259: Absolute chimerism as a tool in monitoring imminent and manifest graft rejection after hematopoietic cell transplantation with nonmyeloablative conditioning

ondary to HIV. Treatment was initiated with D4T (Stavudine), 3TC (Lamivudine) and Efavirenz achieving undetectable viral load and increasing CD4 count. Patient also received Erythropoietin (EPO) and granulocyte-colony stimulating factors (G-CSF) showing an increased number of white blood cells (WBC) but continued with high transfusional requeirment. We had to stop treatment in October because of liver failure and lactic acidosis. In November we changed Stavudine for Tenofovir and reiniciated treatment. Viral load was always undetectable and CD4 count was 500 cells/ul. However megakaryocytopoiesis and erythropoiesis did not respond, requiring many transfusions. Coombs Direct Test (CDT) and Coombs Indirec Test (CIT) were positive.He showed an immunohaematologic profile with 1 autoantibody (Anti-e) and 3 alloantibodies (Anti-Jka, Anti-Lua, Anti-Cw). As he had an identical twin, he was submitted to a syngeneic BMT. Although he was heavily transfused (421 Units ), we did not want to increase immunosuppression so as not to have viral reactivation. The conditioning regimen consisted of Cy 50 mg/kg/qd x 4, and in order to lower the risk of engrafment failure, peripheral blood stem cells were used to maximize the number of donor cells infused (11 10 CD34 cells/kg). At the transplantation the patient was in high-risk. The antiretroviral treatment was not discontinued. No graft versus host disease (GVHD) profilaxis was needed. Neutrophils and platelets engrafted at day 11. After 10 months of transplantation he continues in complete haematologic remission. Serum antibodies, CDT and CIT are negative.Viral load remains undetectable (b-DNA).