Michael Paley and Lynn Hassman

Analysis of HLA-B27+ anterior uveitis

Uveitis is associated with multiple rheumatic diseases, from inflammatory arthritis to vasculitis. In particular, approximately half of patients with HLA-B27+ spondyloarthritis develop anterior uveitis, however, the mediators of this eye disease are not well understood. In addition, incomplete control of ocular inflammation can lead to cataract, glaucoma, and permanent vision loss. As a result, there is a need to better understand the pathophysiology of ocular inflammation in order to better tailor uveitis therapy and provide critical insight into systemic rheumatologic disease.

We hypothesize that human uveitis is driven by autoreactive T cells responding to ocular antigens. Our hypothesis is based on observations that CD4 and CD8 T cells infiltrate the eye in anterior uveitis and that the MHC class I molecule HLA-B27 is strongly associated with anterior uveitis. However, it is still unknown whether antigen presentation at the site of inflammation (e.g. eye) or at a distant organ (e.g. gut) is the initiating stimulus. Moreover, prior studies had technical limitations. To better elucidate the pathogenesis of this disease, we created a biorepository of blood and ocular samples from subjects with HLA-B27+ anterior uveitis. Preliminarily, we performed simultaneous single cell RNA sequencing (scRNAseq) and single cell T cell receptor (TCR) sequencing (scTCRseq) on 4 paired ocular and blood samples, allowing us to address our Specific Aims.

Michelle Elvington

Establishing C3(H2O) as a biomarker in SLE and defining its role in B lymphocyte function

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by autoantibody production, immune complex formation, and complement activation and deposition in tissues. Complement activation by immune complexes drives type II & III hypersensitivity reactions, leading to inflammatory responses in target tissues. Failure to remove cellular debris, a process that is highly dependent on complement, is also an important tenet of SLE pathophysiology. The role of complement in the activation of immune cells is well-documented. Complement deposition in tissues serves as a diagnostic tool, especially in the kidney, and decreased serum complement components C4 and C3 are markers of active disease. C3 continuously activates at a low level in the fluid phase by spontaneous hydrolysis of the internal thioester bond. Within microseconds this form of C3 becomes covalently bound to a target (such as a microbe or cell) or interacts with water to form C3(H2O). Interest in C3(H2O) in disease processes has recently been renewed due to the discovery of the intracellular complement system (ICS) whose dysfunction is increasingly associated with debris clearance and autoimmunity. In a follow-up report to our identification of the ICS, I made an additional key observation of a process whereby C3(H2O) is loaded into the cell interior where it can be stored or cycled back out of the cell. Thus, C3(H2O) has two main functions: (1) serves as a surveillance system via being a trigger for alternative pathway (AP) activation on a target and (2) supplies this form of C3 for the ICS. In a process involving the uptake of C3(H2O), a variety of cells have been shown to cleave C3(H2O) intracellularly into C3a and C3b. Further, these cleavage products engage intracellular complement receptors and drive changes in immune cell cytokine production. 

Moreover, preliminary data indicates that serum C3(H2O) generation is substantially elevated in patients with SLE compared to healthy controls. While it is not known what drives increased C3(H2O) levels or what role it plays for immune cell function in patients with SLE, we suspect that elevated C3(H2O) may contribute to dysfunction of the ICS. While clinical assays exist for C3 and certain of its fragments, there was no quantitative and straight-forward assay to measure C3(H2O). My recent development of an ELISA specific for C3(H2O) which does not cross-react with native C3, C3b or C3b-derived fragments gives us the unique opportunity to investigate C3(H2O)’s role in human disease and to address how its presence may be participating in immunoinflammatory conditions. I hypothesize that increased C3(H2O) generation contributes to dysfunction in SLE and thus C3(H2O) serves as a marker of disease activity. 

Chieh-Yu Lin and Kory Lavine

Cellular and Transcriptomic Landscape of Cardiac Sarcoidosis

Sarcoidosis is a multisystem rheumatic disease without clear etiology. Cardiac involvement by sarcoidosis is identified in a subset of patients, with a prevalence ranging from 5-25%. Cardiac sarcoidosis has recently gained increasing attention, as it portends an unfavorable prognosis accounting for nearly 85% deaths in sarcoidosis patients. Today, it remains challenging to diagnose and effectively treat active cardiac sarcoidosis. Endomyocardial biopsy has limited sensitivity and diagnostic utility due to the patchy distribution and subepicardial predominance of disease. The pathognomonic findings of noncaseating granulomas are only identified in about 20% of the biopsy specimens. Given issues related to sampling bias, FDG PET imaging is the current standard of care, but the results are unsatisfactory. Importantly, treatment options for cardiac sarcoidosis are limited. Nonselective anti-inflammatory therapies such as corticosteroids and azathioprine represent the primary pharmacological treatment options. Unfortunately, these agents have limited efficacy and there is a paucity of clinical data to support their use. The rationale of using such modalities are largely extrapolated from non-cardiac sarcoidosis patients. TNF-alpha antagonists, such as infliximab, have shown promising results for severe/refractory sarcoidosis. However, the efficacy for cardiac sarcoidosis is unclear. 

These observations highlight a clinically unmet need to develop new approaches to diagnose and treat cardiac sarcoidosis. Surprisingly, little is understood regarding the pathological mechanisms that govern the initiation and progress of this devastating disease. We believe that a comprehensive understanding of the cellular composition and transcriptomic landscape of cardiac sarcoidosis in humans represents a critical first step towards obtaining the requisite information to begin to generate effective diagnostic tools and treatment options.