Antiviral drugs Flashcards
What are the features of the influenza genome?
- Eight segments
- ssRNA
- Negative sense
What is the function of the influenza M2 ion channel?
Triggers uncoating of genome when virus is exposed to low pH
What surrounds the influenza nucleocapsid?
Lipid bilayer envelope
Which two spike proteins are located in influenza envelope?
- Haemagglutinin
2. Neuraminidase
What is the function of haemagglutinin?
Mediates initial attachment of virus to host cell
How is the influenza nucleocapsid released from its envelope?
Haemagglutinin undergoes structural rearrangement following attachment, endocytosis and acidification
What is the function of neuraminidase?
- Prevents viral aggregation
- Facilitates release from host cells
- Possible role as virulence factor
What is responsible for antigenic drift and shift in influenza?
Variations and mutations in neuraminidase and haemagglutinin
What do anti-herpes agents target?
Virally-encoded DNA polymerases
How do viral DNA polymerases act?
In the same manner as eukaryotic DNA polymerases
Join 5’-OH of base being added to 3’-OH of sugar in polymerised strand of DNA
What is the distinguishing feature of purine analogues?
All lack cyclic sugar of 2’-deoxyguanosine
Why is aciclovir selective for virus-infected cells?
- Only virus-infected cells have thymidine kinase required to monophosphorylate drug
- Drug preferentially binds to viral DNA polymerase
Why do ganciclovir and penciclovir permit chain extension?
They have 3’OH moieties
What is contained in an HIV virion?
- Two copies of ssRNA genome
- Reverse transcriptase
- Aspartic protease
What is the role of HIV reverse transcriptase?
Converts ssRNA to dsDNA
How is HIV DNA integrated into the human genome?
Integrase enzyme
What are the properties of the HIV reverse transcriptase?
- Poor fidelity
- Many frequent transcription errors
- High degree of sequence variation among viral genome copies that are produced
What is the role of the HIV aspartic protease?
Cleaves polyprotein allowing maturation of HIV proteins and capsid formation
How do non-nucleoside reverse transcriptase inhibitors work?
Bind to enzyme near catalytic site and denature it
How do nucleoside reverse transcriptase inhibitors work?
Bind to target enzyme by mimicking naturally occurring nucleosides and terminate DNA chains once they are incorporated because they lack a 3’OH moiety
How are nucleoside reverse transcriptase inhibitors activated?
Phosphorylated by host cell enzymes
What is often co-administered with pyrimidine analogues?
Hydroxyurea
What is the role of hydroxyurea?
Inhibit ribonucleotide reductase
What is the effect of inhibiting ribonucleotide reductase?
Decreases intracellular pool of pyrimidine nucleotides
