Thus, the SD-ELISA technique opens up new possibilities for convenient screening of human sera against diverse dairy proteins and potential modifications

Thus, the SD-ELISA technique opens up new possibilities for convenient screening of human sera against diverse dairy proteins and potential modifications. against human CSN1S1 (31 positive and 17 unfavorable) was examined by the newly developed SD-ELISA to exclude cross-reactivity. Twenty human sera showed an IgG-mediated reaction against bovine CSN1S1. Eleven of these sera were positive for the reactivity against human CSN1S1, and nine were negative. In conclusion it was exhibited that the overall performance of SD-ELISA is comparable to established ELISA without loss in sensitivity or specificity. Based on the advantages of this method in particular no need for time-consuming and expensive antigen production and purification the SD-ELISA is a potent alternative to convenient methods for identification and especially high-throughput screening of new antigens in the field of food allergies. Keywords:Autodisplay, SD-ELISA, IgG-mediated cross-reactivity, Bovine casein, Humans1-casein == 1. Introduction == Caseins are one of the major milk proteins of most mammalian species [1]. Eighty percent of bovine milk proteins are caseins 3-Methyladenine [1,2] withS1-casein (CSN1S1) being the most abundant protein. In contrast, the casein portion constitutes only approximately 40% in human milk [3]. Most caseins are phosphoproteins and ameliorate the intestinal uptake of calcium-phosphates and other minerals by incorporating them into clusters of diverse casein family members, termed micelles [4]. Besides its role for the suckling infant, bovine milk proteins are abundant ingredients in a typical western diet [3]. It is known, that bovine CSN1S1 is usually a major food allergen, stimulating allergic reactions [58]. Symptoms include digestive problems, skin allergies, and anaphylactic shocks [9]. The detection of an immunoglobulin G (IgG) reaction against CSN1S1 could not unequivocally be associated to 3-Methyladenine cows milk allergy (CMA). In contrast to IgG-reaction 89% of CMA patients show an immunoglobulin E (IgE) reaction against bovine CSN1S1 [10]. For bovine CSN1S1, there are six IgG epitopes recognized [11,12]. The most acknowledged binding domain name for the IgG antibodies in cows milk allergy was found between amino acids 1536 of bovine CSN1S1 [11]. Phosphorylation did not display any influence around the antibody reaction against bovine CSN1S1 in this study, because epitopes were not phosphorylated [13]. The concentration of serum IgG antibodies to bovine milk proteins is dependent upon the duration of exposure 3-Methyladenine to cows milk during early infancy [14]. In a prior study, an IgG-mediated antibody reaction against human CSN1S1 in sera of healthy breast-fed adults by a surface display (SD) 3-Methyladenine ELISA was detected [15]. The SD-ELISA is based on the autodisplay technology [16,17] and allows the screening of human sera on antibody reactions against antigens without further purification steps of the recombinant antigen. The aim of this study was to establish a SD-ELISA for the detection of IgG antibody reactions against bovine CSN1S1, and evaluate its sensitivity, specificity and precision in comparison to an established indirect ELISA. Subsequently, it was intended to investigate its applicability by analyzing a possible cross-reactivity of the IgG mediated reaction in human sera against the bovine and the human CSN1S1. The SD-ELISA technique may subsequently be used for the detection of various potential antigens and modifications thereof in patients with cows milk allergy. == 2. Materials and methods == MMP14 == 2.1. Human sera == Twenty human sera which were tested for their IgG-mediated antibody reaction with an indirect ELISA previously (10 sera with an IgG-mediated reaction against bovine CSN1S1 and 10 sera without a reaction) [10], were used to establish the SD-ELISA against bovine CSN1S1. In addition, a total amount of 48 human sera of healthy adult individuals with known reactivity against human CSN1S1 (31 with and 17 without antibodies as previously decided [15]) were analyzed for an IgG-mediated antibody reaction against bovine CSN1S1 by the newly established SD-ELISA. Sera were obtained, treated and stored as explained before [10,15]. == 2.2. Materials == Goat anti-human IgG conjugated with horseradish peroxidase was obtained from Beckman Coulter (Krefeld, Germany), rabbit anti-bovine casein was obtained from GeneTex Inc. (Irvine, CA, USA), goat anti-rabbit IgG conjugated with horseradish peroxidase was obtained from SigmaAldrich (product number A0545 Munich, Germany), goat anti-rabbit IgG conjugated with fluoresceine isothiocyanate (FITC) was obtained from Bethly 3-Methyladenine (Montgomery, TX, USA), restriction endonucleases were purchased from New England Biolabs (Ipswich, MA, USA), 3,3,5,5tetramethylbenzidine (TMB) was obtained from SigmaAldrich (Munich, Germany). Maxisorpmicroplates were purchased from Nunc (Langenselbold, Germany). == 2.3. Bacterial strains and plasmids for bovine CSN1S1 surface display == Escherichia colistrain UT5600(DE3) (Fara 14 leuB6 azi-6 lacY1 proC14 tsx-67 entA403 trp E38 rfbD1 rpsL109 xyl-5 mtl-1 thi1, ompT-fepC266).