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Background Atopic dermatitis (AD) is a chronic inflammatory skin disease affecting up to 20% children and 9% adults worldwide. AD patients are often sensitized against a broad variety of allergens and more than 90% of them suffer from skin superinfections with Staphylococcus aureus.

Zusammenfassung: Typ I Allergie ist eine Immunglobulin E (IgE)-mediierte Uberempfindlichkeitsreaktion, die mehr als 25 % der Bevolkerung betrifft. Die serologische Diagnose beruht auf IgE Antikorper Nachweis und wird zur Zeit mit Allergenextrakten durchgefuhrt. Allergenextrakte werden durch Extraktion aus Allergenquellen (z. B. Birkenpollen) gewonnen und enthalten eine Vielzahl allergener und nicht-allergener Molekule, deren Konzentration im Extrakt nur schwierig zu standardisieren ist. Allergenextrakte sind in der Allergiediagnostik geeignet, um die Sensibilisierung eines Patienten gegen eine Allergenquelle festzustellen, sie konnen aber keine Information liefern, gegen welche Komponenten (= einzelne Allergene) des Extraktes der Patient allergisch reagiert. Fortschritte in der rekombinanten DNS-Technologie haben es ermoglicht, die krankheitsauslosenden Molekule in den haufigsten Allergenquellen zu charakterisieren und als rekombinante Allergene herzustellen. Die erweiterte Diagnostik basierend auf rekombinanten Allergenen erlaubt es dem Allergologen, das individuelle IgE-Reaktivitatsprofil eines Patienten gegen die einzelnen Komponenten in einem Extrakt zu erstellen. Diese Informationen ermoglichen Kreuzsensibilisierungen gegen Allergenquellen, die immunologisch verwandte Allergene besitzen, nachzuweisen, therapeutische Strategien zu optimieren und auch den Verlauf der Erkrankung wahrend der spezifischen Immuntherapie mit herkommlichen Allergenextrakten zu kontrollieren. Basierend auf der „Komponenten-spezifische Diagnostik” mit rekombinanten Allergenen kann in Zukunft auch die spezifische Immuntherapie mit genau jenen rekombinanten Allergenen durchgefuhrt werden, gegen die der Patient tatsachlich sensibilisiert ist. Hypoallergene Derivate mit reduzierten allergenen Eigenschaften befinden sich bereits in klinischer Erprobung. Summary: Type I allergy is an immunoglobulin E (IgE)-mediated hypersensitivity disease affecting more than 25 % of the population. Currently, in vitro diagnosis of allergy is performed with allergen extracts, containing a variety of allergenic and non-allergenic molecules, and their allergen content is often cumbersome to standardize. While it is possible to use crude allergen extract-based diagnostic tests to define allergen containing sources, they cannot identify the disease-eliciting molecules. With the introduction of molecularbiology techniques into the field of allergen characterization, the identities of many important allergens have been revealed and increasing numbers of recombinant allergens have become available, leading to new forms of component-resolved diagnosis (CRD) based on recombinant allergens. Using recombinant allergens in in vitro diagnostic devices, a patient`s individual IgE reactivity profile can be established. The presence of IgE to cross-reactive allergen components can thus be determined and used to predict clinically relevant sensitization to allergen sources which contain immunologically related allergens. Moreover, component-resolved diagnosis can assist the clinician in choosing optimal therapeutic strategies among available treatment forms (e.g. allergen extract-based immunotherapy) and to monitor the success of the applied therapeutic measures. Based on CRD, component-resolved forms of immunotherapy are currently being developed using recombinant allergens with reduced allergenic activity.

Background: Polcalcins are pollen-specific allergens with two EF-hand calcium-binding sites that exhibit strong cross-reactivity. Our objective was to isolate and express the cDNA coding of the EF-hand calcium-binding allergen from lilac pollen and to study cross-reactivity with other polcalcins from related and nonrelated pollen sources with different specific antibodies and sera from two different populations. Methods: Specific cDNA was amplified by PCR, cloned and expressed in Escherichia coli. Purification was achieved by gel permeation and ion exchange chromatographies. ELISA titration and inhibition assays were performed using the recombinant forms of Syr v 3, Ole e 3, Che a 3 and Phl p 7 with sera from two Spanish regions with different sensitization profiles, as well as Phl p 7- and Ole e 3-specific polyclonal rabbit antisera, and an Ole e 3-specific monoclonal antibody. Results: Syr v 3 displays two EF-hand consensus sites and 8863 Da of theoretical molecular mass. The allergen consists of 80 residues with identities ranging from 66 to 87% with polcalcins included in this study. Syr v 3, Ole e 3, Che a 3 and Phl p 7 showed a similar IgG- and IgE-binding capacity although differences at quantitative level were observed depending on the population of patients’ sera. Conclusion: Syr v 3 is a polcalcin with structural and antigenic similarities to the members of this family. Diagnosis of polcalcin-sensitized patients could be performed whatever polcalcin used, whereas for immunotherapy, primary sensitization to a particular allergenic source should be considered.

The key event of allergic inflammation, allergen-induced crosslinking of mast cell-bound IgE antibodies, is accompanied by release of inflammatory mediators, cytokines, and proteases, in particular beta-tryptase. We provide evidence that protease-mediated cleavage of allergens represents a mechanism that regulates allergen-induced mast cell activation. When used in molar ratios as they occur in vivo, purified beta-tryptase cleaved major grass and birch pollen allergens, resulting in defined peptide fragments as mapped by mass spectrometry. Tryptase-cleaved allergens showed reduced IgE reactivity and allergenic activity. The biological relevance is demonstrated by the fact that lysates from activated human mast cells containing tryptase levels as they occur in vivo cleaved allergens. Additionally, protamine, an inhibitor of heparin-dependent effector cell proteases, augmented allergen-induced release of mediators from effector cells. Protease-mediated allergen cleavage may represent an important mechanism for terminating allergen-induced effector cell activation.