For the second time, a person living with HIV appears to have cleared the virus after a stem celltransplant replaced his infected immune cells with donor cells resistant to infection, scientists report inNature today (March 5). These mutations are in a gene called CCR5, which HIV normally recognizes in immune cells and uses like a key to enter and infect them.
"While there are important limitations to applying this study to a HIV cure globally, this second documented case does reinforce the message that HIV cures are possible".
The patient voluntarily stopped taking HIV drugs to see if the virus would come back.
Brown, who had been living in Berlin, has since moved to the United States and, according to HIV experts, is still HIV-free.
"If we can understand better why the procedure works in some patients and not others, we will be closer to our ultimate goal of curing HIV". That patient had a leukemia that could be treated with a blood stem-cell transplant, and his transplant team used cells that carried a mutation that eliminates one of the proteins that HIV uses to attach to cells.
The researchers say the latest findings show that Brown's case was not a one off, and that there are ways to target the CCR5 receptor to treat HIV.
Advancements in antiretroviral drugs have greatly increased the life expectancy of people diagnosed with HIV in recent years.
Approximately 37 million people are now infected with HIV globally, and more than 35 million people have died from AIDS or related illnesses. It includes cure researchers who systematically assess changes in the HIV reservoir resulting from stem cell transplantation, and who provide treatment and monitoring guidance to the collaborating transplant doctors.
The researchers caution that the approach is not appropriate as a standard HIV treatment due to the toxicity of chemotherapy, but it offers hope for new treatment strategies that might eliminate HIV altogether.
The donor - who was unrelated - had a genetic mutation known as "CCR5 delta 32", which confers resistance to HIV.
Unlike for Brown, radiotherapy wasn't required and the London patient experienced far less severe consequences than Brown, but Gupta believes the chemotherapy used against the lymphoma was an essential part of its success, temporarily destroying fast-dividing cells so replacement could occur. First, a patient's blood cells and bone marrow are destroyed. Brown had also received a transplant without functioning CCR5 genes.
The identification of the HIV virus ultimately led to the development of therapies that specifically target the virus' ability to make new copies of itself.
The transplant went relatively smoothly, Gupta said, but there were some side effects, including the patient suffering a period of "graft-versus-host" disease - a condition in which donor immune cells attack the recipient's immune cells. But there will always end up being patients with HIV that end up needing a stem cell transplant for unrelated reasons. About 1% of people of European descent have two copies of this mutation and are resistant to HIV infection.
OECD Cuts Global Growth Forecasts for 2019 & 2020
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