Lecture 35 - HIV and AIDS

Question 1

What is the scope of HIV infection worldwide compared to TB and malaria?

Answer 1

HIV = 37 million infected
TB = 2 billion infected
Malaria = 500 million

Question 2

Why do we still study HIV?

Question 3

How effective is HIV as a pathogen? What does this imply about its evolution?

Answer 3

HIV has low transmission rates and high fatality
Implies that it is recently evolved and not yet balanced

Question 4

If HIV is a poor pathogen, how can HIV spread so rapidly?

Answer 4

Initially in homosexual men that has since spread to heterosexual population
30% of early cases were drug users/needle sharers

Question 5

What are the main genes of HIV?

Answer 5

gag: codes for matrix and capsid proteins
pol: codes RTase, protease, integrase
env: codes surface glycoproteins (gp120, gp41)

Question 6

How are the genes processed?

Answer 6

make a long mRNA, transcribe gag, gag+pol, or env

Question 7

What is the structure of HIV?

Answer 7

gp120:
gp41:
matrix:
capsid proteins:
RTase
integrase:

Question 8

Course of Infection of HIV

Answer 8

1. HIV enters host cell in infected macrophages and eosinophils.
2. HIV is shed
3. HIV infects humortal T cells in lymph nodes

Question 9

How does HIV enter Th cells?

Answer 9

1. gp120 (spike protein) binds to CD4 (receptor on Th cell) and coreceptor CCR5
2. gp41protein initiates membrane fusion and enters the cell

Question 10

What does HIV do once it is in Th cells?

Answer 10

3. RNA is uncoated and reverse transcribed
4. dsDNA enters nucleus integrates into host DNA
5. gene is transcribed, new virus made

Question 11

How does HIV infection kill humoral T cells? What effect does this have?

Answer 11

I. HIV infects healthy T cells.
II. Pyroptosis (apoptosis with inflammation)
III. Inflammation recruits new T cells
Repeat

Question 12

What is the course of a typical HIV infection?

Answer 12

Initial infection is mild: acute retroviral syndrome (ARS)

Question 13

What three HIV tests are commonly used? Which two are used to screen patients

Answer 13

1. Indirect ELISA
2. Western blot

Question 14

Know the commonly used thresholds for predicting AIDS and secondary infections

Answer 14

Look at viral titer
<200/mL: AIDs rarely develops

~1000/mL: AIDs will take >10 years to develop

> 100,000/mL: AIDs will develop in 2-3 years

Question 15

Name 5 major HIV-associated secondary infections

Answer 15

1. Pneuomocystis carinii
2. Toxoplasma gondi
3. CMV - herpesvirus
4. Tuberculosis
5. Thrush

Question 16

What is modern HIV treatment

Answer 16

Chemotherapy prolongs onset of AIDs
A. HAART (highly active anti-retroviral therapy)
B. ATRIPLA

Question 17

Why is it hard to develop a vaccine against HIV?

Answer 17

1. HIV develops resistance to drugs
2. low therapeutic index
3. high cost

Question 18

Possible vaccine?

Answer 18

N6 antibody could provide broad protection