Need and value of targeted immunosuppressive therapy in giant cell arteritis

Impaired IL-6-induced JAK-STAT signaling in CD4+ T cells associates with longer treatment duration in giant cell arteritis

INTRODUCTION

The IL-12-IFNγ-Th1 and the IL-6-IL-23-Th17 axes are considered the dominant pathogenic pathways in Giant Cell Arteritis (GCA). Both pathways signal via activation of the downstream JAK/STAT proteins. We hypothesized that phosphorylated STAT (pSTAT) signatures in circulating immune cells may aid to stratify GCA-patients for personalized treatment.

METHODS

To investigate pSTAT expression, PBMCs from treatment-naive GCA-patients (n = 18), infection controls (INF, n = 11) and age-matched healthy controls (HC, n = 15) were stimulated in vitro with IL-6, IL-2, IL-10, IFN-γ, M-CSF or GM-CSF, and stained with CD3, CD4, CD19, CD45RO, pSTAT1, pSTAT3, pSTAT5 antibodies, and analyzed by flow cytometry. Serum IL-6, sIL-6-receptor and gp130 were measured by Luminex. The change in percentages of pSTAT3+CD4+T-cells was evaluated at diagnosis and at 3 months and 1-year of follow-up. Kaplan-Meier analyses was used to asses prognostic accuracy.

RESULTS

Analysis of IL-6 stimulated immune cell subsets revealed a significant decrease in percentages of pSTAT3+CD4+T-cells of GCA-patients and INF-controls compared to HCs. Following patient stratification according to high (median>1.5 pg/mL) and low (median<1.5 pg/mL) IL-6 levels, we observed a reduction in the pSTAT3 response in GCA-patients with high serum IL-6. Percentages of pSTAT3+CD4+T-cells in patients with high serum IL-6 levels at diagnosis normalized after glucocorticoid (GC) treatment. Importantly, we found that patients with low percentages of pSTAT3+CD4+T-cells at baseline require longer GC-treatment.

CONCLUSION

Overall, in GCA, the percentages of in vitro IL-6-induced pSTAT3+CD4+T-cells likely reflect prior in vivo exposure to high IL-6 and may serve as a prognostic marker for GC-treatment duration and may assist improving personalized treatment options in the future.

Cytokine producing B-cells and their capability to polarize macrophages in giant cell arteritis

OBJECTIVE

The lack of disease-specific autoantibodies in giant cell arteritis (GCA) suggests an alternative role for B-cells readily detected in the inflamed arteries. Here we study the cytokine profile of tissue infiltrated and peripheral blood B-cells of patients with GCA. Moreover, we investigate the macrophage skewing capability of B-cell-derived cytokines.

METHODS

The presence of various cytokines in B-cell areas in temporal artery (n = 11) and aorta (n = 10) was identified by immunohistochemistry. PBMCs of patients with GCA (n = 11) and polymyalgia rheumatica (n = 10), and 14 age- and sex-matched healthy controls (HC) were stimulated, followed by flow cytometry for cytokine expression in B-cells. The skewing potential of B-cell-derived cytokines (n = 6 for GCA and HC) on macrophages was studied in vitro.

RESULTS

The presence of IL-6, GM-CSF, TNFα, IFNγ, LTβ and IL-10 was documented in B-cells and B-cell rich areas of GCA arteries. In vitro, B-cell-derived cytokines (from both GCA and HC) skewed macrophages towards a pro-inflammatory phenotype with enhanced expression of IL-6, IL-1β, TNFα, IL-23, YKL-40 and MMP-9. In vitro stimulated peripheral blood B-cells from treatment-naïve GCA patients showed an enhanced frequency of IL-6+ and TNFα+IL-6+ B-cells compared to HCs. This difference was no longer detected in treatment-induced remission. Erythrocyte sedimentation rate positively correlated with IL-6+TNFα+ B-cells.

CONCLUSION

B-cells are capable of producing cytokines and steering macrophages towards a pro-inflammatory phenotype. Although the capacity of B-cells in skewing macrophages is not GCA specific, these data support a cytokine-mediated role for B-cells in GCA and provide grounds for B-cell targeted therapy in GCA.

