118. Changes in the frequency of T-regulatory cell subsets can distinguish disease activity in ANCA vasculitis
Creators: name: Christian Agosto-burgos1, 2
name: Wu2, Eveline Y
name: Henderson2, Candace
name: Yichun Hu2
name: Hogan2, Susan
name: Dominic  Ciavatta1,2,3
name: J. Charles  Jennette1, 2
name: Ronald J.  Falk1, 2
name: Meghan  Free1, 2
Publisher: name: Zenodo
Year: 2022
Subjects: Vasculitis
ANCA
Abstracts
Giant Cell Arthritis
MPA
GPA
EGPA
Takayasu
IgA vasculitis

description: <strong>Background:</strong> Anti-neutrophil cytoplasmic autoantibody (ANCA) vasculitis is characterized by cycles of remitting and relapsing stages. Previous data demonstrate that T-regulatory cells (Tregs) are defective in ANCA vasculitis and that the expression of a FoxP3 variant lacking exon 2 in CD4+ T cells (FoxP3Δ2) is negatively correlated with suppressive capacity. Furthermore, the major grade of Treg dysfunctionality is exhibited during active disease suggesting that Treg biology could be exploited as a biomarker of disease activity and as a therapeutic target in ANCA vasculitis. Previous studies regarding Tregs in ANCA vasculitis examined bulk Tregs. However, with the recent advances in Treg biology, it is evident that Tregs are a heterogeneous group of immunoregulatory cells. Changes in the phenotype, frequency, and suppressive capacity of Treg subsets have been identified in other autoimmune diseases. However, in ANCA vasculitis, Treg heterogeneity and its implications in disease prognosis and treatment remain unexplored. We hypothesized that changes in the frequency of Treg subsets will distinguish disease activity in ANCA vasculitis. <strong>Methods:</strong> Patients with ANCA vasculitis and healthy controls were enrolled according to approved study guidelines Institutional Review Board (IRB study 97-0523). Active disease and remission were defined as a BVAS ≥ 3 or BVAS of 0 and with or without clinical and/or laboratory evidence of disease within 3 months of the sample, respectively. Blood samples from study participants were collected to measure the frequency of Treg subsets using Mass Cytometry, and data were analyzed using Cytobank. Non-parametric Mann-Whitney test was used to assess the significance of the changes in the frequency of Treg subsets. Non-parametric discriminant analysis using Normal Kernel Density estimation was applied to determine the optimal combination of Treg markers to distinguish disease activity status. A value of p £ 0.05 was considered significant for both statistical methods. Results: We found that patients in remission have expanded frequency of Tregs regardless of the administration of Rituximab. No association between disease activity and the frequency of FoxP3Δ2 CD4+ T cells were observed in our cohort. Additionally, FoxP3Δ2 CD4+ T cells are CD127<sup>high</sup> and CD25<sup>low</sup> suggesting that they are not bonafide Tregs. Interestingly, both CCR7+ and CD103+ Tregs are expanded during active disease. In contrast, CXCR3+ Tregs are decreased during active disease and their frequency was negatively correlated with the BVAS score. We also discovered that CXCR3+ Tregs are preferentially reduced in patients with renal involvement. Furthermore, we demonstrated that a combination of the frequency of CXCR3+, CCR7+, and CD103+ Tregs more accurately distinguishes disease activity than individual markers. Conclusions: Little is known about what underlies Treg dysfunctionality in ANCA vasculitis. This is the first study to identify changes in specific Treg subsets and their possible implications in disease. Understanding Treg heterogeneity and implications for organ involvements could open an avenue for the development of new therapeutic approaches. Our data demonstrate, that changes in the frequency of CXCR3+, CCR7+, and CD103+ Tregs reflect disease activity. Further studies will examine whether these subsets are the underlying cause of Treg dysfunctionality in ANCA vasculitis. Furthermore, as CXCR3 Tregs have been shown to be protective against autoimmune diseases in murine models, they are poised to become a prime candidate for new therapies tailored to patients with renal ANCA vasculitis. <strong>Disclosures</strong>: None. <strong>Figure 1</strong> <strong>A combination of the frequency of CXCR</strong><strong>3+, CCR7+, and CD103+ Tregs distinguishes active disease in ANCA vasculitis:</strong> The frequency of CXCR3+, CCR7+, and CD103+ was measured using Mass cytometry and plotted in a three-dimensional plot. Non-parametric discriminant analysis using Normal Kernel Density estimation was applied to determine the optimal combination of Treg markers to distinguish disease activity status. A value of p £ 0.05 was considered significant.