Wednesday April 21,1999
Announcements:

Lecture notes:

Sexual Transmission: male to male, male to female, female to female.
*Women are 20-23 times more likely to receive than transmit the virus in heterosexual transmission.

Transmission by blood and blood products: Infected illegal drug "works"

Transfusion: Risk- 1 in 50,000 to 1 in 100,000.

Factor 8 (Almost no risk now- heat treated or bioengineered now)

Mother (Infected) to infant
*1/4 infected in mom's uterus.
*more are infected by breast milk.

HIV is a fragile retrovirus. (retroviruses contain copies of reverse transcriptase which can make DNA from RNA.)

Exposure: exchange of body fluids which contain enough virus to infect cells. (semen, blood, vaginal fluids, possibly
mother's milk)

Infection: 1. The virus has a protein on its membrane called gp120. It finds and binds to the protein called CD4 on the
surface of a T4 lymphocyte. Also infects monocytes and glial cells in brain.

2. The virus dumps its RNA and reverse transcriptase into the cell.

3. Reverse transcriptase directs production of a DNA copy of the viral RNA.

4. DNA with viral is inserted into the HOST DNA. It is now called a provirus.

5. The viral genes sit and wait until the host T4 cell is activated by an infection.

6. Viral RNA is produced and makes viral proteins.

7. The virus is assembled and "buds" off from the cell.

8. These go on to infect other cells.

This is called the asymptomatic stage of infection. (there are some slight variations on this theme in some types of cells with CD4 on their surfaces.)

There are three possible outcomes after successful infection by the virus.

1. The person will remain asymptomatic. Asymptomatic people are infectious. Most HIV infections are transmitted by asymptomatic people.
2. The person can progress to ARC - AIDS related complex. "pre-AIDS"
3. The person can progress from ARC to AIDS.

1. HIV antigen coated onto wells of plate.
2. Patients serum added to the plate
3. If antibodies are present they will stick to HIV antigen on plate.
4. Excesses is washed away.
5. "enzyme linked reagent" added that sticks to antibodies. Anti-IgG + enzyme and then wash again.
6. Color change indicated presence of antibodies, when reagent added.

If positive test results 2^nd Eliza test done, if still positive another test called Western Blot test is done to confirm.

• not always
• It could mean you are not infected
• It could also mean that you have not yet made enough antibodies to be detected by the test.
• To make resonably sure you are not infected engage in no risky behavior for 3-6 months and retest.

1. Viral envelope proteins mutate frequently.
2. Humans do not develop very effective antibodies to HIV.
3. Humans make several different antibodies to HIV.
4. "Enhancing antibody effect" The presence of antibodies to this virus makes symptoms worse.
5. HIV is a complicated retrovirus. (7 genes instead of 3)
6. Difficulty of getting models for infection study

• Don't use drugs and don't have sex with people who do.
• Abstain from sex
• Delay sexual activity
• Sexual fidelity
• Choose partners carefully
• Don't have sex with people who have multiple partners
• Don't use alcohol or drugs if you are planning to engage in intercourse.
• Avoid exchange of body fluids by using condoms properly.