HIV Flashcards
HIV is a part of what family of viruses?
Lentivirus
There are two types of HIV, HIV-1 and HIV-2. Which one is common in the U.S.? Where is the other found?
Type one is common in the U.S., HIV-2 is west Africa
How long does it take for the HIV virus to cause an acute illness after initial infection?
2-6 weeks
What are the first symptoms of HIV?
non-specific, flu-like symptoms
How long does seroconversion take in an HIV infection?
6-9 weeks
True or false: there is a “window period” in HIV patients, where they are infected with HIV, but do not produce antibodies
True
What are the stages of HIV/AIDS?
- Acute stage (nonspecific symptoms)
- Latent phase
- ARC (severe symptoms)
- AIDS
What type of CAs are AIDS patients susceptible to?
Kaposi’s sarcoma
Non-hodgkin’s lymphoma
What causes cachexia of AIDS pts?
TNF-alpha
Which cells does HIV attack?
mainly CD4+ cells (Th cells)
What is the clinical definition of AIDS?
CD4+ count below 200 cells/mm^3
Once in the bloodstream, the virus attaches to what CD4 protein on T lymphocytes or mononuclear phagocytes? What happens after this?
gp120
This undergoes a conformational change to allow gp41 to insert into the plasmamembrane
What are the different coreceptors that various HIV strains will binds to?
CCR5 (called “R5” viruses)
CXCR4(called “R4” viruses).
(both are called “R5X4” virus strains)
HIV viruses that preferentially use CCR5 coreceptors usually infect which cells?
Macrophages
HIV viruses that preferentially use CXR4 coreceptors usually infect which cells?
T-cell
True or false: there is no switching the preference of HIV viruses between the CCR5 and CXR4 corecptor
False–will shift throughout infection
What are the two options for an HIV virus once it has entered a cell?
Replicate or insert into DNA
What is a proviral state?
Where a virus exists only in the DNA of a host cell
What signals HIV viruses in the proviral state to replicate?
NF(kappa)B is known to bind to HIV long terminal repeats (LTR’s) which control transcription of viral genes.
What are the two cytokines that induce HIV transcription and viral replication in T lymphocytes?
Tumor necrosis factor-alpha and IL-2
What are the 6 cytokines that induce HIV transcription in macrophages?
IL-1, IL-3, IL-6, TNF-α, IFN-gamma and GM-CSF
What is the major role that macrophages play in helping the HIV virus?
Infected monocytes and macrophages are not as susceptible to lysis by the virus as T cells and may serve as an in vivo reservoir for the virus. This may serve to transport the virus throughout the body.
Normal individuals have a peripheral blood CD4:CD8 of (BLANK), however AIDS patients may have a ratio as low as (BLANK).
2, 0.5
What are the five ways in which the HIV virus kills Th cells?
- lysis of T cells
- interfere with protein production
- Syncytia formation of infected and uninfected T cells
- ADCC by antibody binding to gp120
- CTL destruction
What are the two other mechanisms in AIDS that lead to immunodeficiency besides the death of T cells?
- Binding of free gp120 of uninfected T cells
2. Destruction of follicular network of lymphoid organs
What is the protein HIV produces that down regulates class I MHC? What is the effect of this?
Nef protein which makes infected cells invisible to CTL’s
True or false: Individuals who are infected with a strain of HIV that has a defective Nef gene do not progress to AIDS
True
What accounts for the initial decline in the amount of HIV virus seen in pts: antibodies or CTLs?
CTLs
What are the two major reasons that immune responses to the HIV virus are not effective?
- Insertion of DNA = undetectable
2. Virus has high mutation rate d/t reverse transcriptase
What is the most frequent cause of death in pts with AIDS?
Fatal pneumonia from Pneumocystis carinii
What are the three major obstacles/features of the HIV virus that makes vaccine development problematic?
- Genetic diversity/mutation
- Transmission occurs w/in cells
- Viral progression in the face of the immune response
1% of caucasians carry a mutation in what gene that leads to resistance against developing HIV-1?
CCR5–(still susceptible to CXR4 strains)
How long does it take for antibodies against HIV proteins to be detected serologically?
6-9 weeks
What is the initial screening technique used to test for HIV?
ELISA
What are the components of the ELISA for HIV?
Binding H9 antigens to a solid phase. pts serum antibodies bind. tagged antibodies to the pts antibody
What are the two major sources of false positive tests of the ELISA for HIV?
- Multiparous females
2. Autoimmune pts
What is used to r/o a false positive ELISA for HIV?
Second ELISA, then western blot.
What is the PCR testing for HIV?
Detecting viral DNA by adding DNA polymerase + specific primer to DNA of pts
What is RT-PCR?
Same as PCR, but detects RNA presence by using reverse trancriptase, then DNA pol.
Which test would you use to determine whether a neonate has been infected with HIV from the parent? Why wouldn’t you use one of the other tests?
PCR or antigen detection ELISA. Cannot use others since mother’s antibodies will be present in baby.
