Background/Purpose: Children with Juvenile Dermatomyositis (JDM) have variable responses to the available immunosuppressive drugs, with less than optimal outcomes, making it essential to characterize their variable inflammatory response. It is recognized that Myositis Specific Antibodies (MSA) are each associated with different clinical features and disease course, but scarce information is available comparing the differences in genetic regulation among these MSAs . The purpose of this study was to compare RNASeq data from PBMCs obtained from untreated children with new onset JDM positive for p155/150 — the most common MSA — with the RNASeq data from age related controls, as well as JDM who were either positive for MJ or who did not have a recognized MSA. Clinically, children with p155/140 often follow a more variable and recurrent disease course than those patients with other MSA’s.

Methods: Newly diagnosed, untreated children with JDM were recruited for this IRB approved study (2008-13457), after obtaining age-appropriate informed consent: there were 75% girls, mean age 7.2 ±4.1; Mean DAS=12/20, while the controls had 80% girls, but were slightly older, 16.9±2.9. JDM disease activity was assessed using the Disease Activity Scores (DAS) which range from 0-20. MSA were determined by immunoblot and immunoprecipitation, (Oklahoma Research Laboratory): 4 of the JDM were positive for p155/140, 2 were MJ+, and 2 were negative for MSA, compared with 5 healthy pediatric controls. RNASeq libraries were generated from PBMC RNA using the Clontech stranded high input ribosomal depletion total RNA kits. The samples were sequenced on either an Illumina HiSeq2500 or HiSeq300 in paired-end mode. Serum levels of antibody to specific cytokines were determined by Mesoscale.

Results: The untreated JDM had active disease with a mean DAS-total=12.1. The RNASeq data identify 96 genes (adjusted p-value < 0.05) differentially expressed between JDM who were p155/140+ and JDM who either had anti-MJ antibody or were negative for MSA. The overall expression pattern of these genes is also different from the healthy controls. Pathway and gene ontology analysis reveals significant enrichment of this gene list in immune response, especially the interferon signaling (P=2*10-15). We identified among this gene list, OSA1,2,3, TNF, MX1,2, TRIM 14, 22, 25, IFNG, TNFαA1P3, TNFSF-10, TGFBR3, IL-2RB, and others, clearly indicating enhanced immune activation in the children positive for p155/140. Determination of some of the many cytokines involved in the JDM inflammatory pathway showed significant increases in p155/140 sera vs controls: Interferon- γ: p= 0.013, IL-10:p= 0.0056, IL-6: p=0.026; IL-8: p=0.011; TNF-α p=0.003892.

Conclusion: We have shown, for the first time, using RNASeq, that the MSA, p155/140 not only identifies children with JDM who will have a difficult diseases course — but that this MSA is also associated with specific enhanced immune activation. Speculation: Further definition of the specific differences in gene activation associated with the individual MSA’s may lead to more targeted therapeutic interventions, and may provide a means of assessing the child’s response to therapy.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/rnaseq-detection-of-gene-dysregulation-in-pbmcs-from-juvenile-dermatomyositis-positive-for-p155140-myositis-specific-antibody/