HIV

• structure of HIV:

  Capsid

  • Inside the centre of the HIV virus is a protein called the capsid.
  • The capsid contains the genetic material and enzymes.
• structure of HIV:

  RNA

  • The genetic material for HIV consists of two strands of single-stranded RNA.
  • The RNA is inside the capsid.
• structure of HIV:

  Enzymes

  • The enzymes inside the capsid include reverse transcriptase and integrase.
  • Reverse transcriptase and integrase are important to the role of HIV in infection.
• structure of HIV:

  Viral envelope

  • The capsid is enclosed by a viral envelope.
  • The viral envelope has glycoproteins on its surface.
  • The glycoproteins bind to the cell surface membrane of TH cells to infect the cells.
• replication of HIV:

  1. Bind to TH cells

  • The glycoproteins on the surface of HIV binds to receptor proteins on the cell surface membrane of TH cells.
• replication of HIV:

  2) Release of the capsid

  • The capsid is injected into the TH cells.
  • The RNA and enzymes (reverse transcriptase and integrase) are released from the capsid.
• replication of HIV:

  3) Reverse transcriptase

  • Reverse transcriptase is an enzyme that converts the single-stranded RNA from the HIV into double-stranded DNA.
  • The DNA moves into the nucleus of the TH cells.
• replication of HIV:

  4) Integrase

  • Integrase is an enzyme that inserts the HIV DNA into the TH cells DNA.
• replication of HIV:

  5) Expression

  • The genes in the HIV DNA are expressed in the TH cells.
  • The HIV proteins are synthesised and new HIV RNA is made.
• replication of HIV:

  6) Release of HIV

  • New HIV viruses are released from the TH cells.
  • The TH cells die.
  • The HIV viruses can infect more cells.
• binding to T helper cells

  glycoproteins on the surface of HIV binds to receptor proteins of T helper cells.
• insertions of the capsid

  the capsid is inserted into the T helper cell.
• RNA and enzymes

  RNA, reverse transcriptase and integrase are released from the capsid.
• reverse transcriptase converts single-stranded RNA into DNA.
• integrase inserts the DNA into DNA of T helper cells.
• gene expression

  the HIV genes are expressed and new HIV viruses are produced.
• AIDS:

  Cause

  • When an HIV virus infects a TH cell and replicates, the cells are killed.
  • As HIV spreads through the body and more TH cells are killed, the immune system weakens.
  • The weak immune system makes the individual highly susceptible to infection by other pathogens. This is AIDs.
• AIDS:

  Symptoms

  • Initial symptoms of HIV are similar to flu (chills and fever). The symptoms are seen within four weeks of infection.
  • As the immune system is weakened, individuals will be more vulnerable to infections (e.g. tuberculosis).
  • Eventually, AIDs sufferers may die from one of these infections.
  • AIDs can take a very long time to develop (up to 10 years).
• AIDS:

  Treating HIV

  • HIV is a virus so it cannot be treated with antibiotics.
  • Antibiotics specifically target the enzymes and ribosomes in bacteria.
  • Antibiotics cannot be designed to target the enzymes in viruses because viruses use the host enzymes and ribosomes to replicate.
• AIDS:

  Potential treatment

  • Treating HIV is difficult because it is a virus.
  • HIV has some virus-specific enzymes (e.g. reverse transcriptase).
  • Antiviral drugs can be designed to target the reverse transcriptase enzyme.
• Acquired immune deficiency syndrome (AIDs) is a condition that is caused by HIV infection.
• AIDS:

  Location

  • AIDs is most common in East and Southern Africa.
  • 19.4 million people in East and Southern Africa were living with HIV/AIDS at the end of 2016.
• AIDS:

  Prevalence

  • Approximately 36.7 million people worldwide were living with HIV/AIDS at the end of 2016.
• AIDS:

  Infection

  • Approximately 1.8 million individuals worldwide became newly infected with HIV in 2016 (5,000 new infections per day).