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The characteristics of Kiwi Fruit allergy.

Project Code: T07038

30/11/2006

Allergy and Inflammation Sciences, University of Southampton.
Lucas, J ; Warner, J; Hourihane, J; Lewis, S

1. Background

Kiwi fruit is a native plant of the Yangtze River Valley region of China. In 1904 three plants were taken to New Zealand – almost all of the fruit cultivated outside China are now descendants of those three plants! Kiwi fruit started to be grown commercially in New Zealand in the 1930s and 1940s but it was not until the 1960s and 1970s that they began to export the fruit to America. It has since been cultivated in many countries, and in the past 30 years has become a common food throughout the world including the UK. A new form of kiwi fruit is now grown commercially, and marketed under the name Zespri™ Gold. Exports were first made to the UK in 2000 and this novel food is increasingly available in North America and Europe.

Acute allergy to kiwi fruit was first described in the medical literature in 1981, and there have since been reports of the allergy presenting with a wide range of symptoms from localised rashes to breathing problems. Anecdotally, kiwi fruit allergy is becoming more common in the UK, and the reactions are sometimes severe. There has been very little research into this allergy and no studies in the UK. There have been no clinical studies to investigate the allergic potential of gold kiwi. FSA funded TO7025 confirmed that kiwi fruit allergy appears to be increasingly common and that the reactions can be severe, especially in young children. This study builds on those findings.

2. Aims and Objectives

To build on the findings of FSA funded TO7025.
To use kiwi fruit as a model, to provide an illustration of the way in which post-marketing surveillance should be conducted to detect allergy to newly introduced foods.
To investigate what proteins in kiwi fruit are responsible for causing allergic reactions.
To understand how digestion of kiwi fruit affects its potential to cause allergic reactions.
To investigate whether people with kiwi fruit allergy are likely to be allergic to Zespri Gold.

3. Approach

People with symptoms of kiwi fruit allergy were invited to complete a questionnaire with details about their allergy. Some of these people also had allergy testing- skin tests, blood tests (specific IgE) and food challenges. A small group of people had a food challenge with Zespri™ Gold.

Laboratory investigations studied the kiwi fruit proteins involved in causing allergy. Additionally blood from allergic volunteers was used to study the antibodies that cause people to be allergic.

To investigate the effects of digestion on the allergenicity of kiwi fruit, it was digested under laboratory conditions and blood from allergic individuals was used to determine whether they would still react.

4. Outcomes

The results of this study confirmed that kiwi fruit should be considered a significant food allergen, capable of causing severe, life-threatening reactions. Young children and infants with kiwi fruit allergy usually reacted the first time that that they ate the fruit and reactions were often severe. Although some adults also have severe reactions, they were more likely to have milder symptoms.

We demonstrated that the methods currently used to detect food allergy are not always accurate. Attempts were made to improve the accuracy of tests, but further work is required.

4.1. Lessons from kiwi fruit allergy concerning the need for post-marketing surveillance of new foods.

The increase in kiwi fruit allergy has occurred during a period of increased kiwi fruit consumption as well as a general rise in the incidence of atopy and allergy.
Severe reactions to kiwi fruit were described by the early reactors (1970 and 80s), but the number of subjects was too low for any one clinician to recognise it as anything other than an idiosyncratic response.
There has been a changing pattern in the patients who react to kiwi fruit. When the fruit was first introduced into the diet in the 1970s, the reactors were adults, probably reflecting consumption characteristics. In the last decade, the allergy has continued to increase in adults, but has also become prevalent amongst children and infants.
In the absence of a national post-marketing surveillance strategy it is not possible to identify allergy to a new food as a significant problem until it a large number of people have developed allergy. Even a large allergy clinic will not register it as a problem at an early stage.
The surveillance will need to be long term. Cases of allergy may remain rare until the food is regularly consumed by a significant proportion of the population.
Many subjects, including those with severe symptoms have not been seen by an allergist. The paucity of trained allergists in the UK needs to be urgently addressed.
There is currently no requirement by the food producers to declare case reports of reactions to the regulatory bodies.

4.2. The proteins responsible for causing kiwi fruit allergy

We have detected 12 proteins that people with kiwi fruit allergy react to. The kiwi fruit protein, actinidin, has commonly been reported to cause allergy in other European countries. However, it was not the cause of allergic reactions in any of our UK population.
During digestion studies, most of the kiwi fruit proteins were digested to products no longer capable of causing allergic reactions, but some proteins persisted and would continue to be a potential cause of allergy.
Patients with a history of severe reactions to kiwi fruit reacted to proteins that were resistant to digestion. Patients with mild symptoms, confined to the mouth reacted to proteins that are labile to digestion and are easily destroyed in the stomach.
Infants have a relatively high gastric pH and under these conditions kiwi fruit protein digestion is incomplete. Infants are therefore potentially more likely to react to proteins in kiwi fruit.

4.3. Gold kiwi fruit

This was the first study to report the immunogenicity and clinical allergenicity of gold kiwi fruit, demonstrating that people with kiwi fruit allergy are at risk of developing allergy to gold fruit.

5. What it means and why it is important

1. Kiwi fruit allergy is increasing. Reactions can be severe, particularly in young children.

2. The study highlights that without post-marketing surveillance, allergies to new foods may not be detected for many years.

3. The study highlights that the majority of patients who have had life threatening reactions do not have access to an allergy clinic.

4. The study has successfully detected kiwi proteins that are responsible for allergy in this UK population. This is important because once identified, the proteins can be fully characterised. This will create advances in the diagnostic tests, and maybe even treatments, which can be used to mange patients with suspected kiwi fruit allergy.

5. The study has shown that patients with kiwi fruit allergy are likely to also be allergic to gold kiwi (Zespri™ Gold). When cut up, for example in a fruit salad, gold kiwi may look like melon or pineapple.

6. Further work is necessary to determine whether digestion of food allergens might facilitate tests which will predict the severity of allergic reactions. Currently we have no tests to predict severity of reactions.

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