USE OF BACILLUS CALMETTE–GUERIN VACCINATION TO PRESERVE BETA CELL FUNCTION IN TYPE 1 DIABETES MELLITUS

Abstract

INTRODUCTION

The Bacillus Calmette–Guerin (BCG) vaccine is a suspension of live attenuated Mycobacterium bovis used to prevent tuberculosis. It has been shown to modulate immune responses and decelerate the progression of type 1 diabetes mellitus (T1DM).

METHODOLOGY

We report a case of T1DM in partial remission after receiving repeated BCG vaccination. A 57-year-female diagnosed to have T1DM at the age of 53, presented with severe diabetic ketoacidosis requiring intubation. HbA1c on presentation was 14.1% with elevated anti–glutamic acid decarboxylase (anti-GAD) of >250 IU/ml. She was discharged on basal bolus insulin regimen, with a total daily dose (TDD) of 44 units of insulin daily (0.88 units/kg/day).

RESULTS

A total of four doses of BCG vaccination were given within 24 months, with the first dose given 6 months after diagnosis. TDD of insulin was reduced to 24 units/day (0.48 units/kg/day) 3 months after the first dose, TDD further reduced to 16 units/day (0.32 units/kg/day) after the last dose of BCG vaccination. HbA1c levels remained stable at <6% 3.5 years post diagnosis and fasting C-peptide level increased from 32.23 pmol/L to 299.1 pmol/L (reference range 370-1470). Patient achieved partial remission of T1DM, which is defined by HbA1c <6% and TDD of insulin of ≤0.5 unit/kg/day.

CONCLUSION

BCG vaccine plays an important role in preserving pancreatic beta cell function and delaying the progression of T1DM. The impact of BCG vaccine on blood glucose appeared to be driven by the resetting of the immune system. BCG vaccine acts by releasing tumour necrosis factor which reduces the levels of suppressor T-cells that are responsible for pancreatic islet cell destruction in T1DM. BCG vaccine administration also shifts glucose metabolism from overactive oxidative phosphorylation to aerobic glycolysis.