Man unexpectedly cured of HIV in Berlin — have scientists found a new way to treat Aids?

A seventh person has been cured of the HIV from a stem cell transplant.

Importantly, the person was only the second person to be cured from a stem cell transplant that did not have HIV-resistant genetic mutation.

That the person was cured without the mutation “gives us more options for curing HIV”, Prof. Christian Gaebler of the Free University of Berlin told New Scientist.

But such stem cell transplants cannot cure just any person with HIV. Such treatments can only be used for people with fatal diseases like cancers —like a last resort— as it is very risky to be attempted in people without fatal diseases.

While the curing of the person with a stem cell transplant even without it having the HIV-resistant genetic mutation is promising, there are serious concerns about the feasibility as well as ethical concerns that mean that such a treatment would not be available to the broader population living with HIV.

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For them, antiretroviral therapy (ART)-led treatment regimen remains the staple. Since its introduction in the 1980s, the ART has been a gamechanger for persons with HIV and they can now have near-equal lifespan and quality of life.

How a genetic mutation & transplants cure HIV

Out of seven people who have been cured of HIV, five people were cured after they received stem cells from donors who had an HIV-resistant genetic mutation.

The mutation, which is called CCR5-delta 32, occurs in the CCR5 gene, that removes the receptor from the cell surface. The lack of the receptor on the cell surface means the HIV cannot enter the cell. Essentially, the virus bounces off the cell and does not infect it.

The mutation is named such because it includes a deletion of 32 base pairs of DNA from the gene.

In theory, stem cell transplant from people with such mutation could cure a person of HIV, but this is not practical as only 1 per cent of the Northern European population has such a mutation. This means that finding donors is extremely difficult.

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In any case, such a treatment is so dangerous that it is only reserved for people who have a fatal disease along with HIV, such as aggressive cancers like leukemia.

But this is not a universal cure

The treatment regimen involving such transplants is so risky that it is estimated to have a mortality rate of 10-20 per cent.

Under this treatment regimen, powerful chemotherapy completely destroys a person’s existing immune system that also kills HIV-infected cells along with the cancer. Once the person’s immune system has been removed, donor’s stem cells are transplanted that build a new immune system from scratch for the person.

If the donor has the CCR5-delta 32 mutation, the person will be immune to HIV — thanks to the new immune system.

But the fact that this seventh patient was cured even without the CCR5-delta 32 mutation has added a new dimension to the understanding of HIV’s cure.

In this person’s case, since a donor with the both the copies of CCR5-delta 32 mutation was not available, doctors in 2015 used stem cells from a donor that carried one regular and one mutated copy of the CCR5 gene. At the time of the transplant, the person was on ART.

Three years after the transplant, the person stopped taking ART and, as per Gaebler of Free University of Berlin, HIV was not detected in his body. For seven years now, the person has remained free for HIV.

Gaebler told New Scientist, “It’s amazing that 10 years ago his chances of dying of cancer were extremely high and now he’s overcome this deadly diagnosis, a persistent viral infection and he’s not taking any medications – he’s healthy.”

The case has upended the understanding about the cure of HIV. So far, scientists believed that, after chemotherapy, cures relied on any virus lurking in the recipient’s remaining immune cells being unable to infect the donor cells, Gaebler told New Scientist.

But this case suggests that cures can be achieved as long as non-resistant donor cells are able to destroy any of the patient’s remaining original immune cells before the virus can spread to them, Gaebler said.

Such immune reactions are often driven by differences in the proteins displayed on the two sets of cells as these make the donor cells recognise residual recipient cells as a threat to eliminate, Gaebler said.

The findings suggest that a wider pool of stem cell transplants than original thought, including those without two copies of the CCR5 mutation, could potentially cure HIV, according to Gaebler.