Design of Extracorporeal Specific Antibody Filters

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DESCRIPTION (provided by applicant): The proposed research will develop and study specific antibody filters (SAFs) for extracorporeal capture of anti-A blood group antibodies (Abs) causing hyperacute organ rejection. Recipient anti-A represents the most clinically significant impediment to ABO-incompatible transplantation. The SAFs will consist of hollow fiber membranes with A antigens (Ags) attached to the fiber lumenal surfaces. The targeted Abs bind to the Ags during whole blood perfusion of the SAF and are removed. We will establish design and operational principles for the SAF and exploit these to develop a SAF that can capture clinically useful levels of anti-A from circulating blood. The specific aims of the proposed research are to: 1. Synthesize trisaccharide and related tetrasaccharide A antigens. Using these we will immobilize several synthetic Ag conjugates to test membranes and assess their Ab binding interactions and functional capacity as related to Ag type and composition, including use of spacer molecules. We will fabricate mini-SAF modules with the most promising synthetic Ag conjugates, and we will verify their Ab binding characteristics and assess preliminary blood biocompatibility in bench perfusion experiments. 2. Evaluate the mass transfer characteristics of Ab capture in SAF modules using a bench-top perfusion loop. We will study the dependence of Ab clearance on key operating parameters, including Ag type and loading on fibers, lumenal flow rate, inlet antibody concentration, ultrafiltration rate, and the effects of red cells. We will compare experimental clearances to theoretical simulations of Ab transport in SAF fibers to obtain a predictive model of SAF performance for aiding in design, development and operation of the SAF. 3. Design and fabricate SAF modules capable of reducing normal anti-A levels from whole body blood volumes down to the accepted clinical target for ABO-incompatible transplantation. Perform in-vitro evaluation of Ab capture from these "clinical" SAFs. Perform acute calf experiments to assess anti-A capture in-vivo and the overall in-vivo biocompatibility of the "clinical" SAF prototypes. While anti-A removal is the subject of this grant, the proposed work will provide a scientific framework for the design and operation of effective SAF devices targeting other pathogenic Abs including anti-B blood group Abs, a less clinically significant but still important impediment to ABO-incompatible transplantation.