Nonmyeloablative conditioning is sufficient to allow engraftment of EGFP-expressing bone marrow and subsequent acceptance of EGFP-transgenic skin grafts in mice.
Immunologic reactions against gene therapy products may prove to be a frequent problem in clinical gene therapy protocols. Enhanced green fluorescence protein (EGFP) is commonly used as a marker in gene transfer protocols, and immune responses against EGFP-expressing cells have been documented. The present study was designed to investigate the effect of a pharmacologic, nonmyeloablative, conditioning regimen on the development of EGFP+ donor/recipient mixed bone marrow chimerism and ensuing tolerance to EGFP-expressing transplants. To this end, C57BL/6J (B6) mice were treated with soluble formulations of either busulfan (Busulfex) or the closely related compound treosulfan, followed by transplantation of bone marrow cells from EGFP-transgenic (B6-EGFP.Tg) donor mice. Such conditioning regimens resulted in long-term persistence of donor EGFP+ cells among various hematopoietic lineages from blood, bone marrow, and thymus. Stable hematopoietic chimeras transplanted at 10 to 17 weeks after bone marrow transplantation (BMT) with B6-EGFP.Tg skin grafts all accepted their transplants, whereas non-EGFP chimeric B6 control animals were able to mount rejection of the EGFP+ B6 skin grafts. Control third-party grafts from major histocompatibility complex (MHC)-mismatched mice were rejected within 20 days, indicating that acceptance of EGFP-expressing skin grafts was the result of specific immune tolerance induction by the transplantation of EGFP-transgenic bone marrow. Long-term tolerance to EGFP in chimeric recipients was confirmed by the absence of anti-EGFP-reactive T cells and antibodies. These results broaden the therapeutic potential for using hematopoietic molecular chimerism in nonmyeloablated recipients as a means of preventing rejection of genetically modified cells.
Andersson
Goran
G
BioTransplant Incorporated, Boston, MA 02129, USA.
Illigens
Ben M W
BM
Johnson
Kevin W
KW
Calderhead
David
D
LeGuern
Christian
C
Benichou
Gilles
G
White-Scharf
Mary E
ME
Down
Julian D
JD
D000818:Animals; D001854:Bone Marrow Cells / Q000378:metabolism; D016026:Bone Marrow Transplantation; D002066:Busulfan / Q000008:administration & dosage; D015316:Genetic Therapy / Q000379:methods; D006084:Graft Rejection / Q000517:prevention & control; D006085:Graft Survival; D049452:Green Fluorescent Proteins; D007108:Immune Tolerance / Q000276:immunology; D008164:Luminescent Proteins / Q000096:biosynthesis* / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D016038:Skin Transplantation; D014161:Transduction, Genetic; D019076:Transgenes; D019172:Transplantation Conditioning / Q000379:methods*
D008164:Luminescent Proteins; D049452:Green Fluorescent Proteins; D002066:Busulfan