IMPLANTATION OF AUTOLOGOUS SKIN FIBROBLAST GENETICALLY-MODIFIED TO SECRETE CLOTTING FACTOR-IX PARTIALLY CORRECTS THE HEMORRHAGIC TENDENCIESIN 2 HEMOPHILIA-B PATIENTS

Objective. To examine the safety and effects of gene therapy for hemop hilia B by implantation of autologous fibroblasts genetically modified to secrete clotting factor IX (hFIX). Patients and Methods. Two hemop hilia B patients LD and LW were selected from one family to accept gen e transfer study. The hFIX protein of both patients were about 100 ng/ ml plasma and hFIX activity was about 2%. The autologous skin fibrobla sts of the two patients were genetically modified by retrovirus-mediat ed gene transfer with XL-IX and N2CMVIX vector (HBSF-IX). Human. hFIX protein was measured by ELISA. hFIX activity was measured by one-stage clotting assay and barium citrate sorbent method. hFIX inhibitor was assayed by Bethesda methods. Human hFIX cDNA was detected by PCR. HBSF -IX cells were mixed with collagen for injection after safety assessme nts. Results. The HBSF-IX cells from the two patients secreted hFIX at high levels in vitro. After implantation of autologous HBSF-IX cells, no treatment-related side effects were observed. Plasma hFIX protein in both patients increased over 2 folds after several injections of HB SF-IX cells and persisted for more than 420 days. Blood clotting activ ity increased significantly in both patients, hemorrhagic tendencies h ave been partially corrected after treatment. Further elevation of hFI X can be achieved by repeating the same treatment 420 days later in Pa tient LD. Conclusions. Implantation of autologous fibroblast genetical ly modified to secrete human hFIX offers a simple, safe and effective approach to gene therapy of hemophilia B.