An Exploratory, Single-center, Two-part Study to Characterize Cutaneous Lupus Erythematosus and Investigate the Effect of an Immune Challenge by Comparing CLE Patients With Healthy Volunteers

Cutaneous lupus erythematosus (CLE) is a rare but burdensome autoimmune disease that includes various subtypes including acute cutaneous LE (ACLE), subacute cutaneous LE (SCLE), intermittent cutaneous LE (ICLE) i.e., lupus tumidus (LET) and chronic cutaneous LE (CCLE). These subtypes differ in lesion morphology and histopathology, however disease stratification is often a challenge.

Knowledge on mechanisms involved in the pathogenesis and pathophysiology of CLE is growing, however much remains unknown. The current concept regarding the onset of the disease comprises a genetic background predisposing to CLE triggered by factors such as UV light, what leads to cellular stress and eventually to the release of DNA components in keratinocytes (Fetter et al., 2022). Activation of both Toll-like receptor (TLR)-dependent and TLR-independent inflammatory signalling cascades leads to increased expression of several cytokines, in particular type I interferon (IFN). Type I interferon mediates increased expression of proinflammatory chemokines via the JAK-STAT pathway, leading to recruitment of immune cells, release of cytokines and a chronic reactivation of innate immune pathways.

Findings on the pathogenesis of the disease have led to the development of several targeted therapies that are currently being investigated in clinical trials. However, blockage of one important pathway might not suffice for decreasing disease activity given the limited efficacy of selective IFN antibodies in clinical trials (Kalunian et al., 2016), (Khamashta et al., 2016) (Werth et al., 2017).

Only few biomarkers for CLE have been validated and widely incorporated into clinical practice (Zhu et al., 2021). Type I interferon-inducible proteins can be potentially used to assess disease severity of SCLE and CDLE (Braunstein et al., 2013). Furthermore, low complement in CLE patients may be related to poor prognosis and increased risk of developing systemic disease (Vera et al., 2010) (Vera et al., 2010).

Therefore, the objectives of the current study are to evaluate disease-related characteristics in CLE patients and to evaluate the variability between patients using a deep phenotyping approach, and to investigate the immune response of CLE patients following an ex vivo and in vivo imiquimod skin challenge. The study consists of an observational (part A) and interventional (part B) part in CLE patients and healthy volunteers.- With this approach the investigators aim to characterize objectively measured disease characteristics and detect novel biomarkers for CLE(-subtypes).