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HIV Flashcards

1
Q

which cells does HIV attack

A

T-cells
- and uses them to make copies of itself

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2
Q

when HIV destroys so many of your cells, what disease does it lead to

A

AIDS

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3
Q

what are some opportunistic infections among gay white men

A
  • pneumocystis carinii pneumonia (PCP)
  • Kaposi’s sarcoma
  • reactivated TB
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4
Q

abnormal low lymphocyte counts are found in people with

A

HIV/AIDS

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5
Q

how is HIV transmitted

A
  • contact with bodily fluids: blood, semen, vaginal secretions, and breast milk
  • sex
  • injection drug use
  • mother-to-child
    • teratogens (TORCHeS)
    • during birth
    • breastfeeding
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6
Q

sexual transmission of HIV is enhanced by

A
  • breaks or tears in mucosal surface
  • ulceration or inflammation (STDs)
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7
Q

HIV is what kind of virus

A

retrovirus

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8
Q

what are some features of retroviruses

A
  • contain RNA genomes that get reverse-transcribed into DNA
  • viral genomes permanently integrate into the host genome as a “provirus”
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9
Q

what are some features of retroviruses

A
  • contain RNA genomes that get reverse-transcribed into DNA
  • viral genomes permanently integrate into the host genome as a “provirus”
    • if the cell is activated, the provirus is t
      transcribed and translated
    • otherwise the provirus remains latent
      (“proviral latency”)
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10
Q

HIV’s genome is diploid, which means it contains 2 identical copies of (+) or (-) ss RNA

A

(+) ss RNA

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11
Q

HIV has two glycoprotein spikes, what are they and what is their function

A
  • gp120 = binds to CD4 receptor and a chemokine co-receptor on host cell (attachment)
  • gp41 = facilitates fusion of viral and cell membranes
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12
Q

true or false - reverse transcriptase is a viral enzyme encoded by HIV

A

true

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13
Q

what kind of activity does reverse transcriptase have

A

RNA-dependent DNA polymerase activity
- synthesizes DNA from an RNA template

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14
Q

what are the three activities that reverse transcriptase does and what does it lack

A
  1. DNA synthesis from the RNA template
  2. ribonuclease H (RNA degradation)
  3. DNA-dependent DNA synthesis
    - lacks proofreading ability
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15
Q

describe how HIV establishes latency

A
  • viral genomes permanently integrate into the host genome as a “provirus”
  • the enzyme, integrase, catalyzes this process
  • the provirus may be transcribed and translated to produce virus
  • otherwise, the provirus remains latent (“proviral latency”)
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16
Q

can the immune system eliminate a latent virus

A

no

17
Q

describe HIV replication

A
  • cell transcribes provirus into mRNA
    • HIV genomic RNA
    • mRNA is translated into long protein
      chains
  • chains cleaved into viral proteins and enzymes
    • by protease enzyme
18
Q

describe HIV assembly

A
  • HIV components accumulate in virions
  • viable HIV virions released by budding
  • host immune cells killed in process
  • as CD4+ T cells die, host becomes vulnerable to opportunistic infections
19
Q

what are the main cellular targets of HIV? what do they infect? what receptors do they use?

A
  • M-tropic (“R5”) HIV strains
    • typically infects macrophages
    • use CD4 and CCR5 receptors
  • T-tropic (“X4”) HIV strains
    • infects only CD4+ T cells
    • use CD4 and CXCR4 receptors
20
Q

when does M-tropic and T-tropic HIV strains infect

A
  • M-tropic strains
    • predominate early in infection
    • most infections start with a M-tropic strain
  • T-tropic strains
    • predominate later in an infection, during
      progression to AIDS as M-tropic strains
      evolve into T-tropic strains
    • less infective than M-tropic strains
21
Q

what is stage 1 of an HIV infection

A

acute/primary HIV infection
- two to four weeks after infection with HIV, patients may experience a flu-like illness
- large amount of virus in their blood and very contagious during this stage

22
Q

what is stage 2 of an HIV infection

A

clinical latency
- HIV enters a period of dormancy
- HIV is still active but reproduces at low levels
- patients may not experience any symptoms of illness
- near the end of latent stage, the patient’s viral load starts to increase and the CD4 T cell count begins to decrease, leading to increased susceptibility to opportunistic infections

23
Q

what is stage 3 of an HIV infection

A

AIDS
- patients are diagnosed with AIDS when their CD4 T cell count drops below 200 cells or when they develop certain opportunistic illnesses

24
Q

HIV induced loss of immune cells leads to

A

immunodeficiency

25
Q

what are anti-retroviral drugs designed to do

A

block replication

26
Q

what are the four selective targets of HIV retroviral drugs

A
  1. entry/fusion inhibitors
  2. site of action of AZT and other reverse transcriptase inhibitors
  3. integrase inhibitors
  4. site of action of protease inhibitors
27
Q

why is HIV treatment complicated

A
  1. can’t clear all virus from the host
  2. patients must remain on these drugs for their lifetime (expensive, poor, aadherence)
  3. antiviral resistance
    • reverse transcriptase lacks proofreading
      activity, so HIV’s cell surface antigens
      (gp120 and gp41) acquire mutations at a
      high rate
28
Q

people with HIV need what kind of treatment

A

HAART treatment
- combination drug therapy because then there will be no new mutants

29
Q

how does someone prevent HIV

A
  • screening and treating those who are HIV+ as a prevention
  • behavior modification -> safe sex practices, not sharing needles, etc
  • circumcision reduces infection through sexual activity
  • preexposure prophylaxis -> truvada (two anti-retroviral drugs) taken orally once daily
  • no vaccine
30
Q

what are some challenges with HIV

A
  • there is no vaccine
    • can’t stop taking antiviral drugs due to
      reservoirs of latent virus
  • there is, as of yet, no cure
    • can’t clear the virus from an infected
      individual
  • viruses evolve drug resistance
    • requires combination therapy
  • drugs are expensive
  • AIDS is becoming a third world disease
31
Q

describe the CCR5alpha32 allele

A
  • a naturally occurring mutant allele of the CCR5 gene where deletion of 32 base pairs make the receptor nonfunctional
  • CCR5alpha32 individuals do not become infected by HIV even if they are exposed
  • most HIV infections are initially M-tropic but later evolve into T-tropic
32
Q

define functional cure for HIV

A

some replication-competent virus might be present, but it is controlled without drugs and, therefore will allow for long periods of drug-free remission

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