Proinflammatory Adaptive Cytokine and Shed Tumor Necrosis Factor Receptor Levels Are Elevated Preceding Systemic Lupus Erythematosus Disease Flare

Systemic lupus erythematosus (SLE) is a multifaceted autoimmune disease characterized by variable immune dysregulation, disabling symptoms and progressive organ damage (1). Given the heterogeneous nature of SLE, recognition and early treatment to prevent tissue and organ damage is clinically challenging. Validated disease activity clinical instruments assess and weigh changes in signs and symptoms within each organ system. The Safety of Estrogens in Lupus Erythematosus National Assessment-Systemic Lupus Erythematosus Disease Activity Index (SELENA-SLEDAI (2)) is a reliable measure of clinical disease activity (1). However, the traditional biomarkers incorporated in the SELENA-SLEDAI are not necessarily the earliest, or sufficient biologic signals of worsening disease. In addition, proposed serologic markers of disease activity, alone or in combination, including anti-dsDNA, complement, complement split products, and inflammatory markers (ESR and CRP), are limited in their clinical utility due to inconsistent correlation with disease activity (3, 4). Despite clinical instruments of disease activity and improved treatment regimens to temper chronic inflammation, SLE patients may experience an average of 1.8 disease flares annually (5). Treatment typically relies on rapidly acting, toxic agents such as steroids. Earlier identification and treatment of flares might prevent significant organ damage and improve the quality of life for patients with SLE (6). Further, uncovering early markers of clinical flares may provide mechanistic insight to improve the development and selection of targeted preventative treatments. Certain cytokines and chemokines are known to be involved in SLE pathogenesis and disease flare. IL-6, TNF-α, and IL-10, as well as Th1 and Th2 type cytokines, are implicated in SLE disease activity (7–9); elevated IL-12 has been detected prior to disease flare (10). Th17 pathway mediators are elevated in samples from SLE patients with increased disease activity (11) and sequelae, including cutaneous (12), serositis (12), and renal (13) manifestations. In addition to an increase in inflammatory mediators with elevated disease activity, regulatory pathways are diminished, including decreased TGF-β (14) and the potential for altered T-regulatory cell populations (15–19) and/or activity (20), suggesting an imbalance between inflammatory and regulatory mediators in promoting flares (21). This study builds on previous work by concurrently evaluating soluble inflammatory and regulatory mediators in the context of altered disease activity with ensuing SLE disease flare. In addition to soluble mediators of inflammation, SLE flares might also involve altered regulation of membrane-bound or soluble receptors expressed by activated immune cells (7). Members of the TNF(R)eceptor superfamily act as co-stimulatory molecules on B and T-lymphocytes and form a prototypic pro-inflammatory system (reviewed in (22)). The ligand/receptor pairings are either membrane bound or can be cleaved by proteases as soluble proteins that cluster as trimers to either block ligand/receptor interactions or to initiate receptor-mediated signal transduction. Multiple members of the TNFR superfamily are implicated in SLE. The classical ligand TNF-α interacts with two TNFRs, TNFRI (p55) and TNFRII (p75), both of which have been associated with altered SLE disease activity (7). In addition, expression and cleavage of Fas, FasL (23), and CD40L [CD154] (24) are increased in SLE patients. BLyS and APRIL, key regulators of B cell survival and differentiation, are important SLE therapeutic targets (25). In a study of 245 SLE patients followed for two years, with power to account for some confounding factors such as medications, increased BLyS levels associated with increased disease activity (4, 26). Furthermore, a neutralizing anti-BLyS monoclonal antibody can reduce risk of disease flare over time (27), suggesting that BLyS may help regulate disease activity in some patients (28). However, their roles in ensuing disease flares are presently unknown. This study explores the inflammatory and regulatory pathways potentially dysregulated early in lupus flare before clinical symptoms are reported. Plasma samples and clinical data were evaluated from SLE patients and matched, healthy controls participating in the SLE Influenza Vaccination Cohort (29). Using an xMAP multiplex approach, European-American (EA) SLE patients with impending disease flare 6 or 12 weeks after vaccination were found to have increased pre-flare inflammatory adaptive cytokines, chemokines, and shed TNFR superfamily members, with decreased regulatory mediators of inflammation, compared to matched patients with stable disease. These results enabled the development of a combined soluble mediator score that reflects pre-flare immune status in SLE patients who go on to flare.