Not even the Marvel Universe can match the exclusive club to which Thomas Kahlert belongs. The cheery 62-year-old Berliner is one of only 13 people worldwide known to have been cured of HIV, the virus that, if left untreated, attacks the human immune system with devastating results.
Last December, Kahlert chose anonymity when Berlin’s Charité university hospital went public with the news it had cured him of the so-called human immunodeficiency virus. But now Kahlert, certain that his HIV is gone for good, is going public.
“The whole thing was explained to me many times and, even now, I don’t understand it fully,” says Kahlert with a gleam in his eye.
We meet at the historic redbrick Charité campus, a calm refuge in the heart of Berlin and a place of many big medical breakthroughs. It was here in the 19th century that Robert Koch and Emil von Behring discovered the causes and pathogens behind tuberculosis, diphtheria and cholera.
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Cell research at the Charité, led by Rudolf Virchow, meanwhile, ushered in modern forensic medicine and revealed the roots of leukaemia, the form of cancer that brought Kahlert to the attention of doctors here in 2015.
He had been a clinic employee since 1988 but told neither his work colleagues nor his family that he had tested positive for HIV in 2009. Charité doctors prepared to treat his leukaemia with a stem cell transplant: breaking down his immune system with chemotherapy and then, with a transplant from a stem cell donor, effectively rebuilding a new immune system inside him.
Doctors then discovered something interesting. “I have a particular cell mutation meaning the HI-virus can’t dock as easily on my cells and my donor, Andrea, has it, too,” says Kahlert.
“But the focus was always the leukaemia because, as the doctors put it back then, you can live life perfectly well with HIV, but not with leukaemia.”
The leukaemia treatment was successful and, after years building back up his immune system, Kahlert decided to take a radical next step: halt the antiretroviral treatment that kept his HIV in check.
“My doctor said, as a medic, he advised against it,” remembers Kahlert, “but, as a person, he said he was just as curious as I was to see what – if anything – would happen.”
What happened was: nothing. No surge of the virus and no side effects. That triggered a new battery of Charité investigations, from blood tests to rectoscopies, to check whether the virus was lurking somewhere in his body, waiting for an opportunity to surge once more.
All tests came back negative, and his Charité doctors published their findings in Nature. They are still trying to find out the how and why.
One theory is that rebuilding Kahlert’s “new” immune system at speed, within a month of the stem cell transplant, outsmarted the virus. Another theory is that the donor’s stem cells had natural “killer” characteristics to tackle the virus head-on.
It all carries echoes of the first HIV cure in 2008, also at the Charité, when Timothy Ray Brown underwent stem-cell therapy for leukaemia and was later found to be free of the virus.
Though his cure made worldwide headlines, it hinged on Brown having a rare gene mutation shared by just one per cent of the population.
Prof Christian Gaebler, head of the infectious diseases clinic at the Charité Infectology Clinic, says Kahlert’s genetic mutation is more common, shared by about 16 per cent of the German population. Prof Gaebler heads a new Berlin Centre for HIV Cure. Its aim is to “make a HIV cure or long-term remission a genuine treatment option”.
“We want to find ways to eliminate the virus from the body or keep it permanently in check without resorting to a risky stem cell transplant,” he said, “so that this treatment approach is suitable for as many patients as possible.”
The new institution carries the honorary names of Thomas Kahlert, which he calls a “great honour”, and Timothy Ray Brown, who died in 2020 after his leukaemia returned.
Kahlert and the Charité are at pains to point out that these are early days. For most of the estimated 30 million people living with HIV today, access to modern medication reduces the virus to a treatable chronic condition.
But after beating TB, diphtheria and cholera, Charité researchers are quietly confident they can crack HIV and end an epidemic that has claimed at least 41 million lives through related illnesses.
Kahlert hopes he will live to see a vaccine made available to all. For now, he describes himself as a “happy man” inside his exclusive HIV-cured club. “I had two illnesses at the same time, either of which could have been fatal, and I survived both,” he said. “I am so grateful and am enjoying my life.”
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