HIV

Question 1

What is a retrovirus?

Answer 1

A virus that contains the enzyme reverse transcriptase, which causes the reaction that turns viral RNA into a complementary strand of DNA.

Question 2

After infection, what is the first thing HIV does inside the body?

Answer 2

Binds to a CD4 protein on a host cell. Most typically this is a T-helper cell

Question 3

After binding to the CD4 protein, what does HIV do next?

Answer 3

The protein capsid fuses to the host cell’s cell-surface membrane and released its RNA and enzymes into the host cell

Question 4

When inside the cell, what do the RNA and enzymes do?

Answer 4

Turn the viral RNA into a complementary strand of DNA

Question 5

After the DNA is formed, where does it move to?

Answer 5

the host (T-helper) cell’s nucleus. Here it is inserted into the cell’s DNA

Question 6

Outline how HIV replicates using Th cells?

Answer 6

• HIV enters the bloodstream
• the attachment proteins on HIV bind to CD4 protein on Th cell’s cell-surface membrane
• the capsid fuses with the Th cell’s cell membrane
• the viral RNA and reverse transcriptase enter the Th cell
• HIV RNA converted into HIV DNA , using reverse transcriptase
• HIV DNA moves into nucleus and binds to Th cell DNA
• HIV mRNA is made, which contains the instructions for the formation of viral proteins (enzymes, attachment proteins, reverse transcriptase, capsid)
• new HIV particle formed
• HIV leaves the Th cell, taking some of it’s cell surface membrane with it (budding)

Question 7

Why do you wash in between steps in the ELISA test?

Answer 7

to remove any unbound antibodies, preventing false positive results

Question 8

Describe the structure of the human immunodeficiency virus (HIV)

Answer 8

-RNA (as genetic material);
-Reverse transcriptase;
- (Protein) capsomeres/capsid;
-(Phospho)lipid (viral) envelope
- Attachment proteins;

Question 9

How is the ELISA test shows the presence of HIV antibodies?

Answer 9

• HIV antigens bound to bottom
• sample added
• HIV antibodies bind to the HIV antigens
• secondary antibodies added with an enzyme attached
• will bind to primary antibodies
• substrate added = colour change
  WASH BETWEEN STEPS

Question 10

How does a control show that the ELISA test has worked?

Answer 10

shows that the sample has diffused/moved

Question 11

Why are viruses described as acellular and non-living?

Answer 11

• no cell-membranes
• do not respire or synthesise own proteins