Two more HIV patients have no signs of the virus in their blood following bone marrow transplants, according to the Boston researchers who treated them.
However, experts stopped short of calling the two cured and said the treatment is not a viable option for the majority of HIV patients.
The findings were presented Wednesday at the International AIDS Society Conference in Kuala Lumpur, Malaysia.
The two men, whose identities are being withheld, had been on antiretroviral (ARV) drug therapy for years before being diagnosed with lymphoma, a cancer of the lymph nodes.
Both underwent intensive chemotherapy followed by bone marrow transplants to treat the cancer. They remained on antiretroviral therapy.
Approximately four months after the transplant, doctors were still able to detect HIV in their blood, but six to nine months later, all traces of the virus were gone.
“Because of those findings, we thought it was justified to take the patients off of their therapy to see what happens,” said Dr. Timothy Henrich, who conducted the clinical trial.
“Now, in a normal person who has HIV, who has been on long-term antiretroviral therapy, usually the virus comes back within two to four weeks after stopping therapy.”
Some patients make it up to eight weeks before the virus returns, said Henrich, a researcher at Harvard Medical School and Brigham and Women’s Hospital in Boston, but the virus returns eight to 10 weeks after therapy is stopped in the vast majority of patients.
Not so for these two, however.
“We are now recording 15 weeks after therapy and eight weeks after therapy for our two patients, and to date we are unable to detect HIV rebounding in the bloodstream after we stopped the therapy,” Henrich said.
“We do weekly monitoring, as well. We’ve been looking at the virus in the blood and the cells in the blood essentially every week since we’ve taken them off therapy, and we have not been able to detect the virus at this time.”
The two men are being compared to Timothy Ray Brown, also known as the “Berlin Patient.” Brown is thought to be the first person ever “cured” of HIV/AIDS.
In 2007, Brown had a stem cell transplant to treat his leukemia. His doctor searched for a donor with a rare genetic mutation called CCR5 delta32 that makes stem cells naturally resistant to HIV infection.
Today, the virus is still undetectable in Brown’s blood, and he is still considered to be “functionally cured.” A functional cure means the virus is controlled and will not be transmitted to others.
The stem cell transplant procedure, however, is very dangerous because a patient’s immune system has to be wiped out in order to accept the transplant.
Using a bone marrow transplant to treat HIV is not a feasible treatment for most patients, and only 1 percent of Caucasians—mostly Northern Europeans—and no African Americans or Asians have the CCR5 delta32 mutation, researchers say.
The transplant is still not a practical strategy for the majority of HIV patients, and the risk of mortality is up to 20 percent, Henrich says.