A genetic mutation in a stem cell transplant may have been the key.

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Scientists are hopeful that this new case could be a breakthrough for HIV treatment. Getty Images.

A man in London has been in remission from HIV for the past year and a half, making him the second known adult to be in remission and potentially cured of the infection.

The patient — who’s been named “the London patient” — received a bone marrow transplant from a donor who carried a genetic mutation that’s resistant to HIV. Now, nearly 18 months after coming off antiretroviral therapy (ARV), doctors claim that recent highly sensitive tests show no trace of the virus.

The study’s lead author Dr. Ravindra Gupta, a professor at University College London and HIV biologist who helped treat the patient, said that there is no sign of virus but that it’s technically too soon to say he’s been fully cured.

But the patient is in remission and is being monitored closely.

“Finding a way to eliminate the virus entirely is an urgent global priority, but is particularly difficult because the virus integrates into the white blood cells of its host,” Gupta said in a statement.

The research team published their findings in the medical journal on Tuesday and is presenting details of the case at the Conference on Retroviruses and Opportunistic Infections in Seattle.

The case comes a decade after the first person — an American named Timothy Brown, aka the Berlin patient — was cleared of the virus. Like the London patient, in addition to chemotherapy, Brown received a bone marrow transplant to treat cancer.

For years, doctors attempted to replicate the treatment with other HIV-positive cancer patients. It wasn’t until the London patient, who was diagnosed with Hodgkin’s lymphoma in 2012, that doctors achieved the same results.

“By achieving remission in a second patient using a similar approach, we have shown that the Berlin patient was not an anomaly, and that it really was the treatment approaches that eliminated HIV in these two people,” Gupta said.

Both patients received stem cell transplants from donors with the rare genetic mutation known as ‘CCR5 delta 32.’ CCR5 is the most commonly used receptor by HIV-1. This specific mutation — CCR5 delta 32 — prevents the virus from using CCR5 as a receptor to enter host cells. In other words, the HIV-1 virus cannot exist without normal CCR5 receptors.

Consequently, many doctors believe that replacing the host’s immune cells with donor cells that do not contain the CCR5 receptor seems to be way to prevent the HIV from returning after treatment.

“The similarities between Timothy Ray Brown and this new London patient are really important,” Mitchell Warren, the executive director of global HIV prevention organization AVAC, told Healthline. “We have two patients who received these transfusions with a very particular genetic element of what they were getting in their bone marrow transplant — clearly, that seems to be why both are in these remissions.”

According to the London patient’s doctors, the London patient’s bone marrow transplant went smoothly. However, like Brown, the London patient experienced some nasty side effects, including graft-versus-host disease in which the donor immune cells attack the recipient’s immune cells.

Experts aren’t sure whether the mutation alone is the cure-all here. Some suspect graft-versus-host may have also played a part in the disappearance of the HIV cells.

Bone marrow transplants are no easy feat.

Researchers believe that while the treatment offers hope for a cure to eliminate AIDS, it cannot be a widely used solution to cure everyone with HIV.

“The limitations of bone marrow transplants for [a] cure are that there is significant toxicity from the procedure, which include adverse effects from the chemotherapy that must obliterate the person’s existing immune system,” Dr. Joseph P. McGowan, the medical director at Northwell Health HIV Service Line Program in Manhasset, NY, told Healthline.

On top of that, there’s the need to find a genetically matching donor — which is rare — along with the risk that the transplanted cells will not grow properly and the procedure could fail entirely, adds McGowan. There’s also a high risk of infection and death during and after the procedure.

Approximately 37 million people worldwide are currently infected with HIV, and HIV has killed nearly 35 million since the virus exploded in the 1980s. Each year, nearly 1 million people die from HIV-related causes.

As of now, the only way to effectively treat HIV is via antiretroviral drugs that suppress the virus.

“Current antiretroviral therapy is safe and effective at suppressing HIV to undetectable levels, preventing HIV transmission, allowing restoration of immune function often to normal levels, and can allow people to achieve normal life expectancy,” McGowan noted.

Those with the virus must take the drugs their entire life. This is incredibly challenging for individuals in third world countries, the research team said.

Looking forward, researchers hope to use these two cases to find new strategies for treating HIV.

“[The case] creates a huge amount of momentum around both the idea of ending the epidemic and around eventually finding a cure,” Warren said.

Many new treatment options are already being explored. One option may be gene therapy, which could potentially edit the CCR5 receptor in individuals with HIV. against the virus is another route being evaluated, according to Warren.

All in all, these new findings will surely direct much of the future research around treating and curing AIDS at a much larger scale.

A man in London is now the world’s second known patient to be cured of the AIDS virus. Researchers hope to use this case to identify a more large-scale cure.