血液制品的现状与展望

血液制品特指血浆蛋白制品和相应的重组制品。根据临床应用的效能,血液制品可以分为白蛋白类、免疫球蛋白类、凝血因子类和微量蛋白制品等不同种类。血浆白蛋白制品是最早应用于战伤救治的血液制品,高纯白蛋白、重组白蛋白以及重组白蛋白融合药物的研发和上市开创了血液制品的新局面。肌肉注射用免疫球蛋白因其制备工艺相对简单,使用方便,价格低廉且不良反应可以接受而一直在临床实践中应用;静脉注射用免疫球蛋白随着新的适应症不断发现,其应用范围越来越广;皮下注射用免疫球蛋白的出现使免疫球蛋白的使用更加方便,已经成为静脉注射用免疫球蛋白安全有效的替代品;针对特定病原体的特异性免疫球蛋白在临床上更具有不可替代的作用。凝血因子和重组凝血因子类制品主要用于相应的先天性遗传性缺陷患者,纤维蛋白原、因子Ⅶ、因子Ⅷ、von Willebrand因子复合物、因子Ⅸ和凝血酶原复合物、因子Ⅺ、因子ⅩⅢ等制品的应用取得了良好的治疗效果。因子Ⅶa和活化凝血酶原复合物对于治疗产生凝血因子抑制物的血友病病人具有十分明显的效果。纤维蛋白原类制品和凝血酶在外科止血方面发挥着重要的作用。多种微量血浆蛋白制品已经上市,如蛋白C、抗凝血酶、α1-抗胰蛋白酶和组织纤溶酶原激活剂等。部分微量血浆蛋白制品也在研发和临床试验过程中,如C1-抑制剂、补体系统Ⅰ因子、α2-巨球蛋白、血清胆碱酯酶、铜蓝蛋白以及纤维结合蛋白等。尽管多种重组血浆蛋白制品已经上市,血浆来源的制品仍将具有其不可替代的特殊地位,血浆蛋白新品种的研发仍是热点。目前,我国血液制品的研发与国外存在着较大的差距,我国血液制品企业面临着机遇与挑战。     

Chromatography in plasma fractionation: benefits and future trends

Industrial-scale chromatographic fractionation and purification methods have been used increasingly in the last few years for plasma fractionation. This has resulted in the development of a new generation of therapeutic plasma derivatives, especially coagulation factors, protease inhibitors and anticoagulants. Implementation and combination of ion-exchange, affinity and size-exclusion chromatography have allowed the development of new therapeutic products with improved purity and safety for treating congenital or acquired plasma protein deficiencies in patients. More recently, the benefit of chromatographic purification of plasma proteins in the removal of plasma-borne viruses has been revealed. Development of packing materials with improved characteristics for industrial applications, including higher capacity and rigidity, should further promote the use of chromatography as an essential plasma fractionation tool and confine more and more the traditional ethanol precipitation methods to the final processing stages used to recover albumin.     

Degradation of immunoglobulins,protease inhibitors and interleukin-1 by a secretory proteinase of Acanthamoeba castellanii

The effect of a secretory proteinase from the pathogenic amoebae Acanthamoeba castellanii on host's defense-oriented or regulatory proteins such as immunoglobulins, interleukin-1, and protease inhibitors was investigated. The enzyme was found to degrade secretory immunoglobulin A (sIgA), IgG, and IgM. It also degraded interleukin-1 alpha (IL-1 alpha) and IL-1 beta. Its activity was not inhibited by endogenous protease inhibitors, such as alpha 2-macroglobulin, alpha 1-trypsin inhibitor, and alpha 2-antiplasmin. Furthermore, the enzyme rapidly degraded those endogenous protease inhibitors as well. The degradation of host's defense-oriented or regulatory proteins by the Acanthamoeba proteinase suggested that the enzyme might be an important virulence factor in the pathogenesis of Acanthamoeba infection.     

Enzymes of snake venoms

Snakes' venom is a mixture of biologically active substances, containing proteins and peptides. A number of these proteins interact with haemostasis system components. Activators and inhibitors affecting blood coagulation and fibrinolysis systems are of special interest. Venom components can be classified into three main groups, such as procoagulants, anticoagulants and fibrinolytic enzymes according to their action. This review is focused on enzymes from Agkistrodon halys halys venom. They are thrombine-like enzyme, named Ancystron-H, flbrinogenolytic enzyme, protein C activator and platelet aggregation inhibitor. Ancystron-H is used for determination of fibrinogen level in blood plasma of patients undergoing heparin treatment and blood coagulation inhibitors accumulation. The fibrinogenolytic enzyme can be used as the instrument for protein-protein interactions in fibrinogen-fibrin system. The protein C activator is used for protein C level determination in blood plasma with different pathologies. Functions of the platelet aggregation inhibitor, belonging to disintegrins group, can be used for development of antithrombotic preparations. Information about the use of snake venoms in science and medicine is presented.     

