Antivirals

Question 1

What is the viral life cycle?

Answer 1

1. Attachment- to target epithelial cell
   2.Penetration- epithelial cell engulfs virus by endocytosis
   3.Uncoating- viral contents released
   4.Gene expression and replication - viral RNA enters nucleus, replicated by viral RNA polymerase
   5.Assembly- new phage particles
   6.Virion release

Question 2

What are problems with antiviral treatment?

Answer 2

*difficult to identify lead compounds with selective toxicity
*viruses intracellular parasites- cell permeability issues
*delay in appearance of symptoms- hard to start in time
*replication peaked when symptoms appear

Question 3

What factors of viruses reduce efficiency of immune control?

Answer 3

*many viruses able to change
*antigenic drift as result of accumulation of genetic mutations (influenza, SARS- CoV-2)
*often more than one antigenic variant isolated from infected patient
*antigenic shift or recombination

Question 4

What spikes are present on the envelope of influenza viruses?

Answer 4

*haemagglutinin spikes (HA)
*neuraminidase spikes (NA) - help with release of virus’s from surface of cells

Question 5

How are influenza A viruses subtyped?

Answer 5

Depending on their HA and NA spike proteins

Question 6

What is influenza A well known for?

Answer 6

Genetic changes
*antigen drift- accumulation of mutations in viral antigenic proteins
*antigen shift- reassortment of gene segments between viruses

Question 7

What is antigenic drift?

Answer 7

Accumulation of mutations in viral antigenic proteins
Mistakes made by viral RNA dependent RNA polymerase during replication causes viruses with new antigenic variants
Virus with new variant selected and different strain circulates in population and accumulates

Question 8

What is antigenic shift?

Answer 8

Reassortment of gene segments between viruses
*two strains of same virus infect same cell
*viral reassortment between viruses

Question 9

What drugs are used for influenza?

Answer 9

*Neuraminidase inhibitors
*Tamiflu (oral) Relenza (inhaled)
*reduces symptoms

Question 10

What are the two strains of herpes simplex virus?

Answer 10

*HSV-1- oral herpes
*HSV-2- genital herpes

Question 11

Are HSV infections lifelong?

Answer 11

Yes
Persist in inactive but persistent form- outbreaks occur periodically

Question 12

What kind of drugs are used for HSV’s?

Answer 12

Nucleoside analogues
*Acyclovir- DNA replication inhibitor- converted by kinases- acyclovir triphosphate inhibits DNA polymerase- termination of nucleotide chain
*no effect on host DN polymerase

Question 13

What infection does the human varicella-zoster virus (VZV) cause?

Answer 13

Chickenpox
Reinvention = shingles

Question 14

What drug can be used for treatment and prophylaxis of VZV?

Answer 14

Acyclovir

Question 15

What activates acyclovir?

Answer 15

Thymidine kinase

Question 16

What other drug can treat HSV1, HSV2 and VZV?

Answer 16

Non-nucleoside DNA replication inhibitor
Foscarnet