GENE-EXPRESSION ANALYSIS RELATED TO OLIVE POLLEN ALLERGY

Analysis of gene-expression profiles by microarrays can be very useful to characterize new potential candidate genes, key regulatory networks, and to define phenotypes or molecular signatures to improve the diagnosis or classification of the disease. We have used this approach in the study of one of the major causes of allergic diseases in Mediterranean countries, the olive pollen response, in order to find differential molecular markers among five clinical groups, Non-allergic, Asymptomatic, Allergic but not to olive pollen, Non-treated, olive pollen allergic patients and Olive pollen allergic patients (under specific-immunotherapy). The results of gene-expression by principal components analysis (PCA) clearly showed five clusters of samples that correlated with the five clinical groups. Analysis of differential gene-expression by multiple testing, and functional analysis by KEGG and Gene-Ontology revealed differential genes and pathways among the 5 clinical groups. The study population comprised 28 subjects, selected from a previous immunological study (Aguerri et al. Eur. J. Inflammation 2012, in press), from Andalusia, who were recruited in 2 olive pollen exposure situations: during (April-June) and outside the pollen season (October-December). We established 5 groups, and 6 subjects from each group were selected for gene-expression analysis: Group 1, non-allergic subjects; Group 2, asymptomatic subjects (diagnosed with olive pollen allergy by skin testing, with no seasonal respiratory symptoms [rhinitis and/or asthma], and who consulted for adverse reaction to drugs); Group 3, patients who were allergic, but not to olive pollen; Group 4, non-treated olive pollen–allergic; and Group 5, olive pollen–allergic patients (receiving olive pollen–specific immunotherapy).The subjects were unrelated and recruited at the Allergy Service of 4 hospitals in Andalusia (Granada, Jaén, Sevilla, and Málaga). Olive pollen–allergic patients fulfilled the following criteria: seasonal rhinitis and/or asthma from April to June, a positive skin prick test result for O. europaea pollen extract (ALK Abelló, Madrid, Spain), and no previous immunotherapy. Informed consent was obtained from each subject. Ethical approval for the study was obtained from the Ethical and Research Committee of the participating hospitals. PBMCs were isolated from heparin-containing peripheral blood samples taken during and outside pollen season, by gradient centrifugation on Lymphoprep (Comercial Rafer, Zaragoza, Spain) following the manufacturer’s instructions.