Identification of clonally expanded T-cell receptor sequences in giant cell arteritis

Background: Arterial wall inflammation in giant cell arteritis (GCA) is characterized by T-cell infiltration and granuloma formation. There have been limited studies investigating the diversity of the T-cell receptor (TCR) repertoire in GCA patients. Here we aim to identify disease-relevant TCRs. Methods: We sequenced the TCR repertoires in peripheral blood and biopsies from 72 GCA patients and compared them to repertoires of 60 age-matched controls. Applying K-nearest neighbours classification based on tcrdist3, an established TCR similarity measure, we identified GCA-associated TCRs across multiple model hyperparameters and experimental replicates. Results: We observed that species richness and Shannon diversity were significantly lower (P=0.0003 and P=0.004, respectively) in GCA peripheral blood TCR repertoires compared with age-matched controls. 1526 TCRs were identified that were consistently associated with GCA, 63 TCRs were also detected in TAB repertoires. Identical GCA-associated TCRs were observed in paired blood and tissue samples from 21/30 GCA cases. 57% of GCA-associated TCRs were fitted into 10 clusters, which displayed distinct TCR sequences and TCR V and J segment usage. TRBV20-1*01, TRBV4-3*01, TRBV4-2*01 and TRBV4-1*01 segments were over-represented and occurred at least 10% more often among GCA patients than age-matched controls. Only 27/1526 TCR sequences had matches reported in public databases, reducing the likelihood that these targeted common infectious agents. Conclusions: Our data provide evidence of circulating T-cell clonal expansions in GCA patients. Certain TCR sequence patterns were over-represented in GCA subjects. As more TCR sequences directed at human antigens become available, further analysis may ultimately reveal whether these TCRs bind a common target antigen

Age, anticoagulants, hypertension and cardiovascular genetic traits predict cranial ischaemic complications in patients with giant cell arteritis

\ua9 Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ on behalf of EULAR.Objectives: This project aimed to determine whether cranial ischaemic complications at the presentation of giant cell arteritis (GCA) were associated with pre-existing cardiovascular (CV) risk factors, CV disease or genetic risk of CV-related traits. Methods: 1946 GCA patients with clinicodemographic data at GCA presentation were included. Associations between pre-existing CV-related traits (including Polygenic Risk Scores (PRS) for CV traits) and cranial ischaemic complications were tested. A model for cranial ischaemic complications was optimised using an elastic net approach. Positional gene mapping of associated PRS was performed to improve biological understanding. Results: In a sample of 1946 GCA patients (median age=71, 68.7% female), 17% had cranial ischaemic complications at presentation. In univariable analyses, 10 variables were associated with complications (likelihood-ratio test p≤0.05). In multivariable analysis, the two variables with the strongest effects, with or without PRS in the model, were anticoagulant therapy (adjusted OR (95% CI)=0.21 (0.05 to 0.62), p=4.95 710-3) and age (adjusted OR (95% CI)=1.60 (0.73 to 3.66), p=2.52 710-3, for ≥80 years versus <60 years). In sensitivity analyses omitting anticoagulant therapy from multivariable analysis, age and hypertension were associated with cranial ischaemic complications at presentation (hypertension: adjusted OR (95% CI)=1.35 (1.03 to 1.75), p=0.03). Positional gene mapping of an associated transient ischaemic attack PRS identified TEK, CD96 and MROH9 loci. Conclusion: Age and hypertension were risk factors for cranial ischaemic complications at GCA presentation, but in this dataset, anticoagulation appeared protective. Positional gene mapping suggested a role for immune and coagulation-related pathways in the pathogenesis of complications. Further studies are needed before implementation in clinical practice

Somatostatin Receptor PET/MR Imaging of Inflammation in Patients With Large Vessel Vasculitis and Atherosclerosis

