Infectious Diseases

Question 1

Name 3 major structural viral components

Answer 1

1. Envelope
2. Capsid
3. RNA

Question 2

How many genes to simple retroviruses have?

Name them.

What is each ones general function?

Do other types of genes to complex viruses contain?

Is HIV a simple or complex Virus?

Answer 2

4 genes

1. GAG - structural proteins (capsid)
2. PRO - protease
3. POL - reverse transcriptase & integrase
4. ENV - envelope

Complex retrovirus have Regulatory Genes

HIV is a complex retrovirus

Question 3

What cell type does HIV infect?

Answer 3

CD4+ T Cells

Question 4

What 3 enzymes does the HIV virus contain?

What does each one do?

Answer 4

1. Reverse Transcriptase - transcribes single stranded viral RNA into double stranded DNA.
2. **Integrase - integrates new viral DNA into host DNA in nucleus **
3. Protease - cleaves polyproteins made from GAG and POL genes. Helps make new viruses.

**R.I.P. **with HIV

Question 6

How many viral RNA strands are there per HIV virion?

Answer 6

2

Question 7

Name the 5 HIV drug classes?

How does each one work?

Answer 7

1. Binding (attachement) Inhibitors - stops HIV from binding to receptors on CD4 T cell (there are various methods)
2. Membrane Fusion Blockers - stops viral gp41 from folding and fusing with T cell.
3. Reverse Transcriptase Inhibitors - blocks synthesis of new viral DNA
   
   1. Neucloside analogues - cause chain termination
   2. Non-Neucleoside analogues - interfere with binding of viral RNA to RT
4. Integration Inhibitors - inhibit integration into host DNA
5. Protease Blockers - blocks production of new viruses

Question 8

With so many HIV drugs and treatments, why is the HIV virus difficult to eliminate?

What is one method of treatment to overcome this problem?

Answer 8

HIV mutates everytime it is processed by reverse transcriptase (high rate of transcription errors) which leads to drug resistance.

Combination Therpy (“Drug Cocktails”) - use many differnt types of drugs at one to stop the virus from replicating and eventually mutating.

Question 9

Describe the structe of HIV?

Answer 9

• Lipid bilayer envelope with dense cylindrical core and external glycoprotein spikes
• 2 RNA genomes per virion
• Major surface antigen is glycoprotein gp120 & gp41

Question 10

What do the HIV surface glycoproteins gp41 and gp120 do?

Answer 10

• gp41 - fusion of viral envelope with host membrane
• gp120 - binding CD4 receptor and coreceptor

Question 11

Is HIV an oncovirus (transforming) or a lentivirus (non-transforming)?

Answer 11

HIV is a Lentivirus (non-transforming) - it eventually kills the cell it invades.

An oncovirus causes rapid cell growth and immortalization. It alters the life cycel of cell. It does not kill the host cell. Think cancer (onco = oncology)

Question 12

What is a provirus? Is HIV a provirus?

Answer 12

A provirus is a virus that has been integrated into the hosts DNA?

Yes, HIV integrates itself into the host DNA via integrase.

An endogenous retrovirus is a provirus that is integrated into the DNA of a sperm/egg cell and can be passed to offspring.

Question 13

Describe how HIV is replcated?

Answer 13

The virus binds to cell, fuses viral and cell membranes, transcribes RNA to viral DNA (reverse transcription), enters nucleus and integrates into cellular DNA. Sometime later cell produces viral mRNA, and genomic RNA and produces viral proteins, assembles and buds off cell.