TGF beta Plasmid Construction and Delivery for the Prevention of Type 1 Diabetes

Abstract

Studies of animals with spontaneous autoimmune diabetes have revealed that autoreactive T cells that mediate islet beta cell destruction can be manipulated by the administration of Th-2 cytokines. Using gene delivery to express the targeted protein, we can overcome the need for frequent administration of cytokines on account of their short half-lives. In this study, the effect of hTGF beta gene delivery was evaluated both in vitro and in vivo using an adenovirus vector (Ad) constructed with an hTGF beta cDNA. In vitro transfection assays of the construct in HepG2, beta cell lines, and islets showed good expression levels of hTGF beta and activation of smad3. Ad-hTGF beta enhanced differentiation and proliferation in the beta cell line or islets without causing apoptosis. Of interest, Ad-hTGF beta transduction in CD4(+)CD25(-)T cells resulted in a significant enhanced expression of CD25 and a regulatory T cell-specific transcription factor, Foxp3. To evaluate in vivo efficacy, Ad-hTGF beta was intravenously injected into 7-week-old NOD mice and compared to the transduction using the vector only. The Ad-hTGF beta group had persistent gene expression for longer than 5 weeks, and high TGF beta serum level was secreted. There was no difference in the degree of insulitis between the Ad-hTGF beta group and controls. Although we found favorable in vitro results, such as decrease in islet apoptosis, enhanced proliferation and differentiation, and increase in the level of CD4(+)CD25(+) regulatory T cells, there was no difference in reduction of the development of T1D between controls and Ad-hTGF-beta-injected mice. Nevertheless, if we find the appropriate mode and timing of TGF beta gene transduction, Ad-hTGF beta gene therapy might be useful in therapeutic cytokine delivery for the treatment of T1D.