Antithrombin-heparin cofactor: An inhibitor of plasma kallikrein

Human antithrombin-heparin cofactor is a naturally occurring plasma inhibitor of serine proteases generated during activation of the coagulation and fibrinolytic systems. We have demonstrated that purified preparations of this inhibitor also neutralize the esterolytic activity of human kallikrein as well as the ability of the enzyme to release kinins. When an excess of inhibitor is present, the inactivation process follows pseudo-first-order kinetics. Furthermore, the addition of heparin to mixtures of kallikrein and antithrombin-heparin cofactor results in a doubling of the rate and extent of enzyme neutralization. Disc gel analysis of incubation mixtures of kallikrein and excess antithrombin-heparin cofactor, with and without heparin, revealed that the enzyme band had vanished in conjunction with the emergence of two new electrophoretic species. These two new components probably represent stoichiometric complexes of kallikrein and antithrombin-heparin cofactor since a twofold increase in the concentration of enzyme doubled the concentration of these new molecular species. In plasmas which contain adequate levels of other protease inhibitors, antithrombin-heparin cofactor does not appear to be a quantitatively important inactivator of kallikrein. This is suggested by our finding that the addition of heparin at concentrations as high as 50 units/ml did not increase the inhibitory capacity of normal plasma directed against this enzyme. However, plasma from patients with hereditary angioedema had little neutralizing activity directed against kallikrein and revealed a marked increase in this inhibitory capacity when therapeutic concentrations of heparin were added. Our observation suggests that this acidic mucopolysaccharide may prove useful in controlling acute attacks of this disorder.     

Variation of some serum proteins in red deer, Cervus elaphus L

Various electrophoretic techniques, immunoblotting and inhibitions of trypsin and chymotrypsin were used to study the variability of serum proteins in farmed red deer, Cervus elaphus L., of Czechoslovakian origin. Easily interpretable polymorphisms were observed in transferrin (variants A, B1, B2, C) and vitamin D binding protein, GC (variants D, F, I, S). Great variability was observed in the protease inhibitors PI2, PI3, PI4, PI5, and PI8 and in unidentified zones in the vicinity of albumin, but no genetical or physiological interpretation for this variability is yet available. Haemopexin, alpha 1 glycoprotein, protease inhibitors PI1, PI6 and PI7 were monomorphic.     

Safety aspects in the manufacturing of plasma-derived coagulation factor concentrates.

Plasma-derived coagulation factor concentrates, prepared using traditional manufacturing processes, have transmitted viral diseases, especially AIDS, hepatitis B and hepatitis C to patients. To date, more extensive selection of blood donors, improved screening procedures of each plasma donation for direct and indirect viral markers, and newly developed virucidal procedures, especially pasteurization and solvent-detergent, together with extraction technologies of plasma proteins based on high-resolution chromatographic separations, have diminished considerably the risks of transmitting these pathogenic agents. To ensure safety, each production process must be carefully validated, following a rigorous scientific approach to assess its ability to inactivate or eliminate viruses. In addition, Good Manufacturing Practices must avoid any variation from these validated viral inactivation processes and must eliminate risks of potential downstream contamination of purified plasma fractions following viral inactivation or elimination steps. Other side-effects associated with conventional low-purity preparations, such as acute haemolytic anemia due to contamination by isohaemagglutinins, or immunosuppression possibly due to an overload in fibrinogen and immunoglobulins, have not been reported following infusion of highly purified coagulation factor concentrates. Present state-of-the-art virus inactivation and protein-purification technologies have significantly improved the safety of plasma coagulation factor concentrates.     

Regulated serine proteinase lytic system on mammalian sperm surface: There must be a role

Serine proteases play key roles in many biological processes, regulating surface proteins that are key-points in signaling pathways. Several studies have reported the presence of members of this protease family in sperm from various species. The precise regulation of their activity is thought to be performed by specific endogenous or extrinsic inhibitors. The contribution of the sperm serine to proteases to fertilization has been demonstrated by synthetic inhibitors and several single knock out experiments, but to date, there is no evidence that links a single enzyme to a single step of fertilization. The explanation for the failure in the understanding of the “one-enzyme-one-process” hypothesis may be that sperm have multiple serine proteases as a mechanism to ensure the success of fertilization. In addition to the classical purification and expression studies, we summarized recent advances in proteomics and performed a bioinformatics search of proteases and inhibitors, providing support for the idea of redundancy. This review summarizes current knowledge about serine proteases and their inhibitors in sperm capacitation and maturation, identifies questions that need to be answered, and provides a reference for future research.     

