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Bone Marrow Transplant: A Cure For AIDS?

Posted Nov 24 2008 7:59am

It was reported on TIME magazine that a Berlin hematologist, Gero Huetter, has claimed that he had cured an HIV infection in a 42-year old man through bone marrow transplant he had performed at Berlin’s Charité hospital two years ago.  The patient had been suffering from advance stage leukemia and HIV and, after transplant of bone marrow from a donor naturally resistant to HIV, he seemed to be “virus free”.  

Read the full text of the article here.

This “discovery”, expectedly, would cause some more of the prudent scientists to be wary.  There are, after all, very few known persons to be resistant to HIV infection (estimated to be 1% of the European population) and bone marrow transplants are risky procedures.  To proceed with the bone marrow transplant, one has to kill all existing diseased bone marrow cells of the patient before introducing the transplant and this puts the patient at high risk because of a vulnerable immune system.  However, if the claim is correct, it would be one of those celebrated moments in the history of medicine and science.

But how come there are people who’re resistant to the HIV like the Europeans?

The hypothesis formulated explains that the resistance to HIV infection was a result of selective pressure arising from the Black Death and Great Plague pandemics in Europe (bubonic plague).  Mutation in one of the chemokine receptors, CCR5, provided protection against Yersinia pestis, the bacterium responsible for the plague, which was said to be using same mechanism as HIV to gain entry into cells.  The smallpox virus, Variola major, has also been suggested as the cause of selective pressure to develop mutation of CCR5.  It was hypothesized that  HIV and pox viruses both infect leukocytes resulting in dysfunction of cellular immunity, and gain entry to leukocytes by using chemokine receptors.  CCR5 acts as a part of the key to letting in HIV into cell by binding with glycoprotein 120 which is located on the surface of the HIV particle.  The same glycoprotein also binds with CD4 and forms a complex with the bound CCR5 to let in the HIV into the cell (helper T-cells, monocytes, macrophages, dendritic cells, glial cells).  Specifically, the mutation consists of a 32 nucleic acid deletion (a CCR5 delta 32 mutation) that in the homozygous state (if the person has two mutant copies of the CCR5), can provide almost complete resistance to HIV infection.  In the heterozygous state (person has only one copy of the mutant CCR5), it allows for a slower progression of the disease, if the person gets infected with HIV.  Although, according to Dr. Michael Marmor, Professor of Environmental Medicine and Medicine at New York University School of Medicine, studies found that  bisexual and homosexual Caucasian men with one copy of the mutation had a 70% reduced risk of HIV infection compared with men who didn’t carry the mutation at all.  Resistance, however, in both the homozygous and heterozygous states would not confer complete protection as there were uncommon strains of HIV that utilize other chemokine receptors aside from CCR5.

Even if, at this stage, scientists have been quite pessimistic about the idea of finding a cure for AIDS and HIV, still there may be hope in finding a solution to the cure.  Perhaps, if the claim is true, this will pave the way to more studies that can find ways to re-engineer patient’s cells, specifically the bone marrow, to change it in such a way as what a transplant does, without having the patient undergo the risky procedure.  But as scientists have predicted, this discovery, if ever there’ll be one, will be decades away.  

It’s a rather discouraging prediction, considering how HIV infection is still rampant in many countries around the globe ( 39.4 million around the globe suffering from HIV as of end of 2004  and an increasing number of deaths related to AIDS in the Philippines ).  But, at least, we’re moving forward.  And hopefully, soon, the elusive cure shall be found.

 

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