83. HUMAN IMMUNODEFICIENCY VIRUS (HIV)

Question 1

1. When was HIV discovered?

Answer 1

• in 1981
• it was isolated in 1983

Question 2

2. What are the two types of HIV?

Answer 2

1. HIV-1
2. HIV-2

Question 3

3. What cell in the body does HIV infect?

Answer 3

• it affects the T-helped Lymphocytes (Th-cells)
• it only affects them because they carry the CD4
  Receptor

Question 4

4. How does HIV attach itself onto the Host Cell?

Answer 4

• the Viral HIV Glycoprotein attaches itself to the CD4
  Receptor
• this is found on the surface of the Host’s T-Helper
  Lymphocytes

THE GLYCOPROTEIN OF HIV IS:
- 120 glycoproteins long

Question 5

5. What does HIV cause?

Answer 5

• it causes AIDS
• this is an Acquired Immuno Deficiency Virus

Question 6

6. What do the T-helper Cells do?

Answer 6

• they activate the B cells to produce antibodies
• Cytotoxic C-Cells will attack the target cells

IT THE T-HELPER CELLS ARE NOT ACTIVE:
- only pathogens will exist in the host cell’s body

Question 7

7. What are the steps of the HIV Replication Cycle?

Answer 7

1. Attachment
2. Reverse Transcriptase
3. Integrase
4. Translation
5. Protease
6. Assembly
7. New Virus leaves the Host Cell

Question 8

8. What happens during: Attachment?

Answer 8

• the virus attached itself the CD4 receptor of the host
  cell
• this is found on the cell membrane
• a single RNA genome from the Virus will enter the cell

Question 9

9. What happens during: Reverse Transcriptase?

Answer 9

• this enzyme will synthesise the virus RNA into DNA

Question 10

10. What happens during: Intergrase?

Answer 10

• the virus DNA will integrate into the genome of the
  Host Cell
• Transcription will take place

THIS CONVERTS THE VIRAL DNA AND HOST DNA:
- into a new strand of pathogenic RNA
- this viral RNA leaves the nucleus of the Host Cell

Question 11

11. What happens during: Protease?

Answer 11

• Translation will take place
• a Virus Protein is formed

PROTEASE:
- is an enzyme
- it cuts up the protein

Question 12

12. What happens during: Assembly?

Answer 12

• the viral protein fragments will reconstruct
• they do this by themselves
• this forms a new virus

Question 13

13. Which enzymes does the Anti-Retroviral Therapy target?

Answer 13

• Reverse Transcriptase
• Integrase
• Translation
• Protease

Question 14

14. What is the most serious pandemic of the 21st Century?

Answer 14

• AIDS
• 25 million people died
• 40 million people are infected

Question 15

15. What is the infection rate of AIDS?

Answer 15

• 6 million people are killed per year

Question 16

16. How long after someone contracts HIV, do they develop AIDS?

Answer 16

• 10 to 15 years after the infection
• they can be asymptomatic during this period of time
• this allows them to transmit the disease

PEOPLE WITH HIV WILL START TO DEVELOP AIDS SYMPTOMS:
- when the number of their T-helper cells falls under 200
cells per mm³ of blood

Question 17

17. How much has Anti-retroviral therapy helped to increase life expectancy?

Answer 17

• it has increased it by 5 to 20 years
• it allows people to live a life as normal as possible

Question 18

18. What kind of infections do people with AIDS suffer from?

Answer 18

• they suffer from opportunistic infections
• this is because they are severely immuno
  compromised

Question 19

19. What are the main two categories of diseases that AIDS patients will experience?

Answer 19

1. Opportunistic Infections
2. Malignant Tumours

Question 20

20. What are some examples of Opportunistic infections?

Answer 20

1. CANDIDIASIS
   - this is a type of yeast
2. TOXOPLASMOSIS
   - this is a type of protist
3. PNEUMONIA
   - this is a type of bacteria

Question 21

21. What are some Malignant Tumours associated with AIDS?

Answer 21

1. KAPOSI SARCOMA
   - this is a malignant tumour
   - it effects the endothelial cells
   - these are found in blood vessels
2. BURKITT’S LYMPHOMA:
   - this cancer affects the B-cells
   - it results in swollen lymph nodes

