BCG and Plasma Amyloid in Non-Demented Adults

Overview

BCG vaccination, the most widely used vaccination in the world, is used to reduce risk of tuberculosis infection; it is used for other mycobacterial infections as well, benefiting leprosy and Buruli ulcer. BCG has "heterologous" effects that aids in an array of non-mycobacterial and viral infections as well as bladder cancer. It is the heterologous effect, sometimes called the "off-target" effect that may offer benefit in Alzheimer's disease. Population studies and studies of adults receiving BCG show a lessened risk of Alzheimer's disease. The study will see if BCG vaccination will alter a plasma test for amyloid, a biomarker for cerebral amyloid.

Alzheimer's disease (AD) is commonly regarded as Alzheimer's dementia. It is now understood that changes in the brain that result in late-onset AD dementia start years or even decades prior to clinical dementia. Biomarkers aid in diagnosing AD however, currently approved biomarkers have drawbacks as they are invasive and expensive. The two most commonly used biomarkers are amyloid PET scan and spinal tap for amyloid and tau. A new plasma amyloid test has received "Breakthrough Device Designation" from the US-FDA. As an investigational tool, this blood test for amyloid peptides 42/40 levels accurately predicts brain amyloidosis in cognitively normal individuals. In the past 100 years, four billion doses of BCG vaccination have been given for tuberculosis prevention. A favorable effect with BCG for non-tuberculous mycobacteria is also recognized in cervical lymphadeniits, leprosy and Buruli's ulcer. Recently, BCG has found favorable use in autoimmune diseases type 1 diabetes (T1D) and multiple sclerosis (MS); moreover, a protective role by BCG for Alzheimer's disease has been described. Adult exposure to BCG lessened the risk of AD by four-fold. This is an interventional pilot study to test 50 non-demented adults measuring their plasma amyloid 42/40 level prior to BCG prime/boost followed with the same plasma amyloid testing 9 months after vaccination. Sub-clinical CMV infection is felt to drive immune senescence and increase the risk of AD; we will test for CMV antibodies and we will measure lymphocyte phenotype prior to BCG and at study end to look for an immune-modulating effect on this indicator of immunosenescence.