Fassio siaic firenze 2013 -def

AOU Careggi SOD Immunologia e Terapie Cellulari SIAIC Toscana-Emilia Romagna 12 Aprile 2013

Diagnostica
molecolare
nell’allergia
alimentare

Filippo Fassio
SOD Immunologia e Terapie Cellulari
Direttore Prof. E. Maggi


Diagnostica allergologica: evoluzione…


La diagnosi di allergia alimentare…

The history of an immediate reaction consisting of
typical allergic symptoms within 2 h of ingestion,
supported by positive tests for specific IgE antibodies,
is usually sufficient to establish a presumptive
diagnosis for suspected IgE-mediated reactions.


La diagnosi di allergia alimentare…


Limiti dei test diagnostici…
The fact that many foods are usually consumed at the same time,
may obscure identification of the triggering allergen.
Higher concentrations of food-specific IgE and larger skin test wheals
correlate with an increased likelihood of a reaction upon ingestion.
Unfortunately, these tests are not sufficiently sensitive or
specific to establish a diagnosis without supporting evidence.

Therefore, in the diagnosis of food allergy a convincing history of
reaction is the key but only a well-performed OFC can give a
definitive diagnosis.
ORAL FOOD CHALLENGE



«Tali risultati sono però influenzati da molteplici variabili e sono
stati validati su popolazioni non europee. La loro riproducibilità
nella popolazione italiana è quantomeno da confermare».


Allergia o sensibilizzazione?
1. Unfortunately, the serum or skin test results are not
accurately predictive of the nature or severity of reaction to
the particular allergen.
2. It is well established that the presence of food-specific IgE
(i.e. sensitization) is not intrinsically diagnostic of food allergy.
3. Several studies have demonstrated that less than 40% of
patients with positive PSTs or food specific IgE have OFC-
proven food allergy
4. Additionally, reactions may occur in patients with negative
test results presumably because the test may be missing
some essential proteins or epitopes


Allergia o sensibilizzazione?

Component resolved diagnostics may provide a
diagnostic and prognostic platform for differentiating
subjects with food allergy from those with
sensitization based on crossreactivity, for prediction of
severity of reactions based on sensitization to proteins
with greater risk of severe reactions, and prediction of
natural history


“Allergen component-resolved testing might help to
identify patients sensitized to food, latex, or venom
who are at increased risk of anaphylaxis after
exposure to these allergens versus those who are
sensitized but clinically tolerant to these allergens”


Allergia all’Arachide…

BMJ 2008:337;a2880



Dei 91 bambini
sensibilizzati
all’arachide,
allergia confermata
in 19 casi (21%)

JACI 2010; 125: 191



JACI 2010; 125: 191

Una valutazione allergologica con
approccio CRD, può aiutare ad
identificare i “veri” allergici?



La differenza più marcata tra
sensibilizzati ed allergici è evidenziata
dalla risposta ad Ara h2



JACI 2009;124(4):771-8.e5


Allergia all’Arachide…differenze geografiche

Ara h 2 Ara h 9


Allergia a frutta e verdura fresca


Allergia al kiwi…
• It is nowadays among top ten food allergy sources in Europe
• Kiwifruit allergy can be due to monosensitization or
associated with pollen (grass, birch) or latex allergy


Allergia al kiwi…
• The papain-like cysteine protease, actinidin (Act d 1), represents a
major allergen and is also abundantly expressed (up to 50% of
soluble protein fraction)
• This highly active protease may also account for the rapid
degradation of other proteins including allergens, which in turn
affects the varying quality of test solutions for Skin Prick Tests (SPTs)

The diagnostic sensitivity of the extract
ImmunoCAP was 17% compared with 77% when
taking all the individual allergen tests together


Allergia al kiwi…

• sensitization to Act d 1 and Act d 3 was
significantly linked with anaphylactic
reactions in the patients
• Sensitization to Act d 2, Act d 8 and Act d 11
increased the specificity of the test
• Act d 7 and Act d 9 reactivity decreased
specificity


Allergia al kiwi…
• sensitization to Hev b 11, the latex chitinase, was predominantly
found in the kiwifruit–latex allergic patients, thus representing a
marker for the latex–kiwifruit syndrome
• in all these recent studies sera were identified that did not
display IgE directed to any of the allergens tested so far and it
may well be that the panel of kiwifruit allergens awaits
completion

Kiwi gold: Act d 1 ↓↓↓
(circa 50 volte meno)


Allergia al pomodoro…

• In Germany 9% among birch pollen allergic patients reported
tomato-induced allergic symptoms
• As a result of the potential of tomatoes to induce unspecific
histamine liberation the allergenic properties of that vegetable
have been mainly neglected in the past
• In a Spanish investigation only 16% of tomato-sensitized
patients reported symptoms upon tomato ingestion



• 45% of tomato allergic patients reacted to LTP
• 65% to a protein suspected to be profilin
• 15% of patients recognized only the LTP and experienced
more severe symptoms to tomato



• Tomato seeds are rich in proteins and constitute 70%
storage protein such as globulins
• Recently, a legumin and a vicilin were identified as putative
tomato seed allergens



• In summary, tomato is a complex allergenic vegetable and
the reliability of the single allergens for molecular
diagnosis has to be confirmed in future studies


Allergia alla nocciola…
Dosaggio IgE totali (RIST): 37 kU/l
Dosaggio IgE specifiche per inalanti: tutte < 0.10 kUI/l

Dosaggio IgE specifiche per Il prick test è risultato
alimenti: positivo per:
• Nocciola 3,07 kUI/l • Nocciola ( +++)
• Noce 0,12 kUI/l • Noce (+/-)
• Pinolo (+/-)



Negativo!


Microarray…

112 allergeni
(Thermo Fisher)

103 allergeni
(Phadia)

89 allergeni
(VBC genomics)

…ma in natura ce ne sono DI PIU’…


Non conta solo la quantità!
Pazienti 

Allergeni (103) 


Conclusioni
Niente panico, ma individuare i soggetti che
possono più facilmente avere reazioni gravi!

Gli allergeni molecolari possono aiutare a
stratificare il rischio, ma…

…attenzione alle differenze geografiche!
(anche nello studio della letteratura)


Conclusioni

Ci sono alimenti per i quali (come CRD) siamo più
avanti…

…ma non così tanto!

Per altri alimenti (anche importanti) siamo più
indietro…

Ci possiamo accontentare di 4 molecole per 2 alimenti?
(il pomodoro ed i suoi semi)


Microarray…

112 allergeni
(Thermo Fisher)
Pazienti 

103 allergeni
(Phadia)

89 allergeni
(VBC genomics)

Allergeni (103) 


Conclusioni


Allergome…in caso di bisogno

www.allergome.org


Possiamo fermarci qui?

Grazie!
fassio.filippo@gmail.com

Fassio siaic firenze 2013 -def

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