Murine model of Rh incompatibility for alternative therapy and serologic reagents

DESCRIPTION (provided by applicant): Antibodies that distinguish common Rh specificities cannot be induced in normal mice. Our hypothesis is that this is most likely due to the shaping of their immune repertoires by the murine Rh homologue, and that these specificities would be produced by mice whose repertoires are shaped in the presence of human Rh proteins. The goal of this project is to create strains of mice expressing human RH transgenes and use them to develop a mouse model of Rh incompatibility, which would have commercial potential in at least three areas: 1) Development of alternative therapies for treatment of Rh hemolytic disease of the newborn (HDN), a severe and potentially fatal syndrome, the prevention of which relies on a diminishing supply of human source material with ever-present risks from emerging or surreptitious infectious agents; 2) Production of murine monoclonal Rh serologic reagents with promise for specificity superior to those currently in use; and 3) Future development of reagents to prevent alloimmunization to blood group antigens. HDN has been treated successfully with Rh immune globulin since the 1960's. The success of the treatment, though, has reduced the Rh immune globulin supply by decreasing the number of individuals sensitized to the D antigen. For this reason, and because of the concern over the use of blood-derived products, alternative therapies are needed, but there is no reliable experimental system in which to develop and test them. The long-term goal of this project is to establish such a system for development of methods to not only prevent not only HDN, but to target prevention of alloimmunization to blood group antigens in general. Importantly, this project will provide a unique and accurate model system with the potential to study a broad range of clinically relevant issues in transfusion medicine, such as HDN, transfusion reactions, and IVIg therapy. In addition, the model could be used to address many basic questions in transfusion medicine dealing with composition and assembly of the erythrocyte Rh complex, immune tolerance, and immunosuppression. The proposal consists of two specific aims: 1. Construction of mice transgenic for the human RHD and RHce genes. Constructs containing human RHD and RHce cDNAs will be used for creation of the transgenic mice. When mice carrying the transgenes have been identified, their erythrocytes will be characterized for expression of human Rh blood group antigens. 2. Induction of Rh-specific antibodies and placental antibody transfer in RH transgenic mice. Rh-specific antibodies will be induced in the transgenic mice as proof of our hypothesis and the validity of this system as a model of HDN. The final validation of the system will be demonstration of placental transfer of D-specific antibodies in sensitized females by testing erythrocytes from their fetuses or neonates for bound anti-D by the direct antiglobulin test (DAT) and elution of anti-D. The long-term goal of this program is to develop alternatives treatments for preventing hemolytic disease of the newborn (HDN). This need exists because of the diminished supply of Rh immune globulin and concern that blood-derived products are not without risk. This project will provide a unique and accurate model system with the potential to study a broad range of clinically relevant issues in transfusion medicine, such as HDN, transfusion reactions, and IVIg therapy.