After the so-called “Berlin” and “London” patients, a third is considered HIV-free after a stem cell transplant
Researchers have reported a third case of a person cleared of HIV after undergoing a stem-cell transplant aimed at curing his leukemia.
The study, published today in the journal Nature, describes the case of a 53-year-old male patient who underwent a bone marrow stem-cell transplant to treat his leukemia. Like the “London” and “Berlin” patients, the donor had a rare mutation that confers resistance to certain strains of HIV, like HIV-1.
“This underlines that these approaches are promising and also reproducible, since it does not remain an isolated case,” said Jürgen Rockstroh in a statement. Rockstroh is a professor and head of infectiology at Germany’s University Hospital Bonn who was not involved in the research.
However, researchers point out, the treatment has not been successful for several other patients who have received it.
The third patient to be “cured” via transplant
Although there’s still debate on what being “cured of HIV” means, the new case adds to the two previous cases of HIV cure using the same type of stem cell transplant as the Berlin patient and the London patient.
It is hard to prove conclusively that someone is cured of HIV because the virus can remain hidden inside very long-lived immune cells, and the methods available to detect them are limited, HIV expert Sharon Lewin and colleague Jennifer Zerbato wrote in The Lancet in 2020.
Why the treatment appears to work
There’s a receptor in the HIV virus’s target cells called CCR5.
All three cases involved HIV-1 positive patients who underwent a stem cell transplant from a donor with both copies of a rare but naturally occurring CCR5 mutation.
Individuals with this mutation have lower or no expression of the CCR5 receptor in their cells, conferring protection against certain strains of the HIV virus.
The transplant essentially replaces the patient’s immune system with the one that is resistant to HIV.
The “Düsseldorf patient”
The patient, whose identity has not been revealed, was positive for type 1 HIV (HIV-1) and was monitored by researchers at Düsseldorf University Hospital for more than nine years after his transplant in February 2013.
The patient had a type of leukemia called acute myeloid leukemia. Leukemia is a type of cancer that affects the bone marrow, which is the spongy tissue inside our bones that makes new blood and immune cells.
The patient continued taking antiviral medicine for HIV until November 2018, when the researchers decided to stop the treatment because, they reported, it was the only way to know if the patient had been cured.
Four years after stopping antiretroviral therapy, the researchers could not detect any traces of HIV viruses capable of infection and measured waning levels of HIV-1 specific antibodies.
Genetic material of the HIV virus was mostly undetectable except for sporadic traces detected in some blood and lymph tissues samples. These results are strong evidence that the HIV-1 had been cured, the researchers said.
Stem-cell transplant as an HIV treatment
Although this study adds to two previous cases of successful “curing” of HIV, it does not mean that stem-cell transplants are a safe and viable alternative to HIV treatment.
“Another key limitation of [the transplant] is the associated pronounced toxicity.”, said Boris Fehse, head of the University Medical Center Hamburg-Eppendorf’s cell and gene therapy research department, in a statement. He was not involved in the study.
Bone marrow transplants require drugs that suppress the immune system, which can increase the risk of infections and potentially lead to so called graft-versus-host disease, where the transplanted immune cells target the host tissue, added Fehse.
The authors caution that this type of stem-cell transplant is not low-risk or easily scalable. The study, they say, rather serves as further evidence that gene-editing therapies targeting CCR5 receptors may be the key to curing HIV-1.
Edited by: Clare Roth
Author: Esteban Pardo