Proteomic but not enzyme-linked immunosorbent assay technology detects amniotic fluid monomeric calgranulins from their complexed calprotectin form

• Published in: Clinical and diagnostic laboratory immunology Vol. 12; no. 7; pp. 837 - 844
• Main Authors: Buhimschi, Irina A, Buhimschi, Catalin S, Weiner, Carl P, Kimura, Tatsuji, Hamar, Benjamin D, Sfakianaki, Anna K, Norwitz, Errol R, Funai, Edmund F, Ratner, Elena
• Format: Journal Article
• Language: English
• Published: United States American Society for Microbiology 01-07-2005
• Subjects: Amniotic Fluid - metabolism; Antibodies and Mediators of Immunity; Biomarkers - analysis; Calgranulin B - analysis; Chorioamnionitis - metabolism; Defensins - analysis; Female; Humans; Mass Spectrometry; Pregnancy; Proteomics - methods; Sensitivity and Specificity
• ISSN: 1071-412X; 1098-6588
• DOI: 10.1128/CDLI.12.7.837-844.2005

Four proteomic biomarkers (human neutrophil peptide 1 [HNP1], HNP2 [defensins], calgranulin C [Cal-C], and Cal-A) characterize the fingerprint of intra-amniotic inflammation (IAI). We compared proteomic technology using surfaced-enhanced laser desorption-ionization-time of flight (SELDI-TOF) mass spectrometry to enzyme-linked immunosorbent assay (ELISA) for detection of these biomarkers. Amniocentesis was performed on 48 women enrolled in two groups: those with intact membranes (n = 27; gestational age [GA], 26.0 +/- 0.8 weeks) and those with preterm premature rupture of the membranes (PPROM; n = 21; GA, 28.4 +/- 0.9 weeks). Paired abdominal amniotic fluids (aAFs)-vaginal AFs (vAFs) were analyzed in PPROM women. Quantitative aspects of HNP1-3, Cal-C, Cal-A, and calprotectin (a complex of Cal-A with Cal-B) were assessed by ELISA. SELDI-TOF mass spectrometry tracings from 16/48 (33.3%) aAFs and 13/17 (88.2%) vAFs were consistent with IAI (three or four biomarkers present). IAI (by SELDI-TOF mass spectrometry) was associated with increased HNP1-3 and Cal-C measured by ELISA. However, immunoassays detected Cal-A in only 4 of the AFs even though its specific SELDI-TOF mass spectrometry peak was identified in 19/48 AFs. Calprotectin immunoreactivity was decreased in AFs retrieved from women with IAI (P = 0.01). In conclusion, IAI is associated with increased HNP1-3 levels. In the absence of isoform-specific ELISAs, mass spectrometry remains the only way to discriminate the HNP biomarker isoforms. Monomeric Cal-A is not reliably estimated by specific ELISA as it binds to Cal-B to form the calprotectin complex. Cal-C was reliably measured by SELDI-TOF mass spectrometry or specific ELISA.