Microbiology 21 - Antivirals

Question 1

What is the mechanism of action of acyclovir?

Answer 1

Guanosine analogue that prevents elongation of DNA

Activated by viral thymadine kinase

Question 2

Which viruses is acyclovir particularly useful for?

Answer 2

VZV

HSV 1 + 2

Question 3

Which antiviral is used in HSV encephalitis?

Answer 3

High dose IV acyclovir

Start empirical treatment immediately if suspected. If confirmed, treat for 14-21 days.

Question 4

What is ganciclovir used for?

Answer 4

Pretty much only for treatment of CMV in the imunocompromised and neonates

Question 5

What is the main side effect of ganciclovir?

Answer 5

Bone marrow toxicity

Avoid in bone marrow transplant patients. Use foscarnet instead

Question 6

When is foscarnet used?

Answer 6

To treat CMV in patients where ganciclovir is contra-indicated (eg neutropaenic patients)

It is nephrotoxic though

Question 7

Which antiviral is most useful for treating RSV (bronchiolitis in children)?

Answer 7

Ribavarin - but there is a lack of good evidence for its efficacy

Question 8

What drug is given to infant groups at high risk of RSV?

Answer 8

Palivizumab

E.g infants with bronchopulmonary disease, SCID etc.

Question 9

Which antiviral is most useful for treating haemophagocytic lymphohistiocytosis in covid?

Answer 9

Anakinra (IL-1 receptor agonist)

Question 10

What is the best treatment for paediatric adenovirus infection?

Answer 10

Combination of cidofovir and IV Ig

Question 11

What treatment can clear chronic hep B in 3-7% of patients?

Answer 11

48 week course of pergolated interferon gamma

Question 12

Owl’s eyes inclusion bodies:

Owl’s eyes cells:

Answer 12

CMV infection

Reed-Sternberg cell (Hodgkin’s Lymphoma)

Question 13

Which antiviral drug does not require activation by viral kinase

Answer 13

Foscarnet, Cidofovir

Ganclicovir needs viral kinase to be activated

Question 14

What is letermovir?

Answer 14

New CMV prophylaxis drug that can be used in bone marrow transplant patients.

It is a CMW DNA Terminase inhibitor

Question 15

Two main important surface proteins in influenza virus?

Answer 15

Haemagglutinin: Helps viral entry into cells

Neuraminidase: Helps virus to budd/cleave off

Question 16

Oseltamivir (Tamiflu) MOA:

Answer 16

Directly inhibits the viral neuraminidase

Prevent release of new viruses from the cell.

Question 17

Disease caused by BK virus and treatment?

Answer 17

Haemorrhagic cystitis (treat with intravesicular cidofovir)

Nephropathy (treat with IVIG- cannot use cidofovir as it is nephrotoxic)

Question 18

Foscarnet and cidofovir MOA and toxicity?

Answer 18

Inhibits dna polymerase (guanine/base pair analogues that insert into dna and terminate its prolongation)

Nephrotoxic

Used when ganciclovir is C/I such as in bone marrow transplant patients

Not dependent on viral kinases so other drugs like aciclovir (dependent on viral thymadine kinsase- immunocompromised people with HSV quickly develop resistance) or ganciclovir might get resistance patterns but then we can use foscarnet or cidifovir