HIV

• Human Immunodeficiency Virus affects the human immune system. It eventually lead to acquired immune deficiency syndrome. AIDS is a condition where the immune system deteriorates and eventually fails. This makes someone with AIDS more venerable to other infections like pneumonia.
• HIV infects and eventually kills helper T-cells, which act as the host cells for the virus.
• During the initial infection period, HIV replicates rapidly and the infected person may experience severe flu-like symptoms. After this period HIV replication drops to a lower level. This is the latency period. During the latency period the infected person won't experience symptoms.
• People with HIV are classed as having AIDS when symptoms of their failing immune system start to appear or their helper T-cell count drops below a certain level.
• HIV Structure:

  • Attachment protein
  • RNA
  • Envelope
  • Capsid
  • Reverse Transcriptase
• HIV attachment proteins are foreign antigens that can be recognised by the immune system. During replication, the virus can change parts of he structure of its attachment proteins - this is antigenic variation and it helps HIV evade destruction by the immune system.
• HIV Replication:

  • HIV can only reproduce inside the cells of the organism it has infected. HIV replicates inside the helper T-cells of the host. It doesn't have the equipment to replicate on its own, so it uses those of the host cell.
  • When HIV particles emerge from a cell, the cell ruptures and dies.
• HIV Replication P1:

  1. The attachment protein attaches to a receptor molecule on the cell membrane of the host helper T-cell.
  2. The capsid is released into the cell, where it uncoats and releases the genetic material into the cell's cytoplasm.
  3. Inside the cell, reverse transcriptase is used to make a complementary strand of DNA from the viral RNA template.
• HIV Replication P2:

  4. From this, double-stranded DNA is made and inserted into the human DNA.

  5. Host cell enzymes are used to make viral proteins from the viral DNA found within the human DNA.

  6. The viral proteins are assembled into new viruses, which bud from the cell and go on to infect other cells.