Background: Assessing inflammatory disease activity in large vessel vasculitis (LVV) can be challenging by conventional measures. Objectives: We aimed to investigate somatostatin receptor 2 (SST2) as a novel inflammation-specific molecular imaging target in LVV. Methods: In a prospective, observational cohort study, in vivo arterial SST2 expression was assessed by positron emission tomography/magnetic resonance imaging (PET/MRI) using 68Ga-DOTATATE and 18F-FET-βAG-TOCA. Ex vivo mapping of the imaging target was performed using immunofluorescence microscopy; imaging mass cytometry; and bulk, single-cell, and single-nucleus RNA sequencing. Results: Sixty-one participants (LVV: n = 27; recent atherosclerotic myocardial infarction of ≤2 weeks: n = 25; control subjects with an oncologic indication for imaging: n = 9) were included. Index vessel SST2 maximum tissue-to-blood ratio was 61.8% (P < 0.0001) higher in active/grumbling LVV than inactive LVV and 34.6% (P = 0.0002) higher than myocardial infarction, with good diagnostic accuracy (area under the curve: ≥0.86; P < 0.001 for both). Arterial SST2 signal was not elevated in any of the control subjects. SST2 PET/MRI was generally consistent with 18F-fluorodeoxyglucose PET/computed tomography imaging in LVV patients with contemporaneous clinical scans but with very low background signal in the brain and heart, allowing for unimpeded assessment of nearby coronary, myocardial, and intracranial artery involvement. Clinically effective treatment for LVV was associated with a 0.49 ± 0.24 (standard error of the mean [SEM]) (P = 0.04; 22.3%) reduction in the SST2 maximum tissue-to-blood ratio after 9.3 ± 3.2 months. SST2 expression was localized to macrophages, pericytes, and perivascular adipocytes in vasculitis specimens, with specific receptor binding confirmed by autoradiography. SSTR2-expressing macrophages coexpressed proinflammatory markers. Conclusions: SST2 PET/MRI holds major promise for diagnosis and therapeutic monitoring in LVV. (PET Imaging of Giant Cell and Takayasu Arteritis [PITA], NCT04071691; Residual Inflammation and Plaque Progression Long-Term Evaluation [RIPPLE], NCT04073810

Somatostatin receptor PET/MR imaging of large vessel inflammation in active compared with inactive vasculitis and atherosclerosis

Abstract Background Use of 18F-FDG PET in large vessel vasculitis (LVV) is limited by non-specific uptake due to arterial remodelling and/or atherosclerosis leading to diagnostic uncertainty. Purpose To investigate somatostatin receptor 2 (SST2) as a novel inflammation-specific PET imaging target in LVV. Methods In a prospective observational cohort study, we tested the ability of PET/MRI using two somatostatin receptor tracers (68Ga-DOTATATE and 18F-FET-βAG-TOCA) to differentiate active from inactive LVV, and aortic atherosclerosis in patients with recent myocardial infarction. Ex vivo mapping of the imaging target was performed using immunofluorescence microscopy, imaging mass cytometry, and bulk, single-cell and single-nuclei RNA sequencing of temporal artery biopsies from LVV patients. Results Sixty-one participants were included (LVV, n=27; myocardial infarction ≤2 weeks, n=25; control subjects with an oncological indication for imaging, n=9). LVV patients (mean age 58 [SD 16] years; 78% female; 63% active or grumbling disease) had giant cell arteritis (n=13), Takayasu arteritis (n=13), or unspecified LVV (n=1). Baseline index vessel SST2 PET maximum tissue-to-blood ratio (TBRmax) was 61.8% (95% CI 31.5–99.0%, p&amp;lt;0.0001) higher in patients with active/grumbling LVV than inactive LVV, and 34.6% (95% CI 15.1–57.6%, p=0.0002) higher than recent myocardial infarction (Fig. 1a–c; arrow: PET signal; arrowhead: aortic thickening; asterisk: aortic atherosclerosis), with good diagnostic accuracy (AUC ≥0.86, p&amp;lt;0.001 for both). None of the control subjects without LVV or MI had increased arterial SST2 PET signal (Fig. 1d). Mean aortic TBRmax was strongly correlated with Indian Takayasu Clinical Activity Score (r=0.82 [95% CI 0.46–0.95], p=0.001) and maximum wall thickness on MRI (r=0.68 [95% CI 0.31–0.87], p=0.002). SST2 PET/MRI was generally consistent with 18F-FDG PET/CT in LVV patients with contemporaneous scans (Fig. 1a, b), but with very low background signal in the brain and heart allowing for unimpeded assessment of nearby coronary, myocardial, and intracranial artery involvement. On follow-up imaging after a mean 9.3 (SD 3.2) months, clinically effective treatment for LVV was associated with a 0.49 ±SEM 0.24 (p=0.04; 22.3%) reduction in SST2 PET TBRmax, with good scan-scan repeatability in inactive LVV patients with no change in treatment (ICC 0.86, 95% CI 0.04–0.99). SST2 localised to macrophages, pericytes, and perivascular adipocytes in inflamed arterial specimens (Fig. 2; a: H&amp;E; b: imaging mass cytometry; arrow: SST2/CD68 co-staining). SSTR2-expressing macrophages co-expressed pro-inflammatory markers (S100A8, S100A9). Specific SST2 radioligand binding was confirmed by autoradiography in LVV specimens. Conclusion This is the first study to examine SST2 PET/MRI in LVV and to provide histological and gene expression data for validation. Here we show this novel approach holds major promise for diagnosis and therapeutic monitoring in LVV. Funding Acknowledgement Type of funding sources: Foundation. Main funding source(s): Wellcome Trust; Imperial NIHR Biomedical Research Centre </jats:sec

