Preparation of monoclonal antibodies against human interleukin-35 and their application in a quantitative ELISA for interleukin-35 detection

Abstract

To establish a quantitative ELISA for human interleukin-35 (IL-35) detection, we cloned cDNAs encoding the 2 subunits IL-27EBI3 and IL-12p35 of IL-35 by RT-PCR and transformed the cDNAs into Escherichia coli BL21 star (DE3) by recombinant DNA technology. IL-27EBI3 and IL-12p35 were expressed as recombinant proteins and used as immunogen to immunize Balb/c mice. Spleen cells from the positive serum mice were isolated and fused with SP-2/0 myeloma cells. We obtained the hybridoma cell lines stably secreting target antibodies by indirect ELISA screening of the cell supernatants with recombinant IL-27EBI3 and IL-12p35 as antigen and consecutive subcloning of the cells in the well with positive supernatant. Following further measurement of supernatant titers of the antibodies and identification of their antigen specificity, we obtained a hybridoma cell line 3B11 that stably secrets antibody against IL-27EBI3 and a hybridoma cell line 3A10 that secrets antibody against IL-12p35. Both monoclonal antibodies (mAbs) were identified as the subtype of IgG1. Finally, using the anti-IL-27EBI3 mAb from 3B11 as the capture antibody and the anti-IL-12p35 mAb from 3A10 as the secondary antibody, we established a quantitative double-antibodies sandwich ELISA for IL-35 detection with streptavidin-biotin amplification system. Results demonstrated that the quantitative assay had a detection range of 3.12-200 pg/mL, a detectability of 1.26 pg/mL, and a crossing-reactive rate of 0.1%. The intra-batch RSD and the inter-batch RSD of the quantitative assay were 5.1%-5.6% and 5.6%-7.2%, respectively, and the fortified recovery was 89%-103%. Therefore, the sandwich ELISA assay for IL-35 meets the qualification of quantitative analysis and laid a stable foundation for the development of quantitative ELISA kit for IL-35 detection.