Mapping epitopes of U1-70K autoantibodies at single-amino acid resolution

David James Haddon, Justin Ansel Jarrell, Vivian K. Diep, Hannah E. Wand, Jordan V. Price, Stephanie Tangsombatvisit, Grace M. Credo, Sally Mackey, Cornelia L. Dekker, Emily C. Baechler, Chih Long Liu, Madoo Varma, Paul J. Utz

Research output: Contribution to journalArticlepeer-review

9 Scopus citations

Abstract

The mechanisms underlying development of ribonucleoprotein (RNP) autoantibodies are unclear. The U1-70K protein is the predominant target of RNP autoantibodies, and the RNA binding domain has been shown to be the immunodominant autoantigenic region of U1-70K, although the specific epitopes are not known. To precisely map U1-70K epitopes, we developed silicon-based peptide microarrays with >5700 features, corresponding to 843 unique peptides derived from the U1-70K protein. The microarrays feature overlapping peptides, with single-amino acid resolution in length and location, spanning amino acids 110-170 within the U1-70K RNA binding domain. We evaluated the serum IgG of a cohort of patients with systemic lupus erythematosus (SLE; n = 26) using the microarrays, and identified multiple reactive epitopes, including peptides 116-121 and 143-148. Indirect peptide ELISA analysis of the sera of patients with SLE (n = 88) revealed that ∼14% of patients had serum IgG reactivity to 116-121, while reactivity to 143-148 appeared to be limited to a single patient. SLE patients with serum reactivity to 116-121 had significantly lower SLE Disease Activity Index (SLEDAI) scores at the time of sampling, compared to non-reactive patients. Minimal reactivity to the peptides was observed in the sera of healthy controls (n = 92). Competitive ELISA showed antibodies to 116-121 bind a common epitope in U1-70K (68-72) and the matrix protein M1 of human influenza B viruses. Institutional Review Boards approved this study. Knowledge of the precise epitopes of U1-70K autoantibodies may provide insight into the mechanisms of development of anti-RNP, identify potential clinical biomarkers and inform ongoing clinical trails of peptide-based therapeutics.

Original languageEnglish (US)
Pages (from-to)513-523
Number of pages11
JournalAutoimmunity
Volume48
Issue number8
DOIs
StatePublished - Nov 17 2015

Bibliographical note

Publisher Copyright:
© 2015 Taylor & Francis.

Keywords

  • RNP
  • SLE
  • Silicon-based peptide microarray
  • ribonucleoprotein
  • systemic lupus erythematosus

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