15: Immunology of HIV

Question 1

Acute HIV syndrome

Answer 1

flu like symptoms 2-6 wks after infection

• active virus replication occurs in blood and CSF. Lymphoid organs are seeded with the virus

Question 2

seroconversion

Answer 2

typically occurs 6-9 weeks after exposure to the virus

this is when HIV antibodies are made and put in serum

before this is window period when patient is viremic but tests would be negative

Question 3

Latent phase

Answer 3

HIV nearly undectable in blood, but replicating in lymph tissue

asymptomatic

Question 4

AIDS-related complex (ARC)

*Not all patients go through ARC

Answer 4

fever, night sweats, weight loss, diarrhea, skin conditions, lymphadenopathy

some have oral cadidiasis and or chronic mucocutaneous herpes infection

*without treatment die quickly

Question 5

AIDS

Answer 5

Recurrent infections with opportunistic pathogens
Tumors
AIDS-induced dementia
Progressive wasting “cachexia”

Question 6

clinical definition of AIDS

Answer 6

CD4 counts below 200 cells/mm3

Question 7

Infectious process of HIV

Answer 7

1. virus binds CD4 on cell surface with GP120
2. conformation change in GP120
3. conformation change in GP41
4. opens PM and allows fusion
5. viral genetic material enters cell

Question 8

What does the virus need to bind?/ main chemokine receptors used by HIV

Answer 8

CD4, CCR5, and CXCR4

Question 9

R5 viruses

Answer 9

use CCR5

macros and mem. T

Question 10

R4 viruses

Answer 10

use CXCR4

Tcells

R5 viruses will generally transition to R4 viruses to create more CD4 damage later in the disease process

Question 11

proviral state

Answer 11

integrated into host genome and waiting

Question 12

what binds the HIV long terminal repeats which control viral transcription

Answer 12

NFkB and SP1

Question 13

induces HIV trx/replication in T cells

Answer 13

TNFalpha and IL2

Question 14

induces HIV replication in monocytes and macrophages

Answer 14

IL-1,3,6 TNFalpha IFNgamma GM-CSF

Question 15

more prone to lysis by HIV

Answer 15

tcells

macros and monos may serve as in vivo reservoir and transport the virus throughout the body

Question 16

responsible for AIDS dementia complex

Answer 16

direct virus infection of neurons or destruction of neurons by macrophage-derived cytokines

Question 17

CD4: CD8 ratio

Answer 17

Normal 2:1

AIDS 1:2

Question 18

Mechanisms for killing T cells

Answer 18

1. direct lysis by budding HIV
2. virus production interferes with cellular prtn synthesis –> cell death
3. syncytia formation of infected and uninfected cells
4. Binding of free GP120 to infected and unifected T cells –> anitbody response and ADCC
5. CTL mediated destruction of virus infected cells

Question 19

Binding of free GP120 to unifected T cells

Answer 19

cant bind class II MHC

Question 20

HIV Nef protein

Answer 20

downregulates the expression of class I MHC make infected cells invisible to CTLs

w/o Nef protein: no AIDS

Question 21

HIV resistant individuals

Answer 21

• truncated CCR5 variants

- female African sex workers because of potent CTL responses

Question 22

ELISA

Answer 22

checks to see if antibodies to HIV are present

-uses antigens cultured in H9 cell line

Question 23

Problems with ELISA

Answer 23

False positives
- antibodies to the H9 cell line happens with multipreggers and autoimmune disease, transfusions and organ/tissue transplantation

Question 24

Western Blot

Answer 24

HIV antigens arranged in band size and antibodies from patient will attempt to attach to them

• no high false positive because has to be at right band length, not just bound

Question 25

HIV + diagnosis

Answer 25

Two positive ELISA tests and One positive Western blot

Question 26

PCR

Answer 26

Detects viral genomes integrated into cell DNA

• NEONATES infected from mom test

Question 27

RT-PCR

Answer 27

Uses RNA, detects free virus in body fluids

*Tests the viral load

Question 28

Check neonate with:

Answer 28

1. PCR
2. switched ELISA with antibody on wall being bound by antigen
3. HIV culture