Antinuclear antibodies (ANA) have been reported to occur in >50% of patients with juvenile rheumatoid arthritis (JRA) (1-4). Although ANA are

Objective. To determine the antibody profiles in sera from patients with juvenile rheumatoid arthritis (JRA).Methods. Immunoblotting using nuclear extracts and recombinant high-mobility group (HMG) nonhistone chromosomal proteins.Results. Antibodies directed against HMG-17 were found in 47% of antinuclear antibody (ANA)-positive patients with pauciarticular-onset JRA and in 16% of ANA-positive patients with polyarticular-onset JRA. HMG-17 values of 6% and 8%, respectively, were detected in ANA-negative patients with JRA and in those with nonrheumatic diseases.Conclusion. There is evidence for a high prevalence of anti-HMG-17 antibodies in sera of patients with pauciarticular-onset JRA.Juvenile rheumatoid arthritis (JRA) is a complex childhood disease of varying severity and prognosis and is a leading cause of childhood disability. Antinuclear antibodies (ANA) are found in serum samples from many children with JRA, but very little is known about the antigenic specificities and the prognostic value of ANA in JRA patients. The presence of antibodies to histones, especially to histone H1, and to the high-mobility group (HMG) nonhistone nucleosomal proteins HMG-I and HMG-2 in the sera of ANA-positive patients with JRA has been demonstrated recently by the use of immunoblotting techniques (1-3). In followup experiments with the recombinant HMG-17 protein as antigen, the additional immunoreactive band observed at 17-kd in perchloric acid extracts could be identified as the high-mobility group chromosomal protein HMG-17. This small protein is present in the nuclei of all higher eukaryotes and binds to DNA and histones (4). In this study, we report our findings of antibodies against the HMG-17 protein in a high percentage of ANA-positive pauciarticularonset JRA patient sera. PATIENTS AND METHODSPatients. Serum samples from 153 ANA-positive JRA patients (119 girls and 34 boys) admitted to the Rheumatic Children's Hospital (Garmisch-Partenkirchen. FRG) were examined in this study. All patients had an established diagnosis of JRA, according to the American College of Rheumatology (formerly, the American Rheumatism Association) criteria (5). The mean age of those with pauciarticular-onset JRA was 9.4 years (range 2-26 years), and it was 12.9 years (range 3-25 years) in those with polyarticular-onset JRA.The children were further classified according to clinical features: 57 of the 116 patients with pauciarticularonset JRA had uveitis, and 3 of the 37 patients with polyarticular-onset JRA had uveitis. None of the patients had been treated at any time with D-penicillamine, sulfasalazine, or related drugs. Sera from 54 ANA-negative JRA patients and from 6S age-matched children who were treated for temporary, nonrheumatic illnesses were used as controls.

Objective. To extend our work on the mapping of B cell epitopes on nucleosomal high mobility group (HMG) proteins in the sera of patients with juvenile rheumatoid arthritis (JRA).Methods. Seventy-seven pauciarticular-onset JRA serum samples from antinuclear antibody (ANA)-positive patients and 42 polyarticular-onset JRA patient sera found to react with HMG-2 by immunoblotting were used in this study. To identify B cell epitopes on HMG-2, recombinant HMG-2 protein fragments were used in enzyme-linked immunosorbent assay (ELISA) and in competition ELISA experiments with a set of overlapping synthetic peptides. Fine epitope mapping was achieved by oligopeptide synthesis, followed by immunoblotting.Results. Pauciarticular, but not polyarticular, JRA patient sera were found to recognize a lysine-rich major epitope (KKGKKKDP), which is located in the linker region of the HMG box domains of the HMG-2 nonhistone chromosomal protein. No significant immunoreactions were observed in sera from ANA-negative JRA patients and in sera from children with nonrheumatic diseases, indicating that this epitope seems to be specific for pauciarticular-onset JRA.Conclusion. In addition to our previous finding that JRA sera will react with a defined epitope on HMG-17, pauciarticular JRA patient sera were also found to recognize a defined epitope on the HMG-2 protein, thus suggesting the importance of this epitope in the etiology of JRA. Antinuclear antibodies (ANA) are found in a high proportion of sera from children with juvenile rheumatoid arthritis (JRA) (1,2). However, to date, very little is known about the antigenic specificities and the prognostic value of ANA in JRA. Recently, we demonstrated the presence of autoantibodies to the high mobility group (HMG) nucleosomal proteins HMG-1, HMG-2, and HMG-17 in the sera of ANA-positive patients with JRA (3,4). These small chromosomal proteins are among the most abundant, ubiquitous, and evolutionary conserved nonhistone proteins found in the nuclei of higher eucaryotes. Using immunoblotting techniques, we found that sera from patients with pauciarticular-onset JRA and polyarticular-onset JRA recognized the HMG-112 proteins with similar frequencies (40% versus 30%), whereas the pauciarticular-onset JRA patient sera had a higher prevalence of anti-HMG-17 antibodies than did the polyarticular-onset JRA sera (47% versus 16%) (4). No significant reactions with the HMG-14 protein were observed on immunoblot. Competition enzyme-linked immunosorbent assay (ELISA) experiments defined the octapeptide, PKPEP-KF' K, at positions 34-42 in the HMG-17 protein, as a major B cell epitope, which was recognized by more than 70% of the HMG-17-positive JRA sera (5).In this report, an extension of our work on the mapping of B cell epitopes on HMG proteins in JRA patient sera is presented. For partial epitope mapping, polymerase chain reaction (PCR)-generated recombinant HMG-2 (rHMG-2) protein fragments were used in ELISA experiments with pauciarticular and polyarticular JRA patient sera. By using a set of ove...

Autoantibodies against the nonhistone nucleosomal protein HMG-17 have been detected in a high percentage of ANA-positive patients with pauciarticular-onset JRA4. Here we report on the epitope mapping of the HMG-17 autoantigen with a set of overlapping and nested synthetic peptides spanning the entire amino acid sequence of the human HMG-17 protein. Competition ELISA experiments defined a proline and lysine rich octapeptide PKPEPKPK as the major epitope recognized by more than 70% of the HMG-17 positive JRA sera. Point mutations introduced in the autoimmune peptide determined the amino acid residues important for autoantibody recognition. Computer based sequence comparison shows close homology between the HMG-17 autoimmune epitope and certain infectious organisms, supporting the possibility that molecular mimicry is an important factor in the etiology of JRA.