Aids Lifecycle 4u4t5v

AIDS Lifecycle Images and concept by The Museum of Science and Industry, Chicago and The Chedd-Angier Production Company, Watertown, MA.

AIDS Lifecycle Stage 1 • HIV, the virus that causes AIDS, is ed from one person to another through sex, sharing needles, or using contaminated blood products. A mother can also HIV to her new baby. The virus travels through the bloodstream to many different places in the body.

AIDS Lifecycle Stage 2 • The immune system, which helps the body fight off illness, fights back in three ways: with... • ...custom-made antibodies...

AIDS Lifecycle Stage 2

• ... macrophages which eat up all foreign invaders, and ...

AIDS Lifecycle Stage 2

• killer T-cells which seek out and destroy cells that are already infected with the virus.

AIDS Lifecycle Stage 3 • This defense is coordinated by these -- the helper T cells. But HIV has an ingenious battle strategy: it attacks the T cells themselves, crippling the body's defenses. •Infected helper T-cells (foreground)

AIDS Lifecycle Stage 4 • Here's how it works: HIV has a special shape on its surface which, like a piece of a jigsaw puzzle, fits perfectly into a shape on the T cell. This shape is a protein called CD4. The virus can now enter and infect the cell. AIDS virus attaching to a CD4 receptor on a helper T-cell

AIDS Lifecycle Stage 5 • The virus's genetic information -- called RNA -- is transcribed into a form that is identical to the cell's genetic information -called DNA. The virus, now in the form of DNA, hides out inside the nucleus of the cell, escaping from the body's defenses. HIV RNA being transcribed to DNA

AIDS Lifecycle Stage 6

After a while, HIV comes out of hiding and begins to reproduce.

AIDS Lifecycle Stage 6 • The DNA is transcribed into many copies of RNA, which produce proteins for the new viruses.

AIDS Lifecycle Stage 7

The proteins are cut into usable pieces and packaged with the RNA.

AIDS Lifecycle Stage 8 • The new viruses then bud from the cell. Each new virus may then go on to infect and destroy other T cells, weakening the immune system’s defense. Infected T-cell budding new viruses

AIDS Lifecycle Stage 9 • After a lot of T cells are destroyed, the person is said to have AIDS. A person with AIDS will probably develop one or many opportunistic infections -diseases that make people sick only when their immune systems are weakened. A person with AIDS will usually die of these opportunistic infections.

Opportunistic infections in the bloodstream of a person with AIDS

Stopping HIV: Strategy 1 • This is a promising place to try to stop AIDS, by helping the immune system early on in its fight against HIV. One possibility is an AIDS vaccine. Here's how it would work:An uninfected person is exposed to a form of the virus which does not cause illness, but which does stimulate the body's defenses. • The immune system is tricked into producing millions of killer T cells and antibodies custom-made to fight the virus. • Some of these defenses stay in the body.

Stopping HIV: Strategy 1 • Later, if the person is infected with HIV, the immune system has a head start in its battle. • But there are problems with this approach. – Scientists have to make sure the vaccine itself doesn't make people ill. – HIV is constantly changing, so the defenses stimulated by a vaccine might not be effective in fighting the actual virus. – And if even a single virus escapes by hiding out inside a cell, it could go on to make thousands of copies of itself.

• So although this is a promising place in the life cycle to stop AIDS, there is still a lot of work to do before we have an effective vaccine.

Stopping HIV: Strategy 2 • To stop the virus here, we would have to keep it from ever attaching to a T cell. Let's see how this would work. • This shape on the T cell is a protein called CD4. If a lot of artificial, decoy CD4 is given to an infected person, then HIV could attach to the decoys instead of to the T cells.

Stopping HIV: Strategy 2 • The problems here are that the decoy CD4 does not remain in the body very long, and it does not attach well to HIV circulating in the bloodstream. But improved decoy CD4 might eventually be used for an intense, short-term battle against a new infection.

Stopping HIV: Strategy 3 • This is an excellent place to try to stop AIDS, and in fact there are many drugs now in use that work at this step in the life cycle. Drugs that work at this step look like the building blocks used to make DNA. But they're faulty building blocks, so once they're used, the building process comes to a halt. • And if the virus cannot turn its RNA into DNA, it cannot hide out in the cell, and it cannot reproduce. It sounds great, but there are problems with these drugs.

Stopping HIV: Strategy 3 • HIV is constantly changing, and eventually it is no longer tricked by these faulty building blocks. HIV becomes resistant to these drugs, and the life cycle continues the same as before. Another problem is that these drugs can damage non-infected cells which also need to make DNA to reproduce. • This is a good place to break the life cycle, but it's not a cure.

Stopping HIV: Strategy 4 • There are some possibilities that may stop AIDS at this step in the life cycle. Scientists are trying to make drugs to stop the production of the virus's proteins. Without these proteins, the virus cannot survive. • They're also working on a drug that would prevent the proteins being cut into usable pieces. Proteins in long uncut strands are useless, and the life cycle would be broken.

Stopping HIV: Strategy 4 • This is a promising place to break the life cycle, but these drugs are not a cure: they would only slow down the replication of the virus.

Stopping HIV: Strategy 5 • This is a very late stage in the life cycle of HIV. But it might eventually be a last resort for stopping AIDS. • Scientists are working on ways to boost an AIDS patient's immune system at this step, so that when new viruses bud from infected cells, the body's defenses are strengthened and ready to fight back. There also are many drugs now available to treat opportunistic infections, which are often the cause of death in people with AIDS.

Stopping HIV: Strategy 5 • This research is promising. But this late stage of HIV's life cycle is a very difficult place to stop AIDS.