Age, Anti-coagulants, Hypertension and Cardiovascular Genetic Traits predict Cranial Ischaemic Complications in patients with Giant Cell Arteritis

Objectives: This project aimed to determine whether cranial ischaemic complications at the presentation of giant cell arteritis (GCA) were associated with pre-existing cardiovascular (CV) risk factors, CV disease or genetic risk of CV-related traits. Methods: 1946 GCA patients with clinicodemographic data at GCA presentation were included. Associations between pre-existing CV-related traits (including Polygenic Risk Scores (PRS) for CV traits) and cranial ischaemic complications were tested. A model for cranial ischaemic complications was optimised using an elastic net approach. Positional gene mapping of associated PRS was performed to improve biological understanding. Results: In a sample of 1946 GCA patients (median age=71, 68.7% female), 17% had cranial ischaemic complications at presentation. In univariable analyses, 10 variables were associated with complications (likelihood-ratio test p≤0.05). In multivariable analysis, the two variables with the strongest effects, with or without PRS in the model, were anticoagulant therapy (adjusted OR (95% CI)=0.21 (0.05 to 0.62), p=4.95×10−3) and age (adjusted OR (95% CI)=1.60 (0.73 to 3.66), p=2.52×10−3, for ≥80 years versus &lt;60 years). In sensitivity analyses omitting anticoagulant therapy from multivariable analysis, age and hypertension were associated with cranial ischaemic complications at presentation (hypertension: adjusted OR (95% CI)=1.35 (1.03 to 1.75), p=0.03). Positional gene mapping of an associated transient ischaemic attack PRS identified TEK, CD96 and MROH9 loci.Conclusion Age and hypertension were risk factors for cranial ischaemic complications at GCA presentation, but in this dataset, anticoagulation appeared protective. Positional gene mapping suggested a role for immune and coagulation-related pathways in the pathogenesis of complications. Further studies are needed before implementation in clinical practice

Somatostatin Receptor PET/MR Imaging of Inflammation in Patients With Large Vessel Vasculitis and Atherosclerosis

Background: Assessing inflammatory disease activity in large vessel vasculitis (LVV) can be challenging by conventional measures. Objectives: We aimed to investigate somatostatin receptor 2 (SST2) as a novel inflammation-specific molecular imaging target in LVV. Methods: In a prospective, observational cohort study, in vivo arterial SST2 expression was assessed by positron emission tomography/magnetic resonance imaging (PET/MRI) using 68Ga-DOTATATE and 18F-FET-βAG-TOCA. Ex vivo mapping of the imaging target was performed using immunofluorescence microscopy; imaging mass cytometry; and bulk, single-cell, and single-nucleus RNA sequencing. Results: Sixty-one participants (LVV: n = 27; recent atherosclerotic myocardial infarction of ≤2 weeks: n = 25; control subjects with an oncologic indication for imaging: n = 9) were included. Index vessel SST2 maximum tissue-to-blood ratio was 61.8% (P < 0.0001) higher in active/grumbling LVV than inactive LVV and 34.6% (P = 0.0002) higher than myocardial infarction, with good diagnostic accuracy (area under the curve: ≥0.86; P < 0.001 for both). Arterial SST2 signal was not elevated in any of the control subjects. SST2 PET/MRI was generally consistent with 18F-fluorodeoxyglucose PET/computed tomography imaging in LVV patients with contemporaneous clinical scans but with very low background signal in the brain and heart, allowing for unimpeded assessment of nearby coronary, myocardial, and intracranial artery involvement. Clinically effective treatment for LVV was associated with a 0.49 ± 0.24 (standard error of the mean [SEM]) (P = 0.04; 22.3%) reduction in the SST2 maximum tissue-to-blood ratio after 9.3 ± 3.2 months. SST2 expression was localized to macrophages, pericytes, and perivascular adipocytes in vasculitis specimens, with specific receptor binding confirmed by autoradiography. SSTR2-expressing macrophages coexpressed proinflammatory markers. Conclusions: SST2 PET/MRI holds major promise for diagnosis and therapeutic monitoring in LVV. (PET Imaging of Giant Cell and Takayasu Arteritis [PITA], NCT04071691; Residual Inflammation and Plaque Progression Long-Term Evaluation [RIPPLE], NCT04073810