The complete genomic DNA sequence of the highly attenuated vaccinia strain modified vaccinia Ankara (MVA) was determined. The genome of MVA is 178 kb in length, significantly smaller than that of the vaccinia Copenhagen genome, which is 192 kb. The 193 open reading frames (ORFs) mapped in the MVA genome probably correspond to 177 genes, 25 of which are split and/or have suffered mutations resulting in truncated proteins. The left terminal genomic region of MVA contains four large deletions and one large insertion relative to the Copenhagen strain. In addition, many ORFs in this region are fragmented, leaving only eight genes structurally intact and therefore presumably functional. The inserted DNA codes for a cluster of genes that is also found in the vaccinia WR strain and in cowpox virus and includes a highly fragmented gene homologous to the cowpox virus host range gene, providing further evidence that a cowpox-like virus was the ancestor of vaccinia. Surprisingly, the central conserved region of the genome also contains some fragmented genes, including ORF F5L, encoding a major membrane protein, and ORFs F11L and O1L, encoding proteins of 39.7 and 77.6 kDa, respectively. The right terminal genomic region carries three large deletions all classical poxviral immune evasion genes and all ankyrin-like genes located in this region are fragmented except for those encoding the interleukin-1 beta receptor and the 68-kDa ankyrin-like protein B18R. Thus, the attenuated phenotype of MVA is the result of numerous mutations, particularly affecting the host interactive proteins, including the ankyrin-like genes, but also involving some structural proteins.

Von Willebrand factor, an ultralarge concatemeric blood protein, must bind to platelet GPIbα during bleeding to mediate hemostasis, but not in the normal circulation to avoid thrombosis. Von Willebrand factor is proposed to be mechanically activated by flow, but the mechanism remains unclear. Using microfluidics with single-molecule imaging, we simultaneously monitored reversible Von Willebrand factor extension and binding to GPIbα under flow. We show that Von Willebrand factor is activated through a two-step conformational transition: first, elongation from compact to linear form, and subsequently, a tension-dependent local transition to a state with high affinity for GPIbα. High-affinity sites develop only in upstream regions of VWF where tension exceeds ~21 pN and depend upon electrostatic interactions. Re-compaction of Von Willebrand factor is accelerated by intramolecular interactions and increases GPIbα dissociation rate. This mechanism enables VWF to be locally activated by hydrodynamic force in hemorrhage and rapidly deactivated downstream, providing a paradigm for hierarchical mechano-regulation of receptor–ligand binding.

Stroke is a leading cause of death and disability. The only therapy available is recombinant tissue plasminogen activator, but side effects limit its use. Platelets play a crucial role during stroke, and the inflammatory reaction promotes neurodegeneration. von Willebrand factor (VWF), an adhesion molecule for platelets, is elevated in patients with acute stroke. The activity of VWF is modulated by ADAMTS13 (a disintegrin-like and metalloprotease with thrombospondin type I repeats-13) that cleaves VWF to smaller less-active forms. We recently documented that ADAMTS13 negatively regulates both thrombosis and inflammation. We report that deficiency or reduction of VWF reduces infarct volume up to 2-fold after focal cerebral ischemia in mice, thus showing the importance of VWF in stroke injury. In contrast, ADAMTS13 deficiency results in larger infarctions, but only in mice that have VWF. Importantly, infusion of a high dose of recombinant human ADAMTS13 into a wild-type mouse immediately before reperfusion reduces infarct volume and improves functional outcome without producing cerebral hemorrhage. IntroductionIschemic stroke is a leading cause of death and disability around the world. Each year in the United States approximately 795 000 persons have a new or recurrent stroke. 1 Thrombolytic therapy with tissue plasminogen activator (tPA), which leads to fibrin degradation and promotes clot lysis, is beneficial for ischemic stroke. 2,3 However, tPA use is restricted to the first few hours after stroke. In addition, tPA may increase the incidence and severity of cerebral hemorrhage and edema formation. 2,3 Thus, there remains a clear need to identify new therapeutic agents for minimizing the effects of stroke. In addition to their effect on coagulation, such agents could also target platelet adhesion and the inflammatory process that follows ischemic stroke.von Willebrand factor (VWF) is a large multimeric glycoprotein that is important in platelet adhesion and thrombus formation. 4 At least in mice, VWF appears more important in arterial thrombosis than fibrin, 5 the substrate of tPA/plasmin. More recently, VWF was also shown to contribute to leukocyte adhesion and inflammatory cell recruitment. 6,7 VWF is stored in an ultra-large form (UL-VWF; Ͼ 20 million kDa) in platelet ␣-granules and Weibel-Palade bodies of endothelial cells from which it is released during injury or inflammation. 8,9 If not immediately consumed for platelet adhesion, the UL-VWF is cleaved by ADAMTS13 (a disintegrin-like and metalloprotease with thrombospondin type I repeats-13) to smaller less-adhesive multimers that circulate in plasma. ADAMTS13 is a metalloprotease of approximately 190 kDa 10 present in plasma at a concentration of 0.5 to1 g/mL in humans. 11 Ischemia is a potent inducer of Weibel-Palade body secretion, 12 thus making the infarct area highly thrombogenic even after thrombolysis.VWF deficiency is associated with the most common bleeding disorder in humans, von Willebrand disease. 13 In contrast, deficiency of ADAMTS13 is se...

