Background/Purpose: The disease progression of patients (pts.) with type-I interferon (IFN)-mediated diseases undergoing treatment with JAK1 and JAK2 inhibitors is monitored in part by measuring the transcription of a 28 IFN response gene (IRG) signature in whole blood with Nanostring technology, a 28-gene standardized IFN score is calculated. We sought to determine differences in 28-gene standardized IFN scores and in the patterns of IRG signatures among peripheral blood mononuclear cells (PBMCs), isolated monocytes, dendritic cells, neutrophils, and skin biopsies in the Type-I IFN-mediated diseases CANDLE (chronic atypical neutrophilic dermatosis with lipodystrophy and elevated temperatures) and SAVI (STING-associated vasculopathy with onset in infancy) compared to whole blood IRG signatures.

Methods: RNA was extracted from pt. and healthy control whole blood, PBMCs, monocytes, neutrophils, dendritic cells (DC), and skin biopsies. After cells isolation by Ficoll (PBMC), CD14 (monocytes) or CD123 (DC) magnetic bead isolation and density gradient separation with red blood cell lysis (neutrophils), RNA was extracted. Transcript counts for 28 IRGs and 4 additional genes were measured with a NanoString instrument, normalized based on the expression of 4 housekeeping genes in the sample, and scored as the sum of the 28-genes’ z-scores compared to expression in the same cells or tissues in a cohort of healthy controls.

Results: Both CANDLE (n=4) and SAVI (n=5) patients have significantly greater 28-gene standardized IFN scores in whole blood, PBMCs than healthy controls (n=10). Higher IFN scores were seen in SAVI PBMCs as compared to SAVI whole blood, while CANDLE PBMC IFN scores were not different compared to CANDLE whole blood.SAVI PBMCs had significantly higher 28-gene IFN scores than CANDLE PBMCs (2003 ±2301 vs. 352.3 ±285.5, p=0.0082). In addition, SAVI PBMCs transcribed higher levels of IFNA2 (7068 ±14434 vs. 3.158 ±0.657) and IFNB1(8452±16468 vs. 2.119 ±0.619) than PBMCs from CANDLE pts., corroborating RNAseq data that demonstrates highest Type-I IFN expression in the monocytes followed by dendritic cells of SAVI pts.  One family of 3 patients with SAVI who had a novel STING missense variant had very elevated IFN scores in their PBMCs, while their whole blood IFN score was not considered to be elevated. Nanostring performed on RNA from skin tissue from 3 CANDLE and 3 SAVI pts. demonstrated a distinct distribution of the 28 IRGs in comparison with whole blood, with a relatively higher contribution of CXCL10to the 28-gene IFN score.

Conclusion: High expression of Type-I IFNs and IRGs in the PBMCs of SAVI pts. may demonstrate the role of myeloid cells in the amplification of constitutive IFN signaling in SAVI. In addition, pts. with a SAVI phenotype but a negative IRG signature in whole blood may only have an IRG signature in the PBMC fraction. Differences in IRG transcription profiles demonstrate that responses to IFN signaling are not uniform among cell subsets in different Type-I IFN-mediated diseases.

Funding for this study was provided in part by the Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/interferon-response-gene-expression-differs-in-whole-blood-peripheral-blood-mononuclear-cells-monocytes-dendritic-cells-neutrophils-and-skin-tissue-in-patients-with-the-autoinflammatory-interfero/