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      Platelet activation determines the severity of thrombocytopenia in dengue infection

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          Abstract

          Thrombocytopenia is common in patients with dengue virus (DENV) infections. With a focus on understanding the possible mechanism of thrombocytopenia in DENV infections we described a direct correlation between activation and depletion of platelets in patients. Our data showed a sharp decrease in platelet counts at day 4 of fever in patients. The high DENV genome copies in platelets correlated directly with the elevated platelet activation along with increased binding of complement factor C3 and IgG on their surface at day 4. Recovery in platelet count was observed on day 10 through day 6 and 8 with simultaneous decrease in platelet activation markers. Further, our in vitro data supported the above observations describing a concentration-dependent increase in platelet activation by DENV serotype-2. The high copy number of DENV2 genome in the platelet pellet correlated directly with platelet activation, microparticle generation and clot formation. Furthermore the DENV2-activated platelets were phagocytosed in large numbers by the monocytes. The DENV2-mediated lysis and clearance of platelets were abrogated in presence of platelet activation inhibitor, prostacyclin. These observations collectively suggest that platelet activation status is an important determinant of thrombocytopenia in dengue infections. A careful strategy of inactivation of platelets may rescue them from rapid destruction during DENV infections.

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          Carfilzomib, pomalidomide, and dexamethasone for relapsed or refractory myeloma.

          Treatment options for patients with heavily pretreated relapsed and/or refractory multiple myeloma remain limited. We evaluated a novel therapeutic regimen consisting of carfilzomib, pomalidomide, and dexamethasone (CPD) in an open-label, multicenter, phase 1, dose-escalation study. Patients who relapsed after prior therapy or were refractory to the most recently received therapy were eligible. All patients were refractory to prior lenalidomide. Patients received carfilzomib IV on days 1, 2, 8, 9, 15, and 16 (starting dose of 20/27 mg/m(2)), pomalidomide once daily on days 1 to 21 (4 mg as the initial dose level), and dexamethasone (40 mg oral or IV) on days 1, 8, 15, and 22 of 28-day cycles. The primary objective was to evaluate the safety and determine the maximum tolerated dose (MTD) of the regimen. A total of 32 patients were enrolled. The MTD of the regimen was dose level 1 (carfilzomib 20/27 mg/m(2), pomalidomide 4 mg, dexamethasone 40 mg). Hematologic adverse events (AEs) occurred in ≥60% of all patients, including 11 patients with grade ≥3 anemia. Dyspnea was limited to grade 1/2 in 10 patients. Peripheral neuropathy was uncommon and limited to grade 1/2. Eight patients had dose reductions during therapy, and 7 patients discontinued treatment due to AEs. Two deaths were noted on study due to pneumonia and pulmonary embolism (n = 1 each). The combination of CPD is well-tolerated and highly active in patients with relapsed/refractory multiple myeloma. This trial was registered at www.clinicaltrials.gov as #NCT01464034.
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            Coagulation abnormalities in dengue hemorrhagic Fever: serial investigations in 167 Vietnamese children with Dengue shock syndrome.

            The pathophysiological basis of hemorrhage in dengue infections remains poorly understood, despite the increasing global importance of these infections. A large prospective study of 167 Vietnamese children with dengue shock syndrome documented only minor prolongations of prothrombin and partial thromboplastin times but moderate to severe depression of plasma fibrinogen concentrations. A detailed study of 48 children revealed low plasma concentrations of the anticoagulant proteins C, S, and antithrombin III, which decreased with increasing severity of shock, probably because of capillary leakage. Concurrent increases in the levels of thrombomodulin, tissue factor, and plasminogen activator inhibitor type 1 (PAI-1) indicated increased production of these proteins. Thrombomodulin levels suggestive of endothelial activation correlated with increasing shock severity, whereas PAI-1 levels correlated with bleeding severity. Dengue virus can directly activate plasminogen in vitro. Rather than causing true disseminated intravascular coagulation, dengue infection may activate fibrinolysis primarily, degrading fibrinogen directly and prompting secondary activation of procoagulant homeostatic mechanisms.
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              Dengue virus binding and replication by platelets.

              Dengue virus (DENV) infection causes ∼200 million cases of severe flulike illness annually, escalating to life-threatening hemorrhagic fever or shock syndrome in ∼500,000. Although thrombocytopenia is typical of both mild and severe diseases, the mechanism triggering platelet reduction is incompletely understood. As a probable initiating event, direct purified DENV-platelet binding was followed in the current study by quantitative reverse transcription-polymerase chain reaction and confirmed antigenically. Approximately 800 viruses specifically bound per platelet at 37°C. Fewer sites were observed at 25°C, the blood bank storage temperature (∼350 sites), or 4°C, known to attenuate virus cell entry (∼200 sites). Dendritic cell-specific intercellular adhesion molecule-3-grabbing nonintegrin (DC-SIGN) and heparan sulfate proteoglycan were implicated as coreceptors because only the combination of anti-DC-SIGN and low-molecular-weight heparin prevented binding. Interestingly, at 37°C and 25°C, platelets replicated the positive sense single-stranded RNA genome of DENV by up to ∼4-fold over 7 days. Further time course experiments demonstrated production of viral NS1 protein, which is known to be highly antigenic in patient serum. The infectivity of DENV intrinsically decayed in vitro, which was moderated by platelet-mediated generation of viable progeny. This was shown using a transcription inhibitor and confirmed by freeze-denatured platelets being incapable of replicating the DENV genome. For the first time, these data demonstrate that platelets directly bind DENV saturably and produce infectious virus. Thus, expression of antigen encoded by DENV is a novel consideration in the pathogen-induced thrombocytopenia mechanism. These results furthermore draw attention to the possibility that platelets may produce permissive RNA viruses in addition to DENV.
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                Author and article information

                Journal
                Sci Rep
                Sci Rep
                Scientific Reports
                Nature Publishing Group
                2045-2322
                31 January 2017
                2017
                : 7
                : 41697
                Affiliations
                [1 ]Disease Biology Laboratory, Regional Centre for Biotechnology, National Capital Region Biotech Science Cluster , Faridabad, India
                [2 ]Department of Biotechnology, Manipal University , Karnataka, India
                [3 ]Vaccine and Infectious Disease Research Center, Translational Health Science and Technology Institute, National Capital Region Biotech Science Cluster , Faridabad, India
                [4 ]Department of Medicine, All India Institute of Medical Sciences , New Delhi, India
                [5 ]Department of Microbiology, All India Institute of Medical Sciences , New Delhi, India
                Author notes
                Article
                srep41697
                10.1038/srep41697
                5282509
                28139770
                fa46e7e2-80db-4775-9ee5-acadc79f2c13
                Copyright © 2017, The Author(s)

                This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/

                History
                : 04 August 2016
                : 21 December 2016
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