Innate-immunity-related Biomarkers in Saliva from Systemic Lupus Erythematous Patients

Objectives: Laboratory tests of blood and/or urine in systemic diseases are nowadays used both for diagnosis and control of disease activity. If biomarkers could be measured in saliva, prediction of onset and recurrence of the severe organ damage might become less invasive. To determine whether this was feasible we investigated the levels of innate-immunity related biomarkers in saliva, serum, and urine from Systemic Lupus Erythematous (SLE) patients and their correlation to each other and to disease activity.
Methods: We included 84 SLE patients and 20 controls from the general population, all participants underwent a thorough clinical examination. Disease activity as measured with the Systemic Lupus Activity Measure (SLAM) and SLE Disease Activity Index (SLEDAI) was recorded. Matched saliva, serum, and urine were collected, and the levels of colony-stimulating factor (CSF)-1, tumor necrosis factor (TNF)-α, interferon-γ-induced protein (IP)-10, monocyte chemoattractant protein (MCP)-1 and calprotectin were analysed by enzyme-linked immunosorbent assays (ELISA) and Bead-based Multiplex immunoassay. Group comparisons were performed using Students t-test and Kruskal-Wallis test. Spearman correlation coefficient was used to assess correlations between the markers and disease activity. The accuracy to discriminate SLE patients from controls was calculated with area under the receiver-operating characteristic curves (AUROC) and 95% confidence intervals (CI).
Results: CSF-1, TNF- α, IP-10 and MCP-1 in saliva and serum provided diagnostic ability to distinguish SLE from controls (area under the curve (AUC) > 0.764 and p<0.001). CSF-1, TNF- α, IP-10 and MCP-1 levels were significantly increased in saliva and serum from SLE patients, whereas calprotectin was elevated only in saliva. Salivary levels of CSF-1 and calprotectin, and CSF-1 and IP-10 in serum correlated positively with measures of disease activity (p<0.05 all comparisons).
Conclusions: CSF-1, TNF- α, IP-10 and MCP-1 in saliva and serum are elevated in systemic lupus erythematosus, and reflect disease activity. This is a promising result suggesting that assessment of potential biomarkers in saliva might aid in diagnosing and monitoring patients with SLE.