Establishment of a protein biochip to detect serum IgG antibodies against IL-2 and soluble CD25 in hemophagocytic lymphohistiocytosis.

Background: Interleukin-2 (IL-2) and soluble CD25 (sCD25) are among the most important cytokines and diagnostic biomarkers in hemophagocytic lymphohistiocytosis (HLH). Detecting serum level of IL-2 and sCD25 is valuable for making clinical diagnosis and treatment decision in HLH.

Methods: Since tests showing serum IgG antibody against IL-2 or sCD25 have never been carried out, a new protein biochip, which was modified with cysteine and activated sophorolipid (Cys-SL), was developed.

Results: Limits of detection on the biochip were 78 pg/ml for IL-2 and 39 pg/ml for sCD25, respectively. The data showed that on-chip seroimmunological responses to IL-2 and sCD25 proteins were 20.8% and 83.1% and the seroprevalence of IL-2 and sCD25 IgG antibodies were 45.5% and 57.2%, respectively. Data collection for the seroprevalence of serum antigen-antibody complex of sCD25 was 68.8%. The new biochip model shared similar sensitivity and specificity to chemiluminescent immunoassay (CLIA) in its measuring capacity of serum sCD25.

Conclusions: We addressed and confirmed the involvement of serum IgG antibodies against IL-2 and sCD25 as well as Ag-Ab complex of sCD25 in HLH patients. Therefore, this biochip platform would offer a new technological substitution for clinical serological diagnosis of HLH.