A London man’s H.I.V. is in long-term remission following a bone marrow stem cell transplant, making him only the second individual in history to be effectively cured of the virus. The case, newly detailed in the journal Nature, marks a promising step forward in the fight against AIDS, but as The New York Times’ Apoorva Mandavilli cautions, it’s unlikely the risky, still unreliable treatment method can be successfully replicated on a wider scale.
Like Timothy Ray Brown, the first—and, until now, only—individual to undergo successful H.I.V. therapy, the so-called “London patient” actually received his stem cell transplant to treat an unrelated form of cancer. As Vox’s Julia Belluz reports, the Londoner, diagnosed with Hodgkin’s lymphoma in 2012, opted for a May 2016 transplant after failing to respond to chemotherapy.
Crucially, Carolyn Y. Johnson explains for the Washington Post, the bone marrow donation not only helped the London patient overcome his Hodgkin’s lymphoma, but also equipped him with a genetic mutation known to make cells nearly immune to H.I.V. Under normal circumstances, the CCR5 gene in question acts like a key of sorts, enabling H.I.V. to penetrate and infect humans’ immune cells. But when CCR5 malfunctions, Time’s Alice Park explains, immune cells are able to strengthen their defense system and ward off the infection.
According to a separate article by The New York Times’ Mandavilli, the Londoner stopped taking anti-H.I.V. drugs in September 2017, more than a year after the transplant. Miraculously, tests conducted in the 18 months since have revealed no signs of lingering H.I.V., although the researchers are quick to point out that the infection could still make a comeback. (Typically, Carla K. Johnson notes for the Associated Press, patients who stop taking the virus-suppressing drugs start exhibiting signs of returning infection within two or three weeks.)
Compared to Brown, the first H.I.V.-positive individual to enter long-term remission, the London patient has responded relatively well to his transplant. Despite contracting a mild case of graft-versus-host disease, in which donor cells assault host ones, he has suffered few severe side effects.
But Brown, also known as the “Berlin patient,” barely survived his treatment: As Gizmodo’s Ed Cara writes, the harsh regimen involved both radiation and chemotherapy, as well as a second transplant to treat relapsing leukemia. At one point, Mandavilli adds, doctors even placed Brown in an induced coma. Still, nearly 12 years after the initial 2007 procedure, he remains H.I.V.-free.
In the decade or so between the Berlin and London patients’ success stories, researchers tried—and failed—to replicate the results of Brown’s transplant. Outlining possible explanations for these unsuccessful attempts, the Post’s Johnson says that stem cell transplants are often used as a last resort, and only in cases where a clinical issue such as cancer is present. It’s difficult to find donors who carry the mutated CCR5 gene; according to Mandavilli of the Times, European consortium IciStem maintains a database of around 22,000 such individuals. In an era when daily pills are capable of controlling H.I.V., few are willing to undergo comparatively risky procedures.
Of the small group of H.I.V.-positive cancer patients who have agreed to undergo transplants similar to Brown’s, several have died from their underlying cancer or complications related to treatment. For others, the technique simply didn’t work, leading some to question whether the Berlin patient’s success was simply an anomaly.
The new London case shows that Brown’s recovery was not a one-time aberration. But as Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, asks Mandavilli, “It was done with Timothy Ray Brown, and now here’s another case—okay, so now what? Now where do we go with it?”
One avenue worth exploring is gene therapy. If researchers can find a way to easily manipulate CCR5, perhaps with CRISPR gene editing, they could open up a path for H.I.V. patients to enter remission without undergoing invasive transplants. Still, perfecting such advanced therapies, if possible, will take years. (The technology is also controversial, as evidenced by public outcry over a Chinese geneticist's recent claim that he removed a pair of twins' CCR5 genes.) It's also worth noting that CCR5 is only capable of tackling one strain of H.I.V. Another form, dubbed X4, uses a separate protein, CXCR4, to attack the host body.
For now, the AP’s Johnson reports, IciStem researchers are focusing their attention on 45 H.I.V.-positive cancer patients who have had or are scheduled to have stem cell transplants. One individual has shown no signs of H.I.V. for several months post-treatment, but it remains too early to tell whether he, like the London patient, is in long-term remission.
Regardless of the results of these 45 procedures, Fauci tells Time’s Park that bone marrow transplants are “absolutely not” a viable treatment option for the vast majority of H.I.V. patients.
“Bone marrow transplants are risky,” Fauci concludes. “I would much rather be on one pill a day with relatively little toxicity than risk a bone marrow transplant so I don’t have to take one pill a day.”