Early endosome antigen 1: An autoantigen associated with neurological diseases

Background: We have identified 36 human sera sent for autoantibody analyses that produce a unique vesicular staining pattern of the cytoplasm of tissu e culture cells. The purpose of this study was to identify the autoantigens that are recognized by the sera that produce this staining pattern and det ermine if the patients have common clinical features. Methods: A serum from one of the patients (MS) with rapidly progressive dem yelinating polyneuropathy was used to isolate a similar to 4.5 kb cDNA inse rt from a HeLa expression library. The purified cDNA (MS-5.1) was character ized by a poly A tail and an open reading frame that encoded 1329 amino aci ds. The derived amino acid sequence was found to be 99% identical to a 180 kd peripheral endosomal protein named early endosome antigen (EEA1). Results: Antibodies from rabbits immunized with the recombinant protein and the prototype human serum produced an identical distinctive speckled cytop lasmic staining pattern. These sera also precipitated the in vitro translat ed recombinant protein and reacted with the isolated recombinant protein in a Western immunoblot. Of the 36 sera that produced an identical staining p attern as the prototype and immune rabbit sera, 8 (22%) had IgG antibodies that recognized the recombinant EEA1 protein when tested by immunoblotting and immunoprecipitation assays. Of the 8 patients with anti-EEA1 antibodies 4 were females, 4 were males, and the mean age was 69 years (range 48 to 8 6 years). Conclusions: Diagnoses included: polyneuropathy, lower motor neuron disease , pigmented retinitis, seronegative polyarthritis, interstitial pulmonary f ibrosis, Raynaud's phenomenon, Wegener's granulomatosis, and proteinuria, T hree of the eight patients with EEA1 autoantibodies died within 1 year afte r EEA1 antibodies were identified.