Immunoluminometric assay for quantification of peroxiredoxin 4 in human serum

BackgroundWe describe the validation of a novel assay for the measurement of peroxiredoxin 4 (Prx4), a potentially secreted antioxidant peroxidase, in human serum.MethodsA sandwich immunoluminometric assay (ILMA) was set up applying monoclonal antibodies against the amino-terminus of human Prx4. Prx4 levels have been determined in serum of healthy individuals and patients with sepsis and have been correlated to the clinically established sepsis marker procalcitonin (PCT).ResultsThe sandwich ILMA detected Prx4 in a range between 0.5 and 128 arbitrary (arb.) U/L and had a functional assay sensitivity of 0.51 arb. U/L. Serum Prx4 was stable for at least 72 h at 4 °C and 21 °C and circulated in a complex of about 330 kDa as characterized by size-exclusion chromatography. Patients with sepsis (n = 45; median, 7.7 arb. U/L) showed significantly higher Prx4 serum levels (P < 0.0001) than healthy controls (n = 274; median, 0.71 arb. U/L). Serum Prx4 was positively correlated to PCT (r = 0.63, P < 0.0001).ConclusionThe newly developed assay reliably detected Prx4 in human serum of healthy and critically ill subjects. Elevated Prx4 in serum of patients with various diseases might serve as a biomarker reflecting increased oxidative stress.