More than three years ago, Australian researchers at St Vincent's Hospital and the Kirby Institute at the University of New South Wales (UNSW) transplanted bone marrow to two HIV-positive men. Now, the men are apparently HIV-free.
The researchers have highlighted the fact that the bone marrow used did not contain both copies of the gene CCR5 delta32, a mutation that protects against the HIV virus, which suggest that bone marrow without this gene could also be used to afford protection againts the virus. Both men, however, have continued antiretroviral therapy—a combination of drugs that stops the progression of the disease—as a protective measure.
“It’s very possible that the Australian men would relapse if they were to stop antiretroviral therapy,” explained Timothy Henrich, an infectious-disease specialist at Brigham and Women’s Hospital in the US, to Nature. That’s why the Australian researchers have been very careful and haven’t said that the men are cured.
So far the only person who has been cured of HIV is Timothy Ray Brown, also known as the ‘2008 Berlin patient’. Ray Brown received a bone marrow transplant too and has been HIV-free for six years. He has stopped taking antiretrovirals.
“This is a terrific unexpected result for people with malignancy and HIV. It may well give us a whole new insight into HIV, using the principles of stem cell transplantation,” said Dr Sam Milliken, Director of St Vincent’s Haematology & Bone Marrow Transplantation and study co-author, in a UNSW press release.
The researchers are still working with the Sydney patients to discover if there is any residual virus and where it’s hiding. Finding where the virus hides is essential to finding a potential cure for HIV.
Although the researchers still don’t know why the patients have undetectable HIV loads, Dr Kersten Koelsch from UNSW’s Kirby Institute explained that one theory suggests the bone marrow therapy helps destroy cells infected with the virus and that remaining infected cells are then destroyed by the patient’s immune system.
“We need more research to establish why and how bone marrow transplantation clears the virus. We also want to explore the predictors of sustained viral clearance and how this might be able to be exploited without the need for bone marrow transplantation,” says Dr Koelsch.
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