title: A novel separation-free assay technique for serum antibodies using antibody bridging assay principle and two-photon excitation fluorometry.
abstract: A new technique for separation-free detection of antigen-specific antibodies is presented. The new technique employs antibody bridging assay principle and the recently developed ArcDia TPX fluorescence detection technology. According to the assay scheme, antibody molecules from the sample bind with one arm to an antigen on polymer microspheres and with the other arm to a fluorescently labeled secondary antigen reagent. Consequently, fluorescent immunocomplexes are formed on the surface of microspheres in proportion to the concentration of the analyte in the sample. The fluorescence signal from individual microspheres is measured by means of two-photon excited fluorescence detection. In order to demonstrate the applicability of the new assay technique, an assay for anti-adenovirus antibodies was constructed. The function of the assay method was tested both with monoclonal anti-adenovirus antibody preparation (standard analyte), and with positive serum samples. Standard class-specific ELISA was used as a reference method. The new assay method provides comparable sensitivity and precision, and wider dynamic range for IgG antibodies than the ELISA method. The standard curve showed linear response (R(2)=0.999) with a dynamic range of three orders of magnitude, detection limit (mean+3S.D.) of 8 pM, and intra-assay signal precision of 5%. Applicability of the new method for clinical serodiagnostics is discussed.
authors.affiliation: Laboratory of Biophysics, Institute of Biomedicine, University of Turku, Finland.
authors.forename: Janne O
authors.initials: JO
authors.lastname: Koskinen
authors.forename: Jonne
authors.initials: J
authors.lastname: Vaarno
authors.forename: Raija
authors.initials: R
authors.lastname: Vainionpää
authors.forename: Niko J
authors.initials: NJ
authors.lastname: Meltola
authors.forename: Aleksi E
authors.initials: AE
authors.lastname: Soini
mesh_terms: D000818:Animals; D000906:Antibodies / Q000097:blood*; D000914:Antibodies, Viral / Q000097:blood; D000918:Antibody Specificity; D000941:Antigens; D000956:Antigens, Viral; D036022:Capsid Proteins / Q000276:immunology; D005470:Fluorometry / Q000379:methods*; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D007074:Immunoglobulin G / Q000097:blood / Q000302:isolation & purification; D007132:Immunoglobulin Isotypes / Q000097:blood; D007202:Indicators and Reagents; D007700:Kinetics; D051379:Mice; D008863:Microspheres
chemical_list: D000906:Antibodies; D000914:Antibodies, Viral; D000941:Antigens; D000956:Antigens, Viral; D036022:Capsid Proteins; D007074:Immunoglobulin G; D007132:Immunoglobulin Isotypes; D007202:Indicators and Reagents; C018315:hexon capsid protein, Adenovirus