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89 Cards in this Set
- Front
- Back
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What are the 5 steps involved in drug discovery?
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1. target validation
2. assay development 3. drug discovery development 4. clinical trials 5. resistance |
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What are the phases of clinical trials?
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I - test for adverse effects in healthy volunteers
II - test efficacy of drug III - test in thousands to look for complications and long term effects |
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What is the endpoint for anti-virals?
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sustained virologic response (SVR)
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What is the standard treatments from HCV?
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interferon + ribavirin
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What is a major problem for anti-viral treatments?
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development of resistance
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Which two mechanisms are important to deduce with respect to antivirals?
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-mechanism of action
-mechanism of resistance |
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What two parameters determine the severity of an HIV infection?
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-initial CD4+ cell count
-viral load |
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What development played a major role in improvement of HIV therapy?
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development of drug cocktail combations
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Give an examply of a recombination therapy for HIV (general)
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protease inhibitors
+ reverse transcription inhibitors |
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How are drug targets determined?
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determine viral life cycle (basic research)
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What does reverse transcriptase look like?
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-human right hand
-grabs primer template in groove -major target for anti-HIV drugs |
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What does RT do?
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transcribes viral RNA to dsDNA
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What are the 2 main classes of HIV-1 RT inhibitors?
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-nucleoside analogue RT inhibitors (NRTIs)
-non-nucleoside analogue RT inhibitors (NNRTIs) |
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What is a disadvantage of NNRTIs?
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not effective against HIV-2
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Give examples of 3 NRTIs:
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-AZT
-3TC -d4T |
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What do NRTIs do? What do they have in common, structurally?
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-compete with natural dNTPs
-lack 3' OH group required for phosphate attack -next NT cannot be incorported -chain terminators |
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Give 2 examples of NNRTIs:
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-nevirapine
-efavirenz |
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What do NNRTIs do?
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-bind to pocket on RT near active site
-allosteric inhibition |
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Give an example of a one-pill drug combination for HIV:
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atripla
-2 NRTIs -1 NNRTIs -much easier regiment... |
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What is another drug method? Give an example:
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protease inhibitors
-indinavir -competitive inhibitors (occupies substrate-binding site) |
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What is a method of design used to develop competitive inhibitors?
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rational design
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What is a good drug used to boost protease inhibitors?
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ritonavir
-blocks metabolizing enzymes that would degrade protease inhibitor -"PI boosting" |
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Why is eradication of HIV not realistic?
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HIV genome is integrated into the host chromosome as proviral DNA
-would need to eradicate ALL infected cells |
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Does ritonavir + interferon target viral enzymes specifically?
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no
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Which HCV viral proteins would be considered as good drug target?
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all NS proteins
-NS3 = protease -NS5B = polymerase |
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What are some problems with interferon and ribavirin?
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-many non-responders
-development of resistance -relapse |
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What is the main problem with using monotherapy?
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development of resistance
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What are 3 new targets for anti-HIV therapyÉ
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-fusion inhibitors
-entry inhibitors -integrase inhibitors |
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What differs complex retroviruses from simple retrovirusesÉ
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production of accessory genes, along with gag, pol, env
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Which enzymes are present in the viral capsidÉ
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pol: IN and RT
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Which protein cleaves gp160 to the 2 suface glycoproteins on HIVÉ
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cellular proteases (furin..)
