L14 Human Immunodeficiency Virus

Question 1

How can HIV be transmitted?

Answer 1

Sexual

Mechanical
- needles/tattoing/piercing
- surgery/blood transfusion

Vertical
- prenatal : placental
- perinatal : during birth
- post natal : breast milk

Question 2

Which type of HIV leads to AIDS?

Answer 2

HIV-1

Question 3

What is SIV?

Answer 3

Simian immunodeficiency virus which is a milder disease and less virulent

Question 4

What is the cellular response to HIV-1?

Answer 4

The immune system initiate anti-HIV antibody and cytotoxic T cell production

The immune response is weakened as memory T cells are destroyed

Question 5

List opportunistic infection associated with HIV-1 infection

Answer 5

• pneumocystis sp.
• TB
• malaria
• HPV

Question 6

List anti-HIV therapies

Answer 6

Triple therapy - highly active anti-retroviral therapy
Nucleosides analogues - competitive inhibitor of RT
Peptide analogues - competitive inhibitor of HIV protease
Anti-CCR5 therapy - individuals with mutation in the CCR5 gene are highly resistant to HIV

Question 7

How does HIV cause AIDS?

Answer 7

The HIV virus attacks and weakens the immune system
The person is now at risk of getting life-threatening infections and cancers
CD4 cells are destroyed which normally fight off infections
-> this illness is called AIDS

Question 8

What is the life cycle of HIV?

Answer 8

1) binding
2) fusion
3) reverse transcription
4) intergration
5) replication
6) assembly
7) budding

Question 9

Explain the binding stage in HIV life cycle

Answer 9

The virus binds to receptors on the surface of CD4 cells

These are helper T cells that are a type of white blood cell that alert other immune cells there’s an infection in your body

Question 10

Explain the fusion stage in HIV life cycle

Answer 10

Once HIV is bound to CD4 receptors it initiates the fusion of its envelope with the membrane of the CD4 cell using a glycoprotein called GP120

The virus can now enter the CD4 cell

Question 11

Explain the reverse transcription stage of HIV life cycle

Answer 11

The virus converts its RNA into DNA by releasing an enzyme called reverse transcriptase

This allows the viruses genetic info to enter the nucleus of the CD4 cell

Question 12

Explain the intergration stage of the HIV life cycle

Answer 12

Once RNA is converted to DNA, HIV releases intergrase inside the nucleus of the CD4 cell

The virus uses this enzyme to combine its DNA into the DNA of the CD4 cell

Question 13

Explain the replication stage of the HIV life cycle

Answer 13

The HIV can use the CD4 cells machinery to generate viral proteins and to produce more RNA

This allows more viral particles to be made

Question 14

Explain the assembly stage of the HIV life cycle

Answer 14

New HIV proteins and RNA are sent to the edge of the CD4 cell and become immature HIV.

These viruses are non-infectious in their current form

Question 15

Explain the budding stage of HIV life cycle

Answer 15

The immature viruses push out of the CD4 cell

They release an enzyme called protease which modifies proteins in the virus and creates a mature and infectious version

Question 16

Describe the structure of a HIV molecule

Answer 16

• two identical single-stranded RNA molecules that are enclosed within the core of the virus particle
• capsid
• envelope and envelope protein
• enzymes : intergrase, protease and reverse transcriptase