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Virology 11-20 > #16 viral chemotherapy > Flashcards

#16 viral chemotherapy Flashcards

1
Q

what is amantadine used for and how does it work?

A
  • used for influenza virus
  • stops entry/fusion of the virus
  • amantadine is a M2 ion channel blocker
  • it binds to the ion channel and stops the ion channel activity
  • therefore stops the acidification of the endosome
  • influenza HA protein cannot undergo conformational changes and will not fuse and enter the cell
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2
Q

what is Relenza and tamiflu used for and how do they work?

A 
- used for influenza 
 they are NA inhibators 
- they stop exit of the virus 
- the drugs have a higher affinity to the NA binding pocket than sialic acid does therefore the drug will bind to NA and not allow it to bind with sialic acid for cleavage and release 
- the drug outcompetes sialic acid
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3
Q

how does a nucleoside become a nucleotide?

A

nucleosides have no phosphate groups. cellular enzymes add 3 phosphate groups onto the nucleoside to make it into a nucleotide for DNA production
Mono, di, and tri phosphate groups are added

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4
Q

what type of drug is acyclovir and what is it used for

A
  • it is used for HSV

- nucleoside analogue / guanosine analogue

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5
Q

how does acyclovir work?

A
  • acyclovir is a guanosine analogue
  • it has the same structure as guanosine except is has an incomplete ribose ring
  • the HSV early protein thymidine kinase will add the first phosphate group onto acyclovir monophosphate
  • cellular kinases will then add the di and tri phosphate to make acyclovir triphosphate
  • acyclovir triphosphate has a high affinity for the replication complex used during DNA polymerisation therefore it will be incorporated into the growing DNA strand of HSV
  • as acyclovir triphosphate has no 3’ hydroxyl group it will terminate the DNA elongation
  • this is a chain termination event
  • prevents new viral DNA from being made
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6
Q

what is valacyclovir and how does it work in comparison to acyclovir

A

used for HSV
nucleoside analogue
it is in the same family as acyclovir
acts in the same way
it has a valine side chain that allows it to circulate better
cellular enzymes need to cleave the valine side chain off to make the drug active in the cell (its a prodrug)

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7
Q

what is ribavirin and how does it work, what is it used for

A
  • it is a guanosine anologue
  • It inhibits replication for many DNA and RNA viruses through different mechanisms - generic drug
  • can be in mono, di or tri phosphate forms
  • mono-phosphate form will reduce nucleic acid synthesis
  • triphosphate form alters viral mRNA formation
  • many viruses that use a 5’ CAP will pick this drug up as a 5’ CAP but it will not be able to function as a 5’ CAP
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8
Q

what is ribavirin used for

A
  • used for different viruses DNA or RNA
  • commonly used for a mystery RNA virus
  • used for RSV and pneumonia
  • influenza
  • Hep. C
  • Haemorragic fevers
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9
Q

what does the most successful drug for HIV act on?

A
  • the CCR5 molecule on host cell

- other drugs that act on Gp41 or Gp120 do not work well as the virus is highly mutagenic

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10
Q

what drug targets CCR5 for HIV?

how does it stop HIV infection

A

Maraviroc

- it binds to CCR5 and stops entry/fusion process of HIV

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11
Q

what is the downside of targeting CCR5 receptor in HIV infection?

A
  • the virus may select for CXCR4 receptor

- need to test patient to see if they have any of these strains when using the drug

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12
Q

what are the best targets for HIV drugs?

