Immunochemical characterization of six monoclonal antibodies to human apolipoprotein A-I: Epitope mapping and expression

S. Marcovina, S. Fantappie, A. Zoppo, G. Franceschini, A. L. Catapano

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We have produced and characterized six urine monoclonal antibodies to human apolipoprotein A-I named A-I-9, A-I-12, A-I-15, A-I-16, A-I-19, and A-I-57. All monoclonal antibodies were specific for apolipoprotein A-I and bound between 55% and 100% of 125I-labeled high density lipoproteins (HDL) in a fluid phase radioimmunoassay. All antibodies possessed a higher affinity to apoA-I in HDL than to free, delipidated apoA-I. Two of them, particularly A-I-12 and A-I-15, which were directed to the same or very close epitopes on the molecule, recognized very poorly the delipidated protein. Binding of apoA-I to phospholipid restored the immunoreactivity of the monoclonal antibodies ot the protein suggesting that lipids play and important role in determining the immunochemical structure of apoA-I. Using CNBr fragments and synthetic peptides, the epitopes for the antibodies were mapped as follows: A-I-19, CNBr fragment 1; A-I-12 and 15, CNBr fragment 2; A-I-9 and A-I-16, CNBr fragment 3; A-I-57, CNBr fragment 4. Antibody A-I-57 failed to recognize a mutant form of apoA-I, A-I(Milano) (Arg173 → Cys) by immunoblotting and by competitive radioimmunoassay demonstrating that substitution of a single amino acid in human apoA-I may cause the loss of an antigenic determinant.

Original languageEnglish
Pages (from-to)375-384
Number of pages10
JournalJournal of Lipid Research
Issue number3
Publication statusPublished - 1990


  • apolipoprotein A-I(Milano)
  • conformational changes
  • delipated apolipoprotein A-I
  • high density lipoprotein

ASJC Scopus subject areas

  • Endocrinology


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