Enzyme immunoassays for the detection of bacterial antigens utilizing biotin-labeled antibody and peroxidase biotin--avidin complex

This report describes the use of biotin-labeled antibodies in sensitive enzyme immunoassay systems for the measurement of bacterial antigens. Biotinylated immunoglobulins could be reproducibly formulated using N-hydroxysuccinimide biotin ester to link biotin to the immunoglobulin. Binding of the biotinylated antibody to solid-phase antigen was efficiently measured by reaction with a complex consisting of biotinylated antibody and unlabeled avidin. This immunoassay system was at least as sensitive as ones which utilized enzyme-labeled or fluorescein-labeled antibodies for the detection of antigens from Streptococcus pneumoniae and Haemophilus influenzae type b. In the case of Streptococcus pneumoniae the assay system could detect antigen in the supernatants from broth cultures containing as few as 10(3) organisms/ml. Assay systems utilizing biotinylated antibody and avidin-biotin complex can provide for sensitive, specific assays for the measurement of microbial antigens.