Mapping of natural anti-factor VIII antibodies in plasma pools from healthy donors: use of rationally designed synthetic peptides.

Inhibitor antibodies of blood coagulation factor VIII (FVIII) impair FVIII replacement therapy, constituting a serious complication in haemophilic patients. anti-FVIII antibodies may also develop in a variety of disease-associated autoimmunity. Mapping of human FVIII inhibitors in haemophilia A or autoantibody origin have delineated three major clusters of B-cell inhibitory epitopes (domain A2, A3 and C2). Inhibitory and non-inhibitory FVIII antibodies have also been described in plasma of healthy donors and pools of immunoglobulins. The purpose of this study was to use synthetic FVIII-peptides to more closely define regions of the molecule targeted by natural anti-FVIII antibodies. Predictive algorithms were used for defining the positions of potential continuous epitopes. To investigate the presence of peptide-reactive antibodies in normal plasma pools of healthy donors, a plasma fraction (Cohn fraction II+III) containing all IgG subclasses was purified by affinity chromatography on peptide-Sepharose columns. The results of ELISAs and Western blotting experiments (with the selected peptides and well-defined recombinant FVIII thrombin fragments) confirmed the reaction specificities of the affinity-purified human antibodies. For each IgG preparation, the isotopic subclass was also determined. In the clotting assay, several IgG preparations showed neutralising activity in a dose-dependent manner. Our observations support the recent hypothesis that FVIII inhibitors in haemophilia A and autoimmune disease may originate from the proliferation of natural FVIII-specific B-cell clones.     

Mechanism-based isocoumarin inhibitors for serine proteases: use of active site structure and substrate specificity in inhibitor design

Isocoumarins are potent mechanism-based heterocyclic irreversible inhibitors for a variety of serine proteases. Most serine proteases are inhibited by the general serine protease inhibitor 3,4-dichloroisocoumarin, whereas isocoumarins containing hydrophobic 7-acylamino groups are potent inhibitors for human leukocyte elastase and those containing 7-alkylureidogroups are inhibitors for procine pancreatic elastase. Isocoumarins containing basic side chains that resemble arginine are potent inhibitors for trypsin-like enzymes. A number of 3-alkoxy-4-chloro-7-guanidinoisocoumarins are potent inhibitors of bovine thrombin, human factor Xa, human factor XIa, human factor XIIa, human plasma kallikrein, porcine pancreatic kallikrein, and bovine trypsin. Another cathionic derivative, 4-chloro-3-(2-isothiureidoethoxy) isocoumarin, is less reactive toward many of these enzymes but is an extremely potent inhibitor of human plasma kallikrein. Several guanidinoisocoumarins have been tested as anticoagulants in human plasma and are effective at prolonging the prothrombin time. The mechanism of inhibition by this class of heterocyclic inactivators involves formation of an acyl enzyme by reaction of the active site serine with the isocoumarin carbonyl group. Isocoumarins with 7-amino or 7-guanidino groups will then decompose further to quinone imine methide intermediates, which react further with an active site residue (probably His-57) to form stable inhibited enzyme derivatives. Isocoumarins should be useful in further investigations of the physiological function of serine proteases and may have future therapeutic utility for the treatment of emphysema and coagulation disorders.     

The use of fluorogenic substrates to monitor thrombin generation for the analysis of plasma and whole blood coagulation

Thrombin is central to the process of coagulation and monitoring its activity is a reliable indicator of the rate and extent of coagulation. I have employed a range of fluorogenic peptide substrates as indicators of coagulation via the formation of active thrombin. This system enabled coagulation to be monitored in a kinetic fashion, and the use of fluorescence enabled a wide range of samples to be analyzed including lyophilized plasma containing fibrin, fresh platelet-poor plasma, platelet-rich plasma, and even whole blood. Coagulation could be monitored following triggering by tissue factor, ellagic acid, or each of the proteases preceding thrombin in the coagulation network. Using this assay procedure I have investigated the anticoagulant activities of a number of compounds and the results indicate that this assay would be useful for the kinetic analysis of coagulation in various plasma preparations, or even whole blood.     

