Clinical and immunological biomarker profiling to improve the diagnosis of acute uveitis

Abstract

Background: Uveitis is a leading global cause of blindness. Common aetiologies include infectious or immune-mediated causes, but diagnosis can be delayed and remain challenging. Up to a third of patients have an undiagnosed aetiology and are classified as ‘idiopathic’. Non-invasive biomarkers are urgently needed to expedite early accurate diagnosis in order to refine treatment and improve outcomes. Aims: We sought to characterise clinical and immunological biomarkers which best discriminate between immune-mediated, infectious and idiopathic uveitis. Methods: We prospectively recruited patients with acute uveitis from two tertiary centres in Sydney, Australia between June 2021 and February 2023. Clinical, visual, and serological data was collected in patient phenotyping. 35 cytokines, chemokines and growth factors were analysed in patients’ serum samples and 30 age- and sex- matched healthy controls using a Milliplex® panel. Results: 67 patients (37 female, median age 42 (range 16-79) years), were recruited with a median duration of follow-up of 18.5 months (range 12-37 months). 29, 17, and 21 patients were classified as immune-mediated, infectious, or idiopathic uveitis, respectively. Immune-mediated uveitis patients had a significantly shorter follow-up duration compared to infectious uveitis patients (24 months (4-37) versus 8.5 (4-33), p=0.028). A relapsing disease course was more common in the immune-mediated uveitis group (20/29, 69%), compared with the infectious group (3/17, 18%; p=0.004). 95 affected eyes (immune-mediated n=39, infectious n=24, and idiopathic n=32) were evaluated for visual acuity, retinal nerve fibre layer thickness, macular thickness, visual fields, macular oedema, and intraocular pressure at nadir and latest follow-up. Only macular thickness at nadir was higher in the immune-mediated group (median 270 μm, IQR 260-293) compared to the infectious group (250, 223-277, p=0.03). Of the 35 cytokines/chemokines/growth factors tested, hierarchical cluster analysis and principle component analysis identified nine cytokines which best discriminated between uveitis patients and healthy controls; and six which best discriminated between immune-mediated, infectious and idiopathic uveitis. B cell-attracting chemokine 1 (BCA-1) was elevated in all uveitis groups compared to healthy controls. Patients with immune-mediated uveitis had higher interleukin (IL)-17α levels, while patients with infectious uveitis had lower IL-17α and growth-regulated oncogene-alpha (GROα) levels. Patients with idiopathic uveitis had elevated interleukin gamma-induced protein 10 (IP-10), tumour necrosis factor-alpha (TNF-α), and monocyte chemoattractant protein-1 (MCP-1). Conclusions: Cytokine/chemokine/growth factor analysis offers a non-invasive method for determining biomarker profiles in patients presenting with acute uveitis. We identified a refined panel of 9 biomarkers which drive differentiation between these groups and may be of diagnostic utility. These biomarkers may provide insights regarding underlying disease pathogenesis such as the role of B cell activation and migration to an immune-privileged uvea in all cases of acute uveitis, Th-17 as a major contributor to immune-mediated uveitis, impairment of neutrophil recruitment in infectious uveitis, and the role of Th-1 mediated inflammation in idiopathic uveitis. Idiopathic uveitis likely represents a heterogenous group of aetiologies, and further research regarding underlying disease mechanisms is required.