title: Expression immunoassay.
abstract: Expression immunoassay is a sensitive analytical method that takes advantage of coupled in vitro transcription and translation as a signal amplification technique. Essentially, the immunoassay is performed using a detection antibody that is labeled with an expressible fragment of DNA. The product of expression is a protein that can be used to generate a signal. Here we describe two distinct expression immunoassays; both are based on expression of DNA labels to produce active enzyme molecules which are subsequently detected through their enzymatic activities. The luciferase expression immunoassay uses a 2.1-kb DNA template as a reporter molecule. The DNA is attached to a biotinylated detection antibody via biotin-streptavidin linkage. After the detection antibody is immunoreacted with immobilized antigen and excess antibody is removed, the DNA label is expressed in vitro. A linear relationship exists between the bioluminescent signal, from luciferase activity, and the immobilized antigen. This expression immunoassay allows the detection of 5 x 10(4) antigen molecules. The second expression immunoassay makes use of the well-characterized alpha-complementation of beta-galactosidase by employing an alpha-peptide encoding DNA as a reporter molecule. By monitoring the resulting beta-galactosidase activity with a fluorogenic substrate it was possible to detect as little as 3 fmol of immobilized antigen. Both expression immunoassays are amenable to automation and demonstrate the potential sensitivity that can be achieved using in vitro expression as a signal amplification method.
authors.affiliation: Department of Chemistry and Biochemistry, University of Windsor, 401 Sunset Avenue, Windsor, Ontario, N9B 3P4, Canada.
authors.forename: S R
authors.initials: SR
authors.lastname: White
authors.forename: N H
authors.initials: NH
authors.lastname: Chiu
authors.forename: T K
authors.initials: TK
authors.lastname: Christopoulos
mesh_terms: D000818:Animals; D000941:Antigens / Q000276:immunology / Q000378:metabolism; D019921:Biotinylation; D004247:DNA / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D017930:Genes, Reporter; D005816:Genetic Complementation Test; D007118:Immunoassay / Q000295:instrumentation / Q000379:methods*; D008156:Luciferases / Q000235:genetics / Q000378:metabolism*; D049449:Luminescence; D010455:Peptides / Q000235:genetics / Q000378:metabolism; D014176:Protein Biosynthesis; D012680:Sensitivity and Specificity; D019809:Streptavidin / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic / Q000235:genetics; D001616:beta-Galactosidase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D000941:Antigens; D010455:Peptides; D004247:DNA; D019809:Streptavidin; D008156:Luciferases; D001616:beta-Galactosidase