Immunoenzymometric analysis for plasma von Willebrand factor degradation in diabetes mellitus using monoclonal antibodies recognizing protease-sensitive sites.

High-molecular-weight von Willebrand factor (vWf) multimers were separated from their smaller multimers by molecular-sieve chromatography and were measured by several sandwich enzyme-linked immunosorbent assays (ELISA) with monoclonal antibodies (moABs) against human vWf. The epitopes of these moABs were mapped partially using fragments generated by V-8 protease digests of native vWf. Large multimers were more immunoreactive with the sandwich ELISA using immobilized VW28-1 and enzyme-labeled VW92-3 than with any other ELISA. The epitopes recognized by these two moABs were sensitive to trypsin and plasmin digestion, and the other moABs appeared to be reactive with the extensively digested antigen. Relative reactivities of this ELISA to plasma vWf multimers in diabetes mellitus were significantly reduced compared to those in healthy subjects. These data demonstrate that molecular abnormalities of vWf circulating in diabetic patients may be caused by some plasma proteases that increase in the microcirculation of patients with diabetic vascular diseases.