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What is the size of a retrovirus genomeÉ
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7-10kbp
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What eukaryotic process is involved in gene expressionÉ
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splicing
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What are 5 HIV NS proteinsÉ
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Vif
Vpu Tat Rev Nef |
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What is the cellular receptor for HIVÉ
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CD4+ (binds gp120)
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What are the co-receptors for HIVÉ
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CCR5
CXCR4 |
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What is the primer for HIV reverse transcriptionÉ
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lysine tRNA
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What two types of enzymatic activity are required for reverse transcriptionÉ
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polymerase
RNAaseH |
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Where does proviral DNA appear to integrate in host chromosomeÉ
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active chromatin, more or less randomly
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How is viral mRNA producedÉ
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by cellular machinery for transcription
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What does Tat doÉ
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stimulates full length gene transcription by binding to TAR
-recruits cellular factors + kinase to phosphorylate RNA |
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What three alteractions are made to transcribed RNAÉ
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-5`cap
-3`poly(A) tail -splicing |
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What is the mechanism to halt splicingÉ
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Rev returns to nucleus and binds RRE (full-length RNA generated)
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What are the Gag proteins
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MA p17
CA p24 NC p7 spacer peptides |
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Describe assembly:
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MA has myristyl group; directs CA and NC to inner side of membrane
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What portion of NC binds to viral RNA
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basic N-terminus and zinc fingers
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Name some functions of NC
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RNA chaperone
unwinds tRNA primer facilitates processive DNA synthesis interacts with Vpr |
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What separates Gag from Pol
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ribosomal frameshift
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How often is the Gag-Pol fusion protein transcribed
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about 5% of the time
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What stage of the HIV life cycle does not require cellular factors
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reverse transcription
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What is the first step Integrase takes:
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cleaves GT on 3` ends of viral DNA
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What kind of overhangs are generated in the host chromosome from integraseÉ
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5`
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What part of integration uses cellular enymes
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repair enzymes fill in gaps
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What do integrase inhibitors inhibit
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strand transfer
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Which cellular protein is required for functional integration
What are postulated roles it may play |
LEDGF or p75
ubiquitous nuclear protein -TF or anti-apoptotic protein |
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Where does LEDGF bind with integrase
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IBD (integrase binding domain)
-also binds host chromosome vvia N-terminal domain |
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What is the result of LEDGF binding
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integrase stability increases
protection from proteosomal degradation |
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What happens when LEDGF is not available in the cell
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no integration
LTR circular formation |
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Name an integrase inhibitor
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Raltegavir
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What is an advantage of targeting cellular factors
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not as much mutation as viral proteins
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What is a disadvantage of targeting cellular factors
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toxicity
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Name 3 cellular restriction factors of HIV
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TRIM-5alpha
APOBEC3G Tetherin |
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What does TRIM-5alpha do
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attract proteins from ubiquitin-degradation pathway and directs virus to the proteosome
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What does APOBEC3G do
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edits viral DNA, specifically G to A mutations
also: diminishes viral DNA production |
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How does RT achieve G to A mutations
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G-T wobble
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How does APOBEC3G achieve G to A mutations
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deaminations of C to U
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Which viral protein counters APOBEC3G
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Vif
targets APOBEC3G to proteosome |
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How do APOBEC3G decrease quantity of viral DNA
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glycosylates U in DNA
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Which cellular restriction factor inhibits HIV at late stages in its life cycle
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tetherin
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Which viral protein counteracts tetherinÉ
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Vpu
-removes tetherin from PM -recruits proteosome to degrade tetherin |
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What does tetherin do
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keeps new virions tethered to surface of progenitor cell
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Which innate immune factor can induce tetherin
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INF-alpha
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Where are both tetherin and Vpu found
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membrane-bound
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How is acyclovir activated by herpes virus
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phosphorylated by a TK
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When is acyclovir effective in treating HIV
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when the patient is also infected with herpes
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What is the fidelity of RT
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1 mistake per replication cycle
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What mutations arrive from 3TC monotherapy
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M184I (A to G)
M184V (A to C) |
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What does the M184V mutation confer to the virus
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discrimination against inhibitor
in favour of natural dNTPs via steric hindrance |
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What mutations are derived from AZT monotherapy
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more exonuclease activity
TAMs |
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What are two mechanisms of NRTI resistance
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discrimination (3TC)
excision (AZT) |
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Where are discrimination mutations clustered
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near binding site
M184V |
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Where are excision mutations clustered
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away from binding site
TAMs |
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How does excision work
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ATP attacks chain terminator to form a dinucleotide tetraphosphate
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What are TAMs and M184V mutations to one another
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antagonistic
M184V decreases excision TAMs decrease discrimination |
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What antiviral contains a 3`OH group
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entacavir
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What are 3 mechanisms for entacavir`s action
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1. de facto chain termination
2. delayed chain termination 3. base-pair confounder |
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Which mutations work against Entacavir
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M184V
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What are promising viral protein targets for HCV treatment
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NS3 protease
NS5B polymerase |
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What type of anti-viral for HCV is being developed now
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protease-inhibitor
telaprivir |