Protease from a strain of bacteria E. coli A2, specifically cleaving actin

A novel bacterial protease specifically hydrolyzing actin with the formation of a stable fragment with Mr of 36 kDa was obtained. This protease was shown to be synthesized at the stationary phase of bacterial culture growth. The actin hydrolysis by bacterial protease was inhibited by o-phenanthroline, EDTA and p-chloromercuribenzoate but not by N-ethyl-maleimide, phenylmethylsulfonylfluoride, Leu-peptin, pepstatin and other serine proteinase inhibitors. The protease was stable within the pH range of 4.5-8.5 and had an activity optimum at pH 7.0-8.0. The protease activity was maintained for 40 min at 45 degrees C and for 30 min at 50 degrees C; at 65 degrees C the enzyme was fully inactivated by 5 min heating. The protease preparations causing quantitative conversion of actin into a 36 kDa fragment did not hydrolyze casein, albumin, ovalbumin, lysozyme, DNAase I, RNAase, myosin, alpha-actinin, tropomyosin and troponin. It was assumed that the protease under consideration is a neutral metalloprotease specifically hydrolyzing actin.     

Recent developments in the mechanistic enzymology of the ATP-dependent Lon protease from Escherichia coli: highlights from kinetic studies

Lon protease, also known as protease La, is one of the simplest ATP-dependent proteases that plays vital roles in maintaining cellular functions by selectively eliminating misfolded, damaged and certain short-lived regulatory proteins. Although Lon is a homo-oligomer, each subunit of Lon contains both an ATPase and a protease active site. This relatively simple architecture compared to other hetero-oligomeric ATP-dependent proteases such as the proteasome makes Lon a useful paradigm for studying the mechanism of ATP-dependent proteolysis. In this article, we survey some recent developments in the mechanistic characterization of Lon with an emphasis on the utilization of pre-steady-state enzyme kinetic techniques to determine the timing of the ATPase and peptidase activities of the enzyme.     

Introduction to the blood coagulation cascade and cloning of blood coagulation factors

The coagulation cascade that occurs in mammalian plasma involves a large number of plasma proteins that participate in a stepwise manner and eventually give rise to the formation of thrombin. This enzyme then converts fibrinogen to an insoluble fibrin clot. This series of reactions involves a number of glycoproteins that particupate as enzymes as well as cofactors. These proteins that circulate in the blood in a precursor or zymogen form are multifunctional proteins that share many common segments or domains. One group includes the vitamin K-dependent glycoproteins (prothrombin, factor IX, factor X, and protein C) that show considerable homology in both their amino acid sequences and their gene structures. The proteins that participate in the contact or early phase of the blood coagulation cascade include plasma prekallikrein, factor XII, and factor IX. The amino-terminal regions of both factor XI and plasma prekallikrein contain four tandem repeats of about 90 amino acids, and these tandem repeats show considerable amino acid sequence homology. Factor XII contains four different domains in the amino-terminai region of the protein, including a kringle structure, two growth factor domains, and type I and type II finger domains. The finger domains were first identified in fibronectin. The carboxyl-terminal portion of plasma prekallikrein, factor XII, and factor XI contains the serine or protease portion of the molecule. These various plasma proteins that share common domains appear to have evolved by gene shuffling that may have, in some cases, involved introns.     

A new type of lectin discovered in a fish, flathead (Platycephalus indicus), suggests an alternative functional role for mammalian plasma kallikrein

A skin mucus lectin exhibiting a homodimeric structure and an S-S bond between subunits of ~40 kDa was purified from flathead Platycephalus indicus (Scorpaeniformes). This lectin, named FHL (FlatHead Lectin), exhibited mannose-specific activity in a Ca(2+)-dependent manner. Although FHL showed no homology to any previously reported lectins, it did exhibit ~20% identity to previously discovered plasma kallikreins and coagulation factor XIs of mammals and Xenopus laevis. These known proteins are serine proteases and play pivotal roles in the kinin-generating system or the blood coagulation pathway. However, alignment analysis revealed that while FHL lacked a serine protease domain, it was homologous to the heavy-chain domain of plasma kallikreins and coagulation factor XI therefore suggesting that FHL is not an enzyme but rather a novel animal lectin. On the basis of this finding, we investigated the lectin activity of human plasma kallikrein and revealed that it could indeed act as a lectin. Other genes homologous to FHL were also found in the genome databases of some fish species, but not in mammals. In contrast, plasma kallikreins and coagulation factor XI have yet to be identified in fish. The present findings suggest that these mammalian enzymes may have originally emerged as a lectin and may have evolved into molecules with protease activity after separation from common ancestors.     

