The first was the one induced with multiple low doses of streptozotocin (MLD–STZ). STZ is a chemical substance with alkylation properties that interferes with glucose transportation. A single high-dose strategy results in severe toxicity and acute diabetes. Conversely, the multiple low-dose regimen, characterized by minimal β cell toxicity, PF2341066 results in autoantigen release and a possible break in self-tolerance [3]. The T cell dependence of this model is a debated topic, and needs

further evaluation. What is well established is that diabetes in this model cannot be transferred reliably to syngenic recipients by transfer of splenocytes [4]. Non-obese diabetic (NOD) mice are an inbred strain derived from Jcl:ICR mice [5], which develop type 1 diabetes spontaneously. The infiltration in the islets starts around 4–5 weeks, when pockets of lymphocytes are first observed juxtaposed to the pancreatic islets of young NOD mice. As the animals grow older, these mononuclear cells migrate into the islets, and by the time hyperglycaemia occurs destructive insulitis is present. This model is very similar to the human disease. Disease onset, for example, is preceded by infiltration of pancreatic islets by mononuclear cells and is controlled by many quantitative trait loci, particularly major histocompatibility

complex (MHC) class II genes. Diabetes in NOD mice is the most extensively studied model of autoimmune

disease [6, 7]. The discovery of regulatory T cells EX-527 (Tregs) disclosed a new field to be explored in the control of autoimmune pathologies [8]. Heat shock proteins (hsps) are molecules up-regulated in conditions of stress that are highly conserved throughout evolution [9]. Although recent research implicates hsp60 as an autoantigen involved in type 1 diabetes pathogenesis [10], this protein also contributes to protection against autoimmune diseases. It has been described that microbial homologues of mammalian hsps could induce the recruitment of Tregs to inflamed tissues [9]. In this study, we investigated the possible protection against type 1 diabetes through a prime-boost vaccination strategy. This strategy consists in priming the system with the antigen administered in one vector and then boosting it with the same antigen, but through another new vector [11]. Thus, we made use of two different vaccines containing mycobacterial hsp65: bacille Calmette–Guérin (BCG) and pVAXhsp65, a DNA vaccine. This association could, theoretically, be interesting because both vaccines have been already tested separately against diabetes and other autoimmune diseases and showed positive results [12-15]. We hypothesized that the prime-boost strategy could expand these beneficial effects. Female NOD mice and male C57BL/6 mice were obtained from the animal facility of State University of Campinas (UNICAMP, Campinas, São Paulo, Brazil).