Treating peanut allergies

04 February 2014

Interview with

Andrew Clark, Addenbrooke's Hospital

About 1 in 100 in the UK has a peanut allergy and it can have a huge impact on the lives of those who are affected.  But this week, researchers at Addenbrooke's Hospital in Cambridge announced the success rate of 84% using a new technique to control the allergy.  Ginny Smith went to the hospital to meet some of the study participants and Dr. Andy Clark who's one of the lead researchers on the project.

Andy - Well, it's a really big problem for us and the population. There are probably half million people in the UK who have peanut allergy. Every year, despite our best efforts, deaths still occur. The difficulty is we don't know in whom those deaths are going to occur. So, children in the past who have had mild reactions have gone on to die from peanut allergy. So, it's really important that this is recognised and it actually drives down the quality of life of people who have peanut allergy. So, it's a really important issue to address.

Ginny - With peanut allergy such a big problem, Andy and his colleagues put together a trial to see if they could cure it. I spoke to 11-year-old Lena who took part in the trial to find out what it involved.

Lena - I had to eat 2mg of peanut to start with and it kept doubling every 2 weeks so I had to come back to the hospital every 2 weeks.

Ginny - And now, how many peanuts can you eat?

Lena - I'm allowed up to 12.5 a day, but I don't really like them. So, I have to eat 5.

Diana - I'm Diana Bardon. I'm Lena's mum.

Ginny - What did you think when you heard about this trial?

Diana - Well, I heard about it a couple of years before Lena joined. We've been under Dr. Clark since Lena was 2, so quite a long time and I was quite excited about it. I asked him about it, but Lena was a bit young to start off with so we waited a year or two until she was old enough really to understand herself, what she would need to do every day.

Ginny - What was it like having a child where you had to be so careful not to let her eat peanuts?

Diana - Well, I wasn't used to this at all. I've come from a family where we've never had any allergies or asthma, eczema, anything at all. So, it was completely alien to me, plus the fact that I'm half American. So, I was weaned on peanut butter. So, not being allowed to have peanuts in the house was - I just couldn't believe that this was happening really.

Andy - So we used something that sounds quite intuitive. We gave them a little bit of what they're allergic to to try and induce tolerance to it in the long term. We gave them a very small amount of peanut and gradually increased it, giving them doses every day, but increasing the amount every 2 weeks.

Ginny - When you say a tiny amount, are we talking one peanut or less?

Andy - Much less. So, we gave 2 mg of peanut protein.

Ginny - How many milligrams of this peanut protein would you get in a whole peanut?

Andy - Sure, that's about 150 mg in an average peanut, but of course, it varies.

Ginny - So, we're talking a 1/70 of a peanut.

Andy - Yes, about that and it's such a small amount as I say it doesn't cause problems.

Ginny - When you say administered it, were they eating this tiny bit of peanut? Was it on the skin?

Andy - Yeah, we measured that out into these tiny doses which increased over time, but each time the child took it, it would be mixed into something that they could take like yogurt or a milkshake. And also, that was used to disguise the taste. So, every 2 weeks, we increase the amount. We roughly double it. So, by the end of 3 or 4 months, they're actually eating whole peanuts in large amounts. So, what we found was over time, the children's tolerance increased so that they would react or have minor reactions to the lower doses. But as we increase the doses, they became more tolerant. So eventually, in the study, 84% of the children could eat the equivalent of 5 peanuts every day without having reactions.

Ginny - When you say they did react a bit to these lower doses, I'm assuming that wasn't full on anaphylaxis.

Andy - That's right. So, mild reactions were quite common. Pretty much, everyone had a bit of mouth-itching with some of the doses. Only one of our participants had a more severe reaction which was treated with adrenaline and we withdrew him from the study.

Ginny - Why do we think this is happening?

Andy - Well, we did some mechanistic work and we looked at the very top level of the immune system where we expect this to be working at cells called basophiles. We found that the basophiles became less sensitive to peanut exposure over time. Now, what's going to be really interesting in the future is to investigate that further and find out what the triggers and switches are for basophil control. Surprisingly, little is known about these really interesting immune cells.

Ginny - What would they be doing normally in someone who didn't have an allergy? What are they for?

Andy - Well, they are a sort of evolutionary hangover from when we used to be colonised with parasites, but we don't need them anymore. It seems that they're becoming distracted with every day proteins that we come across.

Ginny - What do you think the biggest thing is that's changed about your life since you've done this trial?

Lena - I'm allowed much more stuff that says, say for example, with like food labelling that say, "May contain traces of peanuts" so some more chocolate and stuff.

Ginny - That sounds good. So before, you have to be really careful with what kinds of chocolate you ate.

Leina - Yeah. We had to read every single label, absolutely everything.

Ginny - So, is this something that's likely to work for other allergies, perhaps ones that are a bit less severe, but affect a lot of us like hay fever?

Andy - Yes. In fact, there are licensed NHS products now for hay fever and venom allergy. It's also used in the NHS for treating house dust mite allergy and pet allergy.

Ginny - Is this something that in a way, people might have sort of been doing by accident themselves? I know some people find their hay fever's really bad at the beginning of a season, but by the end of it, it sort of seems like it's a bit more under control. Could that be related to this?

Andy - We certainly see that in cat allergy, so, people who are allergic to cats and have hay fever symptoms when they're near their cats get used to it over time. Then we see students for example lose tolerance to their cats when they leave home to go to university and then come back during holiday time, and they get worse symptoms again.

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