BCG vaccine prevents insulitis in low dose streptozotocin-induced diabetic mice

Autoimmune type 1 diabetes mellitus is caused by the immunologic destruction of pancreatic β-cells; therefore, there have been many attempts at immunologic modulation as a block or prevention of the underlying process. The aim of this study is to investigate the effect of BCG vaccination on low dose streptozotocin-induced diabetic (LDSD) mice. The mice were pretreated with BCG 7 days before starting low dose streptozotocin (STZ), observed body weight and blood glucose for 2 months, then analyzed the severity of the STZ- induced insulitis after the animals were sacrificed. In this experiment, the mean body weights in the BCG-STZ group on days 1, 19, 33, 47, and 61 of the experiment were 37.5 ± 3.6, 37.3 ± 3.6, 37.5 ± 3.5, 39.4 ± 3.9, and 39.3 ± 4.5 (g), respectively. Those in the STZ group were 37.7 ± 3.5, 38.3 ± 4.5, 38.4 ± 3.9, 36.2 ± 4.5, and 36.3 ± 4.0 (g), respectively (P < 0.05). The mean blood glucose levels in the BCG-STZ group on days 1, 19, 33, 47, and 61 were 106.5 ± 8, 150 ± 37, 147 ± 54, 143 ± 60, and 142 ± 66 (mg/dl), respectively. Those in the STZ group were 103 ± 12, 196 ± 90, 261 ± 236, 236 ± 91, and 224 ± 89 (mg/dl), respectively (P < 0.05). The numbers developing grade 0, I, II, III, and IV insulitis in the BCG-treated group were 63, 48, 33, 4, and 2, respectively, and in the control group were 16, 23, 31, 45, and 35, respectively. This study indicates that BCG vaccination reduces the development of insulitis and overt diabetes in LDSD mice.