AIDS researchers announced on Wednesday that a fourth person has been "cured" of HIV, but for patients battling cancer too, the procedure is risky as it may be uncomfortable for the tens of millions living with the virus across the world.

The 66-year-old patient, called the City of Hope after the Californian center in which he was treated, was declared in remission in the lead-up to the International AIDS Conference, which begins on Friday in Montreal, Canada.

He is the second this year to be announced as cured after a US woman was dubbed by researchers as the New York patient who had also gone into remission in February.

The City of Hope patient, just like the London and Berlin patients before him, achieved lasting remission after a bone marrow transplant to treat cancer.

The Duesseldorf patient has also previously been said to have reached remission, potentially bringing the number cured to five.

An infectious disease specialist at the City of Hope, Jana Dickter, told AFP that since the latest patient was the oldest to achieve remission so far, his success could be promising for older HIV sufferers who also live with cancer.

Beyond grateful

"When I was diagnosed with HIV in 1988, like many others, I thought it was a death sentence," said the patient, who prefers not to be identified, adding, "I never thought I would live to see the day that I no longer have HIV," he said in a statement at the City of Hope. "I am beyond grateful."

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Dickter commented on what the patient had told her during the early days of the AIDS epidemic in the 1980s, saying, "He saw many of his friends and loved ones become very ill and ultimately succumb to the disease.".

He had "full-blown AIDS" for a while, but was part of the first trials of antiretroviral therapy, which now allows many HIV patients to live with the virus, she said.

After being diagnosed with leukemia in 2019, he received a bone marrow transplant with stem cells from an unrelated donor with a rare mutation in which part of the CCR5 gene is missing, making people resistant to HIV.

He waited until he got his Covid-19 vaccination in March 2021 to stop taking antiretrovirals and has been in remission from both cancer and HIV since.

Reduced chemotherapy worked for him, and this potentially allows older HIV patients with cancer to get the treatment, Dickter said, but warned of this "complex procedure with serious side effects" that "isn't a suitable option for most people with HIV."

HIV expert at the University of California, San Francisco, Steven Deeks, told AFP that the "first thing you do in a bone marrow transplant is you destroy your own immune system temporarily," adding that "You would never do this if you didn't have cancer."

Sharon Lewin, the president-elect of the International AIDS Society which convenes the conference, said that "A cure remains the Holy Grail of HIV research," adding, "We have seen a handful of individual cure cases before and the two presented today provide continued hope for people living with HIV and inspiration for the scientific community."

Deeks, an author of the new research also presented at the conference, said it was an "unprecedented deep dive into the biology of the infected cell" because researchers found that a cell with HIV has many particular characteristics; it can proliferate better than most, it is hard to kill, and it is resilient and difficult to detect, he said. "This is why HIV is a lifelong infection."

However, cases such as the City of Hope patient opened a potential door towards a broadly available cure, possibly using CRISPR gene-editing technology, as per Deeks, who said, "I think that if you can get rid of HIV, and get rid of CCR5, the door by which HIV gets in, then you can cure someone," adding, "It's theoretically possible -- we're not there yet -- to give someone a shot in the arm that will deliver an enzyme that will go into the cells and knock out CCR5, and knock out the virus. But that's science fiction for now."

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