11 March 2011

Gene identified as a cause of peanut allergy

An international collaboration led by the University of Dundee has made a significant breakthrough in understanding the causes of peanut allergy.

Peanut allergy affects 1-2% of children in the UK and may result in a severe or life-threatening allergic reaction. The number of people affected by peanut allergy has increased dramatically over the past 20-30 years, but the causes of the disease are unknown.

Now the collaboration led by researchers in Dundee - working with colleagues in Canada, Ireland, England, and the Netherlands - has identified a gene defect that can triple the risk of a child developing peanut allergy. The gene responsible - Filaggrin - has previously been shown by the Dundee team to be a significant factor in causing eczema and asthma.

'It was a logical next step to investigate whether Filaggrin may also be a cause of peanut allergy, since a child may develop all three of these diseases together,' said Dr Sara Brown, Wellcome Trust Intermediate Clinical Fellow in the Division of Molecular Medicine at Dundee.

'Allergic conditions often run in families, which tells us that inherited genetic factors are important. In addition to that, changes in the environment and our exposure to peanuts are thought to have been responsible for the recent increase in peanut allergy seen in the western world in particular.

'Now, for the first time, we have a genetic change that can be firmly linked to peanut allergy.'

The findings are published today in the Journal of Allergy and Clinical Immunology.

The Filaggrin gene codes for a protein that helps to make the skin a good barrier against irritants and allergens. Changes in the gene decrease the effectiveness of this 'barrier', allowing substances to enter the body and leading to a range of allergic conditions.

The study has found that one in five of all peanut allergy sufferers have a Filaggrin defect. Those with the defect can be three times more likely to suffer peanut allergy than people with normal Filaggrin.

'We knew that people with a Filaggrin defect were likely to suffer from eczema, and that many of those people also had peanut allergy,' said Professor Irwin McLean, one of the world’s leading authorities on Filaggrin, also based at Dundee.

'What we have now shown is that the Filaggrin defect is there for people who have peanut allergy but who don’t have eczema, which shows a clear link between Filaggrin and peanut allergy.

'The Filaggrin defect is not THE cause of peanut allergy but we have established it as a factor in many cases. We don’t yet know enough about the causes of peanut allergy but this is an important step forward.'

Professor McLean said the Filaggrin findings suggest that peanut allergy may be caused by substances entering the body through the skin, though it could also have an effect in the gastro-intestinal area.

He also stressed that as Filaggrin defects were found in only 20% of the peanut allergy cases there is still a lot of work needed to fully understand the genetic risk factors for this complex disease.

The collaboration looked at four different population groups, in Canada, England, Ireland and the Netherlands. This is the first time that any genetic association with peanut allergy has been demonstrated in more than one population, making it more likely to be a genuine risk factor.

NOTES TO EDITORS

The University of Dundee is internationally recognised for its excellence in life sciences and medical research with particular expertise in cancer, diabetes, cardiovascular disease and skin diseases. The University has a top-rated medical school with research expanding from "the cell to the clinic to the community", while the College of Life Sciences is home to some of the world’s most cited scientists and more than 800 research staff from 60 different countries.

The Wellcome Trust is a global charitable foundation dedicated to achieving extraordinary improvements in human and animal health. It supports the brightest minds in biomedical research and the medical humanities. The Trust's breadth of support includes public engagement, education and the application of research to improve health. It is independent of both political and commercial interests. www.wellcome.ac.uk.

For more on the Journal of Allergy and Clinical Immunology see: www.jacionline.org.

Funding
Dr Sara Brown is supported by a Wellcome Trust Intermediate Clinical Fellowship (ref 086398/Z/08/Z); Dr Yuka Asai is supported by a Canadian Institutes of Health Research fellowship, AllerGen CAIDATI training award, and Bruce Katz Travel Fund and Canadian Dermatology Foundation Frederick Kalz bursaries; Prof Heather Cordell is supported by a Wellcome Trust Senior Fellowship (ref 087436); the food allergy assessment of the ALSPAC cohort was supported by the United Kingdom Food Standards Agency (project T07001); Dr Moshe Ben-Shoshan is supported by the AllerGen Network of Centres of Excellence; the Canadian peanut allergy study was supported by grants from the Canadian Dermatology Foundation, the University of Saskatchewan, Department of Medicine Research Fund, the Foundations of the McGill University Health Centre and the Montreal Children's Hospital as well as grants from the Canadian Allergy, Asthma, and Immunology Foundation and the AllerGen Network of Centres of Excellence; Prof Ann Clarke is a National Research Scholar of the Fonds de la recherche en sante de Quebec; Prof Jonathan O’B Hourihane is supported by National Children’s Research Centre, Dublin; ADI is supported by the National Children’s Research Centre, Dublin and the Wellcome Trust; Filaggrin research in the McLean laboratory is supported by grants from the British Skin Foundation, National Eczema Society, Medical Research Council (ref G0700314), the Wellcome Trust (ref 090066/B/09/Z and 092530/Z/10/Z) and donations from anonymous families affected by eczema in the Tayside Region of Scotland .

The patient study is available as a PDF (Patient Study).

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