Albert McKeon

Jul 10th 2020

A Stem Cell Transplant Has Cured Two HIV Patients


Human immunodeficiency virus (HIV) has been traced as far back as a century ago, but it wasn’t identified until the 1980s, when it captured public attention for causing a sweeping wave of deaths.

About 32 million people have died from HIV and AIDS, which is the term for the range of conditions caused by the virus. A cure for HIV has so far been elusive, but hope has flickered anew because two people who received a stem cell transplant are now clear of the disease. Hope, though, can be held with only great reservation because of beliefs in previous efforts for a cure that failed. Not to mention, stem cell transplants are risky for those who don’t have cancer.

Still, any bit of hope for an end to HIV means that work for a cure continues apace, giving the nearly 38 million people living with the disease something to hold onto.

“Berlin” and “London” Patients Are Cured

Antiretroviral therapy medicine controls HIV and prevents complications, but it’s not a remedy. When HIV patients are cured, the world stops to take notice. And the world did just that in 2007, when it was announced someone identified only as the “Berlin Patient” had fully healed from HIV. He was named as such because the announcement was made in the capital of Germany, and he also lived and was treated there.

He initially sought anonymity, but in 2015 revealed his identity: Timothy Ray Brown, an American. “I did not want to be the only person in the world cured of HIV; I wanted other HIV patients to join my club,” Brown wrote in an AIDS Research and Human Retroviruses article.

A leukemia patient, Brown had a stem cell transplant from a donor with a specific genetic mutation that was resistant to HIV. It is believed the transplant populated Brown’s body with cells that are unaffected by the virus. He was also cured of leukemia.

Now, a second cured HIV patient has come forward. In 2019, the virologist Adam Gupta and colleagues revealed that the “London Patient” had received transplanted bone marrow to treat lymphoma and similarly had been healed of HIV, as outlined in a paper they wrote for The Lancet HIV. As seen with Brown, donated bone marrow carried a mutation that blocked HIV from entering the cells of the London Patient, essentially replacing his deficient immune system with one that could fight the virus. His lymphoma is in remission.

Earlier this year, the mystery patient revealed himself: Adam Castillejo, a native of Venezuela who now lives in London. “This is a unique position to be in, a unique and very humbling position,” he told the New York Times in an article that disclosed his identity. “I want to be an ambassador of hope.”

Stem Cell Transplant a Risky Response

The curing of Brown and Castillejo offers only slim hope for HIV patients. But many will take that window of opportunity, narrow as it is. “It’s really important that it wasn’t a one-off, it wasn’t a fluke,” Richard Jefferys, a director at Treatment Action Group, an advocacy organization, told the Times. “That’s been an important step for the field.”

Gupta and his colleagues calculated that the probability of Castillejo staying in remission is 99% if at least 90% of his HIV-susceptible cells retain the bone marrow donor’s CCR5-delta-32 mutation, known as chimerism, as reported by Aidsmap, a publication of NAM, a charity for HIV and AIDS. When last tested, 99% of Castillejo’s peripheral T cells had maintained chimerism.

Still, notwithstanding the successful cases, others in the field urge caution. For instance, in response to The Lancet HIV publication of Gupta and his colleagues’ findings, experts from the Doherty Institute in Melbourne wrote that while the development “is certainly exciting and encouraging…in the end, only time will tell,” according to Aidsmap.

As other experts have advised, this type of stem cell transplant is a high-risk procedure and not a viable medical option for HIV patients who don’t have cancer. But, as Aidsmap noted, researchers are trying to mimic the same effect of chimerism by using gene therapy to delete CCR5 receptors from a person’s T cells or stem cells that create immune cells.

New Developments, New Hope

While a distant possibility despite the successful transplant cases, a cure for HIV doesn’t seem as distant to those who have the virus and benefit from knowing there is even a small chance. Such experiments speak to effort, which leads to progress despite failures.

Consider how at this year’s Conference on Retroviruses and Opportunistic Infections, it was announced that a four-year-old with HIV had successful antiretroviral therapy that started two days after birth. The child has now been in remission for three years.