HIV

Question 1

Describe retroviruses.

Answer 1

enveloped
single stranded (+)
two copies

Question 2

How do retroviruses replicate?

Answer 2

through DNA intermediate using reverse transcriptase

Question 3

Which two retrovirus cause disease?

Answer 3

Deltaretrovirus - complex (HTLV)

Lentivirus - complex (HIV-1, HIV-2)

Question 4

What is RNA dependent DNA pol used for?

Answer 4

A DNA polymerase enzyme that catalyzes the process of reverse transcription.

Question 5

What is integrase

Answer 5

viral protein that helps entry

Question 6

What three major proteins do retroviruses have?

Answer 6

gag
pol
env

Question 7

What are the 6 accessory genes for HIV1?

Answer 7

tat
rev
nef
vif
vpr
vpu

Question 8

Where does the retrovirus assemble and bud?

Answer 8

plasma membrane

Question 9

Gag encodes for?

Answer 9

Structure:
matrix
capsid
nucleocapsid

Question 10

Pol encodes for?

Answer 10

enzymes
reverse transcriptase (acts in cytoplasm)
integrase (integrates provirus DNA into host DNA)
protease (cleaves GAG protein; inhibits replication cycle)

Question 11

Env encodes for?

Answer 11

Envelope proteins:
Surface Glycoproteins
Transmembrane Protein

Question 12

What are the two regulatory proteins for HIV?

Answer 12

tat (transactivator - increase transcription)

rev (regulator of viral expression)

Question 13

Is nef (negative regulation factor) a regulator?

Answer 13

NO, it down regulates CD4 and MHC class II

Question 14

Why would nef downregulate CD4 and MHC II?

Answer 14

Virus wants to replicate before cell is attacked.

Question 15

What is the function of vpu (Viral protein U)?

Answer 15

promotes degradation of CD4 and enhances release of virus from cell membrane

Question 16

What is the function of vpr (Viral Protein R)? ***

Answer 16

• transports DNA to nucleus

- increases virion production

Question 17

What is the function of vif (viral infectivity)? ***

Answer 17

affects particle infectivity

Question 18

Which two coreceptors are used for binding?

Answer 18

CCR5 (CD4 and macrophages)

CXCR4 (CD4 and T cell lines)

Question 19

Viral DNA is formed be what process?

Answer 19

reverse transcription

Question 20

What regulates transcription?

Answer 20

tat (transactivator)

Question 21

What allows export of virus from nucleus?

Answer 21

rev (regulator of viral expression)

Question 22

What helps virus release from cell membrane?

Answer 22

vpu (viral protein U)

Question 23

How are HTLVs transmitted?

Answer 23

blood, sexual, vertical

Question 24

HTLV-2 is more common in what population?

Answer 24

IV drug users

Question 25

Where is HTLV-1 prevalent?

Answer 25

Japan, Caribbean, tropics

Question 26

What are the clinical manifestations of HTLV-1?

Answer 26

``` inflammation spinal cord atrophy hyper-reflexivity leg weakness urinary and fecal incontinence ```

Question 27

What is HTLV-2 associated with?

Answer 27

atypical T-cell hairy leukemia

Question 28

Where did HIV come from?

Answer 28

chimpanzee (SIV-simian immunodeficiency virus)

Question 29

List the four groups of HIV-1.

Answer 29

Group M - major Group N - man from Cameroon Group O - outlier "West Central Africa" Group P - woman from Cameroon (gorilla simian immunodeficiency)

Question 30

How many clades (subtypes) of group M are identified?

Answer 30

9 (A, B, C, D, E, F, G, H, I, J, K)

Question 31

HIV-2 has how many groups?

Answer 31

8 (A, B, C, D, E, F, G, H)

Question 32

Which receptor does an M-tropic R5 virus use?

Answer 32

CCR5

Question 33

Which receptor does a T-tropic X4 virus use?

Answer 33

CXCR4

Question 34

Which protein is embedded in the membrane?

Answer 34

Gp41

Question 35

Which protein is the head of the stalk?

Answer 35

Gp120

Question 36

Describe the two types of conformational changes due to gp41 and gp120.

Answer 36

GP120 binds to Tcell and promotes binding of chemokine receptor. GP41 undergoes a conformational change that exposes the fusion peptide which inserts into the Tcell membrane.

Question 37

Patients initiating treatment for Tb should also be screened for what infection?

Answer 37

HIV

Question 38

What is the 2-step laboratory test to diagnose?

Answer 38

Serum ELISA | confirmed by Western blot or Immunofluorescense

Question 39

What are some alternative tests for initial diagnosis?

Answer 39

rapid oral antibody test | results in 5 to 40 minutes

Question 40

What are some tests that may be performed post-diagnosis?

Answer 40

Quantition of virus in blood: HIV-1RT-PCR Early marker of infection: Western blot for p24 antigen correlate of HIV disease: CD4/CD8 Tcell ratio

Question 41

Be able to read western blot

Answer 41

Negative: total absence of bands associated with HIV1 (gp160/120, p24) Positive: presence of at least 2 of the following bands: p24 gp41 gp120/160

Question 42

How does a western blot work?

Answer 42

Control lane with proteins that are present in HIV-1 Patient's serum lane is compared for bands +Positive Must have at least 2 bands p24 gp41 gp120/160

Question 43

What does p24 band indicate in HIV infection?

Answer 43

early infection

Question 44

What is acute HIV infection?

Answer 44

time between infection and seroconversion - must see detectable HIV RNA or DNA or p24 - cannot be antibody based test