Doctors and experts are baffled by the case of a 42-year old male American patient living in Berlin whose 10-year long HIV infection appears to have been “cured” by a bone marrow transplant given to treat his acute myeloid leukemia.
The patient, who wishes to remain anonymous, was given the bone marrow transplant some 20 months ago, using cells from a donor with a natural genetic resistance to HIV, and his doctors reported last week that they could find no trace of the virus in his system: it’s not in his bone marrow, blood, lymph nodes, intestines, or brain, they told the press on Wednesday.
“We have waited every day for a bad reading”, said Dr Gero Hütter last week. Hütter is a hematologist in the Clinic for Gastroenterology, Infections and Rheumatology at the Charité-Medical University in Berlin, Germany, where the patient is being treated. He first reported the case at a conference in February this year, according to a report in MedPage Today.
Apart from a very few people with a unique mutation in an immune cell, once a person is infected with HIV there is no cure. The gene is called CCR5 and the mutation is called dubbed delta32: it blocks a receptor that HIV uses to get into cells.
However, this case suggests it may be possible to select specific donor stem cells from a person with the unique mutation, implant them into an HIV infected patient, or at least one who has acute myeloid leukemia, and then “cure” them of HIV.
It was no accident that the patient received bone marrow from a donor who had the rare immune cell mutation that protects against HIV infection. The doctors knew the patient had HIV so they deliberately chose a donor with two copies of the mutated CCR5 gene. The mutation occurs in about 3 per cent of Europeans said the researchers.
The transplant was successful and there were no “remarkable irregularities” said the doctors, apart from the fact that the HIV treatment ceased on the day the patient received the transplant and he has not had any since. Not only has the leukemia disappeared, but so has the HIV, it seems.
However, even if it turns out that the patient has been “cured” using donated bone marrow, neither the patient’s doctors nor bone marrow transplant experts consider bone marrow transplant an effective and safe way to treat HIV patients. Not only is it very expensive it is also very high risk: it kills one third of patients. Before a patient can have a bone marrow transplant their own bone marrow has to be completely destroyed, effectively knocking out their immune system and leaving them extremely vulnerable to even the mildest of infections.
What this study does, if the results can be replicated by others, is establish what scientists call “proof of concept”, that is there is a suggestion that “gene therapy” could be a potential treatment for HIV.
It might be too early to say for certain that the virus is no longer in the patient’s system: it could be hiding or the doctors may have missed it.
There is currently no cure for HIV which can hide in the body in so-called “reservoirs”. Hütter and colleagues told the press they had looked in all the usual places, but they could not exclude the possibility that the patient still has HIV, said a Reuters report.
“The virus is tricky,” said Hütter, and “It can always return”.
Sources: MedPage Today, Reuters.
Written by: Catharine Paddock, PhD