Identification of New Autoantigens by Protein Array Indicates a Role for IL4 Neutralization in Autoimmune Hepatitis

Abstract

Autoimmune hepatitis (AIH) is an unresolving inflammation of the liver of unknown cause. Diagnosis requires the exclusion of other conditions and the presence of characteristic features such as specific autoantibodies. Presently, these autoantibodies have relatively low sensitivity and specificity and are identified via immunostaining of cells or tissues; therefore, there is a diagnostic need for better and easy-to-assess markers. To identify new AIHspecific autoantigens, we developed a protein microarray comprising 1626 human recombinant proteins, selected in silico for being secreted or membrane associated. We screened sera from AIH patients on this microarray and compared the reactivity with that of sera from healthy donors and patients with chronic viral hepatitis C. We identified six human proteins that are specifically recognized by AIH sera. Serum reactivity to a combination of four of these autoantigens allows identification of AIH patients with high sensitivity (82%) and specificity (92%). Of the six autoantigens, the interleukin-4 (IL4) receptor fibronectin type III domain of the IL4 receptor (CD124), which is expressed on the surface of both lymphocytes and hepatocytes, showed the highest individual sensitivity and specificity for AIH. Remarkably, patients' sera inhib- Autoantibodies specific for proteins or nonprotein antigens (dsDNA, snRNP, carbohydrates) are often the serological hallmark of autoimmune diseases. Autoantibodies can be simply an epiphenomenon secondary to a chronic inflammatory milieu (1), but they can also play a direct pathogenetic role, as antithyroglobulin antibodies do in Hashimoto's thyroiditis (2).Autoimmune hepatitis (AIH) 1 is a chronic necro-inflammatory disease of unknown etiology that affects predominantly women with an incidence of 1 to 2 per 100,000 per year and a prevalence of 10 to 20 out of 100,000 (3, 4). AIH is subdivided into two major types on the basis of autoantibody reactivity (5). Antibodies to nuclei and/or to smooth muscle characterize type 1 AIH, whereas antibodies to a liver-kidney microsomal constituent define patients with type 2 AIH. Because the detection of these autoantibodies is done by means of immunofluorescence on rodent multi-organ sections (liver, kidney, stomach), there are problems with the standardization and interpretation of the immunostaining patterns (6). To overcome these methodological problems, the International Autoimmune Hepatitis Group established an international committee to define guidelines and develop procedures and reference standards for more reliable testing (7,8). Although ELISA and bead assays with purified or recombinant autoantigens are under development (9), they actually represent a

Transitioning from Idiopathic to Explainable Autoimmune Hepatitis

“…Six plasma membrane autoantigens have been implicated in type 1 autoimmune hepatitis, including liver arginase, cytokeratins, heat-shock proteins, and valosin-containing protein [138]. The interleukin-4 receptor (CD124) has high individual sensitivity and specificity for autoimmune hepatitis, and it generates functional autoantibodies that neutralize interleukin-4 [139].…”

Review of overlap syndromes of autoimmune liver diseases. Difficulties in the diagnosis and treatment

“…Újabb specifi kusabb autoantigének is ismertek (interleukin-4-receptor fi bronektin típusú III domén, riboszomális fehérje S20, DNS/RNS kötő fehérje, Alba (acetylation lowers binding affi nity) -like, deoxiuridintrifoszfatáz, humán tropomiozin-ellenes antitest), de kimutatásuk nem mindenhol lehetséges, és diagnosztikus, valamint kórjelző értékük sem ismert teljesen [5,16,17].…”

EMBnet.journal 18 Suppl. B

“…A schematic view of flow chart is shown in Figure 1. In the first step ( Figure 1, panel A), protein arrays were developed to screen serum samples of patients affected by Autoimmune Hepatitis (AIH) and healthy controls (HD); characteristic of patients and protein platform generation were described in recent publication (Zingaretti et al, 2012). Briefly, fluorescence signals were detected by using a ScanArray Gx PLUS (PerkinElmer, Bridgeport Avenue Shelton, USA) and scanned images were imported in a house developed software for the successive image analysis.…”

“…Each array was depicted as a set of quantitative descriptors and analyzed by PLS-DA method in an attempt to classify samples according to their intrinsic protein expression profile. Moreover, the assessed model was able to extract antigens of interest representative of a different protein profile in Autoimmune Hepatitis (AIH) patients compared to Healthy donors (HD) (Zingaretti et al, 2012).…”