Staphylococcal protein A-enzyme immunoglobulin conjugates: Versatile tools for enzyme immunoassays

This report described the use of peroxidase-labeled staphylococcal protein A to prepare conjugates suitable for direct enzyme immunoassays (EIAs). Such conjugates were used to develop direct EIA systems for the measurement of two antigens associated with human infections, human rotavirus and Haemophilus influenzae type b polysaccharide. Both systems were as sensitive or more sensitive than currently available EIAs for the measurement of standard antigens. In addition, both systems could be utilized to correctly identify the antigens in clinical specimens obtained from sick patients. Efficient enzyme conjugates prepared with enzyme-labeled staphylococcal protein A were simple to formulate providing that immunoglobulin of the appropriate animal species was available as the source of antibody. The use of such conjugates might increase the availability of practical EIA systems for the measurement of a wide range of medically important antigens.