Biodistribution and efficacy of donor T lymphocytes in a murine model of lysosomal storage disease.

Lymphocyte-directed gene transfer has been proposed as potential therapy to treat certain congenital immunological deficiencies as well as other genetic diseases such as lysosomal storage diseases (LSDs). To understand better the extent to which adoptively transferred peripheral T lymphocytes (PTLs) are able to ameliorate LSDs we utilized the beta-glucuronidase-deficient mouse as a model system. PTLs (1 x 10(7)) isolated from the spleen of syngeneic mice overexpressing ( approximately 8-fold) human beta-glucuronidase (GUSB) were injected intravenously into young adult beta-glucuronidase-deficient mice without myeloablative conditioning. Using biochemical and histochemical assays, we were able to track the donor lymphocytes in vivo. Donor lymphocytes were detected in relatively high numbers in liver, spleen, small intestine, mesenteric lymph node, and thymus for at least 5 months, the last time point of analysis. Although liver and spleen had the highest total GUSB activity, histopathologic analysis demonstrated minimal to no correction of lysosomal distention at all time points studied. By contrast, we have shown in earlier studies that administration of similar numbers of macrophages reduced lysosomal storage in several organs, including liver and spleen. To understand this difference in efficacy, we compared the relative level of GUSB released into the medium by nonactivated and activated PTLs as well as by macrophages. Macrophages released >50-fold excess enzyme compared to either activated or nonactivated PTLs. These data suggest that a LSD can be more effectively treated by directing a gene therapy approach to a hematopoietic lineage other than T lymphocytes.