Paris (AFP) – AIDS researchers announced that a fourth person has been "cured" of HIV, but the dangerous procedure for patients also battling cancer may be little comfort for the tens of millions living with the virus worldwide.

The 66-year-old man, named the "City of Hope" patient after the Californian centre where he was treated, was declared in remission in the lead up to the International AIDS Conference, which begins in Montreal, Canada.

He is the second person to be announced cured this year, after researchers said in February that a US woman dubbed the New York patient had also gone into remission.

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

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

Jana Dickter, an infectious disease specialist at the City of Hope, told AFP that because the latest patient was the oldest yet to achieve remission, his success could be promising for older HIV sufferers who also have cancer.

Dickter is the lead author of research on the patient which was announced at a pre-conference in Montreal but has not been peer reviewed.

'I am beyond grateful'

"When I was diagnosed with HIV in 1988, like many others, I thought it was a death sentence," said the patient, who does not want to be identified.

"I never thought I would live to see the day that I no longer have HIV," he said in a City of Hope statement. "I am beyond grateful."

Dickter said the patient had told her of the stigma he experienced during the early days of the AIDS epidemic in the 1980s.

"He saw many of his friends and loved ones become very ill and ultimately succumb to the disease," she said.

He had "full-blown AIDS" for a time, she said, but was part of early trials of antiretroviral therapy, which now allows many of the 38 million with HIV globally to live with the virus.

He had HIV for 31 years, longer than any previous patient who went into remission.

After being diagnosed with leukaemia, 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 getting vaccinated for Covid-19 in March 2021 to stop taking antiretrovirals, and has been in remission from both HIV and cancer since.

Reduced-intensity chemotherapy worked for the patient, potentially allowing older HIV patients with cancer to get the treatment, Dickter said.

But it is a complex procedure with serious side effects and "isn't a suitable option for most people with HIV", she added.

Steven Deeks, an HIV expert at the University of California, San Francisco who was not involved in the research, said the "first thing you do in a bone marrow transplant is you destroy your own immune system temporarily".

"You would never do this if you didn't have cancer," he told AFP.

'Holy Grail'

Also announced at the AIDS conference was research about a 59-year-old Spanish woman with HIV who has maintained an undetectable viral load for 15 years despite stopping antiretroviral therapy.

Sharon Lewin, president-elect of the International AIDS Society which convenes the conference, said that it was not quite the same as the City of Hope patient, because the virus remained at a very low level.

"A cure remains the Holy Grail of HIV research," Lewin said.

"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."

She also pointed to a "truly exciting development" towards identifying HIV in an individual cell, which is "a bit like finding a needle in a haystack".

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".

The researchers identified that a cell with HIV has several particular characteristics.

It can proliferate better than most, is hard to kill, and is both resilient and hard to detect, Deeks said.

"This is why HIV is a lifelong infection."

But he said that cases such as the City of Hope patient offered a potential roadmap towards a more broadly available cure, possibly using CRISPR gene-editing technology.

"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," Deeks said.

"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."

Paris, France - Stem cell scientists say they have created "synthetic embryos" without using sperm, eggs or fertilisation for the first time, but the prospect of using such a technique to grow human organs for transplantation remains distant.

The breakthrough was hailed as a major step forward, though some experts said the result could not fully be considered to be embryos and warned of future ethical considerations.

In research published in the journal Cell this week, scientists at the Weizmann Institute of Science in Israel said found a way to have mouse stem cells self-assemble into embryo-like structures in the lab.

They started by collecting cells from the skin of mice, then made them return to the state of stem cells.

The stem cells were then placed in a special incubator designed by the researchers, which continuously moved to mimic a mother's womb.

The vast majority of the cells failed to form anything.

But 50 -- 0.5 percent of the 10,000 total -- collected themselves into spheres, then embryo-like structures, the researchers said.

After eight days -- around a third of the 20-day mouse gestation period -- there were early signs of a brain and a beating heart, they added.

They were described as 95-percent similar to normal mouse embryos.

- 'Time will tell' -

If human organs could one day be grown in a lab, the technique could provide life-saving transplants for thousands of people every year.

Stem cell scientist Jacob Hanna, who led the research, told AFP, "The big problem for transplantation is that you need to find a matching donor and the DNA is never identical to the patient."

But using the new technique, one day scientists could take cells from a patient's liver, for example, use them to make stem cells, grow a synthetic embryo then "transplant them back into the patient", Hanna said.

"The cell will be made from the patient, so it will be the exact DNA -- no need to find donors and there can be no rejection," he added.

While they were the most advanced synthetic embryo-like structures ever grown, some scientists not involved in the research warned against calling them "embryos".

"These are not embryos," French stem cell scientist Laurent David told AFP.

He preferred to call them embryoids, the name for a group of cells that resemble an embryo.

However, David welcomed the "very convincing" research, which he said could allow further experiments to understand exactly how organs form.

Beyond organs, Hanna said the embryoids could also help identify new targets for drugs and potentially help find solutions for a range of issues such as pregnancy loss, infertility, endometriosis and preeclampsia.

"Time will tell," he said.

Hanna, a Palestinian who led the research at the institute in Israel, said, "Science is my escape from the harsh reality I face while living in my homeland."

"And I am one of the very 'lucky' ones," he added.

The first author of the Cell study is a PhD student from the Palestinian enclave of Gaza, who needs a special permit regularly renewed to allow him to work at the institute in the Israeli city of Rehovot, Hanna said.

- Ethical implications -

Hanna has founded a company, Renewal Bio, that he said "will be focusing on testing potential clinical applications of human synthetic embryoids".

He said they had ethical approval for such testing in Israel and it was legal in many other countries such as the US and UK.

"We should remember that synthetic embryos are embryoids and not real embryos and do not have the potential to become viable," he said.

But researchers not involved in the study said it was very early to consider using such a technique for humans.

Alfonso Martinez Arias of Spain's Pompeu Fabra University said the breakthrough "opens the door to similar studies with human cells, though there are many regulatory hoops to get through first and, from the point of view of the experiments, human systems lag behind mouse systems".

And aiming to get similar results from human cells is likely to open an ethical can of worms.

"Although the prospect of synthetic human embryos is still distant, it will be crucial to engage in wider discussions about the legal and ethical implications of such research," James Briscoe of Britain's Francis Crick Institute said.

jdy-dl/gil