Bile salt export pump-reactive antibodies form a polyclonal, multi-inhibitory response in antibody-induced bile salt export pump deficiency
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Date
2016-02-01
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Abstract
Progressive familial intrahepatic cholestasis type 2 (PFIC-2) is caused by mutations in ABCB11, encoding the bile salt export pump (BSEP). In 2009, we described a child with PFIC-2 who developed PFIC-like symptoms after orthotopic liver transplantation (OLT). BSEP-reactive antibodies were demonstrated to account for disease recurrence. Here, we characterize the nature of this antibody response in 7 more patients with antibody-induced BSEP deficiency (AIBD). Gene sequencing and immunostaining of native liver biopsies indicated absent or strongly reduced BSEP expression in all 7 PFIC-2 patients who suffered from phenotypic disease recurrence post-OLT. Immunofluorescence, western blotting analysis, and transepithelial transport assays demonstrated immunoglobulin (Ig) G-class BSEP-reactive antibodies in these patients. In all cases, the N-terminal half of BSEP was recognized, with reaction against its first extracellular loop (ECL1) in six sera. In five, antibodies reactive against the C-terminal half also were found. Only the sera recognizing ECL1 showed inhibition of transepithelial taurocholate transport. In a vesicle-based functional assay, transport inhibition by anti-BSEP antibodies binding from the cytosolic side was functionally proven as well. Within 2 hours of perfusion with antibodies purified from 1 patient, rat liver showed canalicular IgG staining that was absent after perfusion with control IgG. Conclusions: PFIC-2 patients carrying severe BSEP mutations are at risk of developing BSEP antibodies post-OLT. The antibody response is polyclonal, targeting both extra- and intracellular BSEP domains. ECL1, a unique domain of BSEP, likely is a critical target involved in transport inhibition as demonstrated in several patients with AIBD manifest as cholestasis.
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Funding Information: Expert technical assistance by Paulina Philippski, Nicole Eichhorst, Annette Tries, and Nathalie Walter is gratefully acknowledged. The authors thank “Hamburg macht Kinder gesund” and the “YAEL-Stiftung” for supporting the database on liver-transplanted children at the University Medical Center Hamburg-Eppendorf. Finally, the authors gratefully acknowledge Robin Marceca (founder of pfic.org) for her outstanding support throughout this study. Funding Information: Expert technical assistance by Paulina Philippski, Nicole Eichhorst, Annette Tries, and Nathalie Walter is gratefully acknowledged. The authors thank ?Hamburg macht Kinder gesund? and the ?YAEL-Stiftung? for supporting the database on liver-transplanted children at the University Medical Center Hamburg-Eppendorf. Finally, the authors gratefully acknowledge Robin Marceca (founder of pfic.org) for her outstanding support throughout this study. Publisher Copyright: © 2016 by the American Association for the Study of Liver Diseases.
Keywords
3.2 Clinical medicine, 1.1. Scientific article indexed in Web of Science and/or Scopus database, Hepatology
Citation
Stindt, J, Kluge, S, Dröge, C, Keitel, V, Stross, C, Baumann, U, Brinkert, F, Dhawan, A, Engelmann, G, Ganschow, R, Gerner, P, Grabhorn, E, Knisely, A S, Noli, K A, Pukite, I, Shepherd, R W, Ueno, T, Schmitt, L, Wiek, C, Hanenberg, H, Häussinger, D & Kubitz, R 2016, 'Bile salt export pump-reactive antibodies form a polyclonal, multi-inhibitory response in antibody-induced bile salt export pump deficiency', Hepatology, vol. 63, no. 2, pp. 524-537. https://doi.org/10.1002/hep.28311