Two men have been declared free of HIV following a bone marrow transplant to treat cancer, adding to hope that a cure for the disease could be achievable.
Scientists at the International Aidss conference in Washington, revealed that the men were found to have no detectable levels of the virus in their blood or cells.
The results for the two men, both treated in a Boston clinic, mirror those of Timothy Brown, the "Berlin patient" who is the only known person to have been cured of Aids.
One of the researchers, Dr Timothy Henrich, of Brigham and Women's hospital, told ABC News: "We expected HIV to vanish from the patients' plasma, bit it is surprising that we can't find any traces of HIV in their cells."
Brown is a gay US citizen who was diagnosed with HIV in 1995. He maintained his drug treatment regime in order to stop the virus developing into Aids. He was diagnosed with myeloid leukemia in 2006 and was given a bone marrow transplant.
The transplant was taken from a donor who had a natural mutation to the gene that ordinarily aids the spread of HIV cells. Brown was found to have no trace of HIV cells inside his body following the treatment.
Scientists stressed that the two men in Boston are not completely cured of the disease, which could remain in their body in undetectable quantities.
Dr Daniel Kuritzkes, who also oversaw the study, told NBC News: "We're being careful not to do that [tell the men they are cured]. We are not saying, 'You are like the Berlin patient'."
Both of the patients were sufferers of Hodgkin's Lymphoma, while one also had other blood cancers. They received mild chemotherapy and maintained their HIV medication throughout their treatment before having bone marrow transplants.
The scientist who studied the patients believe this was a key aspect, as the antiretroviral drugs were able to protect the donated marrow from HIV while it rid the body of cancer.
Within nine months of their transplants the men were found to have no trace of HIV, even in the smallest genetic building blocks.
The findings will add weight to a call by Françoise Barré-Sinoussi, one of the first to idnetify the Aids virus, who has called for a new cure-based global strategy for Aids treatment.
Although bone marrow transplants are too expensive and risky as a treatment for all Aids patients, and the two men differ from Brown in that they must continue their antiretroviral drug regime, the findings provide further ground for progress towards a cure.
The conference also heard about a small group of HIV patients in France who were able to stop their drug regime without any resurgence of the virus.
The group of 14 patients, dubbed the "Visconti cohort", were given treatment with antiretroviral drugs as son as possible after infection, which then continued for three years, before being stopped.
Despite stopping the treatment, the cohort's HIV virus levels did not increase, maintaining low levels in their system.
Asier Saez Cireon, from the Institute Pasteur in France, said the research was exciting as it showed that medical treatment could create a state mirroring that of the already known 'elite controllers' - rare cases of people infected with the disease who do not become ill.