Gene therapy compositions for the prevention and/or treatment of autoimmune diseases. The present invention relates to vectors, preferably plasmids that comprise specific promoters, that encode insulin-like growth factor I (IGF-I) or a functional biological equivalent thereof, which will be used to prevent or treat Type 1 Diabetes (DT1) and/or other autoimmune diseases. Moreover, the invention comprises the method of preventing or treating DT1 by means of the expression of IGF-I, or a functional biological equivalent thereof, in hepatic cells. IGF-I was capable of interrupting the immune attack against pancreatic β cells, thereby preventing the loss of β cell mass and, consequently, maintaining normal levels of circulating insulin.
