Tuberculosis Vaccine May Alter Brain Immunity Linked To Alzheimer's Risk, Study Finds

A vaccine widely used to prevent tuberculosis may also influence the brain's immune environment and Alzheimer's-related biomarkers, according to a year-long clinical study published in Communications Medicine.

Researchers at Mass General Brigham found that the Bacillus Calmette-Guérin (BCG) vaccine enhanced immune responses and altered amyloid-beta biomarkers in older adults without evidence of Alzheimer's disease. The changes were not observed in participants who already showed biological signs of the disease.

The study involved 23 adults aged 55 years and older, including 12 participants without Alzheimer's pathology and 11 with biomarker evidence of the disease. Researchers collected blood and cerebrospinal fluid samples at regular intervals over one year following BCG vaccination.

Immune Changes Extend Beyond Tuberculosis Protection

The researchers found that BCG increased the responsiveness of immune cells to subsequent immune challenges, indicating broader effects on immune function beyond tuberculosis protection.

Unlike many immune-stimulating therapies, the heightened immune activity was not accompanied by an increase in inflammatory markers, which are associated with neurodegeneration.

"The immune system and the brain may be far more connected than we once thought," said senior and co-corresponding author Steven Arnold