For just the second time ever a HIV patient is in sustained remission from the virus in what was hailed by experts Tuesday as proof that the AIDS-causing condition could one day be curable.

Ten years almost to the day since the first confirmed case of an HIV-infected person being rid of the deadly disease, a man known only as the “London patient” has shown no sign of the virus for nearly 19 months, doctors reported in the journal Nature.

Both patients underwent bone marrow transplants to treat blood cancers, receiving stem cells from donors with a genetic mutation present in less than one percent of Europeans that prevents HIV from taking hold.

“It is a landmark. After 10 years of not being able to replicate (the first case), people were wondering if this was a fluke,” said lead author Ravindra Gupta, a professor at the University of Cambridge.

“I think it is important to reaffirm that this is real and it can be done,” Gupta told AFP.

The findings will be presented later Tuesday at a medical conference in Seattle, Washington.

Millions of people infected with HIV around the globe keep the disease in check with so-called antiretroviral therapy (ARV), but the treatment does not rid patients of the virus.

Close to 37 million people are living with HIV worldwide, but only 59 percent are receiving ARV. Nearly one million people die every year from HIV-related causes.

A new drug-resistant form of HIV is also a growing concern.

The first sustained remission survivor, announced in 2009 as “the Berlin patient” and later named as American Timothy Brown, was given two transplants and underwent total body irradiation to treat leukaemia — a process that nearly killed him.

Gupta said that while a second successful transplant did not constitute a generalised cure, his team’s work showed that even milder forms of treatment can achieve full HIV remission.

“There are a number of learning  points here,” he said. “Radiation has a lot of side-effects and leads to a delayed recovery of the bone marrow, so it’s really good that we’ve shown you don’t need radiation.

“The Berlin patient also had two rounds of chemotherapy because the first one didn’t work. We’ve done ours just once, and it was also a milder form, which is important,” he added.

– ‘HIV is curable’ –

Both patients received stem cell transplants from donors carrying a genetic mutation that prevents expression of an HIV receptor, known as CCR5.

The London patient was diagnosed with HIV infection in 2003 and had been on antiretroviral therapy since 2012.

Later that year, he was diagnosed with advanced Hodgkin’s Lymphoma, a deadly cancer.

He underwent a stem cell transplant in 2016 from a donor with two copies of a CCR5 gene variant, which is resistant to most HIV-1 virus strains.

“CCR5 is something essential for the virus to complete its life-cycle and we can’t knock out many other things without causing harm to the patient,” said Gupta.

“We know that CCR5 can be knocked out without any serious consequences because people are walking around without that gene.”

CCR5 was the target in the genome of the controversial gene-edited twins born last year in China, whose father is HIV-positive.

Experts cautiously welcomed Tuesday’s announcement, with Mark Dybul, co-chair of the Towards an HIV Cure initiative, calling the London case “as important as it is exciting”.

The International AIDS Society said in a statement Tuesday that results from the second patient “reaffirm our belief that there exists a proof of concept that HIV is curable”.

Sharon Lewin, director of the Peter Doherty Institute for Infection and Immunity, told AFP that the second case showed a cure was “feasible”.

“We can try to tease out which part of the transplant might have made a difference here, and allowed this man to stop his anti-viral drugs,” she added.

– New communities –

After the bone marrow transplant, the London patient remained on ARV for 16 months, at which point treatment was stopped.

Regular testing has confirmed that the patient’s viral load remained undetectable since then.

Gupta said he hoped to expand research on the stem-cell transplant technique to focus on communities in Africa, where the HIV-beating mutation does not naturally occur.

“Expanding remission to populations that are affected disproportionately is quite important,” he told AFP.

AIDS in key dates

AIDS emerged as a mysterious disease in the 1980s to spread across the world and claim millions of lives. For only the second time a patient has now been found in long-term remission – and most likely cured – from HIV, the virus that causes the disease.

