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BACKGROUND: Cross-reactivity reactions between allergenic polygalacturonases (PGs) from different biological sources, especially foods and pollens from the Oleaceae family, have been described using Salsola kali PG (Sal k 6). No PG from olive pollen has been characterized to date, hampering further knowledge about cross-reactions through PGs. OBJECTIVES: The aim of this work was to determine the potential allergenicity of the PG from olive pollen and clarify its role in cross-reactivity. METHODS: A cDNA-encoding olive pollen PG sequence was subcloned into the pET41b vector and used to transform BL21(DE3) Escherichia coli cells to produce a His-tag fusion recombinant protein. The allergenic properties of olive pollen PG were determined by immunoblotting and ELISA in comparison to Sal k 6. The cross-reactivity potential of the protein with other pollen sources was analyzed by inhibition immunoassays. RESULTS: The existence of other isoforms of Ole e 14 with different allergenicity was confirmed by proteomics and a meta-analysis of the recently reported olive genome. Sal k 6 showed a higher IgE recognition than Ole e 14 regardless of patient sensitization, suggesting the existence of more allergenic Ole e 14 isoforms in olive pollen. IgG and IgE inhibition assays supported the existence of cross-reactions between them and with other PGs from Oleaceae and Poaceae plant families. CONCLUSIONS: A new allergen from olive pollen, Ole e 14, has been identified, produced as a recombinant isoform, and structurally and immunologically characterized. Its role in cross-reactivity has been confirmed and, due to its smaller IgE binding capacity, it could have an important role for therapeutic purposes.

Analysis of gene-expression profiles by microarrays is useful for characterization of candidate genes, key regulatory networks, and to define phenotypes or molecular signatures which improve the diagnosis and/or classification of the allergic processes. We have used this approach in the study of olive pollen response in order to find differential molecular markers among responders and non-responders to this allergenic source. Five clinical groups, non-allergic, asymptomatic, allergic but not to olive pollen, untreated-olive-pollen allergic patients and olive-pollen allergic patients (under specific-immunotherapy), were assessed during and outside pollen seasons. Whole-genome gene expression analysis was performed in RNAs extracted from PBMCs. After assessment of data quality and principal components analysis (PCA), differential gene-expression, by multiple testing and, functional analyses by KEGG, for pathways and Gene-Ontology for biological processes were performed. Relevance was defined by fold change and corrected P values (less than 0.05). The most differential genes were validated by qRT-PCR in a larger set of individuals. Interestingly, gene-expression profiling obtained by PCA clearly showed five clusters of samples that correlated with the five clinical groups. Furthermore, differential gene expression and functional analyses revealed differential genes and pathways in the five clinical groups. The 93 most significant genes found were validated, and one set of 35 genes was able to discriminate profiles of olive pollen response. Our results, in addition to providing new information on allergic response, define a possible molecular signature for olive pollen allergy which could be useful for the diagnosis and treatment of this and other sensitizations.

We present a case of urticaria caused by antihistamines in a patient with nonsteroidal anti-inflammatory drug (NSAID) sensitivity. A 35-year-old man experienced, on 2 separate occasions, immediate generalized urticaria during treatment with ibuprofen and naproxen, respectively. A single-blind, placebo-controlled oral challenge (SBPCOC) with piroxicam was carried out, and resulted in urticaria and angioedema 3 hours later. Two hours after initial clinical resolution, the patient developed multiple wheals on the trunk and upper limbs. He described similar delayed reactions after oral antihistamine administration on previous occasions. SBPCOCs with acetaminophen and etoricoxib were performed, with good tolerance. Skin prick and patch tests with loratadine and cetirizine were negative. After an SBPCOC with loratadine, the patient developed generalized urticaria 90 minutes after intake. Tolerance to fexofenadine 180 mg was confirmed. We describe the first case of a possible new subset of antihistamine urticaria, and suggest calling this NSAID-sensitive antihistamine-induced urticaria/angioedema.