Sensitive immunometric assays for secretory peroxidase and myeloperoxidase in human saliva

We have developed specific immunoassays for secretory peroxidase (SP) and for myeloperoxidase (MP) (polymorphonuclear leukocyte-derived peroxidase) in human saliva. Antibodies against SP and MP were produced using bovine milk lactoperoxidase (LP) and human MP as the immunogens, respectively. The methods developed are non-isotopic immunometric assays using biotinylated antibodies and avidin-enzyme conjugate. The detection limit was 0.1 ng/ml and the performance time less than 3 h for both assays. The determination ranges were 0.5-100 ng LP (SP)/ml and 0.5-200 ng MP/ml with intra- and interassay CVs of 4.3% and 15.6% for SP and 3.7% and 10.8% for MP, respectively. The mean analytical recoveries were 108.9% (SP) and 91.5% (MP). These assays correlated well (r = 0.849-0.871) with the colorimetric assays based on the oxidation of thiocyanate or chloride by peroxidases. However, compared to the colorimetric methods the new immunometric assays are much more sensitive and specific for salivary SP and MP. The assays are also more rapid since extensive dialysis to remove endogenous thiocyanate is not required.