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Generic Tuberculosis Vaccine May Help Patients With Type 1 Diabetes
The researchers first reported in 2001 that inducing the expression of tumor necrosis factor (TNF) — previously shown to destroy insulin-autoreactive T cells — cured type 1 diabetes in mice by permitting pancreatic islets to regenerate. Since high doses of TNF are toxic to humans, clinical trials use the bacillus Calmette-Guérin (BCG) vaccine, which safely elevates TNF levels.
A generic drug with more than 90 years of clinical use, BCG is currently approved by the FDA for vaccination against tuberculosis and for the treatment of bladder cancer.
The double-blind phase I trial enrolled six long-term type 1 diabetes patients — diagnosed for an average of 15 years — who were randomly assigned to receive two doses of either BCG or a placebo spaced 4 weeks apart. Blood samples from the participants with diabetes were also compared with samples from six nondiabetic control participants and with samples from 75 additional individuals with diabetes and 15 without.
During the 20-week study period, two of the three participants treated with BCG showed increases in the death of insulin-autoreactive T cells and in levels of protective regulatory T cells. A temporary but statistically significant elevation in C-peptide levels, suggesting a restoration of insulin production, was also observed in the BCG-treated patients.
These findings were consistent with recent trials in Italy, which showed that BCG vaccination could decrease disease activity and prevent the progression of brain lesions in advanced multiple sclerosis, an autoimmune disease also caused by autoreactive T cells vulnerable to TNF-triggered cell death. A recent Turkish study also suggested that repeat BCG administration, but not a single BCG vaccination, could prevent the onset of diabetes in children and that childhood BCG vaccinations prevent the formation of autoantibodies.
For more information, visit the Massachusetts General Hospital Web site.