Exploration of early-life candidate biomarkers for childhood asthma using antibody arrays

Background: Proteomic approaches identifying biomarkers have been applied to asthma to only a very limited extent. Methods: With an antibody array (RayBiotech, Norcross, GA, USA), the relative intensity and rank differences of 444 proteins were compared in 24 plasma samples obtained at age 3, 11 from children with and 12 without asthma diagnoses at ages 5 and 9. Protein candidates identified by antibody array were quantitated by ELISA in an enlarged sample. Proteins found to differentiate children with and without asthma were also examined for association with known Year 1 asthma risk factors, eczema, and wheeze. Results: In the antibody array, four proteins had rank differences between asthma and non-asthma groups (FDR < 0.1). By ELISA, mean log (+/- s.e.m.) erythropoietin (EPO) level (IU/l) was lower (0.750 +/- 0.048 vs. 0.898 +/- 0.035; p = 0.006) and mean (+/- s.e.m.) soluble GP130 (sGP130) level (ng/ml) was higher in the asthma vs. the non-asthma group (302 +/- 13 vs. 270 +/- 8; p = 0.041). The other 2 array proteins (galactin-3 and eotaxin-3) did not differ by ELISA by asthma. EPO related to the asthma risk factor, first year eczema, whereas sGP130 related to first year wheeze. Conclusions: Through two independent assessments, age 3 plasma levels of EPO and sGP130 were found related to childhood asthma.