Two men remain HIV-free two years after bone marrow transplants
One man has had no detectable HIV in his blood cells for two years while the other has been clear for fourStudy suggests stem cells from done bone marrow are protected from being re-infected by HIV

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UPDATED:

12:07 GMT, 27 July 2012

Two men with longstanding HIV infections no longer have detectable HIV in their blood cells years after having bone marrow transplants.

The virus was easily detected in both men in their lymphocytes – blood cells that work to defend the immune system against attack – before the operation. However, it became undetectable eight months after the surgery.

The patients, who were treated at Brigham and Women's Hospital (BWH), have remained on anti-retroviral therapy since the transplant. These drugs work to suppress the virus.

HIV being released into human lymphatic tissue: Scientists have found no HIV in two patient's cells after they had bone marrow transplants

HIV being released into human lymphatic tissue: Scientists have found no HIV in two patients' cells after they had bone marrow transplants

'This gives us some important information,' said Dr Daniel Kuritzkes.

'It suggests that under the cover of anti-retroviral therapy, the cells that repopulated the patient's immune system appear to be protected from becoming re-infected with HIV.'

One patient's bone marrow transplant was two years ago while the other was four years ago.

Over time, as the patients' cells were replaced by donor cells, traces of HIV were lost. The level of HIV antibody, a measure of exposure to HIV, also declined in both men.

'We expected HIV to vanish from the patients' plasma, but it is surprising that we can't find any traces of HIV in their cells,' said Dr Timothy Henrich.

'The next step is to determine if there are any traces of HIV in their tissue.'

Timothy Brown known as the 'Berlin Patient' and the only person to have been cured of AIDS, after having bone marrow from someone known to be resistant to HIV

Timothy Brown known as the 'Berlin Patient' and the only person to have been cured of AIDS, after having bone marrow from someone known to be resistant to HIV

The research team is currently designing studies that would enable them to look for HIV in the tissues. Researchers also plan to study additional HIV-positive patients who have undergone a bone marrow transplant.

Researchers point out that there are two key differences between the Brigham patients and the 'Berlin patient,' Timothy Brown, who was functionally cured of HIV after a stem cell transplant.

In the Berlin patient's case, his donor was specifically chosen because the donor had a genetic mutation that resisted HIV. The Brigham patients' bone marrow transplants were done without any thought to selecting an HIV-resistant donor.

Second, the Berlin patient ceased anti-retroviral therapy after his transplant, while the Brigham patients have remained on anti-retroviral therapy.

Their cases will be presented at the International AIDS Conference at the BWH in Boston.