DAVID GREENE, HOST:
Researchers in London say they have successfully treated a man who had been living with HIV and may have even cured him. This news comes 12 years after a different patient was declared cured of AIDS but only after several years of life-threatening and expensive medical procedures. Joining me now in the studio is NPR science correspondent, Richard Harris.
RICHARD HARRIS, BYLINE: Good morning, David.
GREENE: So what exactly are we learning from London? And what did researchers achieve here?
HARRIS: Well, this is an interesting story, although it's a - I should say right now, it's not a one-off - maybe a two-off since the Berlin patient. But basically, there was a man who was diagnosed with HIV infection in 2003. He was given antiviral drugs, which are very effective in holding the virus in check. And - but in - he developed Hodgkin's disease, a cancer, in 2012. And so the doctors decided to give him a stem cell transplant, which used to be called a bone marrow transplant.
GREENE: Mmm hmm.
HARRIS: Basically, you wipe out somebody's immune system. And you give them a new immune system. Well, it turns out the new immune system they gave this guy had a rare mutation called - a variant of something called CCR5, which is something that the HIV virus uses to get into T cells. It's the way it sort of reinfects.
But he had a mutation that basically didn't - that basically prevented that reinfection from happening. So when his immune system grew back, there was no - basically, he was protected from HIV. So he was on - after the treatment, he was on antiretroviral drugs for about 16 months. And then they thought, well, it - there's no sign of the virus. Let's sort of stop the drugs and see what happens - been 18 months now, they report in the journal Nature. And essentially, the virus has not reappeared in this man.
GREENE: OK, so off drugs for 18 months, the virus not reappeared - does that mean he's cured? I mean, can we use that term?
HARRIS: Well, some commentators are using that term. And that's sort of the exciting bit about this. But the scientists themselves who have done this research say, we are not using the word cure. That is - it's premature at this point. What we are saying is he's in remission. And it's possible he'll stay in remission for a long time, at which point we would declare it. But it's a - it's too early days for the scientists themselves who've done that work.
GREENE: You said one-off maybe two-off.
GREENE: The first patient treated like this, the so-called Berlin patient, the man named Timothy Brown - it's been something like a decade since that famous result. Now we have a second maybe successful result. Why so few?
HARRIS: Well, it's not for want of trying. Scientists have tried on a number of other occasions and not succeeded. But on the other hand, this mutation - this protective mutation is very rare. And a lot of the other attempts did not involve this protective mutation. So the answer is just knocking out somebody's immune system and replacing it in itself is not enough to cure somebody of HIV, which is what they were originally hoping. But that's turning out not to be the case.
GREENE: So it sounds like maybe not so hopeful a moment for people with HIV. This is not necessarily something that could be replicated widely and really help other patients.
HARRIS: That's probably true. I mean, remember, though. By now, we have very effective drugs for treating HIV. People, essentially, live full lifespans with the drugs to keep the virus in check. Unfortunately, it is a lifetime treatment for it. But what the people who are doing this research suggest is, you know, it does occasionally happen that a HIV patient gets cancer and needs a stem cell transplant. They're saying when that happens again, find somebody who has this weird mutation and CCR5 and maybe you can replicate that in other people.
They're also saying it's possible that, you know, this shines a further light on this ailment, saying, maybe there's drugs that could attack this more directly and more effectively. So it's fundamentally useful but not for common treatment.
GREENE: NPR science correspondent, Richard Harris - Richard, thanks a lot.
HARRIS: My pleasure.
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