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Five patients were cured of HIV infection, thanks to a bone marrow transplant from a particular donor. Today, a study conducted on monkeys makes it possible to learn more about the mechanisms specific to this healing. The objective is to be able to make this treatment accessible to as many people as possible tomorrow.
5 known cases of HIV cure
Five patients have already demonstrated that HIV can be cured. The first known case of HIV cure through stem cell transplant was reported in 2009.
A man who was living with HIV was also diagnosed with acute myeloid leukemia, a type of cancer, and underwent a stem cell transplant in Berlin, Germany. Stem cell transplants, also called bone marrow transplants, are used to treat some forms of cancer. Known as the Berlin patient, he received stem cells from someone who carries a mutated CCR5 gene, which normally codes for a receptor on the surface of white blood cells that HIV uses to infect new cells. A CCR5 mutation makes it difficult for cells to infect cells with the virus and can make people resistant to HIV. Since the Berlin patient, four other people have been cured in the same way.
To learn more about the mechanisms behind these healings, a team from Oregon Health & Science University conducted a study on monkeys to better follow the process.
A feat confirmed in primates
This study was conducted with Mauritian cynomolgus macaques. While all 8 monkeys were HIV-positive, four of them underwent stem cell transplantation from HIV-negative donors, and the other half served as a control in the study and did not undergo transplantation.
Of the four who received transplants, two were cured of HIV after being successfully treated for graft disease, which is commonly associated with stem cell transplants. This study marks the first time that research animals cured of HIV have survived long term. Both remain alive and HIV-free today, approximately four years after the transplant.
Beyond the experience proving that the technique can be adapted to monkeys, the scientists were able to set up very precise monitoring of the animals. Their results reveal that two circumstances must coexist for the remedy to work. They were also able to establish the order in which HIV is eliminated from the body – details that may help make this technique more accessible tomorrow.
The Updated Healing Mechanism
First, the transplanted donor’s stem cells helped kill the recipients’ HIV-infected cells by recognizing them as foreign invaders and attacking them, the same way the leukemia transplant process can cure the people with cancer.
Second, in the two subjects who were not cured, the virus managed to “jump” into the cells of the transplanted donor. Another experiment was able to verify that HIV was able to infect donor cells as they attacked HIV. The researchers conclude that preventing HIV from using the CCR5 receptor to infect donor cells is essential for a cure to occur.
The researchers also found that HIV was cleared from the bodies of recovered monkeys in a series of steps. First, the scientists found that HIV was no longer detectable in the blood circulating in their arms and legs. Then they couldn’t find HIV in the lymph nodes or in the bits of immune tissue that contain white blood cells and fight infection. Lymph nodes in the limbs were the first to be HIV-free, followed by lymph nodes in the abdomen.
Gradual elimination of HIV
The gradual way in which scientists have observed the elimination of HIV could help doctors assess the effectiveness of potential cures for HIV. For example, clinicians might focus on analyzing blood drawn from both peripheral veins and lymph nodes.
It may also help explain why some patients who received transplants initially appeared to be cured, before HIV ‘come back’. The researcher hypothesizes that these patients may have retained a small reservoir of HIV in their abdominal lymph nodes which allowed the virus to persist and spread again throughout the body.
Objective: to make this treatment accessible to as many people as possible
The team continues to study the two primates cured of HIV. They plan to learn more about their immune responses, including identifying any specific immune cells involved and which specific cells or molecules have been targeted by the immune system.
“This study helps us understand the mechanisms involved in achieving this healing.“, believes the main author. “We hope our findings will help adapt this remedy for everyone, and ideally through a single injection instead of a stem cell transplant.s”.
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