Two men with HIV have been off AIDS drugs for several months after receiving stem-cell transplants for cancer that appear to have cleared the virus from their bodies, researchers reported on Wednesday.

Both patients, who were treated in Boston and had been on long-term drug therapy to control their HIV, received stem-cell transplants after developing lymphoma, a type of blood cancer.

Since the transplants, doctors have been unable to find any evidence of HIV infection, Timothy Henrich of Harvard Medical School and Brigham and Women's Hospital in Boston told an International AIDS Society conference in Kuala Lumpur.

While it is too early to say for sure that the virus has disappeared from their bodies altogether, one patient has now been off antiretroviral drug treatment for 15 weeks and the other for seven weeks.

Last July Henrich first reported that the two men had undetectable levels of HIV in their blood after their stem-cell treatment, but at that time they were still taking medicines to suppress HIV.

Using stem-cell therapy is not seen as a viable option for widespread use, since it is extremely expensive, but the latest cases could open new avenues for fighting the disease, which infects about 34 million people worldwide.

The latest cases resemble that of Timothy Ray Brown, known as "the Berlin patient", who became the first person to be cured of HIV after receiving a bone marrow transplant for leukaemia in 2007. There are, however, important differences.

While Brown's doctor used stem cells from a donor with a rare genetic mutation, known as CCR5 delta 32, which renders people virtually resistant to HIV, the two Boston patients received cells without this mutation.

"Dr. Henrich is charting new territory in HIV eradication research," Kevin Robert Frost, chief executive officer of the Foundation for AIDS Research, which funded the study, said in a statement.

Scientific advances since HIV was first discovered more than 30 years ago mean the virus is no longer a death sentence and the latest antiretroviral AIDS drugs can control the virus for decades.

But many people still do not get therapy early enough, prompting the World Health Organisation to call for faster roll-out of medicines after patients test positive.

Indian generics companies are leading suppliers of HIV drugs to Africa and to many other poor countries. Major Western HIV drugmakers include Gilead Sciences, Johnson & Johnson and ViiV Healthcare, which is majority-owned by GlaxoSmithKline.

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