Potential HIV "cure" set back

Back in Berlin 2007, an HIV-positive man called Timothy Ray Brown was given a bone marrow transplant using cells from a donor naturally genetically resistant to the virus. Brown, known as the "Berlin Patient", has remained free of the virus since the procedure. 

This incredible result was an impressive result of chance - Brown required a bone marrow transplant to treat leukemia, and the doctors managed to find a donor who not only matched close enough for the transplant to be accepted but carried a mutation in the CCR5 gene. In Europeans, this deletion mutation occurs in both copies of the gene in 1% of the population and significantly reduces the ability of the HIV virus to enter CD4+ T cells (a type of immune cell).

Six years after this procedure, and Brown still remains virus free. The success of this procedure led to great hopes in the treatment of HIV in patients all over the world, although the difficulty of finding donor who matched close enough for transplant and had the CCR5 mutation is an enormous hurdle to overcome.

Are our methods for detecting HIV sensitive enough?

Two HIV+ patients in Boston, one in 2008 and the other in 2010, also received bone marrow transplants to treat leukemia. However their donors did not have the resistance mutation. To the surprise of many doctors, the patients appeared virus free after the procedures and remained that way for years even after discontinuing antiretroviral medication.

Unfortunately now it has been announced that the virus has rebound in both patients. As well as being devastating news to the patients and their families, it has much wider repercussions in the medical world.

After receiving the transplants, the men underwent all sorts of test to measure their viral loads and none were able to detect HIV presence. Yet now it is clear the virus was there all along. This means that the tests we have are not good enough.

There is also the disturbing realisation that people previously described as "cured" may still have the virus lurking somewhere within them. Patients such as the infant cured of HIV will have to be carefully monitored for viral resurgence and those who have seen their viral load reduced to "none" on medication should refrain from discontinuing.

This is a huge set back in research into potential cures for HIV, the virus is even more persistent than previously thought and the design of more sensitive test for viral load is required urgently.