A study suggests that changes to the brain’s immune environment caused by the tuberculosis vaccine BCG may help explain earlier findings linking the vaccine to reduced Alzheimer’s disease risk.
The BCG vaccine, given through the skin to infants and young children, protects against tuberculosis, a bacterial infection that causes severe cough and chest pain.
Research published in Communications Medicine found that BCG increased activity in immune cells near the brain and altered Alzheimer’s-related biomarkers in healthy older adults without physical signs of the disease.
BCG is known for inducing trained immunity, where innate immune cells undergo lasting functional changes after exposure to certain microbes, said co-first author Mahesh Chandra Kodali of Harvard Medical School and Massachusetts General Hospital. This reprogramming can last months or years and affect responses beyond tuberculosis protection, he told PTI.
Previous studies in models, retrospective analyses, and trials indicated BCG may lower Alzheimer’s risk, reduce amyloid buildup in the brain, and ease neuroinflammation.
Researchers recruited 23 adults aged 55 and older, including 11 with Alzheimer’s-related changes and 12 without. They collected cerebrospinal fluid and blood samples over one year after vaccination.
BCG altered immune cell behavior in the fluid around the brain and spinal cord and changed Alzheimer’s-linked markers, the authors reported. Amyloid-beta levels shifted in both cerebrospinal fluid and blood. In participants without pathology, amyloid declined in brain fluid but rose in blood over 12 months. No such shift occurred in those with pathology.
Larger randomized trials are needed to determine if BCG can prevent or treat Alzheimer’s, the researchers said.
