Limited proteolysis of fibrinogen by fibrinogenase from Echis multisquamatis venom

Viscoelastic Study of Hemostasis Disorders Associated with Echis ocellatus Envenoming in North Benin Using a Quantra Analyzer

Echis ocellatus envenomings are a public health problem in West Africa, leading to bleeding and hypocoagulability. The aim of this study was to assess the hemostasis disorders associated with E. ocellatus envenoming. Envenomed patients with an abnormal whole blood clotting test (WBCT) were prospectively included at Tanguiéta, Benin. A WBCT with a sequential reading (i.e., at 20, 30, and 60 min), viscoelastic analysis (VA) using the Quantra analyzer, and blood count were performed on admission. VA and the WBCT were also assessed at 4, 8, 12, 24, 48, and 72 h after antivenom administration. Nineteen patients were included. On admission, the main results were an absence of a clot on VA and a slight decrease in platelets. Clot time gradually decreased over time while clot stiffness, fibrinogen, and platelet contributions to stiffness increased. Sequential reading improved the sensitivity of the WBCT. At H48, all patients with recurrence bleeding after antivenom administration had an abnormal WBCT while patients with a normal WBCT never had bleeding during their follow-up. VA allows the identification of various hemostasis disorders. Hypofibrinogenemia was the main disorder that persisted for several days after treatment. A WBCT with a sequential reading is an effective alternative for monitoring hypocoagulability in the absence of a laboratory.

LIMITED PROTEOLYSIS OF FIBRINOGEN αC-REGION REVEALS ITS STRUCTURE

Aim. The purpose of our study was to compare hydrolytic action of proteases from Gloydius halys halys, Agkistrodon contortrix contortrix and Calloselasma rhodostoma rhodostoma snake venoms and from Bacillus thuringiensis вар. israelensis IMV B-7465 culture medium on αC-regions of fibrinogen molecule. Methods. Products of hydrolysis were characterized by SDS-PAGE under reducing conditions with following Western-Blot using the mouse monoclonal 1-5А (anti-Aα509-610) and ІІ-5С (anti-Aα20-78) antibody. MALDI-TOF analysis of fibrinogen hydrolysis products was performed using a Voyager-DE. Results. Combination of SDS-PAGE, FPLC and MALDI-TOF analysis enabled to detect the peptide bonds cleaved by studied proteases. In particular proteases from Gloydius halys halys and Agkistrodon contortrix contortrix snake venoms cleaved peptide bond Aα413-414. Action of protease from Calloselasma rhodostoma rhodostoma on fibrinogen led to the formation of hydrolytic product generated from C-terminal portion of Aα-chain that corresponded to fragments generated by enzymes from two other snakes. On the other hand protease from Bacillus thuringiensis вар. israelensis IMV B-7465 culture medium cleaved peptide bond Aα504-505. Conclusions. Use of limited proteolysis technique as the source of additional information for computer modeling allowed us to propose an improved model of 3D-structure of fibrinogen αC-regions. This model takes into account the behavior of αC-regions in the physiological condition and contributes to the general knowledge about fibrinogen structure.