3.2.4 HIV

Question 1

What is HIV?

Answer 1

Virus that affects immune system

Question 2

What is AIDS?

Answer 2

Disease where immune system deteriorates & eventually fails

Question 3

What cells do HIV infect and use as a host?

Answer 3

helper T-cells

Question 4

When are people said to have developed AIDS?

Answer 4

When there’s less than 200 mm^-3 helper T-cells numbers so body can’t fight usual harmless pathogens (e.g. flu)

Question 5

HIV has a ______ structure

Answer 5

Spherical

Question 6

What does HIV’s core contain

Answer 6

RNA & proteins

e.g. enzymes: reverse transcriptase, integrase, and protease

Question 7

What is HIV’s outer coating of protein called?

Answer 7

Caspid

Question 8

HIV has a ___ layer called an ______

Answer 8

HIV has a outer layer called an envelope

Question 9

What is the envelope made out of?

Answer 9

Membrane stolen from cell membrane of previous host cell

Question 10

What are sticking from the envelope?

Answer 10

Attachment proteins

(Contains glycoproteins)

Question 11

What do attachment proteins help HIV to do?

Answer 11

To attach to host helper T-cell

Question 12

What is a retrovirus (e.g. HIV)?

Answer 12

Use reverse transcriptase & RNA method

Question 13

Describe how HIV replicates

Answer 13

1. Attachment protein attaches to CD4 cell-surface antigen on host helper T-cell
2. Capsid is released into cell, where it uncoats and releases genetic material (viral RNA) & core proteins into cytoplasm
3. Inside cell, reverse transcriptase is used to make complementary strand of DNA from viral RNA template
4. From this, double-stranded viral DNA is made & inserted into human DNA
5. Host cell enzymes are used to make viral proteins from viral DNA found within human DNA
6. Viral proteins are assembled into new viruses (made by host cell), which bud from cell & go infect other cells

Question 14

What happens during the initial infection period?

Answer 14

HIV replicates rapidly & infected person may experience severe flu-like symptoms

Question 15

What happens after the initial infection period?

Answer 15

HIV replication drops to a lower level = latency period

Question 16

What occurs during the latency period (which can last for years)?

Answer 16

Infected person won’t experience any symptoms

Question 17

What is the effect of AIDS?

Answer 17

Develop diseases that wouldn’t cause serious problems in people with healthy immune system

Question 18

Name 4 factors that affect the progression of HIV to AIDS & survival time with AIDS

Answer 18

1. Existing infections
2. Strain of HIV
3. Age
4. Access to healthcare

Question 19

Describe the initial symptoms of AIDS

Answer 19

Minor infection of mucous membranes (e.g. inside of nose, ears) & recurring respiratory infections

Question 20

Describe the symptoms of as AIDS progress & as no. of immune system cells decrease

Answer 20

Patients become susceptible to more serious infections

e.g. chronic diarrhoea, severe bacterial infections, tuberculosis

Question 21

Describe the symptoms during the late stages of AIDS

Answer 21

• Can develop range of serious infections
• These kill AIDS patients not HIV itself

Question 22

Name an issue when trying diagnose HIV

Answer 22

Symptoms are non-specific

Question 23

Name 2 ways of testing HIV

Answer 23

Blood tests

• Antibodies to HIV
• Looking for HIV specific protein - P24

Question 24

When diagnosing AIDS, what do you need to look at? (2)

Answer 24

• AIDS related symptoms
• No. of helper T cells

Question 25

Name 2 examples of treatments for HIV

Answer 25

* Antiviral drugs * Enzyme inhibitors

Question 26

What do antiviral drugs do?

Answer 26

Slow down the progression of HIV infection and AIDS in an infected person

Question 27

Describe what an integrase inhibitor does

Answer 27

Binds to integrase so viral DNA can’t be transcribed so viral RNA and proteins cannot be produced

Question 28

Describe what an attachment and entry inhibitor does

Answer 28

* During attachment, protein on HIV binds to CD4 receptors * Attachment and entry inhibitors bind to these attachment points

Question 29

Describe what a protease inhibitor does

Answer 29

Prevents protease catalysing the assembly of viral proteins in cytoplasm of host

Question 30

Name 3 reasons why HIV vaccinations are considered unsafe (3)

Answer 30

* Inactive virus may become active * Protein from HIV may harm cells * People may test HIV positive after vaccine used

Question 31

How do antibiotics kill bacteria?

Answer 31

* Interfer with their metabolic reactions * Target bacterial enzymes and ribosomes used in these reactions

Question 32

Why can antibiotics only target bacterial enzymes & ribosomes, and thus not damage human cells?

Answer 32

Bacterial enzymes & ribosomes are different from human enzymes & ribosomes

Question 33

Why can't antibiotics be used to cure viruses?

Answer 33

Don't have their own enzymes & ribosomes (use host cells' ones)

Question 34

What do most antiviral drugs do?

Answer 34

Target few virus-specific enzymes e.g. HIV uses revere transcriptase to replicate ∴ prevented by using reverse-transcriptase inhibitors

Question 35

Name 3 ways HIV spreads

Answer 35

* Unprotected sexual intercourse * Infected bodily fluids * (e.g. like blood from sharing contaminated needles) * From HIV-postive mother to her fetus

Question 36

Not all babies are born infected with HIV & taking ____ \_\_\_\_\_ during pregnancy can reduce chance of baby being HIV-positive

Answer 36

antiviral drugs

Question 37

Why is HIV testing, based on HIV antibody detection, before a baby is 18 months inaccurate?

Answer 37

∵ baby of HIV-positive mother may have some HIV antibodies in their blood regardless of whether or not they're infected

Question 38

When can a virus be described as inactive?

Answer 38

When it's not replicating