Using polyclonal and monoclonal antibodies in regulatory testing of biological products

Polyclonal and monoclonal antibodies are often used in regulatory testing of biologicals (vaccines and related products). One of the most common applications for antibody-based immunoassays is as a batch release test. Batch release tests, whether they measure serological responses to vaccination or they quantify individual antigens by in vitro methods, must provide an acceptable estimate of potency of an individual batch of vaccine. Thus, due consideration must be given to the type of antibody used or quantified in such assays. Differences in specificity and avidity may affect the utility of an assay as an indicator of potency; case examples are given to illustrate these concepts. Concerns associated with antigen quantification assays (e.g., reagent denaturation upon binding to solid substrates, and interference from nontarget antigens or additives in a complex vaccine) are also discussed. International efforts to harmonize test methods in recent years have increased the importance of establishing standardized antibodies. Sources of such antibodies and issues associated with the ongoing availability of antibody supplies are described.