Two men with long-term HIV appear to be free of the disease after they received bone-marrow transplants.
There has been no sign of the virus returning even after both men stopped taking medication, however the team behind the work has said talk of an elusive cure is premature.
The patients had received bone marrow transplants at the Brigham and Women's Hospital in Boston, America, as they were both suffering from blood cancer.
Microscopic view of the HIV virus
After the operation, levels of HIV dropped to undetectable levels as their cells were replaced with those of the donor marrow.
Timothy Henrich, one of the scientists involved, told the International Aids Society conference in Kuala Lumpur: "While these results are exciting, they do not yet indicate that the men have been cured.
"Long-term follow up of at least one year will be required to understand the full impact of a bone marow transplant on HIV persistence."
Even if the men do remain HIV-free, questions will still remain over the usefulness of the technique.
Yusef Azad, directer of policy and campaigns at the UK National Aids Trust, told The Huffington Post UK: "This is a dangerous procedure and is costly.
"I think most people would choose to continue with medication which can be used to manage it."
Current anti-retroviral drugs can cheaply and effectively mange the virus with life expectancy of sufferers far longer that it once was (around 66 for someone aged 20 contracting HIV today).
The associated risk with bone marrow transplants make the procedure only suitable for the most immediately life threatening of circumstances.
Around 15-20% of operations result in death.
Azad also points out the case reported in 2008 of Timothy Ray Brown, an HIV and leukaemia patient treated with a bone marrow transplant.
Brown is still 'cured' today but there is no guarantee he will remain that way.
Azad said: "This appears to be similar but it's early days, it takes some time to be confident it won't return.
"Its important not to create false hope too early."
What the research does do is offer a glimpse into the way the virus is stored in the body. HIV can remain hidden in 'troughs' in tissue and stay at low levels before becoming active again.
Although deaths from HIV are falling, 1.7 million people died in 2011 from the virus.
Around 34 million people are infected world wide, the majority in Sub-Saharan Africa.
Since it's recognition it is believed the disease has been responsible for 30 million deaths.
Azad said: "A real cost effective and acceptable cure is many years off.
"It’s even possible that it won't happen."