Peanut Allergy

• 10% of children are sensitized but only 1-2% have symptoms

• Usually life-long• Symptoms range from local

reactions to anaphylaxis• Very small quantities can give

symptoms

Doctor's challenges

• Is it a genuine peanut allergy or are the symptoms caused by cross reactivity?– Is there a risk for systemic

reactions? – Is strict avoidance necessary?– Is emergency medication

needed?

Genuine or due to cross reactivity?

Common clinical practice

Patient

At 6 yearsAnamnesisSPT to birch

At 16 yearsAnamnesis

SPT to peanutsIgE to peanut

DiagnosisAdvice

Caroline, 16 years

Rhinitis and conjunctivitis+4

Local reactions to peanuts

+4

26 kUA/l

Peanut allergyAvoid peanuts

Emma, 16 years

Rhinitis and conjunctivitis+4

Local reactions to peanuts

+4

28 kUA/l

Peanut allergyAvoid peanuts

Using components in clinical practice

Patient

Anamnesis

Component testing

Ara h 1

Ara h 2

Ara h 3

Ara h 8

Ara h 9

Diagnosis

Advice

Caroline, 16 years

Local reaction to peanutsPollen and peanut allergies

kUA/l

< 0.1

< 0.1

< 0.1

33

< 0.1

Pollen-associated peanut allergy

Suitable for re-introduction

Emergency medication unnecessary

Emma, 16 years

Local reaction to peanutsPollen and peanut allergies

kUA/l

2.1

12.3

3.3

10.3

< 0.1

Genuine peanut allergy

Strict peanut avoidance

Emergency medication necessary

Improved diagnoses and altered advice

Peanut components

Peanut components

Peanut components

Ara h 8

Ara h 3Ara h 9

Ara h 1Ara h 2

Latin name: Ara h = Arachis hypogaea

Peanut components

Peanut components

Peanut components

Ara h 8

Ara h 3

Ara h 9

Ara h 1Ara h 2

Latin name: Ara h = Arachis hypogaea

Ara h 5 CCD

Risk assessment of peanut components

Risk assessment of peanut components

Ara h 1, Ara h 2, Ara h 3

• Peanut-specific markers

• Storage proteins – proteins expressed in legumes,

seeds and nuts

• Present in high amounts

• Stable and heat resistant proteins

that may cause systemic reactions

Ara h 9

• A cross-reactivity marker, associated with allergy to peach and peach-related fruits

• A Lipid Transfer Protein (LTP).– LTPs are present in plant

foods (e.g. nuts and fruits), weed and tree pollen

• Present in low amounts

• Stable and heat resistant protein that may cause systemic reactions

Cross reactivity - peach and peanut

Sensitization to Peanut Ara h 9 likely induced via sensitization to peach

Ara h 8

• Associated with allergy to birch and birch-related tree pollen

• A PR-10 protein, homologous to the birch component Bet v 1

• Labile protein - mainly causing local symptoms

• Present in low amounts

Cross reactivity - birch and peanut

Sensitization to peanut Ara h 8 is likely induced via sensitization to birch

Ara h 5

• A profilin protein• Profilins are

– highly cross-reactive

– expressed in tree-, grass- and weed pollen, in plant-derived foods and latex

– labile proteins, seldom associated with clinical symptoms

– present in very low amounts

Sensitization frequencies and clinical reactions show geographical differences

Sensitization frequencies and clinical reactions show geographical differences

In conclusion

In conclusion

What does Molecular Allergology add?

• Assess the risk for systemic reactions

• Differentiate between genuine peanut

allergy and pollen-related peanut allergy

• Ensure relevant dietary advice and

avoid unnecessary elimination

Extra slides

From the literature

Allergen MW (kD) Comment

Ara h 1 64 Storage Protein (Vicilin)

Ara h 2 17 Storage Protein (Conglutin)

Ara h 3 60 Storage Protein (Glycinin) homology with Ara h 4

Ara h 4 37 Storage Protein (Glycinin) homology with Ara h 3

Ara h 5 15 Profilin, highly cross-reacting, low risk

Ara h 6 15 Storage Protein (Conglutin) Similar to Ara h 2

Ara h 7 15 Conglutin. Homology with Ara h 2

Ara h 8 17 PR-10, Cross-reactive with birch Bet v1. Regional differences

Ara h 9 9,8 Lipid Transfer Protein (LTP), high risk. Regional difference

Ara h 10 16 16 kD Oleosin

Ara h 11 14 14 kD Oleosin

Peanut allergens in Arachis hypogaea

Arachis hypogaea = peanut