A leukemia patient in the United States has become the first woman and only the third person to be cured of HIV after receiving a stem cell transplant from a donor who was naturally resistant to the virus that causes AIDS, according to researchers on Tuesday.

The example of a middle-aged mixed-race woman, presented at the Conference on Retroviruses and Opportunistic Infections in Denver, is also the first to use the umbilical cord blood, a newer strategy that could make the treatment more accessible to more individuals.

Since obtaining the cord blood to treat her acute myeloid leukemia (a malignancy that begins in blood-forming cells in the bone marrow), the woman has been in remission and virus-free for 14 months, without the need for powerful HIV medicines known as antiretroviral therapy.

The two previous examples involved males, one white and one Latino, who got adult stem cells, which are more commonly employed in bone marrow transplants.

"This is now the third report of a cure in this setting, and the first in a woman living with HIV," Sharon Lewin, President-Elect of the International AIDS Society, said in a statement.

The instance is part of a broader study funded by the United States and led by Dr. Yvonne Bryson of the University of California, Los Angeles (UCLA) and Dr. Deborah Persaud of Johns Hopkins University in Baltimore. It intends to follow 25 persons infected with HIV who receive stem cell transplants from umbilical cord blood for the treatment of cancer and other serious illnesses.

Patients in the trial are initially given chemotherapy to eliminate malignant immune cells. Doctors then transplant stem cells from people who have a specific genetic defect that causes them to lack receptors that the virus uses to infect cells.

Scientists believe that these people develop an immune system that is resistant to HIV.

Lewin said bone marrow transplants are not a viable strategy to cure most people living with HIV. But the report "confirms that a cure for HIV is possible and further strengthens using gene therapy as a viable strategy for an HIV cure," she said.

The study suggests that an important element to the success is the transplantation of HIV-resistant cells. Previously, scientists believed that a common stem cell transplant side effect called graft-versus-host disease, in which the donor immune system attacks the recipient’s immune system played a role in a possible cure.