Primary Sjögren's syndrome (pSS) is a complex autoimmune disorder that particularly affects the salivary and lachrymal glands, generally causing a typical dryness of the eyes and of the mouth. The disease encompasses diverse clinical representations and is characterized by B-cell polyclonal activation and autoantibodies production, including anti-Ro/SSA. Recently, it has been suggested that autoantibody profiling may enable researchers to identify susceptible asymptomatic individuals in a pre-disease state. In this pilot study, we used mass spectrometry to analyze and compare the salivary proteomics of patients with established pSS and patients with pre-clinical SS, identifying a common protein signature in their salivary fluid. We found that several inflammatory, immunity-related, and typical acinar proteins (such as MUC5B, PIP, CST4, and lipocalin 1) were differently expressed in pSS and in pre-clinical SSA+ carriers, compared to healthy controls. This suggests that saliva may closely reflect exocrine gland inflammation from the early phases of the disease. This study confirms the value of salivary proteomics for the identification of reliable biomarkers for SS that could be identified, even in a preclinical phase of the disease.
Keywords: autoimmunity; mass spectrometry; preclinical Sjögren’s syndrome; primary Sjögren’s syndrome; salivary proteomics.