A

enzymes! - enzyme inhibators

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13
Q

what is Zidovudine (AZT)

how does it work and what is it used for

A
  • for HIV
  • reverse transcriptase inhibitor
  • thymidine analogue
  • ribose ring has a 3’ zido group instead of a Hydroxyl group
  • it will be phosphorylated by cellular kinases to AZT-triphosphate
  • the AZT-triphosphate is favoured by the viral RT over cellular thymidine triphosphate and will be incorporated into the viral DNA polymer
  • the incorporated AZT triphosphate will prevent DNA chain elongation and will act as a chain terminator
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14
Q

what are NRTIs
what are they used for
what is a NRTI drug

A

they are reverse transcription inhibators
they are used for HIV
- they all lack a 3’ hydroxyl group therefore when incorporated into DNA they act as chain terminators!
- AZT is a NRTI

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15
Q

explain how NRTIs work

A
  • they are nucleoside analogues
  • they all have have a missing 3’ hydroxyl group
  • they are phosphorylated by cellular kinases to make a triphosphate form
  • they will be used by the RT in preference to cellular nucleosides
  • ## they will prevent chain elongation and cause chain termination
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16
Q

can a NRTI inhibit provirus?

A

no they cannot eliminate already exisiting DNA

17
Q

What is a NNRTI

A
  • they are non-nucleoside RT inhibitors
  • they act directly on the RT
  • they are NOT DNA analogues
  • they bind to the binding site in the RT enzyme therefore inhibiting the RT itself
  • they are used in combination with NRTIs
18
Q

how does a HIV protease inhibator work?

A
  • HIV protease inhibitors act by binding directly to the binding site of the viral protease enzyme
  • the protease inhibitor has structural similarity to the amino acid sequence that the protease binds to, but the inhibitor has greater affinity
  • the protease enzyme will be inhibited and blocked from cleaving polypeptides of the virus
  • stops budding virus as it cannot produce its RT, capsid etc. without cleavage therefore it cannot replicate!
19
Q

name a integrase inhibitor for HIV

how does it work

A
  • reltegravir
  • it blocks HIV infection!!!
  • it will bind to the integrase enzyme therefore the integrase cannot perform the strand transfer DNA integration event!
  • the viral DNA cannot incorporate into the host DNA!
  • infection cannot occur!
  • the virus is also incapable of producing infectious particles
  • LTR 1 and 2 circles will build up in the cytoplasm and be cleared by the cell
20
Q

how many classes of HIV drugs are there

A

5

21
Q

how many drugs do you need to combine for HAART therapy?

why?

A
  • at least 3
  • 3 is enough to outpace the virus mutation rate
  • minimises the risk of drug resistance
22
Q

can HIV be cleared?

A

no
even on combination HAART HIV cannot be cleared
pro-virus will exist in patient immune cells for life

23
Q

how does HIV still contribute to immune dysfunction in someone taking HAART therapy?

A
  • the virus will still produce some viral proteins that cause chronic immune activation
  • they drive NON-AIDS related causes of morbidity and mortality
  • such as heart disease, cancers, liver disease
24
Q

do CD4 cells fully recover on HAART?

A

no they do not fully replenish

they do replenish well but not fully

25
Q

what was the first treatment used for EBV?

A
  • interferons
  • used on HbeAg+ carriers
    40% effective
26
Q

what is 3TC and what is it used for

A
  • nucleoside analogue
  • used for EBV
  • has a 3’ SH group instead of a OH on ribose ring
  • targets the cellular RT of EBV
  • very good drug for EBV
27
Q

what is Adefovir and how does it work? what is it used for

A

nucleotide analogue
used for EBV
the drug targets the RT enzyme of the EBV virus
it has the first phosphate group already added on it to improve its efficiency

28
Q

can EBV be cleared using antiviral therapy?

why?

A
  • there is a very low rate of virus clearance
  • the virus is highly resistant mutagenic
  • high cases of relapse after treatment
29
Q

what is the most effective drug for HCV

A

post translational processing inhibators (protease inhibators)

  • they block the HCV NS3-4A protease
  • bind to the active site of the protease and stop it from cleaving
30
Q

what are the two drugs that are used to treat HCV now?

what is the outcome?

A

Ledipasvir and Sofosburvir

  • they are taken as a single tablet
  • both HSV replication inhibators
  • cures more than 95% of patients with HCV

Virology 11-20 (8 decks)

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