1. 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

2. Genuine or due to cross reactivity?
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?

3. Common clinical practice
Patient
At 6 years
Anamnesis
SPT to birch
At 16 years
SPT to peanut
sIgE to peanut
Diagnosis
Advice
Caroline, 16 years
Rhinitis and conjunctivitis +4
Local reactions to peanuts
26 kUA/l
Peanut allergy
Avoid peanuts
Emma, 16 years
Rhinitis and conjunctivitis +4
Local reactions to peanuts
28 kUA/l
Peanut allergy
Avoid peanuts

4. 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 peanuts
Pollen and peanut allergies
kUA/l
< 0.1 33
Pollen-associated peanut allergy
Suitable for re-introduction
Emergency medication unnecessary
Emma, 16 years
Local reaction to peanuts
Pollen 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

5. Peanut components

6. Peanut components

7. Latin name: Ara h = Arachis hypogaea
Peanut components
Ara h 2
Ara h 1
Ara h 8
Ara h 9
Ara h 3
Latin name: Ara h = Arachis hypogaea

8. Peanut components

9. Peanut components

10. Latin name: Ara h = Arachis hypogaea
Peanut components
Ara h 2
Ara h 1
Ara h 8
Ara h 3
Ara h 9
Ara h 5
CCD
Latin name: Ara h = Arachis hypogaea

11. Risk assessment of peanut components

12. Risk assessment of peanut components12

13. 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

14. 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

15. Cross reactivity - peach and peanut
Sensitization to Peanut Ara h 9 likely induced via sensitization to peach 15

16. 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

17. Cross reactivity - birch and peanut
Sensitization to peanut Ara h 8 is likely induced via sensitization to birch

18. 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 18

19. Sensitization frequencies and clinical reactions show geographical differences

20. Sensitization frequencies and clinical reactions show geographical differences

21. In conclusion

22. In conclusion 22

23. 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

24. Extra slides

25. From the literature

26. Peanut allergens in Arachis hypogaea
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
Storage Protein (Conglutin) Similar to Ara h 2
Ara h 7
Conglutin. Homology with Ara h 2
Ara h 8
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
Arachis hypogaea = peanut