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A robust immunoassay for pregnancy-associated plasma protein-A2 based on analysis of circulating antigen: establishment of normal ranges in pregnancy.

Abstract
Pregnancy-associated plasma protein-A (PAPP-A) and PAPP-A2, two homologous metzincin metalloproteases, are both tightly linked to regulation within the insulin-like growth factor (IGF) system because of their specific cleavage of IGF binding proteins. Recent studies suggest that PAPP-A may be involved in clinical conditions related to unwanted cellular growth, and the circulating levels of PAPP-A is an established biomarker in prenatal screening for chromosomal abnormalities. Microarray data indicate that PAPP-A2 has potential as a biomarker for pre-eclampsia. However, well-characterized immunological methods of quantification are not available. We therefore developed monoclonal antibodies against recombinant PAPP-A2. The antibodies were epitope mapped against recombinantly expressed chimeras between PAPP-A2 and PAPP-A. Furthermore, circulating PAPP-A2 was immunoaffinity purified and characterized by sequence analysis and mass spectrometry. Unlike PAPP-A, PAPP-A2 is a noncovalent dimer in which each subunit of 1558 amino acids originates from all of the 22 predicted coding exons. A previously hypothesized variant (PAPP-E) does not exist, but low amounts of a C-terminally truncated PAPP-A2 variant was detected. A sensitive and robust ELISA for full-length PAPP-A2 was developed and used to establish normal ranges of PAPP-A2 through pregnancy. The functional sensitivity of this ELISA at 20% CV was 0.08 ng/ml, and the serum concentration of PAPP-A2 was found to increase during pregnancy in agreement with placental synthesis. The existence of this assay will enable an assessment of the biomarker potential of PAPP-A2 in pre-eclampsia as well as other clinical conditions.
AuthorsS Kløverpris, E Gaidamauskas, L C V Rasmussen, M T Overgaard, C Kronborg, U B Knudsen, M Christiansen, A Kumar, C Oxvig
JournalMolecular human reproduction (Mol Hum Reprod) Vol. 19 Issue 11 Pg. 756-63 (Nov 2013) ISSN: 1460-2407 [Electronic] England
PMID23804707 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
Chemical References
  • Antigens
  • Biomarkers
  • PAPPA2 protein, human
  • Pregnancy-Associated Plasma Protein-A
Topics
  • Animals
  • Antigens (blood)
  • Biomarkers (blood)
  • Female
  • Fetal Diseases (blood, diagnosis)
  • HEK293 Cells
  • Humans
  • Immunoassay (methods)
  • Mice
  • Mice, Knockout
  • Pre-Eclampsia (blood, diagnosis)
  • Pregnancy (blood)
  • Pregnancy-Associated Plasma Protein-A (analysis)
  • Prenatal Diagnosis (methods, standards)
  • Reference Values
  • Sensitivity and Specificity

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