects of aciclovir?
Nausea and headaches
Transient burning sensation on application
How does herpes simplex I present?
Coldsores
How does varicella zoster virus present?
Chicken pox and shingles (in dermatomes)
Idoxuridine is a thymidine analogue, how does it work and how does it differ from aciclovir?
Phosphorylated in cells and incorporated into cellular and viral DNA
Unlike aciclovir it does not block DNA synthesis
Too toxic for systemic use
What kind of anti-viral agent is AZT (zidovudine)?
Nucleoside analogue (thymidine)
What virus is AZT effective against?
HIV1
Describe mode of action of AZT
Inhibits viral RNDA dependent DNA polymerase, preventing further nucleotides incorporating into growing strand of DNA
How can the action of AZT be enhanced?
By aciclovir and interferon
What are the unwanted effects of AZT?
Anaemia, granulocytopaenia (low granulocyte count)
What kind of antiviral agents are reverse transcriptase inhibitors? How do they work?
Non-nucleoside analogues
Inhibit RNA dependent DNA polymerase
What are interferons?
Glycoprotein produced by the body in response to a viral infection and enhance cytotoxic capacity of T lymphocytes
Why are prions?
Infective agents contain no genetic material and are pure proteins, they can cause configurational changes in host
Can instruments in contact with prions be sterilised?
No