Giant cell arteritis successfully treated with subcutaneous tocilizumab monotherapy

Glucocorticoid remains the mainstay for treatment of large vessel vasculitis (LVV) including giant cell arteritis (GCA); however, the disease affects the elderly for whom the adverse effects of glucocorticoid are problematic. Recently, some reports have suggested that intravenous tocilizumab (TCZ) monotherapy is effective for this disease. To date, it remains unknown whether subcutaneous TCZ monotherapy is also effective. Here, we present a first case of GCA successfully treated with subcutaneous TCZ monotherapy. A 75-year-old woman presented with shoulder and hip pain. She was diagnosed with polymyalgia rheumatica (PMR) and treated with low-dose prednisolone (15 mg daily); however, she discontinued glucocorticoid therapy at her discretion due to the psychiatric adverse effect (cognitive dysfunction). Seven months later, her shoulder and hip pain relapsed. Furthermore, ¹⁸F-fluorodeoxyglucose (FDG)-positron emission tomography (PET)/computed tomography (CT) revealed uptake in the descending thoracic aorta, indicating a complication of LVV. She refused to take glucocorticoid for fear of psychiatric adverse effects and chose subcutaneous TCZ monotherapy (162 mg weekly) for treating this life-threatening urgent condition. Nine months later, her shoulder and hip pain resolved and FDG-PET/CT demonstrated no uptake in the descending thoracic aorta, indicating a successful treatment with subcutaneous TCZ monotherapy for the disease. No adverse events and disease relapse were found during observation period. Our case and the literature review suggest that not only intravenous injection but also subcutaneous injection of TCZ monotherapy can serve as an alternative treatment for patients with GCA who have comorbidities or refuse to take glucocorticoid.

Pathogenesis of giant cell arteritis with focus on cellular populations

Giant cell arteritis (GCA), the most common non-infectious vasculitis, mainly affects elderly individuals. The disease usually affects the aorta and its main supra-aortic branches causing both general symptoms of inflammation and specific ischemic symptoms because of the limited blood flow due to arterial structural changes in the inflamed arteries. The pathogenesis of the GCA is complex and includes a dysregulated immune response that affects both the innate and the adaptive immunity. During the last two decades several studies have investigated interactions among antigen-presenting cells and lymphocytes, which contribute to the formation of the inflammatory infiltrate in the affected arteries. Toll-like receptor signaling and interactions through the VEGF-Notch-Jagged1 pathway are emerging as crucial events of the aberrant inflammatory response, facilitating among others the migration of inflammatory cells to the inflamed arteries and their interactions with the local stromal milieu. The increased use of checkpoint inhibitors in cancer immunotherapy and their immune-related adverse events has fed interest in the role of checkpoint dysfunction in GCA, and recent studies suggest a dysregulated check point system which is unable to suppress the inflammation in the previously immune-privileged arteries, leading to vasculitis. The role of B-cells is currently reevaluated because of new reports of considerable numbers of plasma cells in inflamed arteries as well as the formation of artery tertiary lymphoid organs. There is emerging evidence on previously less studied cell populations, such as the neutrophils, CD8+ T-cells, T regulatory cells and tissue residing memory cells as well as for stromal cells which were previously considered as innocent bystanders. The aim of this review is to summarize the evidence in the literature regarding the cell populations involved in the pathogenesis of GCA and especially in the context of an aged, immune system.

Novel PET Imaging of Inflammatory Targets and Cells for the Diagnosis and Monitoring of Giant Cell Arteritis and Polymyalgia Rheumatica

Giant cell arteritis (GCA) and polymyalgia rheumatica (PMR) are two interrelated inflammatory diseases affecting patients above 50 years of age. Patients with GCA suffer from granulomatous inflammation of medium- to large-sized arteries. This inflammation can lead to severe ischemic complications (e.g., irreversible vision loss and stroke) and aneurysm-related complications (such as aortic dissection). On the other hand, patients suffering from PMR present with proximal stiffness and pain due to inflammation of the shoulder and pelvic girdles. PMR is observed in 40-60% of patients with GCA, while up to 21% of patients suffering from PMR are also affected by GCA. Due to the risk of ischemic complications, GCA has to be promptly treated upon clinical suspicion. The treatment of both GCA and PMR still heavily relies on glucocorticoids (GCs), although novel targeted therapies are emerging. Imaging has a central position in the diagnosis of GCA and PMR. While [18F]fluorodeoxyglucose (FDG)-positron emission tomography (PET) has proven to be a valuable tool for diagnosis of GCA and PMR, it possesses major drawbacks such as unspecific uptake in cells with high glucose metabolism, high background activity in several non-target organs and a decrease of diagnostic accuracy already after a short course of GC treatment. In recent years, our understanding of the immunopathogenesis of GCA and, to some extent, PMR has advanced. In this review, we summarize the current knowledge on the cellular heterogeneity in the immunopathology of GCA/PMR and discuss how recent advances in specific tissue infiltrating leukocyte and stromal cell profiles may be exploited as a source of novel targets for imaging. Finally, we discuss prospective novel PET radiotracers that may be useful for the diagnosis and treatment monitoring in GCA and PMR.