HIV Flashcards
which cells does HIV attack
T-cells
- and uses them to make copies of itself
when HIV destroys so many of your cells, what disease does it lead to
AIDS
what are some opportunistic infections among gay white men
- pneumocystis carinii pneumonia (PCP)
- Kaposi’s sarcoma
- reactivated TB
abnormal low lymphocyte counts are found in people with
HIV/AIDS
how is HIV transmitted
- contact with bodily fluids: blood, semen, vaginal secretions, and breast milk
- sex
- injection drug use
- mother-to-child
- teratogens (TORCHeS)
- during birth
- breastfeeding
sexual transmission of HIV is enhanced by
- breaks or tears in mucosal surface
- ulceration or inflammation (STDs)
HIV is what kind of virus
retrovirus
what are some features of retroviruses
- contain RNA genomes that get reverse-transcribed into DNA
- viral genomes permanently integrate into the host genome as a “provirus”
what are some features of retroviruses
- 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”)
- if the cell is activated, the provirus is t
HIV’s genome is diploid, which means it contains 2 identical copies of (+) or (-) ss RNA
(+) ss RNA
HIV has two glycoprotein spikes, what are they and what is their function
- gp120 = binds to CD4 receptor and a chemokine co-receptor on host cell (attachment)
- gp41 = facilitates fusion of viral and cell membranes
true or false - reverse transcriptase is a viral enzyme encoded by HIV
true
what kind of activity does reverse transcriptase have
RNA-dependent DNA polymerase activity
- synthesizes DNA from an RNA template
what are the three activities that reverse transcriptase does and what does it lack
- DNA synthesis from the RNA template
- ribonuclease H (RNA degradation)
- DNA-dependent DNA synthesis
- lacks proofreading ability
describe how HIV establishes latency
- 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”)
can the immune system eliminate a latent virus
no
describe HIV replication
- 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
describe HIV assembly
- 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
what are the main cellular targets of HIV? what do they infect? what receptors do they use?
- 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
when does M-tropic and T-tropic HIV strains infect
- 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
- predominate later in an infection, during
what is stage 1 of an HIV infection
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
what is stage 2 of an HIV infection
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
what is stage 3 of an HIV infection
AIDS
- patients are diagnosed with AIDS when their CD4 T cell count drops below 200 cells or when they develop certain opportunistic illnesses
HIV induced loss of immune cells leads to
immunodeficiency
