Quantitative determination of human interleukin 22 (IL-22) in serum using Singulex-Erenna® technology.

Interleukin-22 (IL-22) is a key mediator of inflammatory processes associated with diseases such as psoriasis, inflammatory bowel disease and rheumatoid arthritis. The measurement of this cytokine in human plasma may provide insight into safety, pharmacodynamics and efficacy of drugs targeting inflammatory pathways. However, commonly used immunoassays are not sufficiently sensitive to measure baseline concentrations of IL-22. Here we describe the analytical validation of an ultrasensitive assay for the measurement of IL-22 in human serum using the Erenna® system by Singulex (Alameda, CA). The lower limit of quantification (LLOQ) of the Erenna assay estimated at 0.2pg/mL was sensitive enough to measure IL-22 in all human serum samples tested. The assay ranged from 0.2 to 100.0pg/mL and showed good dilution linearity. The inter-assay and intra-assay imprecision were <9% and <7% CV respectively. The accuracy determined by spiked recovery in serum samples was >86%. In addition, the results using Erenna assay correlated well with those using the IL-22 Quantikine immunoassay (R&D Systems, Minneapolis, MN) with a coefficient R(2) of 0.9285. However the Erenna assay showed an improved sensitivity by approximately 2 logs. These results show that this novel assay offers a significant improvement over previous methods for high-sensitive quantitative measurement of IL-22 in human serum samples.