Background/Purpose: Juvenile dermatomyositis (JDM) is an inflammatory myopathy characterized by prominent vascular and perivascular inflammation in affected skeletal muscles. The mechanisms of vessel injury in JDM remain unknown. Anti-endothelial cell antibodies (AECA) are frequently detected in inflammatory, infectious, and autoimmune diseases. We hypothesized that autoimmunity to blood vessel antigens may play a role in the pathology of JDM. We therefore, used proteomic approaches to identify target antigens for AECA in plasma from patients with JDM.

Methods: Proteins extracted from human aortic endothelial cells (HAEC) were separated by two-dimensional electrophoresis and transferred onto membranes. Western blotting using plasma from JDM and healthy controls was performed to detect antigens that were positive in JDM plasma, but not in healthy controls. Finally, the detected proteins were identified by peptide mass finger-printing. We next used ELISA assays to corroborate the mass spectrometry data, using plasma samples from 63 patients with JDM, 50 patients with polyarticular juvenile idiopathic arthritis (JIA) and 40 sex- and age-matched healthy controls. Nineteen patients with Kawasaki disease (KD) and 18 additional sex- and age-matched healthy controls were also used for ELISA assays. The differences in antibody levels and the frequency of autoantibodies between the groups were compared by Mann-Whitney U test and by Fisher’s exact test, respectively. P values were determined with a two-tailed tests.

Results: Twenty-two proteins were identified as candidate targets of AECA in plasma from JDM patients. Among these antigens were molecular chaperones such as heat shock cognate 71 kDa protein (HSC70). On ELISA assays, we found significant differences (p< 0.0001) in mean OD ± SD for autoantibodies against HSC70 when children with JDM were compared to healthy controls, and to children with JIA and KD. Autoantibodies to HSC70 were detected in 35% of patients with JDM, in 0% of healthy donors (P< 0.0001), 0% of patients with JIA (P< 0.0001), and 0% of patients with KD (P=0.002). The presence of autoantibodies against HSC70 correlated with the presence of other previously described myositis-associated autoantibodies (MAA). For example, antibodies against NT5C1A and Ro52 were more frequent in patients with autoantibodies against HSC70 than with these MAAs alone (69% vs. 29%, P=0.013 and 43% vs. 15%, P=0.027). The presence of skin ulcers was associated with autoantibodies against HSC70 (59% vs. 17%, P=0.0014). Use of wheelchairs and/or devices was associated with HSC70 autoantibodies (64% vs. 27%, P=0.007). We found significant differences (P=0.019) in mean serum levels of aspartate aminotransferase (AST) in JDM children with (32 ± 15 U/L) vs. without (25 ± 16 U/L) autoantibodies against HSC70.

Conclusion: Autoantibodies to HSC70 in the proteome of HAEC are present in the plasma of patients with JDM, implying that AECA may be involved in the pathophysiology of autoimmune inflammation of blood vessels in JDM. Larger studies will be required to determine the clinical utility of monitoring for these autoantibodies.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/clinical-correlations-of-autoantibodies-against-heat-shock-cognate-71-kda-protein-in-patients-with-juvenile-dermatomyositis/