Anti-eukaryotic initiation factor 2B autoantibodies are associated with interstitial lung disease in patients with systemic sclerosis

Objective Anti-nuclear autoantibodies are known to occur in 85-99% of Systemic Sclerosis (SSc) patients, with each SSc autoantibody correlating with a distinct clinical subset of patients. The objective of this study was to investigate novel SSc autoantibodies in the remaining autoantibody negative patients and establish clinical associations. Methods Serum samples and clinical data were collected from 548 SSc patients. Sera were tested for known SSc autoantibodies by routine serological techniques, with negative samples being further investigated by radiolabelled protein immunoprecipitation (IPP). Sera that immunoprecipitated a novel 30 kDa band were analysed by indirect immunofluorescence and IPP using depleted cell extracts to establish a common reactivity. Mass spectrometry (MS) was used to identify the novel autoantigen and findings were confirmed using commercial antibodies. Sera from 426 patients with other forms of connective tissue disease, 103 patients with rheumatoid arthritis, 114 patients with idiopathic ILD and 150 healthy controls were serotyped as controls. Results A novel autoantigen with a molecular weight of ∼30 kDa was recognised by seven sera with SSc, six of whom had interstitial lung disease (ILD) and by no controls. Six of the patients had diffuse cutaneous involvement and four had overlap features with other autoimmune diseases. Immunodepletion experiments indicated that all samples targeted the same autoantigen and MS identified the novel autoantigen as eIF2B (Eukaryotic Initiation Factor 2B). Conclusion We report a novel autoantibody (anti-eIF2B) in a small number of patients with SSc (approximately 1%) that is closely associated with diffuse cutaneous manifestations and the presence of ILD.