Development of retrovirally marked human T progenitor cells into mature thymocytes

Retroviral vectors have been used in most human gene therapytrials that have been undertaken. Many of these therapies havefocused on the introduction of genes into hematopoietic stemcells with the goal of obtaining expression in the mature Tlymphocytic progeny. It has proven difficult to achieve expressionin the lymphoid lineage, although several groups have demonstratedlow expression of transduced genes in the myelold lineage. Inthis study we used an in vitro thymic organ culture in whichstem/progenitor cells can develop into T cells and all intermediatestages can be studied and manipulated to investigate the fateof a retrovirally introduced Escherlchla coll LacZ gene in thissystem. Here we show that certain conditions can transduce JurkatT cells, three different antigen-specific T cell clones andCD34⁺CD3^–CD4^–CD8^– thymocytes (progenitor Tcells) with high (>80%) efficiency. Moreover, retroviraltransduction with the LacZ gene does not inhibit T and NK celldifferentiation of progenitor cells in fetal thymic organ cultures(FTOC). The LacZ gene also is functionally expressed at allstages of development, although the expression decreases somewhatduring differentiation. This experimental system, combiningFTOC and retroviral transduction, provides a genetic tool forthe study of human T cell development.