Peroxidase-labelled monoclonal antibodies for use in enzyme immunoassay

Desirable characteristics of enzyme-antibody conjugates for use in enzyme immunoassay are labelling uniformity, permanent availability and stability. The use of monoclonal antibodies (McABS) for preparation of enzyme conjugates, in place of polyclonal antibodies, ensures labelling uniformity and permanent availability. The problem of stability still exists. Monoclonal antibody-horseradish peroxidase (McAB-HRPO) conjugates produced in our laboratory showed variable stability. After extensive testing of McAB-HRPO conjugates it became obvious that sodium borohydride, used as a reducing agent, did not result in the production of stable conjugates without enzyme pretreatment with fluorodinitrobenzene (FDNB). Ascorbic acid or ethanolamine used as the reducing agent, resulted in McAB-HRPO conjugates which were stable for periods of ten months or more when stored filter sterilized at 4 degrees C.