Non-isotopic substrate assay employing bacteriolysis products

Abstract

Substrates such as haptens and antigens, and those for receptor proteins and native circulating binding proteins are assayed by determining bacteriolysis products occasioned by bacteriophage infection of host cells, in a modification of the 'chemically modified bacteriophage assay.' Thus, a substrate such as an antigen is conjugated with bacteriophage and the conjugate competes with antigen in the specimen under assay for a limited number of binding sites on antibody. Phage conjugate surviving antibody inactivation is quantified by determining intracellular constituents of host bacteria subsequently infected by the bacteriophage remaining viable, which latter can be related to the levels of antigen originally present in the specimen. A preferred embodiment involves colorimetric assay for beta galactosidase freed by phage lysis of E. coli. Generally, the method is of sensitivity comparable to that of radioimmunoassay, but is attended by substantial advantages not common to the latter technique. The method is far less cumbersome than the plaque-containing techniques hitherto employed in bacteriophage assays.