HIV

• What does HIV lead to?

  AIDS (acquired immune deficiency syndrome)
• What does HIV stand for?

  Human Immunodeficiency Virus
• Structure of HIV

  • Outside is a lipid envelope embedded with attachment proteins
  • Inside is the capsid that contains 2 single strands of RNA
  • Enzyme called reverse transcriptase

  
• What does reverse transcriptase do?

  Catalyses the process of converting RNA to DNA
• Why is HIV a retrovirus?

  Due to reverse transcription
• How is HIV replicated?

  1. HIV enters the bloodstream.
• How is HIV replicated?

  2. The attachment protein on HIV attaches to the CD4 protein on T helper cells.
• How is HIV replicated?

  3.The protein capsid on HIV fuses with the cell-surface membrane, allowing the RNA and enzymes to enter the cell
• How is HIV replicated?

  4.The HIV reverse transcriptase converts RNA to DNA.
• How is HIV replicated?

  5. DNA from HIV moves into the nucleus and is inserted into the cells DNA.
• How is HIV replicated?

  6.The HIV DNA creates mRNA, which contains instructions for the making of new viral proteins and the RNA to go into the new HIV.
• How is HIV replicated?

  7.The mRNA from HIV passes out of the nucleus and uses the cells protein synthesis mechanisms to make new HIV particles.
• How is HIV replicated?

  8.The HIV particles break away from the T helper cell (budding), taking a piece of its cell surface and form a lipid envelope.
• Describe how HIV is replicated (4 marks)?

  • Attachment protein attaches to the receptor protein on the T helper cell
  • RNA and Reverse transcriptase enters the cell
  • Reverse transcriptase converts RNA to DNA and a viral protein is produced
  • The virus is assembled and released from the cell
• How does HIV cause symptoms of AIDS?

  • HIV attacks helper T cells and kills them
  • Without T helper cells the immune response cannot stimulate B cells to produce antibodies or the cytotoxic T cells that kill cells infected by pathogens
  • Memory cells may become infected and destroyed
  • The body cannot produce an immune response and becomes susceptible to other infections or cancers
• What is and ELISA test used for?

  Detecting the presence and amount of a protein in a sample
• How is an ELISA test carried out?

  1. The sample is applied to a surface to which all the antigens in the sample will attach.
• How is an ELISA test carried out?

  2. The surface is washed several times to remove any unattached antigens.
• How is an ELISA test carried out?

  3. The antibody that is specific to the antigen we're trying to detect is added and allowed to bind.
• How is an ELISA test carried out?

  4.The surface is washed to remove excess antibody.
• How is an ELISA test carried out?

  5. A second antibody that binds with the first antibody is added.
• How is an ELISA test carried out?

  6. The second antibody has an enzyme attached to it.
• How is an ELISA test carried out?

  7. The colourless substrate of the enzyme is added.
• How is an ELISA test carried out?

  8. The enzyme acts on the substrate to form a coloured product.
• In an ELISA test how is the amount of antigen present calculated?

  The amount of antigen present is relative to the intensity of the colour that develops.
• Why are antibiotics ineffective against viral diseases like AIDS?

  Antibiotics target bacteria, not viruses.
• Describe the role of antibodies in producing a positive result in an ELISA test (4 marks)

  • The first antibody binds to the complimentary antigen
  • The second antibody has an enzyme attached to it
  • The second antibody attaches to the antigen
  • A colour change is observed
• How does HIV replicate?

  • HIV attachment protein attaches to CD4 protein on the helper T cells
  • Reverse transcriptase copies the viral RNA into a DNA copy
  • With the helper T cells being destroyed the host is unable to produce an adequate immune response