MONOCLONAL-ANTIBODIES SPECIFIC FOR PROTHROMBIN FRAGMENT 1.2 AND THEIR USE IN A QUANTITATIVE ENZYME-LINKED-IMMUNOSORBENT-ASSAY

Prothrombin fragment 1.2 (F1.2) is an activation peptide generated during a critical event of blood coagulation, the conversion of prothrombin to thrombin. As a marker of thrombin generation, F1.2 has clinical potential in assessing thrombotic risk and monitoring anticoagulant therapy. in developing a highly specific, monoclonal antibody-based immunoassay of human plasma Fl.2, we generated six murine anti-F1.2 monoclonal antibodies, using as immunogen a synthetic peptide (sequence: CGSD-RAIEGR) similar to the unique carboxyl terminus of Fl.2. Each antibody bound Fl.2 but not prothrombin. Epitope mapping studies with one antibody (5-3B) showed that optimum binding required six to eight amino acids plus a terminal arginine to emulate the Fl.2 carboxyl terminus. A quantitative sandwich ELISA for human plasma Fl.2 was configured with monoclonal antibody 5-3B as the capture antibody and peroxidase-labeled polyclonal antibodies to the Fl.2 amino-terminal region as detector antibodies. Calibrators were prepared by adding purified Fl.2, 0-10 nmol/L, to Fl.2-depleted plasma. Assay characteristics included the following: mean (+/- SD) analytical recovery of 98% +/- 13%; no interference from lipemia, hemolysis, icterus, or thrombolytic agents; 0.08 nmol/L sensitivity; and mean intra- and interassay imprecision (three lots) <12% at both low and high concentrations of F1.2.