What happened: BCG vaccination and immune-cell changes in cerebrospinal fluid
A human study reports that the tuberculosis vaccine BCG (Bacille Calmette–Guérin) can induce immune changes inside the central nervous system environment. The researchers detected immune-cell signalling changes in cerebrospinal fluid (CSF) and described the pattern as resembling trained immunity (long-lasting heightened innate immune readiness after an initial stimulus).
Reported participant and intervention details:
Number of participants: 23 older adults.Alzheimer’s-related CSF biomarker status: about half had CSF biomarkers consistent with Alzheimer’s disease.BCG schedule: two BCG doses given one month apart.Follow-up duration: one year.Measurements: gene-expression and biomarkers in both blood and CSF.
Reported immune findings in CSF:
CSF monocytes showed gene-activation patterns associated with a more “responsive and alert” immune state.Laboratory re-exposure experiments reportedly did not show stronger responses to BCG itself after re-exposure.Instead, cells reportedly responded more strongly to an unrelated bacterial molecule lipopolysaccharide (LPS), supporting priming/alerting rather than specific memory to BCG.