Diagnostica molecolare nellallergia alimentare Filippo Fassio - - PowerPoint PPT Presentation

• 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…

Higher concentrations of food-specific IgE and larger skin test wheals correlate with an increased likelihood of a reaction upon ingestion.

ORAL FOOD CHALLENGE

Unfortunately, these tests are not sufficiently sensitive or specific to establish a diagnosis without supporting evidence. The fact that many foods are usually consumed at the same time, may obscure identification of the triggering allergen. 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.

• Limiti dei test diagnostici…

«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».

• Limiti dei test diagnostici…

• 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

• 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…

• Allergia all’Arachide…

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

JACI 2010; 125: 191

• Allergia all’Arachide…

JACI 2010; 125: 191

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

• Allergia all’Arachide…

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

• Allergia all’Arachide…

• Allergia all’Arachide…

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

• Allergia al pomodoro…
• 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

• Allergia al pomodoro…
• 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

• Allergia al pomodoro…
• 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 Il prick test è risultato positivo per:

• Nocciola (+++)
• Noce (+/-)
• Pinolo (+/-)

Dosaggio IgE specifiche per alimenti:

• Nocciola 3,07 kUI/l
• Noce 0,12 kUI/l

• Allergia alla nocciola…

Negativo!

• Allergia alla nocciola…

• Microarray…

…ma in natura ce ne sono DI PIU’…

89 allergeni (VBC genomics) 103 allergeni (Phadia) 112 allergeni (Thermo Fisher)

• Non conta solo la quantità!

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…

89 allergeni (VBC genomics) 103 allergeni (Phadia) 112 allergeni (Thermo Fisher)

Allergeni (103)

• Conclusioni

• Conclusioni

• Allergome…in caso di bisogno

www.allergome.org

• Possiamo fermarci qui?

Grazie!

fassio.filippo@gmail.com