SUSTAINED EXPRESSION OF HIGH-LEVELS OF HUMAN FACTOR-IX FROM HUMAN-CELLS IMPLANTED WITHIN AN IMMUNOISOLATION DEVICE INTO ATHYMIC RODENTS

Immunoisolation of allogeneic cells within a membrane-bound device is a unique approach for gene therapy. We employed an immunoisolation dev ice that protects allograft, but not xenograft, cells from destruction , to implant a human fibroblast line (MSU 1.2) in athymic rodents. Cel ls, transduced with the MEG-human factor IX retroviral vector, and exp ressing 0.9 mu g/10(6) cells/day in vitro, were implanted in rats (fou r 40-mu l devices, each containing 2 x 10(7) cells, two subcutaneously , two in epididymal fat) and in mice (two 20-mu l devices, each contai ning 2 x 10(6) cells, subcutaneously). Plasma factor IX levels increas ed for 50 days, reaching maxima of 203 ng/ml (rat) and 597 ng/ml (mous e), and both continued at greater than 100 ng/ml for more than 140 day s. A clone derived from the transduced cells, making 5 mu g of factor IX/10(6) cells/day, was implanted within a device (one 20-mu l device containing 2.5 x 10(6) cells), or without a device (1 x 10(7) cells im planted freely), either subcutaneously or in epididymal fat. The freel y implanted cells expressed transiently, reaching more than 100 ng/ml in each site by day 4, but dropped to zero by day 20 (subcutaneous) or day 90 (epididymal fat). In devices, levels gradually increased to 10 0 ng/ml (subcutaneous) or 300 ng/ml (epididymal fat), remaining high f or more than 100 days. These results show long-term, high-level expres sion of a human protein: (1) when cells are implanted within a cell tr ansplantation device, but not when the cells are freely implanted, and (2) from a transgene driven by a viral promoter. An alloprotective de vice will enable the use of cloned cell lines that can be subjected to stringent quality control assessment that is impossible to achieve wi th autologous approaches.