Quantification of the Major Allergen from Cypress <i>(Cupressus arizonica)</i> Pollen, Cup a 1, by Monoclonal Antibody-Based ELISA

<i>Background:</i> Cypress pollen allergy is an important cause of rhinoconjunctivitis and asthma in Mediterranean countries. Cypress allergenic extracts are difficult to produce since they have low protein and high carbohydrate content, thus accurate standardization of them is essential to guarantee their quality. The aim of this study is to develop a sandwich ELISA for the quantification of Cup a 1, the major allergen of cypress <i>(Cupressus arizonica)</i> pollen extract. <i>Methods:</i> Monoclonal antibodies directed to purified Cup a 1 were produced. Two of them (9C7 as capture antibody and 3D2 as the tracer) were selected to develop a quantitative sandwich ELISA. This ELISA was subsequently evaluated and compared with other techniques. <i>Results:</i> The described ELISA is very sensitive with a detection limit of 8.7 ng/ml and a practical working range of 62.5–1,000 ng/ml. The assay is also highly reproducible with intra-assay and interassay coefficients of variation of less than 10%. The purified Cup a 1, used as standard, presents pectate lyase enzymatic activity. The assay also detected Cup a 1-like proteins in pollen from other Cupressaceae. A good correlation was obtained between Cup a 1 content of 12 <i>C. arizonica</i> pollen extracts and their IgE-binding activity. <i>Conclusions:</i> The described Cup a 1 ELISA is sensitive, specific and reproducible and can be used for the quantification of Cup a 1 in <i>C. arizonica</i> and other related pollen extracts. It also provides a reliable indication of the allergenic activity of the whole cypress pollen extract.