To study both the pathophysiologic and the prognostic value of ADAMTS13 in thrombotic microangiopathies (TMAs), we enrolled a cohort of 35 adult patients combining a first acute episode of TMA, an undetectable (below 5%) ADAMTS13 activity in plasma, and no clinical background such as sepsis, cancer, HIV, and transplantation. All patients were treated by steroids and plasma exchange, and an 18-month follow-up was scheduled. Remission was obtained in 32 patients (91.4%), and 3 patients died (8.6%) after the first attack. At presentation, ADAMTS13 antigen was decreased in 32 patients (91.4%), an ADAMTS13 inhibitor was detectable in 31 patients (89%), and an anti-ADAMTS13 IgG/IgM/IgA was present in 33 patients (94%). The 3 decedent patients were characterized by the association of several anti-ADAMTS13 Ig isotypes, including very high IgA titers, while mortality was independent of the ADAMTS13 inhibitor titer. In survivors, ADAMTS13 activity in remission increased to levels above 15% in 19 patients (59%) but remained undetectable in 13 patients (41%). Six patients relapsed either once or twice (19%) during the follow-up. High levels of inhibitory anti-ADAMTS13 IgG at presentation were associated with the persistence of an undetectable ADAMTS13 activity in remission, the latter being predictive for relapses within an 18-month delay. IntroductionThrombotic microangiopathies (TMAs) are defined by the association of acute mechanical hemolytic anemia, thrombocytopenia, and visceral ischemic manifestations related to the formation of platelet thrombi in the microcirculation. 1 Clinically, TMA includes mainly the thrombotic thrombocytopenic purpura (TTP) and the hemolytic uremic syndrome (HUS) characterized by a multivisceral ischemia and a renal ischemia, respectively. 2 Although mechanisms for HUS remain very heterogeneous, pathophysiology for most forms of TTP is related to a severe deficiency of a plasma metalloprotease, ADAMTS13 (a disintegrin and metalloprotease with thrombospondin type 1 repeats). [3][4][5][6] Physiologically, ADAMTS13 is the specific cleaving protease for von Willebrand factor (VWF), a large multimeric glycoprotein crucial for both platelet adhesion and aggregation in the high stress-associated hemodynamic conditions of the microcirculation. 7 A severe enzymatic deficiency of ADAMTS13 causes highly adhesive unusually large multimers of VWF to accumulate in plasma, which may spontaneously bind to platelets and thus induce the formation of platelet thrombi in the microcirculation. In rare cases, clinically relevant ADAMTS13 severe deficiency is related to compound heterozygous or homozygous mutations of the ADAMTS13 gene (Upshaw-Schulman syndrome). [8][9][10] In most cases, severe ADAMTS13 deficiency is secondary to the development of anti-ADAMTS13 autoantibodies (auto-Abs). [11][12] Anti-ADAMTS13 auto-Abs can be detected in vitro either functionally because of their inhibitory effect on ADAMTS13 enzymatic activity [13][14] or, more recently, physically as immunoglobulin G (IgG) or IgM by enzyme-lin...

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