CHARACTERIZATION OF 10 NEW MONOCLONAL-ANTIBODIES AGAINST PROSTATE-SPECIFIC ANTIGEN BY ANALYSIS OF AFFINITY, SPECIFICITY AND FUNCTION IN SANDWICH ASSAYS

While prostate-specific antigen (PSA) is already an invaluable marker for prostate cancer, there is continuing demand for new anti-PSA antib odies with specific characteristics, e.g, high sensitivity and specifi city and equimolar binding to free PSA (f-PSA) and the PSA-alpha-1-ant ichymotrypsin complex (PSA-ACT), as well as the ability to distinguish between these 2 immunoreactive forms of PSA. We have therefore genera ted and characterized 10 anti-PSA monoclonal antibodies (MAbs). Appare nt dissociation constants (K-d,) of MAbs were determined by direct ELI SA yielding K-d-0.2-164.0 nM. Western blots suggested that 3 of the MA bs (60-1A2, 60-8A2 and 17-1A2) bind to linear epitopes, Sandwich assay s identified 5 major antigenic regions as binding targets of the MAbs. Three combinations of MAbs recognize f-PSA and PSA-ACT in equimolar f ashion with high sensitivity. Two of the MAb combinations are specific for fPSA. Physical analysis of the new antibodies has allowed us to a ssign the MAbs to binding classes (based on their sandwiching capabili ties) and to determine accurate apparent dissociation constants. (C) 1 997 Wiley-Liss, Inc.