Background/Purpose: Clonal hematopoiesis of indeterminate potential (CHIP) is defined by somatic mutations in a set of genes commonly associated with myeloid neoplasms in an otherwise healthy individual. CHIP prevalence increases with age and is associated with all-cause mortality and atherosclerosis. The prevalence of CHIP mutations in systemic vasculitis and other inflammatory diseases has not been well characterized. We examined the prevalence of CHIP in systemic vasculitis across the age spectrum and uncovered functional consequences of CHIP mutations in vasculitis.

Methods: DNA from peripheral whole blood and isolated monocytes was sequenced on an error-correcting targeted sequencing panel to identify clonal hematopoiesis mutations (VAF≥0.5%). Logistic regression was used to assess associations of age, vasculitis, and CHIP. Relative contribution of predictor variables was assessed using standardized beta coefficients. Monocytes were isolated from patients with giant cell arteritis (GCA) and healthy control PBMCs via CD14 magnetic bead separation and stimulated with combinations of IFNg, LPS, and ATP. Cytokine and chemokine expression in the cell culture supernatant was measured via multiplex analysis.

Results: 171 patients with vasculitis [Takayasu’s arteritis, TAK: n=70; mean age=33.7 years; ANCA-associated vasculitis, AAV: n=47; mean age=55.3 years; GCA: n=54; mean age=70.2 years), and age-matched healthy controls (n=120) were studied. CHIP mutations were prevalent in 58% of GCA, 36% of AAV, and 15% of TAK compared to 32%, 23% and 8% of 1:1 age-matched healthy controls for each disease, respectively. Age (b=0.96, p< 0.001) and vasculitis (b=0.46, p=0.004) were independently associated with CHIP. The most common affected genes were DNMT3A (n=69/109,63%) and TET2 (n=19/109,17%). Vasculitis patients with CHIP had lower circulating absolute lymphocyte counts (p=0.03) and higher absolute neutrophil counts (p=0.04) than those without CHIP. The neutrophil-to-lymphocyte ratio was significantly associated with presence of CHIP (p=0.02). Compared to stimulation of CHIP- monocytes, stimulated CHIP+ monocytes had significantly increased expression of IL-8 (LPS+IFNg (p=0.048)), IL-27 (LPS+IFNg (p=0.016)) and CXCL10 (LPS+IFNg (p=0.016)) in monocytes with a VAF of 2.0% or higher and increased expression of TNFa (LPS+IFNg (p=0.012)), MIP-1a (LPS (p=0.034), LPS+IFNg (p=0.012)) and CCL2 (IFNg (p=0.021)) regardless of VAF.

Conclusion: Vasculitis and age are independently associated with CHIP. Peripheral blood from CHIP+ vasculitis patients skews towards myeloid lineages. Monocytes harboring CHIP mutations secrete more CCL2 and CXCL10 when stimulated, which are important chemokines in vascular disease. Inflammation is both a cause and consequence of CHIP.

« Back to ACR Convergence 2022

ACR Meeting Abstracts - https://acrabstracts.org/abstract/complex-relationships-between-inflammation-and-clonal-hematopoiesis-in-systemic-vasculitis/