Characterization of Autoantigens Targeted by Anti-Citrullinated Protein Antibodies In Vivo: Prominent Role for Epitopes Derived from Histone 4 Proteins.
Anti-citrullinated protein antibodies (ACPA) have become an integral part of the clinical definition of rheumatoid arthritis, and are hypothesized to be important in the immunopathogenesis of this autoimmune disease. Several citrullinated proteins have been demonstrated to serve as candidate autoant...
Main Authors: | , , , , , |
---|---|
Format: | Article |
Language: | English |
Published: |
Public Library of Science (PLoS)
2016-01-01
|
Series: | PLoS ONE |
Online Access: | http://europepmc.org/articles/PMC5082836?pdf=render |
id |
doaj-11039e0c097847f09db4ebb9c6da973b |
---|---|
record_format |
Article |
spelling |
doaj-11039e0c097847f09db4ebb9c6da973b2020-11-25T01:49:45ZengPublic Library of Science (PLoS)PLoS ONE1932-62032016-01-011110e016550110.1371/journal.pone.0165501Characterization of Autoantigens Targeted by Anti-Citrullinated Protein Antibodies In Vivo: Prominent Role for Epitopes Derived from Histone 4 Proteins.Xiaobo MengPeyman EzzatiIrene SmolikCharles N BernsteinCarol Ann HitchonHani S El-GabalawyAnti-citrullinated protein antibodies (ACPA) have become an integral part of the clinical definition of rheumatoid arthritis, and are hypothesized to be important in the immunopathogenesis of this autoimmune disease. Several citrullinated proteins have been demonstrated to serve as candidate autoantigens for the ACPA, based on in vitro immune reactions between citrullinated peptides/proteins and RA sera. Yet it remains unclear whether the autoantigens identified in vitro are indeed directly and specifically targeted by the ACPA in vivo. Moreover, it is unclear whether ACPA present in RA sera are directed towards the same spectrum of autoantigens as the ACPA present within the synovial compartment. In this study, we isolated ACPA immune complexes from RA synovial fluids (SF) and sera by using immobilized cyclic citrullinated peptides (CCP3) based immune affinity, and characterized the proteins that are directly and specifically associated with them by mass spectrometry. The results demonstrate that four histone proteins are prominent ACPA autoantigens, with the frequency of detection being histone H4 (89%), H2B (63%), H3 (63%), and H2A (58%) in ACPA positive RA SF. We further demonstrate that a histone 4 peptide containing citrulline at position Cit39 was recognized by 100% of ACPA positive RA SF. An adjacent citrulline residue at Cit40 was recognized by 34% of ACPA positive RA SF. An H4 peptide containing Cit39-40 was recognized in the serum of 94% ACPA positive RA, 77% ACPA positive first-degree relatives (FDR) of RA patients, and 2.5% of healthy controls. The Cit39-40 peptide substantially blocked the ACPA reactivity in both SF and serum. Although the spectrum of ACPA we identified was limited to those isolated using immobilized CCP3 peptides, the findings indicate that H4 is a widely recognized RA autoantigen in both the synovial and serum compartments. The identification of this immunodominant ACPA epitope may be valuable in designing approaches to immune tolerance induction in RA.http://europepmc.org/articles/PMC5082836?pdf=render |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Xiaobo Meng Peyman Ezzati Irene Smolik Charles N Bernstein Carol Ann Hitchon Hani S El-Gabalawy |
spellingShingle |
Xiaobo Meng Peyman Ezzati Irene Smolik Charles N Bernstein Carol Ann Hitchon Hani S El-Gabalawy Characterization of Autoantigens Targeted by Anti-Citrullinated Protein Antibodies In Vivo: Prominent Role for Epitopes Derived from Histone 4 Proteins. PLoS ONE |
author_facet |
Xiaobo Meng Peyman Ezzati Irene Smolik Charles N Bernstein Carol Ann Hitchon Hani S El-Gabalawy |
author_sort |
Xiaobo Meng |
title |
Characterization of Autoantigens Targeted by Anti-Citrullinated Protein Antibodies In Vivo: Prominent Role for Epitopes Derived from Histone 4 Proteins. |
title_short |
