by Transmission electron micrograph of HIV virus particles (pink) replicating from the plasma membrane of an infected immune cell
NIAID
A transplant of umbilical cord stem cells has put a mixed-race woman in remission for HIV for the first time.
The woman, known as the New York patient, has been free of detectable HIV since 2017 after receiving HIV-resistant cord blood-derived stem cells to treat her leukemia. Stem cells are produced by the bone marrow and can turn into different types of blood cells.
Several people have previously gone into remission from HIV after receiving stem cells from adult donors carrying two copies of a naturally occurring mutation of the virus CCR5 Gen. This delta-32 mutation prevents the virus from entering and infecting healthy cells.
With any stem cell transplant, recipients can only receive donations from people with matching tissue types to reduce the risk of their immune systems attacking the transplanted tissue.
Because tissue types are inherited, a person’s ethnicity affects their ability to find a match. With two copies of CCR5 The mutation is rare, occurring in only about 1 percent of people of Northern European descent, and is even rarer in other populations.
To overcome the lack of suitable adult donors, doctors conducted a study in which they infused umbilical cord blood into the New York patient, who identifies as mixed race.
She also received stem cells from a relative. Cord blood may contain fewer stem cells than adult blood, so mixing it with stem cells from a relative gives cord blood a “kick start,” Yvonne Bryson of the University of California, Los Angeles, who co-led the study, said in a statement.
Using cord blood makes finding matching transplants easier, since large stocks of frozen samples have been donated by people who gave birth in hospitals, says Jingmei Hsu of New York Presbyterian Hospital. “Have a bank [of cord blood] really opened the door to help more patients,” she says.
Most people with HIV can reduce the amount of the virus in their blood to undetectable levels by taking antiretroviral drugs, which stop the virus from replicating in their body.
Stem cell transplants would therefore only be an option for people with HIV who also have advanced blood cancer that can be treated with the procedure. The patient from New York no longer needs antiretroviral medication and is also in remission from her leukemia.
Transplantation involves the use of chemotherapy and sometimes radiation to kill a person’s red blood cells before the person is infused with a donor’s stem cells. The recipient is given immunosuppressive drugs to reduce the risk of their immune system rejecting the transplant, making infections more likely.
It takes several months for the donor’s stem cells to repopulate the recipient’s blood cells, says Mario Stevenson of the University of Miami, Florida. “This window is a very high-risk window for the individual.”
The recipient’s body can also reject the transplant in a complication known as graft-versus-host disease (GvHD) when immune cells among the donated stem cells attack the recipient’s own cells.
In previous cases of people living with HIV going into remission after adult stem cell transplantation, some scientists believed that a relatively severe GvHD response was necessary to activate dormant HIV-infected cells so they could be eliminated more effectively, Stevenson says .
However, the New York patient had only mild GvHD symptoms such as gastrointestinal discomfort while still going into remission for HIV, he says. The other patients had more serious complications, such as hearing loss and extreme weight loss.
According to Hsu, the New York patient’s milder symptoms were likely due to the use of cord blood. That blood hasn’t been exposed to many toxins or infections, she says. Its T cells, a type of immune cell involved in GvHD, are therefore less responsive to cells that may not be a perfect match, she says.
“With more success like this story, we can open doors for all patients in these very, very high-risk situations,” says Hsu.
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