TC-325 is safe and highly effective in achieving hemostasis in an anticoagulated severe arterial gastrointestinal bleeding animal model.

SummaryAdhesion of platelets to immobilized fibrinogen appears to play an important role in a variety of physiologic and pathologic phenomena. We previously observed that the fibrinogen concentration used to coat polystyrene wells affected the morphology and distribution of GP IIb/ IIIa receptors on the surface of platelets adherent to the fibrinogen. One possible explanation for these differences is that fibrinogen immobilized at high density adopts a different conformation than fibrinogen immobilized at low density. To address this possibility, we studied the binding of a panel of anti-fibrinogen monoclonal antibodies (mAbs) to fibrinogen immobilized at different coating densities. Three different patterns of binding were observed: 1) a linear increase in binding to wells coated with 1-10 μg/ml fibrinogen, followed by a lesser increase or plateau at higher fibrinogen concentrations (mAbs Fd4-4E1, Fd4-7B3, 1D4, 4-2); 2) minimal reactivity at all fibrinogen concentrations (mAbs GC4-1A12, 2C34); 3) a biphasic response, with a linear increase up to 10 μg/ml fibrinogen and then a significant decline in binding at higher fibrinogen concentrations (mAbs 311, 31A9, FPA 19/7, 9C3, 1C5-A5/2, 44-3). The patterns of mAb binding to fibrinogen immobilized from plasma were similar. Most mAbs that demonstrated a biphasic response bound poorly or not at all to soluble fibrinogen, while mAbs that demonstrated a linear/plateau response were able to bind soluble fibrinogen. At equal surface densities, mAbs that bound biphasically, particularly mAb 1C5-A5/2, were more reactive to urea-denatured than native fibrinogen. mAbs 1C5-A5/2 and 44-3 are specific for γ 1-78 and 95-265, respectively, suggesting that the fibrinogen γ-chain may be sensitive to changes in conformation induced by immobilization. In summary, these data suggest that fibrinogen immobilized at 1-10 μg/ml adopts a conformation unlike soluble fibrinogen, while fibrinogen immobilized at >30 μg/ml adopts a more solution-like conformation. These differences in fibrinogen conformation may partially account for the ability of platelets to bind to immobilized fibrinogen without the addition of agonist, as well as the differences in spreading and GPIIb/IIIa distribution on platelets adherent to high- versus low-density immobilized fibrinogen.

SummaryTwenty-one cardiothoracic surgical patients have been treated with fibrin as a topical hemostatic/sealing agent, prepared from bovine fibrinogen clotted with bovine thrombin. Serum samples have been collected before treatment with fibrin and postoperatively between 1 and 9 days, 3 and 12 weeks, and 6 and 8 months. The titers of anti-bovine fibrinogen antibodies, measured by ELISA specific for immunoglobulins IgG or IgM, increased to maximal values after about 8 or 6 weeks, respectively. After 8 months, IgG titers were on average 20-fold lower than the mean maximal value, while IgM titers returned to the normal range. IgG was the predominant anti-bovine fibrinogen immunoglobulin as documented by ELISA, affinity chromatography and electrophoresis. Anti-bovine fibrinogen antibodies present in patients reacted readily with bovine fibrinogen, but did not cross-react with human fibrinogen as measured by ELISA or by immunoelectrophoresis. A significant amount of antibodies against bovine thrombin and factor V has been found, many cross-reacting with the human counterparts. No hemorrhagic or thrombotic complications, or clinically significant allergic reactions, occurred in any patient, in spite of antibody presence against some bovine and human coagulation factors. The treatment of patients with bovine fibrin, without induction of immunologic response against human fibrinogen, appeared to be an effective topical hemostatic/sealing measure.

The (DD)E complex is the major cross-linked fibrin degradation fragment. Structural components required for maintenance of the (DD)E complex were examined in order to better understand clot structure and the contribution of specific polypeptide chain segments in the process of polymerization. First, the (DD)E complex was reversibly dissociated by peptides derived from the alpha-chain NH2-terminus of fibrin having a minimal sequence of GPR (alpha 17-19). In addition, the complex was partially dissociated by peptide beta 40-54, while beta 50-55 and peptides derived from the fibrin beta-chain NH2-terminus had no effect. Second, monoclonal antibody (mAb) 1B6, specific for the alpha-chain NH2-terminus of fibrin, reacted rapidly with fragment E1, but did not recognize the corresponding epitope on the (DD)E complex. On the other hand, mAb 59D8, specific for GHRPL at the beta-chain NH2-terminus of fibrin, reacted with the (DD)E complex in a dose-dependent manner. Third, the (DD)E complex was irreversibly dissociated by proteolytic cleavage of fragment E1 by either thrombin, which removed GPR from the alpha-chain NH2-terminus, or Crotalus atrox protease III, which released beta 15-42. It has been concluded that fragment E1 contains a composite polymerization site consisting at least of residues alpha 17-19 and beta 20-49, which together maintain the (DD)E complex. These results illustrate that the complex is kept together by complementary binding sites which form a nucleus of linear fibrin polymerization sites. The (DD)E complex can thus be considered as a soluble model of fibrin clot.(ABSTRACT TRUNCATED AT 250 WORDS)

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