Summary: Researchers reveal two nonhuman primates were cured of Simian Immunodeficiency Virus (SIV), the monkey form of HIV, after a stem cell transplant.
The team identified two circumstances that must coincide for a cure to occur and tracked the sequence in which HIV is cleared from the body. The insights may help develop a widespread cure for HIV, which affects around 38 million people globally.
Ultimately, scientists hope to make the cure more accessible and ideally deliverable via a single injection, rather than requiring a stem cell transplant.
- The study found that a successful stem cell transplant can cure HIV, aligning with the five known cases of humans cured of HIV via stem cell transplants.
- The researchers discovered that for a cure to occur, transplanted donor stem cells must kill the recipient’s HIV-infected cells and prevent HIV from using the CCR5 receptor to infect donor cells.
- The team also documented the step-wise fashion in which HIV is cleared from the body, starting from the blood circulating in the limbs, followed by lymph nodes in the limbs and abdomen.
Source: Oregon Health and Science University
New research from Oregon Health & Science University is helping explain why at least five people have become HIV-free after receiving a stem cell transplant.
The study’s insights may bring scientists closer to developing what they hope will become a widespread cure for the virus that causes AIDS, which has infected about 38 million people worldwide.
Published today in the journal Immunity, the OHSU-led study describes how two nonhuman primates were cured of the monkey form of HIV after receiving a stem cell transplant. It also reveals that two circumstances must co-exist for a cure to occur and documents the order in which HIV is cleared from the body — details that can inform efforts to make this cure applicable to more people.
“Five patients have already demonstrated that HIV can be cured,” said the study’s lead researcher, Jonah Sacha, Ph.D., a professor at OHSU’s Oregon National Primate Research Center and Vaccine and Gene Therapy Institute.
The first known case of HIV being cured through a stem cell transplant was reported in 2009. Credit: Neuroscience News
“This study is helping us home in on the mechanisms involved in making that cure happen,” Sacha continued. “We hope our discoveries will help to make this cure work for anyone, and ideally through a single injection instead of a stem cell transplant.”
The first known case of HIV being cured through a 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, which are also called bone marrow transplants, are used to treat some forms of cancer.
Known as the Berlin patient, he received donated stem cells from someone with 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 the virus to infect cells, and can make people resistant to HIV. Since the Berlin patient, four more people have been similarly cured.
This study was conducted with a species of nonhuman primate known as Mauritian cynomolgus macaques, which the research team previously demonstrated can successfully receive stem cell transplants.
While all of the study’s eight subjects had HIV, four of them underwent a transplant with stem cells from HIV-negative donors, and the other half served as the study’s controls and went without transplants.
Of the four that received transplants, two were cured of HIV after successfully being treated for graft-versus-host disease, which is commonly associated with stem cell transplants.
Other researchers have tried to cure nonhuman primates of HIV using similar methods, but this study marks the first time that HIV-cured research animals have survived long term.
Both remain alive and HIV-free today, about four years after transplantation. Sacha attributes their survival to exceptional care from Oregon National Primate Research Center veterinarians and the support of two study coauthors, OHSU clinicians who care for people who undergo stem cell transplants: Richard T. Maziarz, M.D., and Gabrielle Meyers, M.D.
“These results highlight the power of linking human clinical studies with pre-clinical macaque experiments to answer questions that would be almost impossible to do otherwise, as well as demonstrate a path forward to curing human disease,” said Maziarz, a professor of medicine in the OHSU School of Medicine and medical director of the adult blood and marrow stem cell transplant and cellular therapy programs in the OHSU Knight Cancer Institute.
The how behind the cure
Although Sacha said it was gratifying to confirm stem cell transplantation cured the nonhuman primates, he and his fellow scientists also wanted to understand how it worked. While evaluating samples from the subjects, the scientists determined there were two different, but equally important, ways they beat HIV.
First, the transplanted donor stem cells helped kill the recipients’ HIV-infected cells by recognizing them as foreign invaders and attacking them, similar to the process of graft-versus-leukemia that can cure people of cancer.
Second, in the two subjects that were not cured, the virus managed to jump into the transplanted donor cells. A subsequent experiment verified that HIV was able to infect the donor cells while they were attacking HIV. This led the researchers to determine that stopping HIV from using the CCR5 receptor to infect donor cells is also needed for a cure to occur.
The researchers also discovered that HIV was cleared from the subjects’ bodies in a series of steps. First, the scientists saw that HIV was no longer detectable in blood circulating in their arms and legs.
Next, they couldn’t find HIV in lymph nodes, or lumps 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.
The step-wise fashion by which the scientists observed HIV being cleared could help physicians as they evaluate the effectiveness of potential HIV cures. For example, clinicians could focus on analyzing blood collected from both peripheral veins and lymph nodes.
This knowledge may also help explain why some patients who have received transplants initially have appeared to be cured, but HIV was later detected. Sacha hypothesizes that those patients may have had a small reservoir of HIV in their abdominal lymph nodes that enabled the virus to persist and spread again throughout the body.
Sacha and colleagues continue to study the two nonhuman primates cured of HIV. Next, they plan to dig deeper into their immune responses, including identifying all of the specific immune cells involved and which specific cells or molecules were targeted by the immune system.
Funding: This research is supported by the National Institutes of Health (grants AI112433, AI129703, P51 OD011092) and the Foundation for AIDS Research (grant 108832), and the Foundation for AIDS Immune Research. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
In our interest of ensuring the integrity of our research and as part of our commitment to public transparency, OHSU actively regulates, tracks and manages relationships that our researchers may hold with entities outside of OHSU.
In regard to this research, Dr. Sacha has a significant financial interest in CytoDyn, a company that may have a commercial interest in the results of this research and technology. Review details of OHSU’s conflict of interest program to find out more about how we manage these business relationships.
All research involving animal subjects at OHSU must be reviewed and approved by the university’s Institutional Animal Care and Use Committee (IACUC). The IACUC’s priority is to ensure the health and safety of animal research subjects. The IACUC also reviews procedures to ensure the health and safety of the people who work with the animals. No live animal work may be conducted at OHSU without IACUC approval.
Allogeneic immunity clears latent virus following allogenic stem cell transplantation in SIV-infected antiretroviral therapy-suppressed macaques
- Allogeneic immunity clears SIV reservoirs after allogeneic stem cell transplant
- Post-transplant SIV reservoir clearance occurs stepwise, first in blood, then tissues
- CCR5+ allogeneic HSCT can functionally cure macaques of SIV
- SIV spreads to engrafting CCR5+ donor cells despite fully suppressive therapy
Allogeneic hematopoietic stem cell transplantation (alloHSCT) from donors lacking C-C chemokine receptor 5 (CCR5Δ32/Δ32) can cure HIV, yet mechanisms remain speculative.
To define how alloHSCT mediates HIV cure, we performed MHC-matched alloHSCT in SIV+, anti-retroviral therapy (ART)-suppressed Mauritian cynomolgus macaques (MCMs) and demonstrated that allogeneic immunity was the major driver of reservoir clearance, occurring first in peripheral blood, then peripheral lymph nodes, and finally in mesenteric lymph nodes draining the gastrointestinal tract.
While allogeneic immunity could extirpate the latent viral reservoir and did so in two alloHSCT-recipient MCMs that remained aviremic >2.5 years after stopping ART, in other cases, it was insufficient without protection of engrafting cells afforded by CCR5-deficiency, as CCR5-tropic virus spread to donor CD4+ T cells despite full ART suppression.
These data demonstrate the individual contributions of allogeneic immunity and CCR5 deficiency to HIV cure and support defining targets of alloimmunity for curative strategies independent of HSCT.