In vitro effects of Echis carinatus venom on the human plasma proteome

Echis carinatus venom (EV) is a complex mixture of toxins that contribute to its lethality. EV proteolytic activity was analyzed by zymography, chromogenic assays, and SDS-PAGE. To understand the molecular mechanism of the envenomation, we investigated the in vitro effect of EV on human plasma proteins. We looked for EV protein substrates and their proteolytic fragments. We analyzed EV proteolytic activity on standard proteins such as prothrombin or fibrinogen. To set up the optimal EV:plasma protein ratio conditions, plasma was incubated with EV (treated plasma), depleted of abundant proteins, and subjected to SDS-PAGE. Samples from control and treated plasma were also analyzed by 2-DE/MALDI-TOF MS, leading to the identification of four classes of plasma proteins cleaved by EV: proteases, protease inhibitors, binding proteins, and transporters. EV mainly proteolyzes entire proteins but can also act on physiological fragments. In summary, the physiological effects of EV proteases involve other important processes in addition to blood coagulation; complement activation and hemoglobin metabolism are also affected. In particular, the cleavage of protease inhibitors appears to be the mechanism through which the venom neutralizes the body's defenses.     

Proteomic analysis of microvesicles from plasma of healthy donors reveals high individual variability

Healthy blood plasma is required for several therapeutic procedures. To maximize successful therapeutic outcomes it is critical to control the quality of blood plasma. Clearly initiatives to improve the safety of blood transfusions will have a high economical and social impact. A detailed knowledge of the composition of healthy blood plasma is essential to facilitate such improvements. Apart from free proteins, lipids and metabolites, blood plasma also contains cell-derived microvesicles, including exosomes and microparticles from several different cellular origins. In this study, we have purified microvesicles smaller than 220nm from plasma of healthy donors and performed proteomic, ultra-structural, biochemical and functional analyses. We have detected 161 microvesicle-associated proteins, including many associated with the complement and coagulation signal-transduction cascades. Several proteases and protease inhibitors associated with acute phase responses were present, indicating that these microvesicles may be involved in these processes. There was a remarkably high variability in the protein content of plasma from different donors. In addition, we report that this variability could be relevant for their interaction with cellular systems. This work provides valuable information on plasma microvesicles and a foundation to understand microvesicle biology and clinical implications.     

Simultaneous determination of functional coagulation factors and competitive (PIVKA-) inhibitors based on enzyme kinetics

For a plasma containing the competitive (PIVKA-) inhibitors induced by anticoagulant treatment the coagulation time t is related to the concentrations of functional coagulation factors S (substrates) and competitive inhibitors I by t = tmin + el/S + gamma I/S with tmin being the minimum possible coagulation time and e and gamma the sensitivities of the test procedure towards a change in the concentration of functional coagulation factors and competitive inhibitors, respectively. The calibration of the test procedure can be achieved by performing a series of dilutions on an inhibitor-free plasma (determination of tmin and e) and, after that, on a plasma of known inhibitor content (determination of gamma) in both cases recording the parametrizing straight line which results from multiplying the respective equation by S. The content of functional coagulation factors and competitive inhibitors in the plasmas of anticoagulated patients then can be determined simultaneously by treating the patient's plasma like in the calibration for gamma. The proposed method should allow the complete metrological characterization of thromboplastin time reagents without any need for reference thromboplastins.     

Exploiting structural principles to design cyclin-dependent kinase inhibitors

Although cyclin-dependent kinases (CDKs) have been extensively targeted in anti cancer drug design, no CDK inhibitor has yet been approved for use in cancer therapy. While this may in part be because inhibitors clinically evaluated to date have not demonstrated clean inhibition of a single CDK, another contributing factor is an apparent latent functional redundancy in the CDK cell-cycle regulatory system. This further complicates the already challenging goal of targeting CDKs, since it implies that a therapeutically useful inhibitor will have to selectively inhibit more than one CDK family member among the complement of cellular proteins. Despite these difficulties, achieving an appropriate profile of CDK inhibition may yet be possible using ATP-competitive inhibitors, thanks to advances in computational and experimental methods of drug design. However, as an alternative to ATP-competitive inhibitors, inhibitors that interfere with a CDK-specific protein:protein interaction, such as that which occurs at the recruitment site found on several cyclins, may offer a route to a therapeutically useful inhibitory profile.