Handout #3 - HIV Part 2 - Lecture

Question 1

What is the virus that causes AIDS?

Answer 1

HIV

Question 2

What family does HIV belong to?

Answer 2

Retroviridae

Question 3

What genus does HIV belong to?

Answer 3

Lentivirus

Question 4

Lente is from the Latin word for what? And why is that root used in the word Lentivirus?

Answer 4

“Slow.” Lentiviruses have long incubation periods.

Question 5

What cells does HIV attack?

Answer 5

T-helper cells.

Question 6

Why are T-helper cells important?

Answer 6

They activate and regulate our immune system.

Question 7

When is a diagnosis of AIDS made?

Answer 7

When an affected individual has been infected by one or more opportunistic infections and has their CD4+ T count below 200 per ml^3 of blood.

Question 8

What are normal CD4+ T cell levels?

Answer 8

500-1200 cells per ml^3

Question 9

What is the probability of heterosexual transmission of HIV?

Answer 9

~0.005 to 0.0001 per contact.

Question 10

What five conditions are required for transmission of HIV?

Answer 10

Source of infection, means of transmission, host susceptibility, route to susceptible cells in the body, enough virus introduced to cause infection.

Question 11

In absence of drug therapy, what is the risk in infant will be infected with HIV across the placenta?

Answer 11

Approximately 5-10% risk

Question 12

In absence of drug therapy, what is the risk in infant will be infected with HIV during delivery?

Answer 12

Approximately 20%

Question 13

In absence of drug therapy, what is the risk in infant will be infected with HIV via breast feeding?

Answer 13

Approximately 15%

Question 14

What two body fluids are the highest risk in transmission of HIV?

Answer 14

Cerebrospinal fluid (although unlikely to ever contact it) and plasma (much more likely to come into contact with).

Question 15

How does HIV usually enter host cells?

Answer 15

Via mucosal surfaces.

Question 16

What are three ways HIV can enter cells?

Answer 16

Via mucosal surfaces, exposure to the circulatory system, or needle transmission.

Question 17

Compared to non-circumcised males, what risk of HIV do circumcised males have of infection?

Answer 17

Approximately half the risk.

Question 18

Why do circumcised males have a lower risk of infection of HIV?

Answer 18

Reduced mucosal surfaces associated with loss of the foreskin, so the penis is drier.

Question 19

How many membrane layers does the envelope of HIV have?

Answer 19

Two

Question 20

What are some examples of enzymes that HIV requires that are associated with RNA?

Answer 20

Reverse transcriptase, protease, ribonuclease, and integrase.

Question 21

7 steps of HIV reproduction

Answer 21

Attachment, entry, formation of viral DNA, integration, translation, formation of immature virus particles, maturation.

Question 22

Are new strains of HIV likely or unlikely to develop during the initial infection stage?

Answer 22

Unlikely.

Question 23

What sorts of responses do HIV viral proteins stimulate in host cells?

Answer 23

Blockage of host cell protein activity and host protein destruction, cytotoxicity (helps kill host cells), attraction of WBCs (triggers immune system), stimulation of expression of co-receptor proteins, and stimulation of immune system proteins.

Question 24

What stage of HIV Reproduction can a cell not recover from?

Answer 24

Stage 4 - Integration

Question 25

What stimulates transcription of viral HIV genes into viral mRNA?

Answer 25

A combination of host and viral factors.

Question 26

What do most widely used anti-HIV drugs target?

Answer 26

Either protease or reverse transcriptase.

Question 27

What do HIV vaccine development efforts target?

Answer 27

Surface proteins.

Question 28

Where to do the first cells to be infected travel to first?

Answer 28

Lymph nodes, where the virus can access T-cells.

Question 29

Where is the second place that infected cells move to?

Answer 29

Into the bloodstream, where they can access major regions of the immune system such as the GI tract.

Question 30

What stage of infection is the GI tract especially important in?

Answer 30

The acute stage of infection.

Question 31

What do lymphatic tissues in the GI tract contain?

Answer 31

~40% of total WBCs and high numbers of CD4+ T cells.

Question 32

Rapid reproduction of the virus in the GALT facilitates spread of the virus to what other parts of the body?

Answer 32

Other parts of the lymphatic system including the spleen and the bone marrow.

Question 33

What is correlated with the peak of the acute stage of HIV infection?

Answer 33

Massive CD4+ T cell death (30-40% of total population in the GALT).

Question 34

When does viral spread and onset of the acute phase of HIV infection typically occur?

Answer 34

2-3 weeks after initial viral acquisition.

Question 35

What are symptoms of the acute phase of HIV infection?

Answer 35

Similar symptoms as a bad flu: lymph node swelling.

Question 36

What happens after the acute symptoms of HIV infection?

Answer 36

Killer T cells and antibodies produced by B-cells significantly reduce the viral load, and CD4+T cells rise in numbers.

Question 37

In untreated individuals, how long does it take from the acute phase to progress to AIDS?

Answer 37

2-3 years to more than a decade.

Question 38

During the clinical latency phase of HIV infection, the immune system as as a….

Answer 38

Selective mechanism for mutant strains that are more able to escape the immune system. It’s why the viral mutates so much.

Question 39

What happens after lymphoid tissues is destroyed?

Answer 39

Patient starts showing symptoms associated with AIDs.

Question 40

Why does the immune system get destroyed?

Answer 40

A combination of: continuing viral replication which creates persistent antigenic stimulation; ongoing depletion of T cells; inflammation; build up of scar tissue in the lymph nodes.