An HIV positive man in London is the second person ever to be declared in remission from the virus, a new study reveals.
The unidentified patient has been free of the virus for 18 months without viral-suppressing treatment after a stem cell transplant to treat his cancer.
The only other person to have survived the life-threatening technique, and come out of it HIV-free, was so-called 'Berlin patient' Timothy Ray Brown, a US man treated in Germany 12 years ago.
Every other attempt in the intervening years has been unsuccessful, many with devastating, deadly consequences.
Experts hailed the news as a 'milestone' in the fight against HIV, the virus that causes AIDS, but warned that it does not change the reality much for the 37 million people living with HIV.
Aside from HIV, both men were in the advanced stages of cancer - the Berlin patient with leukemia, the London patient with Hodgkin's lymphoma.
For them, a life-threatening and complex stem cell transplant was a last-ditch attempt at survival. For most others, that is an unnecessarily dangerous and improbable option compared to taking a daily pill that suppresses their virus so that it is untransmittable, and allowing them to live a long and healthy life.
Dr Anthony Fauci, head of the HIV/AIDS division at the National Institutes of Health, told DailyMail.com the report was 'elegant, important work' that 'fortifies the proof of concept' shown in the Berlin patient: that donor cells from someone who is HIV-resistant can wipe out a recipient's HIV if they survive the transplant.
HOW A STEM CELL TRANSPLANT CURED THE BERLIN PATIENT AND THE LONDON PATIENT
The vast majority of humans carry the gene CCR5.
In many ways, it is incredibly unhelpful.
It affects our odds of surviving and recovering from a stroke, according to recent research.
And it is the main access point for HIV to overtake our immune systems.
But some people carry a mutations that prevents CCR5 from expressing itself, effectively blocking or eliminating the gene.
Those few people in the world are called 'elite controllers' by HIV experts. They are naturally resistant to HIV.
If the virus ever entered their body, they would naturally 'control' the virus as if they were taking the virus-suppressing drugs that HIV patients require.
Both the Berlin patient and the London patient received stem cells donated from people with that crucial mutation.
WHY HAS IT NEVER WORKED BEFORE?
'There are many reasons this hasn't worked,' Dr Janet Siliciano, a leading HIV researcher at the Johns Hopkins University School of Medicine, told DailyMail.com.
1. FINDING DONORS
'It's incredibly difficult to find HLA-matched bone marrow [i.e. someone with the same proteins in their blood as you],' Dr Siliciano said.
'It's even more difficult to find the CCR5 mutation.'
2. INEFFECTIVE TRANSPLANT LEADS TO CANCER RELAPSE
Second, there is always a risk that the bone marrow won't 'take'.
'Sometimes you don't become fully "chimeric", meaning you still have a lot of your own cells.'
That is one of the two most common reasons for previous attempts failing: their immune system is not fully replaced, then the cancer comes back and they can't survive it.
3. GRAFT-VERSUS-HOST DISEASE: THE OLD IMMUNE SYSTEM ATTACKS THE NEW ONE
The other most common reason this approach has failed is graft-versus-host disease.
That is when the patient's immune system tries to attack the incoming, replacement immune system, causing a fatal reaction in most.
4. UNKNOWN QUANTITIES
Interestingly, both the Berlin patient and the London patient experienced complications that are normally lethal in most other cases.
And experts believe that those complications helped their cases.
Timothy Ray Brown, the Berlin patient, had both - his cancer returned and he developed graft-versus-host disease, putting him in a coma and requiring a second bone marrow transplant.
The London patient had one: he suffered graft-versus-host disease.
Against the odds, they both survived, HIV-free.
Some believe that, ironically, graft-versus-host disease might have helped both of them to further obliterate their HIV.
But there is no way to control or replicate that safely.
-Dailymail
The vast majority of humans carry the gene CCR5.
In many ways, it is incredibly unhelpful.
It affects our odds of surviving and recovering from a stroke, according to recent research.
And it is the main access point for HIV to overtake our immune systems.
But some people carry a mutations that prevents CCR5 from expressing itself, effectively blocking or eliminating the gene.
Those few people in the world are called 'elite controllers' by HIV experts. They are naturally resistant to HIV.
If the virus ever entered their body, they would naturally 'control' the virus as if they were taking the virus-suppressing drugs that HIV patients require.
Both the Berlin patient and the London patient received stem cells donated from people with that crucial mutation.
WHY HAS IT NEVER WORKED BEFORE?
'There are many reasons this hasn't worked,' Dr Janet Siliciano, a leading HIV researcher at the Johns Hopkins University School of Medicine, told DailyMail.com.
1. FINDING DONORS
'It's incredibly difficult to find HLA-matched bone marrow [i.e. someone with the same proteins in their blood as you],' Dr Siliciano said.
'It's even more difficult to find the CCR5 mutation.'
2. INEFFECTIVE TRANSPLANT LEADS TO CANCER RELAPSE
Second, there is always a risk that the bone marrow won't 'take'.
'Sometimes you don't become fully "chimeric", meaning you still have a lot of your own cells.'
That is one of the two most common reasons for previous attempts failing: their immune system is not fully replaced, then the cancer comes back and they can't survive it.
3. GRAFT-VERSUS-HOST DISEASE: THE OLD IMMUNE SYSTEM ATTACKS THE NEW ONE
The other most common reason this approach has failed is graft-versus-host disease.
That is when the patient's immune system tries to attack the incoming, replacement immune system, causing a fatal reaction in most.
4. UNKNOWN QUANTITIES
Interestingly, both the Berlin patient and the London patient experienced complications that are normally lethal in most other cases.
And experts believe that those complications helped their cases.
Timothy Ray Brown, the Berlin patient, had both - his cancer returned and he developed graft-versus-host disease, putting him in a coma and requiring a second bone marrow transplant.
The London patient had one: he suffered graft-versus-host disease.
Against the odds, they both survived, HIV-free.
Some believe that, ironically, graft-versus-host disease might have helped both of them to further obliterate their HIV.
But there is no way to control or replicate that safely.
-Dailymail