A man from London has become the second patient ever to be cured of HIV after a stem cell transplant.
Doctors have reported the successful therapy, saying the man has not taken drugs for the virus for 18 months with no trace of HIV returning.
Experts say stem cell transplants are dangerous, have failed in other patients and are said to be an impractical way to try to cure the millions of people already infected.
The therapy has been successful only once before with ‘Berlin Patient’ Timothy Ray Brown, from the US.
He was treated in Germany 12 years ago and is still free of HIV.
Until now, Timothy is the only person thought to have been cured of infection with HIV, the virus that causes Aids.
But the case of the ‘London patient’, published online by the journal Nature, will now be presented at an HIV conference in Seattle.
The man, who has not been identified, was diagnosed with HIV in 2003 and started taking drugs to control the infection in 2012.
He developed Hodgkin lymphoma that year and agreed to a stem cell transplant to treat the cancer in 2016.
Doctors found a donor with a gene mutation that confers natural resistance to HIV.
About 1 per cent of people descended from northern Europeans have inherited the mutation from both parents and are immune to most HIV.
The donor had this double copy of the mutation.
After the transplant the man voluntarily stopped taking HIV drugs to see if the virus would come back.
Usually, HIV patients expect to stay on daily pills for life to suppress the virus and when drugs are stopped, the virus roars back, usually in two to three weeks.
Lead researcher Ravindra Gupta of University College London said the fact the man has been HIV free for 18 months was ‘an improbable event’.
He added: ‘That’s why this has not been observed more frequently.’
The transplant changed the London patient’s immune system, giving him the donor’s mutation and HIV resistance.
Timothy said he would like to meet the London patient and would encourage him to go public because ‘it’s been very useful for science and for giving hope to HIV-positive people, to people living with HIV,’ he told The Associated Press.
Stem cell transplants typically are harsh procedures which start with radiation or chemotherapy to damage the body’s existing immune system and make room for a new one.
There are complications too. Timothy had to have a second stem cell transplant when his leukaemia returned.
Compared to him, the London patient had a less punishing form of chemotherapy to get ready for the transplant, did not have radiation and had only a mild reaction to the transplant.
Dr Gero Hutter, the German doctor who treated Timothy in Berlin, called the new case ‘great news’ and ‘one piece in the HIV cure puzzle’.