HIV

Question 1

Aspartate protease

Answer 1

Cleavage of proteins

Question 2

Integrase

Answer 2

Integrate DNA into host cell DNA

Question 3

Reverse Transcriptase

Answer 3

Makes DNA from RNA

Question 4

Cone-shaped (conical) capsid composed of

Answer 4

Multiple copies of p24

Non-variable protein

Question 5

HIV envelope contains

Answer 5

Env Protein

Question 6

Cap of env protein contains

Answer 6

Glycoproteins

Question 7

gp 120

Answer 7

attachment to T cells

Question 8

gp 41

Answer 8

fusion and entry into T cells

Question 9

gp120 and gp41 are both formed as

Answer 9

single protein (gp160) then cleaved

Question 10

Gene for gp120

Answer 10

Mutates rapidly (antigenic variation)

Question 11

Antibodies generated against which portion of gp120 (attachment to T cells)

Answer 11

V3 loop portion (highly immunogenic so antibody neutralization inhibited)

Question 12

Gag gene

Answer 12

Codes for long polypeptide that is cleaved into pieces, including p24 (nucleocapsid)

Question 13

Pol gene

Answer 13

Codes for long polypeptide that is cleaved into several enzymes, including reverse transcriptase, integrase and protease).

Question 14

Env gene

Answer 14

Codes for gp160, which is cleaved into gp120 and gp41 (envelope proteins).

Question 15

Regulatory genes (required for replication)

Answer 15

Tat and Rev

Question 16

Tat gene

Answer 16

Activates transcription

Question 17

Rev gene

Answer 17

Transports mRNA from nucleus to cytoplasm

Question 18

Auxiliary Genes

Answer 18

Not required for replication: Nef, viv, vpr, vpu, vpx

Question 19

Nef gene

Answer 19

Decreases CD4 proteins and MHC I on T cell surfaces

Question 20

CCR5 and CXCR4

Answer 20

Major lymphocyte receptors used by HIV particles to enter cells

Question 21

CCR5-tropic virus particles

Answer 21

Replicate in monocytes/macrophages (M-tropic particles)
Can also infect dendritic cells (trafficking to lymph nodes)
Occur early: Sexually transmitted to macrophages

Question 22

CXCR4-tropic virus particles

Answer 22

Replicate more efficiently in T-cells (T-tropic virus particles)
Occur later after infection has developed

Question 23

Mutation in which gene is associated with decreased susceptibility to HIV infection?

Answer 23

CCR5 gene

Question 24

How does HIV enter human cells?

Answer 24

1. HIV attacks cells that have CD4 on surface
2. gp120 binds to CD4
3. HIV particle binds to either CCR5 or CXCR4
4. gp41 allows fusion and entry into human cells

Question 25

Which class of drugs does not work on HIV-2

Answer 25

NNRTIs

Question 26

HIV Time Course: CD4+ Lymphocyte Count

Answer 26

1. CD4 count normal at infection and falls shortly after | 2. Body begins to fight back with CD8+ T cells so CD4 Count increases before slowly dropping over many years

Question 27

HIV Time Course: Viral Load (HIV RNA Copies)

Answer 27

1. Very low at infection then shoots up very high (acute HIV syndrome with dissemination of virus and seeding into lymphoid organs) 2. Body fights back so lowers HIV RNA copies 3. HIV RNA copies slowly increase over many years 4. HIV RNA copies get very high when pt develops AIDs

Question 28

Clinical Latency Period

Answer 28

Pt has no sx but body fighting infection (CD8 cells)

Question 29

Viral Set Point

Answer 29

Lowest level of HIV RNA copies after acute phase. Lower set point = longer time before AIDS onset.

Question 30

Point of maximum CD4 count after acute phase

Answer 30

Higher = longer time before AIDS onset

Question 31

ELISA

Answer 31

Antibody-only test | Sensitive but many false positives

Question 32

Confirmatory test for (+) ELISA

Answer 32

Western Blot (more specific)

Question 33

4th Generation Tests

Answer 33

Combination Antigen/Antibody Tests | Test for both p24 antigen and HIV antibodies

Question 34

Confirmatory test for (+) 4th Generation Test

Answer 34

HIV1-HIV2 antibody differentiation assay

Question 35

Acute HIV Test

Answer 35

HIV RNA testing (viral load) will be high | Level of p24 antibodies not elevated yet

Question 36

Perinatal HIV Test

Answer 36

HIV PCR testing | Maternal HIV antibodies persist for months

Question 37

CD4 < 200

Answer 37

TMP-SMX: Pneumocystis Pneumonia

Question 38

CD4 < 100

Answer 38

TMP-SMX: Pneumocystis and Toxoplasmosis | Itraconazole (Histoplasmosis in endemic areas)

Question 39

CD4 < 50

Answer 39

Azithromycin: MAC