Characterization of Autoantigens Targeted by Anti-Citrullinated Protein Antibodies In Vivo: Prominent Role for Epitopes Derived from Histone 4 Proteins. |
title_full |
Characterization of Autoantigens Targeted by Anti-Citrullinated Protein Antibodies In Vivo: Prominent Role for Epitopes Derived from Histone 4 Proteins. |
title_fullStr |
Characterization of Autoantigens Targeted by Anti-Citrullinated Protein Antibodies In Vivo: Prominent Role for Epitopes Derived from Histone 4 Proteins. |
title_full_unstemmed |
Characterization of Autoantigens Targeted by Anti-Citrullinated Protein Antibodies In Vivo: Prominent Role for Epitopes Derived from Histone 4 Proteins. |
title_sort |
characterization of autoantigens targeted by anti-citrullinated protein antibodies in vivo: prominent role for epitopes derived from histone 4 proteins. |
publisher |
Public Library of Science (PLoS) |
series |
PLoS ONE |
issn |
1932-6203 |
publishDate |
2016-01-01 |
description |
Anti-citrullinated protein antibodies (ACPA) have become an integral part of the clinical definition of rheumatoid arthritis, and are hypothesized to be important in the immunopathogenesis of this autoimmune disease. Several citrullinated proteins have been demonstrated to serve as candidate autoantigens for the ACPA, based on in vitro immune reactions between citrullinated peptides/proteins and RA sera. Yet it remains unclear whether the autoantigens identified in vitro are indeed directly and specifically targeted by the ACPA in vivo. Moreover, it is unclear whether ACPA present in RA sera are directed towards the same spectrum of autoantigens as the ACPA present within the synovial compartment. In this study, we isolated ACPA immune complexes from RA synovial fluids (SF) and sera by using immobilized cyclic citrullinated peptides (CCP3) based immune affinity, and characterized the proteins that are directly and specifically associated with them by mass spectrometry. The results demonstrate that four histone proteins are prominent ACPA autoantigens, with the frequency of detection being histone H4 (89%), H2B (63%), H3 (63%), and H2A (58%) in ACPA positive RA SF. We further demonstrate that a histone 4 peptide containing citrulline at position Cit39 was recognized by 100% of ACPA positive RA SF. An adjacent citrulline residue at Cit40 was recognized by 34% of ACPA positive RA SF. An H4 peptide containing Cit39-40 was recognized in the serum of 94% ACPA positive RA, 77% ACPA positive first-degree relatives (FDR) of RA patients, and 2.5% of healthy controls. The Cit39-40 peptide substantially blocked the ACPA reactivity in both SF and serum. Although the spectrum of ACPA we identified was limited to those isolated using immobilized CCP3 peptides, the findings indicate that H4 is a widely recognized RA autoantigen in both the synovial and serum compartments. The identification of this immunodominant ACPA epitope may be valuable in designing approaches to immune tolerance induction in RA. |
url |
http://europepmc.org/articles/PMC5082836?pdf=render |
work_keys_str_mv |
AT xiaobomeng characterizationofautoantigenstargetedbyanticitrullinatedproteinantibodiesinvivoprominentroleforepitopesderivedfromhistone4proteins AT peymanezzati characterizationofautoantigenstargetedbyanticitrullinatedproteinantibodiesinvivoprominentroleforepitopesderivedfromhistone4proteins AT irenesmolik characterizationofautoantigenstargetedbyanticitrullinatedproteinantibodiesinvivoprominentroleforepitopesderivedfromhistone4proteins AT charlesnbernstein characterizationofautoantigenstargetedbyanticitrullinatedproteinantibodiesinvivoprominentroleforepitopesderivedfromhistone4proteins AT carolannhitchon characterizationofautoantigenstargetedbyanticitrullinatedproteinantibodiesinvivoprominentroleforepitopesderivedfromhistone4proteins AT haniselgabalawy characterizationofautoantigenstargetedbyanticitrullinatedproteinantibodiesinvivoprominentroleforepitopesderivedfromhistone4proteins |
_version_ |
1725005209849036800 |