Genetics and AIDS

The disease still evokes the horror of death and an epidemic. Though we have yet to find a cure, treatments have made great strides in the last 30 years. With the sequencing of the human genome we’re learning more and more about how the HIV virus interacts with humans’ cells.

I want more candy!
You’re lying, right?
My brain hurts!

What is AIDS? And what’s the difference between AIDS and HIV?
HIV is a virus, the Human-Immunodeficiency Virus. It is possible to be infected by the HIV virus, but to not yet have developed AIDS. AIDS, Acquired-ImmunoDeficiency Syndrome, is the disease that develops in most people infected with HIV. HIV attacks the immune system rendering the infected person susceptible to a variety of infections.

Most people? I thought all people with HIV also have AIDS.
When a person is first infected with HIV they do not necessarily have AIDS. AIDS is the collection of symptoms that results from the infection. Since HIV attacks the immune system most symptoms of AIDS are actually other diseases that are able to take over due to the weakened immune system. In most people, without treatment, HIV progresses to AIDS in nine to ten years. Some people, often called long-term non-progressors, though infected with the HIV virus, never develop AIDS.

WHAT?! There are people who are immune to AIDS? How is this possible?
HIV gets into immune cells by activating a specific receptor called CCR5. Some people, about 1% of Europeans, have a variant of this receptor, CCR5-Δ32. HIV is very rarely able to infect people with this variant. This was recently demonstrated in a rather spectacular fashion by a man who was cleared of AIDS and leukemia all in one fell swoop.

AIDS and leukemia? How?
Leukemia is a cancer of the immune cells. One way that this cancer can be treated is by a bone marrow transplant. The bone marrow, aka the middle of your bones, is the place where all blood and immune cells are born. In a bone marrow transplant the bone marrow of the recipient is almost completely wiped out by radiation, then bone marrow from a donor is transplanted. If all goes well, the new bone marrow takes up residence in it’s new home, producing a new and cancer-free immune system.
In this particular case, since HIV lives in immune cells, when the immune cells were killed, most of the HIV died as well. The bone marrow donor was one of the people with an HIV resistant immune system. Since the recipient’s immune system was rebuilt from these resistant immune cells, the HIV virus seems to have been eradicated, two years after the transplant.

That’s great! We’ve cured AIDS!
Well… not quite yet. A bone marrow transplant is really a measure of last resort since about 30% of patients die. It is also very difficult to find a donor who matches. And in addition to this, the procedure is also very time consuming and costly. When it comes to AIDS prevention is really the best cure.

THE BOTTOM LINE Advances in genetics continue to improve our understanding of how HIV affects humans. Though we have yet to find a cure, there are many reasons to hope for a cure in the years to come.

More about AIDS from Wikipedia.
The official government website about AIDS.
More about the man cured of AIDS and leukemia from the Wall Street Journal.
A little more information on the link between AIDS progression and genetics.

Photo by ynse

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