"By achieving remission in a second patient using a similar approach, we have shown that the Berlin patient was not an anomaly, and that it really was the treatment approaches that eliminated HIV in these two people", says virologist Ravindra Gupta from University College London.
The researcher added that while the stem cell transplant technique was not a universal treatment for everyone, it could contribute to the development of other methods that would help to eliminate the virus in people's bodies. He is tested often, and his HIV viral load is undetectable.
The authors of the study published Tuesday have also said the technique may not necessarily be effective for all HIV-infected individuals, specifically those carrying the gene CXCR4. The man stopped taking antiretroviral drugs 18 months ago.
Steven Deeks, an HIV researcher at UCSF, says the results could also boost cure efforts to cripple CCR5 "without the need for heroic interventions such as in the Berlin and London cases".
Reuters reports that the man, whose identity has not been revealed, has tested negative for the virus nearly three years after he received a bone marrow transplant from a donor with an HIV-resistant genetic mutation.
A London man appears to be free of the AIDS virus after a stem cell transplant - marking a potential milestone breakthrough, 12 years after the first success. The donor - who was unrelated - had a rare genetic mutation known as "CCR5 delta 32", that resists HIV infection.
Graphic on how HIV attacks white blood cells
But a very small number of people who are resistant to HIV have two mutated copies of the CCR5 receptor.
Compared to Brown, the London patient had a less punishing form of chemotherapy to get ready for the transplant, didn't have radiation and had only a mild reaction to the transplant.
To learn more about the factors that favor a cure, amfAR, the Foundation for AIDS Research, a New York City-based foundation, in 2014 began to fund a consortium of global researchers who do transplants in HIV-infected people with blood cancers. Another one, number 19 on the list and referred to as the "Düsseldorf patient", has been off anti-HIV drugs for four months. The surprise success now confirms that a cure for HIV infection is possible, if hard, researchers said.
None of this guarantees that the London patient is forever out of the woods, but the similarities to Brown's recovery offer reason for optimism, Gupta said.
Most experts say it is inconceivable such treatments could be a way of curing all patients.
"I'm not sure what this tells us", said Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases.
Scientists are also examining immune modifying therapies. It's far from a cure, but Tebas thinks coupling this approach with other interventions "might be the way of the future".