Amino acid regions 572-579 and 657-666 of the spacer domain of ADAMTS13 provide a common antigenic core required for binding of antibodies in patients with acquired TTP.
Antibodies directed against ADAMTS13 have been detected in the majority of patients with acquired thrombotic thrombocytopenic purpura (TTP). We have previously localized a major antigenic determinant within the spacer domain of ADAMTS13. To identify the amino acid residues of the spacer domain that are involved in binding of anti-ADAMTS13 antibodies, we constructed a series of fifteen hybrids (designated A-O) in which 5-10 amino acids of the spacer domain were exchanged for the corresponding region of ADAMTS1. Plasma from six patients with antibodies directed against the spacer domain was analyzed for reactivity with the ADAMTS13/ADAMTS1 chimeras. Exchange of amino acid residues 572-579 (hybrid C) and 657-666 (hybrid M) completely abolished the binding of antibodies from all six patients analyzed. Regions 580-587 (D), 602-620 (G, H), 629-638 (J), and 667-767 (N) contributed to binding of antibodies from patients 2, 4, and 5 (epitope present within regions CDGHJMN). Antibodies derived from patient 1 required region 602-620 (G, H) for binding (CGHM-epitope). For antibodies of patient 3, residues 564-571 (B), 580-587 (D), and 629-638 (J) were required (BCDJM-epitope), whereas replacement of residues 602-610 (G) and 629-638 (J) greatly diminished binding of antibodies from patient 6 (CGJM-epitope). Despite the presumably polyclonal origin of the antibodies present in plasma of patients, our results suggest that residues 572-579 (C) and 657-666 (M) comprise a common antigenic core region that is crucial for binding of anti-ADAMTS13 antibodies. Other regions that spatially surround this antigenic core further modulate binding of antibodies to the spacer domain.
Luken
Brenda M
BM
Department of Plasma Proteins, Sanquin Research and AMC Landsteiner Laboratory, Amsterdam, The Netherlands.
Turenhout
Ellen A M
EA
Kaijen
Paul H P
PH
Greuter
Mascha J
MJ
Pos
Wouter
W
van Mourik
Jan A
JA
Fijnheer
Rob
R
Voorberg
Jan
J
D051722:ADAM Proteins / Q000737:chemistry* / Q000378:metabolism; D000071120:ADAMTS13 Protein; D000595:Amino Acid Sequence; D000941:Antigens / Q000737:chemistry; D001323:Autoantibodies / Q000737:chemistry; D000939:Epitopes / Q000737:chemistry; D006463:Hemolytic-Uremic Syndrome / Q000378:metabolism; D006801:Humans; D007074:Immunoglobulin G / Q000737:chemistry; D047468:Immunoprecipitation; D008969:Molecular Sequence Data; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011697:Purpura, Thrombotic Thrombocytopenic / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000737:chemistry; D017386:Sequence Homology, Amino Acid
D000941:Antigens; D001323:Autoantibodies; D000939:Epitopes; D007074:Immunoglobulin G; D011993:Recombinant Fusion Proteins; D051722:ADAM Proteins; D000071120:ADAMTS13 Protein; C099604:ADAMTS13 protein, human