Reporter gene expression in fish following cutaneous infection with pantropic retroviral vectors

A central issue in gene delivery systems is choosing promoters that will di rect defined and sustainable levels of gene expression. Pantropic retrovira l vectors provide a means to insert genes into either somatic or germline c ells. In this study, we focused on somatic cell infection by evaluating the activity of 3 promoters inserted by vectors into fish cell lines and fish skin using pantropic retroviruses. In bluegill and zebrafish cell lines, th e highest levels of luciferase expression were observed from the 5 ' murine leukemia virus long terminal repeat of the retroviral vector. The Rous sar coma virus long terminal repeat and cytomegalovirus early promoter, as inte rnal promoters, generated lower levels of luciferase. Luciferase reporter v ectors infected zebrafish skin, as measured by the presence of viral DNA, a nd expressed luciferase. We infected developing walleye dermal sarcomas wit h retroviral vectors to provide an environment with enhanced cell prolifera tion, a condition necessary for integration of the provirus into the host g enome. We demonstrated a 4-fold to 7-fold increase in luciferase gene expre ssion in tumor tissue over infections in normal walleye skin.