Submitted March 2, 2006
Accepted July 3, 2006
Correction of the disease phenotype in canine leukocyte adhesion deficiency using ex-vivo hematopoietic stem cell gene therapy
Thomas R Bauer Jr.*, Mehreen Hai, Laura M Tuschong, Tanya H Burkholder, Yu-chen Gu, Robert A Sokolic, Cole Ferguson, Cynthia E Dunbar, and Dennis D Hickstein
Experimental Transplantation and Immunology Branch, Center for Cancer Research, NIH, Bethesda, USA
Division of Veterinary Resources, Office of Research Services, NIH, Bethesda, USA
Molecular Hematopoiesis Section, Hematology Branch, National Heart, Lung, Blood Institute, NIH, USA
* Corresponding author; email: bauert{at}mail.nih.gov.
Canine leukocyte adhesion deficiency (CLAD) represents the canine counterpart of the human disease leukocyte adhesion deficiency (LAD). Defects in the leukocyte integrin CD18 adhesion molecule in both CLAD and LAD lead to recurrent, life-threatening bacterial infections. We evaluated ex vivo retroviral-mediated gene therapy in CLAD using two non-myeloablative conditioning regimens - 200 cGy total body irradiation (TBI) or 10 mg/kg busulfan - with or without post-transplant immunosuppression. Six of 11 treated CLAD dogs achieved therapeutic levels of CD18+ leukocytes. Conditioning with either TBI or busulfan allowed long-term engraftment, and immunosuppression was not required for efficacy. The percentage of CD18+ leukocytes in the peripheral blood progressively increased over 6-8 months post-infusion to levels ranging from 1.26% to 8.37% at one-year follow-up in the 6 dogs. These levels resulted in reversal or moderation of the severe CLAD phenotype. Linear amplification-mediated polymerase-chain-reaction assays indicated polyclonality of insertion sites. These results describe ex vivo hematopoietic stem cell gene transfer in a disease-specific, large animal model using two clinically applicable conditioning regimens, and they provide support for the use of non-myeloablative conditioning regimens in pre-clinical protocols of retroviral-mediated gene transfer for non-malignant hematopoietic diseases such as LAD.
