7th International Symposium on Molecular Allergology (ISMA 2017)

Abstract

Background: Cross-reactive carbohydrate determinants (CCDs) are a well described cause of non-clinically relevant in vitro cross-reactivity. The ISACTM microarray contains several allergen components purified from natural extracts that are recognized by anti-CCD sIgE (specific immunoglobulin E) and named "CCD-bearing proteins": nPhl p4, nCyn d1, nJug r2, nCup a1, Cry j1, nPla a2. We aimed to describe the relative frequency of recognition of CCD bearing proteins among polysenitized patients in order to aid in the interpretation of microarray results. Methods: Two-thousand and two ImmunoCAP-ISAC 112 (Thermo Fisher) performed between 2012 and 2017 in both children and adult polysensitized patients. Values of the above mentioned CCD-bearing allergens > 0.1 ISU were considered positive. When 2 CCD components were positive in the absence of the genuine marker of the allergenic source (except for Cup a1), patients were categorized as "CCD-sensitized". Results: A total of 1120 patients' sera (55.9%) recognized at least one CCD component, but only 22.2% of the patients were considered as "CCD-sensitized" according to our pre-defined criteria. Among the latter, the most frequently recognized CCD component was nPla a2 (86%), followed by nPhl p4 (84.5%), nCup a1 (82%), nJug r2 (79.3%), being MUXF3 the least recognized (37.2%). Interestingly, the mean sIgE levels to the CCD components nPla a2, nPhl p4 and nJug r2 were significantly higher among those patients also sensitized to markers of genuine sensitization of the same allergen source (Table 1). Mean values of MUXF3 sIgE were 0.238 ISU, bellow the standard cutoff point of 0.35 ISU. nJug r2 positivity was more frequently detected as the only walnut allergen (39.4%), and thus a marker of CCD sensitization, or associated to walnut LTP rJug r3 (39.9%) but scarcely associated with rJug r1 (7.8%). Conclusions: In these polysensitized patients, 22.2% are "CCDsensitized", being nPla a2 and nPhl p4 the most frequently detected and MUXF3 the least. This may be important when interpreting unexpected positivities in the allergen microarray. The mean serum CCD sIgE levels are generally low and in the case of MUXF3, commonly used as CCD marker, it would be misinterpreted as negative if the cutoff point of 0.35 ISU was used.