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Comparing actual data to those of the previous surveys we again got very consistent findings indicating fairly good data quality. In addition our data are comparable to that of international large-scale prevalence studies and registry data. Despite mortality from HIV in patients with hemophilia is keeping on decreasing, HIV still remains an important factor as an HIV/HCV coinfection seems to increase risk of progression of liver disease to cirrhosis and hepatocellular carcinoma [5, 7]. In addition our findings stress the hypothesis that a relevant portion of patients reported dead of cancer might have died of primary hepatocellular carcinoma induced by chronic HCV. The fact that our data does not show an increasing number of patients with inhibitors over the last three decades does not support the thesis that recombinant factor VIII products induce a higher inhibitor risk.

The present review discusses the current concept of receptor-mediated clearance of coagulation factor VIII (FVIII) from the circulation in vivo, which is one of the mechanisms regulating FVIII level in plasma. Several lines of experimental evidence suggest that two receptors from the LDL receptor family, low-density lipoprotein receptor-related protein (LRP) and LDL receptor, cooperate in this process. Administration of receptor-associated protein, a classical antagonist of these receptors, leads to prolongation of FVIII half-life in mice.The elevation of FVIII level and prolongation of its mean residence time, recorded in conditional LRP-deficient mice, directly confirm the physiological role of LRP in mediating clearance of FVIII. Mice with combined LRP and low-density lipoprotein receptor (LDLR) deficiency show a further increase of FVIII level and more impressive, ~5-fold, prolongation of FVIII residence time in the circulation. Receptor-mediated clearance of FVIII is facilitated by heparan sulfate proteoglycans of extracellular matrix, which provide the initial binding of FVIII to the cell surface.We discuss the mapping of the major high-affinity LRP-binding sites to the regions 484-509 and 1811-1818 of A2 and A3 domains of FVIII, respectively; LDLR-binding sites are yet to be identified. Mutagenesis of these sites may result in disruption/reduction of FVIII/receptor interaction and consequently lead to clinically-significant prolongation of FVIII lifetime in the circulation.We demonstrate the feasibility of this approach by the results of Ala-scanning mutagenesis of the A2 LRP-binding site. Generation of a novel recombinant FVIII with prolonged lifetime would meet the demands, improve the efficacy and reduce the cost of FVIII replacement therapy of Hemophilia A. Coagulation factor VIII (FVIII) [1] serves its function in the intrinsic coagulation pathway as a cofactor for the serine protease FIXa in activation of FX to FXa [1, 2]. Genetic or functional deficiency in FVIII phenotypically results in the bleeding disorder Hemophilia A, as the intrinsic pathway is responsible for normal spatial propagation of the clotting process from the surface of tissue factor-bearing cells. The FVIII molecule (~300 kDa, 2332 amino acid residues) consists of three homologous A domains, two homologous C domains and the unique B domain (A1- A2-B-A3-C1-C2). In plasma, FVIII circulates as a metal ion-linked heterodimer consisting of the heavy chain (HCh),which is comprised of the A1 (1-336),A2 (373-719) and B domains (741-1648), and the light chain (LCh), which includes the A3 (1690- 2019), C1 (2020-2172) and C2 (2173-2332) domains. In the circulation, FVIII is tightly non-covalently associated with its carrier protein von Willebrand factor (Kd ~ 0.4 nM),which prevents premature assembly of the Xase complex and protects FVIII from proteolytic inactivation [2, 3]. Limited proteolysis by physiological activators, thrombin or FXa, at Arg372 and Arg740 within FVIII HCh and at Arg1689 within LCh converts FVIII into its active form. In heterotrimeric activated FVIII, the A1 and A3 domains retain the metal ion bridge, and the relatively stable A1/A3-C1-C2 dimer is weakly associated with the A2 subunit through electrostatic interactions [1, 2]. The cofactor activity of FVIIIa in the assembled intrinsic Xase complex is provided by three essential interactions of FVIIIa: with the phospholipid membrane, with the enzyme FIXa and the substrate FX. The high-affinity interaction (Kd ~ 15 nM) between FVIIIa and FIXa is provided by residues 1811-1818 of the A3 domain of LCh [4]. Binding of the A2 domain to FIXa, although with low-affinity (Kd~300 nM), modulates the active site of FIXa and in this way amplifies the enzymatic activity of FIXa by 100-fold [5]. Specifically, the A2 residues 484-509 were shown to be involved in this interaction [6]. The FX-binding site was localized to A1 residues 349-372 of FVIII.

We are presenting an update of our study in which risk factors for the development of inhibitors in patients with hemophilia are to be explored. The ultimate goal is to find out why some children suffering from severe or moderate hemophilia develop inhibitory antibodies during replacement therapy and others do not, and to define genetic and immunological risk factors. The development of inhibitors is one of the most important complications of the replacement therapy in hemophilia affecting mortality and morbidity.The development of inhibitory antigens is based on complex immunological factors, and to date, too little is known about the basic mechanisms of inhibitor development. Risk factors are presumably derived from the immune system. Inhibitory antibodies are mostly IgG-type immunoglobulins, especially subclass 4, rarely subclass 1. During inhibitor formation, CD4+ T cells are directed in a cytokine-dependent manner to the Th1 or Th2 pathway. The development of inhibitors is very likely to be a Th-2 mediated event where cytokines and their receptors, T-cell receptors, and the Major Histocompatibility Complex may also play important roles. One examples of the cytokine connection is a mouse model, in which the development of inhibitors is prevented by the blockade of the co-stimulating factor B7/CD28. Within the scope of our study we want to compare genetic polymorphisms in immune-response associated genes between patients with and without inhibitors and between patients and the normal population: The characterization of genetic polymorphisms including for instance TLR, TNF-a, CD40, IL-10 and IL-1b are emphasized. The correlation between some genotypes or polymorphisms in cytokines and the development of inhibitory antigens is to be studied. Up to now 15 centers agreed to take place in our study. 5 of these already sent samples, amounting to 46 samples of hemophiliacs. We evaluated 10 polymorphisms in different genes in the first 40 patients with Taq-Man-PCR, restriction fragment length polymorphisms (RFLP), ARMS and direct sequence analyzing. Promising results were seen in some polymorphisms, but in most of them so far the number of samples is too small to get significant results.

This large-scale study of 249 children, including 195 with hemophilia A, produced an efficient and systematic examination process for the lower extremity that is easy to learn for hematologists and pediatricians, takes just about 5 minutes, and is highly likely to identify any clinically silent involvement of the joints in question. An appropriate preventive physical therapy and training program can be instituted before the patient sustains impairment of quality of life caused by the disorders identified by the examination process.

This case report demonstrates that, in selected hemophilic patients, simultaneous bilateral knee replacement surgery can be performed with a good outcome without a significant increase in perioperative risk.The overall costs, especially for the FVIII replacement, are significantly lower in the simultaneous bilateral surgery than in the unilateral staged surgery. The authors continue to offer hemophilic patients the option of simultaneous bilateral total knee arthroplasties.