THU0319 Determination of the Serological Profiles in Anti-Ro-52-Positive Patients with Systemic Autoimmune Rheumatic Diseases.
Authors: F. Atzeni, P. Sarzi-Puttini, M. Infantino, B. Olivito, M. Benucci, W. Mayer, A. Ott, M. Manfredi
Journal: Annals of the Rheumatic Diseases (2013)

<h3>Background</h3> Ro-52 is an interferon (IFN)-inducible protein of the tripartite motif (TRIM) family. Antibodies against Ro-52 have been described in patients with different autoimmune diseases such as systemic lupus erythematosus (SLE) and Sjogren's syndrome (SS), which are often associated with anti-Ro-60 antibodies. However, in inflammatory myositis, anti-Ro-52 antibodies are frequently present without anti-Ro-60 antibodies. Ro-52 autoantigen is extraordinarily antigenic and its autoantibodies are directed <i>against</i>both linear and conformational epitopes. <h3>Objectives</h3> The first aim of the study was to evaluate antibodies against the full length of the Ro-52 antigen (Ro-52) and its five fragments, and their association with serological and clinical data. The second aim was to assess the prevalence of anti-full-length Ro-52 and its five fragments in different systemic autoimmune rheumatic diseases (SARDs). <h3>Methods</h3> Serum samples were obtained from 78 SARDs patients and 68 controls (50 healthy donors and 18 patients with other autoimmune diseases). Ro-52 antibodies were measured using four different <b>Methods:</b> Bioplex2200 Multiplex-Biorad (Laboratories Inc. Hercules, CA, USA), ANA Profile3-Blot, Profile Autoimmune Liver Diseases-Blot, and Myositis Profile3-Blot EUROIMMUN AG. (EUROIMMUN AG, Lubeck, Germany). Serum was considered positive for anti-Ro-52 when at least one of these methods revealed their presence. Full-length Ro-52 antigen was expressed in insect cells using the baculovirus system, and five recombinant Ro-52 antigen fragments [Ro-52-1, Ro-52-2, Ro-52-3, Ro-52-4 (partly overlapping Ro-52-1 and -2) and Ro-52-5 (partly overlapping Ro-52-2 and -3)] expressed in <i>E. coli,</i> were coated onto nitrocellulose membranes in a line immunoassay system. Sera were incubated in accordance with the manufacturers standard protocol (30 min serum, 30 min anti-human IgG/alkaline phosphatase, 10 min NBT/BCIP substrate). Prevalence and reaction intensities were automatically evaluated using the commercial computer programme EUROLineScan from EUROIMMUN AG. <h3>Results</h3> All of the samples obtained from the SARDs patients were positive for antibodies against the full-length Ro52 and fragment 2, except those obtained from the myositis patients. None of the sera samples of the patients and controls were positive for anti-Ro-52-3. Moreover, all of the control samples were negative for the full-length Ro52 and all of the fragments. Myositis group (n=3) gave an isolated but very weak reaction with the full length Ro-52 and displayed no reaction with the fragments. In the SARDs patients, the fragment prevalence rates were Ro-52-1= 4/82 (4.9%), Ro-52-2= 79/82 (96.3%), Ro-52-3= 0/82 (0%), Ro-52-4= 6/82 (7.3%) and Ro-52-5= 22/82 (26.8%). <h3>Conclusions</h3> The main epitope is localised on fragment 2, and all diseases have antibodies that target this fragment. Antibody positivity for full-length Ro52 and negativity for all five fragments suggests a diagnosis of myositis. As all of the samples were positive for fragment 2, and only some for fragments 5 or 4, it seems that the target epitope is localized in the middle of fragment 2 or in the area between fragments 4 and 5. Further studies involving a large number of patients are suggested to confirm our findings. <h3>Disclosure of Interest</h3> None Declared