Question 22

22. What are the three ways in which HIV is transmitted?

Answer 22

1. Sexual Intercourse
2. Blood
3. Mother to Child

Question 23

23. How is HIV transmitted through Sexual Intercourse?

Answer 23

• it is transmitted through sperm
• it is transmitted through vaginal fluids

Question 24

24. How is HIV transmitted through Blood?

Answer 24

• it is transmitted by sharing infected needles
• it is transmitted by sharing infected syringes
• it is transmitted through blood transfusions

WHEN IT COMES TO BLOOD TRANSFUSIONS:
- there is a window period
- where the virus is present in the blood
- but cannot be detected
- it is present in very low levels in the blood
- this is how it is transmitted to other people

Question 25

25. How is HIV transmitted from Mother to Child?

Answer 25

- it is transmitted during pregnancy - it is transmitted during birth - it is transmitted through breast feeding BREAST MILK: - carries a large amount of then virus in it - this can infect the child INFECTED MOTHERS: - will often have C-sections

Question 26

26. Can HIV be transmitted through Saliva or Tears?

Answer 26

- no - the viral count is far too low for any transmission to occur

Question 27

27. How is HIV detected?

Answer 27

- the virus can be detected in the Blood - this happens 3-6 weeks after the suspected infection date - the detection depends on the method used

Question 28

28. What are the Diagnostic Methods used for HIV?

Answer 28

1. ELISA - this detects anti-HIV antibodies in the blood - it can be done 6-8 weeks after infection - it is a slower technique 2. RT-PCR - this detects the viral HIV RNA in the blood - this can be done 3 weeks after the infection

Question 29

29. Is there a cure for an HIV Infection?

Answer 29

- no there is not - there is no vaccine available - this is because HIV mutates at a very high rate

Question 30

30. What are the Treatment strategies for HIV?

Answer 30

1. HAART - this is a High Active Anti-Retroviral Therapy - it is a combination of many types of anti-retroviral drugs

Question 31

31. What are the common problems that we find when we use Anti-retroviral therapy?

Answer 31

- toxicity resistance - this is because the components of the virus are mutating - this interferes with the replication cycle of the healthy cells in the body and the infected cells

Question 32

32. What are the three main types of Anti-retroviral Drugs?

Answer 32

1. NUCLEOTIDE ANALOGUES 2. NON-NUCLEOTIDE ANALOGUES 3. PROTEASE INHIBITORS

Question 33

33. What are Nucleotide Analogues?

Answer 33

- they are drugs - they inhibit the replication of the RNA in the virus - the RNA is incorporated into a growing cDNA chain EXAMPLE: - AZT

Question 34

34. What are Non-nucleotide Analogues?

Answer 34

- they are drugs - they inhibit Reverse Transcriptase - this enzyme no longer has activity EXAMPLE: - SUSTIVA - NEVIRAPINE

Question 35

35. What are Protease Inhibitors ?

Answer 35

- they are drugs - they inhibit HIV protease HIV PROTEASE: - is responsible for the polypeptide cleavage of the virus - it allows for new virus particles to mature EXAMPLE: - SAQUINAVIR - RITONAVIR WHEN TREATING HIV: - it is encouraged to give one medication from each category

Question 36

36. What is AZT?

Answer 36

- it is Azido-deoxy-thymidine - it is a Nucleotide Analogue Anti-retroviral drug HOW IT WORKS: - the next nucleotide cannot be incorporated into the growing DNA chain - this is because of the presence of Nitrogen (N₃) instead of -OH - this inhibits the replication of the viral RNA

Question 37

37. Define: HIV Polymorphism.

Answer 37

- HIV has a high rate of mutation - new strains will continue to emerge THE RNA OF THE HIV VIRUS: - is exposed to the enzyme : Reverse Transcriptase - this will form copies of HIV DNA (cDNA) THE REVERSE TRANSCRIPTASE: - will allow for 1 mutation per HIV genome - per replicative cycle