Our research focuses on several biologic and immunologic aspects of transfusion medicine. Three projects deal with questions related to platelet biology. Specifically, Dr. Slichter's project seeks to define the parameters that must be met to allow extension of platelet storage by evaluating the effects of an initial collection injury that may limit storage duration and the role of storage solutions in facilitating extended platelet storage. Dr. Gilligan and Reems'project expects to identify the optimal methods of growing megakaryocytes in culture with the goal of producing platelets or "platelet-like fragments" that function similarly to platelets in maintaining hemostasis. Dr. Josephson's project focuses on the development of foamy virus vectors as a gene transfer system to deliver therapeutic genes into hematopoietic stem cells. The target disease that he will use as a model for his system is congenital amegakaryocytic thrombocytopenia (CAMT). Two additional projects have an immunologic emphasis. Dr. Nelson's project involves transfusing three different types of blood products [standard (unmodified), leukoreduced, or leukoreduced gamma-irradiated] into immunocompetent patients undergoing open-heart surgery. The differences in serologic and cellular immune responses in the three patient cohorts as well as the influence of HLA Class II sharing between donors and recipients on immunologic outcomes will be evaluated. Dr. S. Pratt and Thompson's project addresses issues related to the prevention or reversal of inhibitor antibody formation in patients with acquired or congenital hemophilia A. Modification of T-cell epitopes in FVIII may lead to non-immunogenic FVIII replacement therapy while new peptides or recombinant proteins may be useful in tolerance induction for patients with existing antibodies. Finally, an administrative core will be used to maintain an interactive environment among the SCCOR scientists and provide administrative and statistical support. In summary, we have utilized the established expertise of our scientists to address several important questions in Transfusion Medicine. In addition, most projects involve the skills of one or more Blood Center scientists working within and between the projects to accomplish the objectives of this SCCOR Program. (End of Abstract) PROJECT 1: Strategies to Extend Platelet Storage (Slichter, Sherrill) DESCRIPTION (provided by applicant): The primary objective of these studies is to determine whether platelets (plts) can be stored for longer than the currently-licensed 5 days. Furthermore, does the duration of plt storage depend on the type of plt product being stored (apheresis plts, plt concentrates prepared from plt-rich plasma (PRP), or from buffy coats (BC), pre-storage pooled PRP plt concentrates, or pathogen-reduced apheresis or BC plts), and the medium used for storage;i.e., plasma or a storage solution. The four critical questions that will be addressed in our studies are: 1) does the method of plt collection using apheresis procedures versus preparing plt concentrates from whole blood influence storage duration?;2) does pre-storage pooling of plt concentrates affect plt viability?;3) do plt storage solutions allow plts to be stored longer than plts stored in plasma?;and 4) can pathogen-reduced plts be stored for extended time periods similar to non-pathogen reduced plts? Although in vitro tests will be performed to document post-storage plt counts as well as a variety of assays to determine post-storage plt function, metabolism and apoptosis, the post-storage quality of the extended stored plts will be based on in vivo measurements in normal volunteers and thrombocytopenic patients. Specifically, radiolabeled plt recovery and survival measurements of extended stored autologous plts in normal volunteers will be used to determine post-storage plt viability for all types of plt products stored in plasma versus a storage solution. For plts that are stored for longer than 8 days and/or are stored in a storage solution, transfusion studies in the thrombocytopenic patients will be used to evaluate plt viability by measuring the radiolabeled recovery and survival of the donors'plts following transfusion. Alternatively, patient responses to transfused donor plts will be determined by measuring post-transfusion plt increments, corrected count increments, and days-to-next transfusion. Plt function (i.e., hemostasis) following the transfusion of extended stored donor plts will be monitored by plt count versus bleeding time measurements and by radiochromium-labeled stool blood loss studies. At the conclusion of these studies, we should know how long each type of plts can be stored in plasma or Plasmalyte, the relative merits of each type of plts, and whether the extended stored plts are both viable and functional when given to thrombocytopenic patients. (End of Abstract)