HIV

Question 1

HIV is a part of what family of viruses?

Answer 1

Lentivirus

Question 2

There are two types of HIV, HIV-1 and HIV-2. Which one is common in the U.S.? Where is the other found?

Answer 2

Type one is common in the U.S., HIV-2 is west Africa

Question 3

How long does it take for the HIV virus to cause an acute illness after initial infection?

Answer 3

2-6 weeks

Question 4

What are the first symptoms of HIV?

Answer 4

non-specific, flu-like symptoms

Question 5

How long does seroconversion take in an HIV infection?

Answer 5

6-9 weeks

Question 6

True or false: there is a “window period” in HIV patients, where they are infected with HIV, but do not produce antibodies

Answer 6

True

Question 7

What are the stages of HIV/AIDS?

Answer 7

1. Acute stage (nonspecific symptoms)
2. Latent phase
3. ARC (severe symptoms)
4. AIDS

Question 8

What type of CAs are AIDS patients susceptible to?

Answer 8

Kaposi’s sarcoma

Non-hodgkin’s lymphoma

Question 9

What causes cachexia of AIDS pts?

Answer 9

TNF-alpha

Question 10

Which cells does HIV attack?

Answer 10

mainly CD4+ cells (Th cells)

Question 11

What is the clinical definition of AIDS?

Answer 11

CD4+ count below 200 cells/mm^3

Question 12

Once in the bloodstream, the virus attaches to what CD4 protein on T lymphocytes or mononuclear phagocytes? What happens after this?

Answer 12

gp120

This undergoes a conformational change to allow gp41 to insert into the plasmamembrane

Question 13

What are the different coreceptors that various HIV strains will binds to?

Answer 13

CCR5 (called “R5” viruses)

CXCR4(called “R4” viruses).

(both are called “R5X4” virus strains)

Question 14

HIV viruses that preferentially use CCR5 coreceptors usually infect which cells?

Answer 14

Macrophages

Question 15

HIV viruses that preferentially use CXR4 coreceptors usually infect which cells?

Answer 15

T-cell

Question 16

True or false: there is no switching the preference of HIV viruses between the CCR5 and CXR4 corecptor

Answer 16

False–will shift throughout infection

Question 17

What are the two options for an HIV virus once it has entered a cell?

Answer 17

Replicate or insert into DNA

Question 18

What is a proviral state?

Answer 18

Where a virus exists only in the DNA of a host cell

Question 19

What signals HIV viruses in the proviral state to replicate?

Answer 19

NF(kappa)B is known to bind to HIV long terminal repeats (LTR’s) which control transcription of viral genes.

Question 20

What are the two cytokines that induce HIV transcription and viral replication in T lymphocytes?

Answer 20

Tumor necrosis factor-alpha and IL-2

Question 21

What are the 6 cytokines that induce HIV transcription in macrophages?

Answer 21

IL-1, IL-3, IL-6, TNF-α, IFN-gamma and GM-CSF

Question 22

What is the major role that macrophages play in helping the HIV virus?

Answer 22

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.

Question 23

Normal individuals have a peripheral blood CD4:CD8 of (BLANK), however AIDS patients may have a ratio as low as (BLANK).

Answer 23

2, 0.5

Question 24

What are the five ways in which the HIV virus kills Th cells?

Answer 24

1. lysis of T cells
2. interfere with protein production
3. Syncytia formation of infected and uninfected T cells
4. ADCC by antibody binding to gp120
5. CTL destruction

Question 25

What are the two other mechanisms in AIDS that lead to immunodeficiency besides the death of T cells?

Answer 25

1. Binding of free gp120 of uninfected T cells | 2. Destruction of follicular network of lymphoid organs

Question 26

What is the protein HIV produces that down regulates class I MHC? What is the effect of this?

Answer 26

Nef protein which makes infected cells invisible to CTL’s

Question 27

True or false: Individuals who are infected with a strain of HIV that has a defective Nef gene do not progress to AIDS

Answer 27

True

Question 28

What accounts for the initial decline in the amount of HIV virus seen in pts: antibodies or CTLs?

Answer 28

CTLs

Question 29

What are the two major reasons that immune responses to the HIV virus are not effective?

Answer 29

1. Insertion of DNA = undetectable | 2. Virus has high mutation rate d/t reverse transcriptase

Question 30

What is the most frequent cause of death in pts with AIDS?

Answer 30

Fatal pneumonia from Pneumocystis carinii

Question 31

What are the three major obstacles/features of the HIV virus that makes vaccine development problematic?

Answer 31

1. Genetic diversity/mutation 2. Transmission occurs w/in cells 3. Viral progression in the face of the immune response

Question 32

1% of caucasians carry a mutation in what gene that leads to resistance against developing HIV-1?

Answer 32

CCR5--(still susceptible to CXR4 strains)

Question 33

How long does it take for antibodies against HIV proteins to be detected serologically?

Answer 33

6-9 weeks

Question 34

What is the initial screening technique used to test for HIV?

Answer 34

ELISA

Question 35

What are the components of the ELISA for HIV?

Answer 35

Binding H9 antigens to a solid phase. pts serum antibodies bind. tagged antibodies to the pts antibody

Question 36

What are the two major sources of false positive tests of the ELISA for HIV?

Answer 36

1. Multiparous females | 2. Autoimmune pts

Question 37

What is used to r/o a false positive ELISA for HIV?

Answer 37

Second ELISA, then western blot.

Question 38

What is the PCR testing for HIV?

Answer 38

Detecting viral DNA by adding DNA polymerase + specific primer to DNA of pts

Question 39

What is RT-PCR?

Answer 39

Same as PCR, but detects RNA presence by using reverse trancriptase, then DNA pol.

Question 40

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?

Answer 40

PCR or antigen detection ELISA. Cannot use others since mother's antibodies will be present in baby.