Autoantibodies Against the Complement Regulator Factor H in the Serum of Patients With Neuromyelitis Optica Spectrum Disorder

Barbara Uzonyi, Zsóka Szabó, Eszter Trojnár, Satu Hyvärinen, Katalin Uray, Helle H. Nielsen, Anna Erdei, T. Sakari Jokiranta, Zoltán Prohászka, Zsolt Illes, Mihály Józsi*

*Corresponding author for this work

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Abstract

Neuromyelitis optica spectrum disorder (NMOSD) is an autoimmune inflammatory disease of the central nervous system (CNS), characterized by pathogenic, complement-activating autoantibodies against the main water channel in the CNS, aquaporin 4 (AQP4). NMOSD is frequently associated with additional autoantibodies and antibody-mediated diseases. Because the alternative pathway amplifies complement activation, our aim was to evaluate the presence of autoantibodies against the alternative pathway C3 convertase, its components C3b and factor B, and the complement regulator factor H (FH) in NMOSD. Four out of 45 AQP4-seropositive NMOSD patients (~9%) had FH autoantibodies in serum and none had antibodies to C3b, factor B and C3bBb. The FH autoantibody titers were low in three and high in one of the patients, and the avidity indexes were low. FH-IgG complexes were detected in the purified IgG fractions by Western blot. The autoantibodies bound to FH domains 19-20, and also recognized the homologous FH-related protein 1 (FHR-1), similar to FH autoantibodies associated with atypical hemolytic uremic syndrome (aHUS). However, in contrast to the majority of autoantibody-positive aHUS patients, these four NMOSD patients did not lack FHR-1. Analysis of autoantibody binding to FH19-20 mutants and linear synthetic peptides of the C-terminal FH and FHR-1 domains, as well as reduced FH, revealed differences in the exact binding sites of the autoantibodies. Importantly, all four autoantibodies inhibited C3b binding to FH. In conclusion, our results demonstrate that FH autoantibodies are not uncommon in NMOSD and suggest that generation of antibodies against complement regulating factors among other autoantibodies may contribute to the complement-mediated damage in NMOSD.

Original languageEnglish
Article number660382
JournalFrontiers in Immunology
Volume12
Number of pages13
ISSN1664-3224
DOIs
Publication statusPublished - 27. Apr 2021

Bibliographical note

Publisher Copyright:
© Copyright © 2021 Uzonyi, Szabó, Trojnár, Hyvärinen, Uray, Nielsen, Erdei, Jokiranta, Prohászka, Illes and Józsi.

Keywords

  • aquaporin (AQP) 4
  • autoantibody
  • autoimmunity
  • central nervous system
  • complement
  • factor H
  • inflammation
  • neuromyelitis optica spectrum disorder

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