Here is a look at the trajectory of the fight against the deadly condition:

– 1981: First alert –

In June 1981 US epidemiologists report five cases of a rare form of pneumonia in gay men from California, some of whom had died. Unusual versions of skin cancer are identified in others.

It is the first alert about Acquired Immune Deficiency Syndrome (AIDS), still unknown and unnamed.

Doctors identify “opportunistic infections” among injected drug-users (late 1981), haemophiliacs (mid-1982) and Haitian residents in the United States (mid-1982).

The term AIDS appears for the first time in 1982.

– 1983: Identifying HIV –

In January 1983 researchers in France, Francoise Barre-Sinoussi and Jean-Claude Chermann, working under Luc Montagnier, identify the virus that “might be” responsible for AIDS. It is dubbed LAV.

The following year, US specialist Robert Gallo is said to have found the “probable” cause of AIDS, the retrovirus HTLV-III.

The two viruses turn out to be one and the same, and in May 1986 it becomes officially known as the human immuno-deficiency virus, or HIV.

Barre-Sinoussi and Montagnier win a Nobel prize in 2008 for their discovery.

– 1987: Anti-retroviral treatment –

In March 1987, the first anti-retroviral treatment known as AZT is authorised in the United States. It is expensive and has many side effects.

The World Health Organization (WHO) declares December 1, 1988 the first World AIDS Day, to raise awareness. In June 1989, the number of AIDS cases worldwide is estimated at more than 150,000.

– Early 90s: Falling stars – 

US actor Rock Hudson is the first high-profile AIDS death in October 1985. A host of other stars succumb to the disease, including British singer and Queen frontman Freddie Mercury (November 1991) and Russian dancer-choreographer Rudolf Nureyev (January 1993).

In 1994, AIDS becomes the leading cause of death among Americans aged between 25 and 44.

– 1995-96: New approach – 

A new class of drugs signals the start of combinations of different anti-retroviral therapies.

Called tri-therapies, they provide the first effective treatment for HIV although they are not a cure and remain costly.

In the United States 1996 is the first year in which the number of AIDS deaths declines.

– 1999: 50 million infections –

A report released by WHO and the Joint United Nations Programme on AIDS (UNAIDS) in November 1999 estimates the number of people infected with HIV since it first appeared at 50 million, of whom 16 million have died.

Africa is the hardest-hit continent, with 12.2 million cases.

– 2003: Life-saving PEPFAR – 

In February 2003, US president George W. Bush launches the President’s Emergency Plan for AIDS Relief, or PEPFAR, to combat the spread of AIDS in 15 of the hardest-hit areas of Africa and the Caribbean.

With an initial budget of $15 billion over its first five years, PEPFAR had by 2018 committed $70 billion to the AIDS response.

– 2009: The ‘Berlin Patient’ –

The first known patient cured of HIV is announced. The “Berlin Patient”, later named as American Timothy Brown, underwent two transplants of bone marrow containing a mutation of a gene that blocks HIV from attacking host cells.

He underwent total body irradiation to treat leukaemia and nearly did not survive the process.

– 2012: HIV ‘shield’ –

In July 2012, the first-ever daily pill to help prevent HIV infection is approved by US regulators. Truvada is a pre-exposure prophylaxis, or PrEP, taken by high-risk persons who are HIV-negative in order to prevent them from being infected.

– 2017: Treatment spreads –

For the first time ever, more than half of the global population living with HIV are receiving anti-retroviral treatment, UNAIDS reports in its latest data released in 2017.

There were 36.9 million people living with HIV globally in 2017 according to UNAIDS in its latest annual figures. Since the start of the epidemic 35.4 million have died from AIDS-related illnesses.

– 2019: The ‘London Patient’ –

The second patient with sustained HIV suppression is reported after undergoing a transplant of stem cells with the same mutation as in the Berlin case.

Regular testing has confirmed that the patient’s viral load remained undetectable for 19 months and counting.