title: A novel DNA/histone H4 peptide complex detects autoantibodies in systemic lupus erythematosus sera.
abstract: The detection of anti-dsDNA antibodies is critical for the diagnosis and follow-up of systemic lupus erythematosus (SLE) patients. The presently available assays are characterized by a non-optimal specificity (solid phase assays) or sensitivity (Crithidia Luciliae immunofluorescence test (CLIFT)). To overcome the limits of CLIFT and solid phase chromatin assays, we explored the diagnostic potential of an assay based on plasmid DNA containing a highly bent fragment of 211 bp from Crithidia Luciliae minicircles, complexed with histone peptides.
  
  
  
  Electrically neutral complexes of PK201/CAT plasmid (PK) DNA and histone 4 (H4) peptides were evaluated by electromobility shift assay. Complexes of H4 peptides and PK were absorbed to the solid phase to detect specific immunoglobulin G (IgG) in sera. Sera from 109 SLE patients, 100 normal healthy subjects, and 169 disease controls were tested.
  
  
  
  H4(14-34) containing the consensus sequence for DNA binding interacts with PK, retarding its migration. H4(14-34)/PK complexes were used to test sera by ELISA. Anti-H4-PK antibodies were detected in 56 % of SLE sera (more frequently in patients with skin or joint involvement) versus 5.9 % in disease controls; inhibition assays show that sera react with epitopes present on DNA or on the complex, not on the peptide. Antibody titer is correlated with European Consensus Lupus Activity Measurement (ECLAM) score and anti-complement component 1q (C1q) antibodies, negatively with C3 levels. Anti-H4-PK antibodies compared with CLIFT and solid phase dsDNA assays display moderate concordance.
  
  
  
  The H4/PK assay is a simple and reliable test which is useful for the differential diagnosis and evaluation of disease activity in SLE patients.
authors.affiliation: Department of Clinical and Experimental Medicine, University of Pisa, Via Roma 67, 56126, Pisa, Italy.
authors.forename: Filomena
authors.initials: F
authors.lastname: Panza
authors.affiliation: Toscana Biomarkers Srl, Siena, Italy.|Present address: DIESSE Diagnostica Senese SPA, via Fiorentina 1, 53100, Siena, Italy.
authors.forename: Maria Claudia
authors.initials: MC
authors.lastname: Alcaro
authors.affiliation: Department of Clinical and Experimental Medicine, University of Pisa, Via Roma 67, 56126, Pisa, Italy.
authors.forename: Fiorella
authors.initials: F
authors.lastname: Petrelli
authors.affiliation: Department of Clinical and Experimental Medicine, University of Pisa, Via Roma 67, 56126, Pisa, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Angelotti
authors.affiliation: Department of Clinical and Experimental Medicine, University of Pisa, Via Roma 67, 56126, Pisa, Italy.
authors.forename: Federico
authors.initials: F
authors.lastname: Pratesi
authors.affiliation: Laboratory of Peptide and Protein Chemistry and Biology, Department of Neurosciences, Psychology, Drug Research and Child Health, Section of Pharmaceutical Sciences and Nutraceutics, University of Florence, Via Ugo Schiff 6, 50019, Sesto Fiorentino, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Rovero
authors.affiliation: Department of Clinical and Experimental Medicine, University of Pisa, Via Roma 67, 56126, Pisa, Italy. paola.migliorini@med.unipi.it.
authors.forename: Paola
authors.identifier: 0000-0001-6433-4964
authors.initials: P
authors.lastname: Migliorini
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000974:Antibodies, Antinuclear / Q000032:analysis* / Q000276:immunology; D001324:Autoantigens / Q000276:immunology; D004247:DNA / Q000276:immunology; D024202:Electrophoretic Mobility Shift Assay; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D005260:Female; D006657:Histones; D006801:Humans; D008180:Lupus Erythematosus, Systemic / Q000097:blood / Q000175:diagnosis* / Q000276:immunology; D008297:Male; D008875:Middle Aged; D010957:Plasmids; D012680:Sensitivity and Specificity; D055815:Young Adult
chemical_list: D000974:Antibodies, Antinuclear; D001324:Autoantigens; D006657:Histones; D004247:DNA
keywords: Anti-DNA antibodies; Autoantibodies; Autoimmune diseases; Synthetic peptides; Systemic lupus erythematosus