The AIDS Virus

The Immune System
When a virus enters your body, it starts taking over cells and multiplying. Phagocytes can detect foreign viruses so they start surrounding and swallowing the viruses. While this happens, helper cells come by and meet phagocytes which have swallowed a virus. If the right helper cell meets the phagocyte, it will start reproducing and sending signals to the lymph nodes. When they get the message, antibodies are made and go to help the phagocytes fight off the viruses.

Viruses
A virus is usually composed of one or two strands of DNA surrounded by a protein coat. It attacts a cell by depositing its DNA into the cell. The viral DNA goes to the cell DNA and takes over. All the mRNA will transcribe the new DNA and the new instuctions of the DNA is to make the parts of the virus. This is how the virus will take over a cell and multiply. When the cell is overloaded, t will burst and release the newly made viruses.

Retroviruses
Unlike normal viruses, a retrovirus contains RNA rather than DNA. To take over a cell, they do things in reverse. They make RNA change to DNA (with the help of an enzyme called reverse transcriptase), and then the DNA makes proteins.

HIV
HIV is classified under the group of viruses known as retroviruses. It looks like a sphere with spikes and is extremely small compared to most viruses. The two parts to the virus are the envelope and the core.

Envelope
The envelope has a diameter of 0.0001 mm (about 10,000 nucleotides long). It is a lipid bilayer like that of a human cell. The lipid bilayer has embedded proteins that extend outward. There are usually about 72 of these proteins called Env. Each of these proteins has a stem (made of glycoprotein 41) and cap portion (made of glycoprotein 120). Glycoprotein 120 on the cap lets the HIV attach to a molecule of CD4+ on a T4 cell. Since T4 cells are the messengers to the lymph nodes and they are being killed by HIV, the messages do not get to the lymph nodes. Some helper cells do manage to send the message, however, HIV multiplies much faster than the amount of antibodies that are produced.

Core
The core consists of 3 proteins (p24, p6 and p7), two strands of RNA with the nine HIV genes: gag, pol, env, tat, rev, nef, vif, vpr, and vpu. These genes and proteins make the T4 cells produce new HIV cells, release viruses, create the glycoproteins, and all the other necessary functions needed by the virus.

Infection Process
  1. HIV attaches to T4 cell (glycoprotein 120 to CD4+ molecules)
  2. Virus and cell membranes fuse
  3. Viral RNA released to cell
  4. Viral RNA is fused to make viral DNA
  5. Viral DNA is fused with cell DNA
  6. New DNA orders mass virus particles to be made
  7. New viruses bud off the cell
  8. New viruses use some of their interior proteins to make glycoproteins so the can be able to infect more cells.
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