Identification of discrete epitopes of Ro52p200 and association with fetal cardiac conduction system manifestations in a rodent model.

Congenital heart block (CHB) is a potentially lethal condition characterized by a third-degree atrioventricular block (AVB). Despite anti-Ro52 antibodies being detected in nearly 90% of mothers of affected children, CHB occurs in only 1-2% of anti-Ro/Sjögren's-syndrome-related antigen A (SSA) autoantibody-positive pregnancies. Maternal antibodies have been suggested to bind molecules crucial to fetal cardiac function; however, it remains unknown whether a single antibody profile associates with CHB or whether several specificities and cross-reactive targets exist. Here, we aimed to define further the reactivity profile of CHB-associated antibodies towards Ro52p200 (amino acid 200-239). We first analysed reactivity of a monoclonal anti-Ro52 antibody shown to induce AVB in rats (7.8C7) and of sera from anti-Ro52p200 antibody-positive mothers of children with CHB towards a panel of modified Ro52p200 peptides, and subsequently evaluated their potential to induce AVB in rats upon transfer during gestation. We observed that CHB maternal sera displayed a homogeneous reactivity profile targeting preferentially the C-terminal part of Ro52p200, in contrast to 7.8C7 that specifically bound the p200 N-terminal end. In particular, amino acid D233 appeared crucial to maternal antibody reactivity towards p200. Despite low to absent reactivity towards rat p200 and different binding profiles towards mutated rat peptides indicating recognition of different epitopes within Ro52p200, immunoglobulin (Ig)G purified from two mothers of children with CHB could induce AVB in rats. Our findings support the hypothesis that several fine antibody specificities and cross-targets may exist and contribute to CHB development in anti-Ro52 antibody-positive pregnancies.

Incident cases of primary Sjögren's syndrome during a 5-year period in Stockholm County: a descriptive study of the patients and their characteristics.

OBJECTIVES: To define the incidence rate of primary Sjögren's syndrome (pSS) and the prevalence of extraglandular manifestations (EGMs) at the time of diagnosis of pSS in a prospective, population-based manner. METHOD: This study included all consecutive patients referred to the Department of Rheumatology at Karolinska University Hospital for the investigation of incident pSS from 1 January 2007 to 31 December 2011. Investigation was according to the current criteria for pSS, and examination with a focus on the presence of EGMs was performed. RESULTS: Of the referred individuals, 199 out of 781 were diagnosed with pSS. We found an annual incidence rate of pSS in the Karolinska University Hospital catchment area of 3.1 [95% confidence interval (CI) 2.3-4.3] cases per 100 000 adult inhabitants. The female/male ratio of incident cases was 14/1 [frequency (female) = 0.93, 95% CI 0.89-0.96]. In our cohort, we noted lower figures for severe EGMs such as lung and neurological involvement than previously reported for prevalent pSS. The frequency of autoantibodies including antinuclear antibodies (ANA), anti-Ro/SSA, and anti-La/SSB was also lower compared to other cohorts. In our study, autoantibody-positive patients had cytopaenia significantly more often, and in patients older than 60 years primary biliary cirrhosis (PBC) was more common. CONCLUSIONS: The incidence rate of pSS is 3.1 (95% CI 2.3-4.3) per 100 000 person-years. The prevalence of autoantibodies may be lower than previously reported, and at diagnosis, patients with pSS have few severe EGMs.

Autoantibodies to the functionally active RING-domain of Ro52/SSA are associated with disease activity in patients with lupus.

The Ro52 protein of the Ro/SSA antigen was recently defined as an E3 ligase controlling cytokine production. Autoantibodies from systemic lupus erythematosus (SLE) patients targeting the Ro52-RING domain, containing the E3 ligase activity, have been shown to inhibit the E3 ligase activity of Ro52. The objective of the present study was to investigate correlations between clinical parameters in patients with SLE and levels of Ro/SSA (Ro52 and Ro60) and La/SSB autoantibodies, including autoantibodies directed towards the functional RING and B-box domains of the Ro52 protein. SLE patients (n=232) were clinically examined and disease activity indices collected concurrently to blood sampling. The samples were analyzed for immunological parameters including autoantibodies. Ro52 autoantibody levels were associated with more variables than the other analyzed antibodies and were significantly associated with several individual items related to sSS and the diagnosis of sSS itself (p=0.004). Other associated variables were high sedimentation rate (p=0.0003), levels of immunoglobulins (p=0.0003), and an inverse correlation with levels of lymphocytes (p=0.003) and leukocytes (p=0.01). Antibodies to the RING domain of Ro52, which is the functionally active domain with E3 ligase activity, were significantly correlated with disease activity as measured by the SLAM score. We conclude that autoantibodies against Ro52 and in particular its functional RING domain are important in lupus patients and associated with several clinical and laboratory features of the disease. The impact on disease activity of Ro52-RING specific antibodies was especially noted, and could imply a functional role for these autoantibodies in inhibiting Ro52 activity, which is important for the control of proinflammatory cytokine production, including type 1 interferons.