The development of assays for the detection of fibrin(ogen)olysis based on
COOH-terminal A alpha chain epitopes
JH Sobel, HQ Wu and RE Canfield
Department of Medicine, College of Physicians and Surgeons of Columbia
University, New York, NY 10032.
The COOH-terminal two-thirds of the fibrinogen A alpha chain is a substrate
for both factor XIIIa and plasmin and is, therefore, a source of structural
markers for the clinical detection of fibrin(ogen)olysis. Monoclonal
antibodies (MoAbs) that bind to epitopes within this region (F-102, A alpha
563-578; F-103, A alpha 259-276) have been applied towards the development
of two sensitive and specific enzyme-linked immunosorbent assays (ELISAs).
The first assay, a capture (F-102)-tag (F-103) ELISA, measures plasma
fibrinogen molecules whose A alpha chains are intact. The second assay, a
solution phase competitive ELISA based on MoAb F-102, quantifies
circulating COOH-terminal A alpha chain degradation products (A alpha
FDPs), among the earliest peptides released from fibrinogen during
plasmin-mediated fragment X formation. This assay features a novel
preliminary plasma absorption step on concanavalin A to recover A alpha
FDPs (if present in the sample) in a milieu free of immunologically
cross-reactive fibrinogen. Both ELISAs use highly purified fibrinogen as
the assay standard for quantitation. In control plasmas, circulating A
alpha FDPs accounted for less than 2% of their respective intact fibrinogen
A alpha chain concentration, suggesting a physiologic low level of
proteolysis occurring at the extreme COOH-terminal portion of the molecule.
Plasma A alpha FDPs were elevated (2.3% to 7.8% of their respective intact
fibrinogen A alpha chain concentration) in a group of plasma from patients
with documented, high serum FDPs (21 to 41 micrograms/mL). Application of
the two ELISAs to characterize the course of A alpha chain proteolysis
during thrombolytic therapy (TIMI phase 1) indicated that A alpha FDPs were
a very early marker of the lytic state (detectable 15 minutes after
treatment had been initiated), and that streptokinase and recombinant
tissue plasminogen activator appeared to produce significantly different A
alpha chain degradation profiles.
Volume 84,
Issue 2,
pp. 535-546,
07/15/1994
Copyright © 1994 by The American Society of Hematology
