Tuesday, December 14, 2010

The cure for HIV is Nigh *Updated*

In 2007, an American living in Berlin who was HIV+ contracted Leukemia. He underwent a bone marrow transplant to cure his leukemia and it cured not only his leukemia, but his HIV as well. But this was no ordinary bone marrow transplant. It was from a donor that was not only an unusually good match genetically, but he had a mutation that made him HIV resistant. This is the only known instance of a cure of an HIV infection. But the risks of such a transplant are not trivial. The mortality rate from such transplants is as high as 5% or more. Not to mention the fact that finding suitable donors with just such a rare mutation is not easy either. But what if that problem could be solved? What if you could grow your own custom tailored bone marrow? It should be possible. Craig Venter has already demonstrated that it is possible to grow a completely synthetic organism by replacing the nuclear material in one bacterium with a synthetic one. Further it has been shown that skin cells can be chemically tricked into becoming bone marrow stem cells. And of course the ability to completely sequence a human genome is old hat, again, Craig Venter did that too. So all that is left is to combine the four technologies. DNA from the infected patient is completely sequenced, the HIV resistant mutation is spliced into the patient's DNA and a synthetic copy of the modified DNA is produced. Heck, while they are at it, other beneficial mutations could be spliced in as well. Skin cells from a donor who does not need to be a very close match at all are then stripped of their nuclear material and the material is replaced with the synthetic DNA. The skin cells are cultured and tested to verify that the nuclear transfer was successful and that the cells are now a genetic match with the patient. The cells are then chemically converted to bone marrow stem cells and cultured to again ensure that they are reproducing true to their intended genetic line. Then the patient's bone marrow is destroyed with a combination of radiation and chemotherapy. This is a very delicate point in the process because if any of the bone marrow were to survive the treatment, it would fail. And if the patient were to come down with an infection while immunosuppressed, it would likely kill him. once the original bone marrow is gone, the new hybrid bone marrow is injected. This should then cure the patient, assuming he lives through the procedure. This procedure should also work for other genetic blood disorders like sickle cell, hemophilia, and others.

The White House has determined that synthetic biology poses limited risks and should be allowed to proceed, so there are no regulatory roadblocks to proceed with this methodology beyond those normally required for FDA medical trials.

Further thought on the ethics of this proposal:
Many would argue that such a procedure poses far more risks than the risks inherent in treating the disease through drug therapy. First, I would submit that the mortality and side effect rates from the drugs involved and complications from the disease itself are only PART of the equation. One must also consider the potential to spread the disease to others and THEIR potential mortality rates as well. This is not at all unlike the ethics of the "Tuskegee Experiment" where blacks with known cases of syphillis were left untreated intentionally when a treatment for the disease existed at the time resulting in the spread of the disease to their sexual partners/spouses and congenital defects in their children as well. One must also consider the ability of a person to make a free choice in his or her own medical destiny. Millions of men and women undergo elective surgeries every year for various reasons. All of these surgeries entail a level of risk. Even a root canal procedure has a certain level of risk involved. They take that informed risk into account when they decide to undergo these procedures (or at least they should be, even if they chose not to consider them). So withholding this potential cure on the basis of someone ELSE's determination that the risk or cost is high is unethical. That decision should be the left to the patient since they are the ones that have skin in the game. After all, we all run similar risks every day when we get out on the road to go to work. The patient may value the ability to have unprotected sex with their partners or the ability to become impregnated without expensive IVF procedures higher than an uninterested third party who may have no skin in the game.


Blogger Rorschach said...

A couple of side effects of this proposed procedure worth noting:

First off, since the bone marrow is genetically identical for all practical purposes to the patient, no long term immunosuppressive drugs should be required, unlike conventional bone marrow transplants.

Secondly, this procedure can of course be used for ANY bone marrow transplant, not just to cure leukemia. Why would someone want to do so? well, there is the issue of not having to try to find a good donor match as there is now. The patient is the donor so the genetic match is virtually 100%. Of course for most such transplants, the gene sequencing and nuclear replacement steps are not required, the patient merely needs to supply a sample of skin. But this is not true of transplants to treat hemophilia or sickle cell disease, where the genes are simply broken. Those genes would have to be replaced for the procedure to do any good.

December 16, 2010 9:29 AM  

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