HIV

Question 1

what are the 2 types of HIV? where are they prevalent?

Answer 1

HIV1: US, worldwide
HIV2: western africa, southern asia

–> HIV2 so uncommon that HIV usually refers to HIV1

Question 2

which type of cells does HIV target?

Answer 2

CD4+ cells (T-helper, but also macrophages/dendritic cells)

Question 3

which protein does HIV target?

Answer 3

CD4

Question 4

which protein on the HIV envelope binds to CD4?

Answer 4

gp120

Question 5

how does HIV enter the cell? which receptors/co-receptors are involved?

Answer 5

the molecule gp120 on surface of HIV binds to CD4. needs co-receptor CXCR4 or CCR5 to enter

CXCR4: on t cells
CCR5: on t cells, macrophages, dendritic cells

Question 6

which cells contain the co-receptor CXCR4?

Answer 6

t cells

Question 7

which cells contain the co-receptor CCR5?

Answer 7

t cells, macrophages, dendritic cells

Question 8

people with which mutation are immune to hiv?

Answer 8

mutation of CCR5

Question 9

what kind of virus is HIV?

Answer 9

single strand RNA retrovirus

Question 10

how does a ‘single strand RNA retrovirus’ replicate inside host cells?

Answer 10

• it uses reserve transcriptase to make a complimentary piece of genetic material -> DS proviral DNA
• this DNA gets incoorporated into the host cell DNA

–> virus particles are made

Question 11

how is HIV spread?

Answer 11

sexual intercourse

Question 12

what happens during acute infection of HIV on cellular level?

(start with R5 strain binding to CCR5)

Answer 12

R5 strain of HIV binds to CCR5 coreceptor -> virus inside t cells/macrophages/dendritic cells -> dendritic cells move to lymph nodes -> many more immune cells infected locally -> big spike in HIV in blood

Question 13

how are different strains of HIV made?

Answer 13

errors during replication (still HIV, but targets different cell types = ‘viral tropism’)

Question 14

what are the symptoms of acute HIV infection?

Answer 14

flu-like symptoms

Question 15

acute infection: HIV in blood high or low?

Answer 15

high

Question 16

acute infection: HIV in blood is high. what happens next?

Answer 16

counterattack of immune system -> HIV in blood lowers to stable lower level (and enters chronic phase)

Question 17

after how long is the chronic phase reached after acute infection?

Answer 17

12 weeks

Question 18

how long can the chronic phase be?
why is this?

Answer 18

2-10 yrs

the virus is slowly replicating and t cells are slowly decreasing

body can stil fight off infection relatively well

Question 19

how many t cells are still enough to sustain the chronic phase? (without severe infections)

Answer 19

> 500 t-cells/mm3

Question 20

t-cells between 200-500/mm3 -> which symptoms? hiv or aids?

Answer 20

still hiv

• lymfeadenopathy
• oral candidiasis
• hairy leukoplakia (white patch on tongue due to EBV)

Question 21

t-cells <200/mm3 -> hiv or aids? symptoms?

Answer 21

aids (immune system severely compromised)

• persistant fever, fatigue, weight loss, diarrhea
• aids-defining conditions

Question 22

what are ‘aids-defining’ conditions?

Answer 22

• recurrent bacterial pneumonia
• pneumocystis pneumonia (fungus)
• fungal infections (candidiasis of esophagus)
• tumors (Kaposi, primary lymphoma brain)

Question 23

what are the modes of transmission of HIV?

Answer 23

• sexual intercourse (male to male in US, male to female in developing countries)
• iv drug use
• mother to child (placenta, delivery, breast milk)

less common:
- accidental needle sticks, blood products

Question 24

how to diagnose hiv?

Answer 24

Blood:
- antibody test
- antibody/antigen test (recommended)
- RNA/DNA test (= NAT test; nucleic acid test)

Question 25

treatment hiv?

Answer 25

no cure

antiretroviral therapy (ART):
- combination of medications
- slows replication
- help immune system recover & fight off infections