CRYOPRESERVED CORD-BLOOD MYELOID PROGENITOR CELLS CAN SERVE AS TARGETS FOR RETROVIRAL-MEDIATED GENE TRANSDUCTION AND GENE-TRANSDUCED PROGENITORS CAN BE CRYOPRESERVED AND RECOVERED

To determine future possibilities for gene transfer, we evaluated whether myeloid progenitor cells from human umbilical cord blood (CB) could be frozen, thawed in viable form and transduced with a Neomycin resistance (Neo(R)) gene using retroviral vectors, and If fresh progenitor cells transduced with a Neo gene could be cryopreserved and recovered. Fresh and thawed cryopreserved nonadherent low-density T-lymphocyte depleted (NALT(-)) CB cells were assayed before and after gene transduction for colony formation in the presence of multiple growth factors in the absence and presence of G418. The results demonstrate that the Neo(R) gene could be introduced into thawed cryopreserved myeloid progenitor cells at an efficiency similar to that of fresh cells and that fresh cells transduced with the Neo(R) gene could be frozen in a cryopreserved state and recovered after thawing. proviral Integration, as assessed by PCR/Southern Analysis, confirmed the G418(R) colony data. Proviral integration was detected not cnly in primary G418(R)-colonies, but also in replated colonies in secondary dishes derived from G418(R)-multipotential progenitor cells (CFU-GEMM) suggesting stable integration of the transduced gene into early subsets of replatable progenitors. This information may be of use clinically.