Acyclovir

Question 1

What does acyclovir resemble?

Answer 1

Deoxyguanosine - but doesn’t have the 3’ hydroxyl group

Question 2

When does acyclovir become activated?

Answer 2

When it comes into contact with thymidine kinase

Question 3

How is acyclovir activated - the process?

Answer 3

1) it enter the cell and changes in the presence of thymidine kinase (has high affinity for it) to form acyclo-guanosine monophosphate (acyclo-GMP)
2) it is converted into acyclo GDP using guanylate kinase
3) the acyclo gdp is converted into acyclo gtp by phosphotransferase and is active
3) acyclo gtp works well with viral dna polymerase not host hence it is incorporated

Question 4

What viral infections can acyclovir be used against?

Answer 4

herpes - herpes simplex (1+2), cytomegalovirus, varicella zoster, human herpes virus and EBV

Question 5

What kind of viruses are herpes and what are they characterised by?

Answer 5

double stranded DNA

Latency

Question 6

What is selective toxicity?

Answer 6

Preferential inhibition of metabolic processes of pathogen opposed to host

Question 7

Give examples of other nucleoside analogues

Answer 7

guancylcovir and zidovudine (thymidine analogue)

Question 8

Why does acyclovir work for herpes viruses?

Answer 8

• they code for their own polymerase

- they code for their own thymidine kinase

Question 9

What does thymidine kinase do?

Answer 9

creates a nucleotide by adding a phosphate group to a nucleoside

Question 10

Mechanism of resistance to acyclovir

Answer 10

mutations in TK or DNA polymerase

Question 11

spectrum of activity of acyclovir

Answer 11

herpes virus
antiviral treatment in immunosuppressed is continuous
used for herpes cold sore
infection with chicken pox etc.