Figure 1.

The competitive repopulation assay using fluorescent reporter genes in the dog model. a) The ex vivo transduction is divided into two experimental arms with equivalent numbers of CD34⁺ cells. A vector expressing enhanced green fluorescent protein (EGFP) is used for one experimental arm, and a different vector different expressing enhanced yellow fluorescent protein (EYFP) is used for the other experimental arm. The two experimental arms can differ in a number of ways including vector type, vector envelope pseudotype, ex vivo transduction protocol, source of CD34⁺ cells, or route of infusion. By directly comparing one of these variables in the same dog, inter-animal variability is eliminated, and the best approach can be determined with a small number of animals. b) The use of EG/YFP fluorescent reporter genes allows easy and accurate evaluation of transgene expression by flow cytometry. c) Transgene expression can be evaluated long-term in both myeloid and lymphoid lineages.