T cells mediate resistance to genetically modified bone marrow in lethally irradiated recipients.
BACKGROUND
In order for gene therapy to attain clinical relevance, efficient engraftment and long-term survival of cells that express transduced genes of interest must be achieved. In this study, we examined the extent to which host T cells affect engraftment of syngeneic bone marrow cells engineered to express a retrovirally transduced allogeneic major histocompatibility complex class-I gene.


METHODS
B10.AKM mice were preconditioned with lethal irradiation or lethal irradiation plus transient CD4 and CD8 T-cell depletion in addition to CD40-CD154 costimulatory blockade and were then reconstituted with syngeneic bone marrow cells transduced with retroviruses that carried the gene that encoded H-2K(b) (K(b)). Expression of K(b) on bone marrow-derived cells was then analyzed, and induction of tolerance to K was evaluated.


RESULTS
Mice conditioned using CD4 and CD8 T-cell depletion in addition to CD40-CD154 costimulatory blockade and lethal irradiation showed a significant increase in the frequency of bone marrow-derived cells that expressed K(b) when compared to animals that received lethal irradiation alone. Survival of allogeneic skin grafts that expressed K(b) was significantly prolonged in animals conditioned with anti-CD4, anti-CD8, and co-stimulatory blockade in addition to lethal irradiation (median survival time, 81 days) when compared to mice that received irradiation alone (mean survival time, 31 days; P=0.001).


CONCLUSIONS
Radioresistant host T cells significantly affect the ability to induce tolerance by gene therapy by affecting engraftment of transduced cells that expressed allogeneic major histocompatibility complex class-I genes in the absence of host T-cell depletion and costimulatory blockade, even after lethal irradiation. Thus, radioresistant host T cells are a significant barrier to engraftment of transduced bone marrow progenitors and to the induction of tolerance by gene therapy.
Bagley
Jessamyn
J
Transplantation Biology Research Center, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA.
Tian
Chaorui
C
Sachs
David H
DH
Iacomini
John
J
D000818:Animals; D016026:Bone Marrow Transplantation / Q000276:immunology*; D005260:Female; D005805:Genes, MHC Class I; D015316:Genetic Therapy / Q000379:methods*; D006183:H-2 Antigens / Q000235:genetics*; D007108:Immune Tolerance; D051379:Mice; D012190:Retroviridae / Q000235:genetics; D016038:Skin Transplantation / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology*; D014161:Transduction, Genetic; D019172:Transplantation Conditioning; D014184:Transplantation, Homologous
D006183:H-2 Antigens; C032876:H-2Kb protein, mouse