Infectious origin of Alzheimer's disease: Amyloid beta as a component of brain antimicrobial immunity.
Level 5 - mechanism / opinion, no new human data
Narrative review synthesizing mechanistic hypotheses and secondary literature without systematic review methodology or new human data.
PubMed 36395147 · doi:10.1371/journal.ppat.1010929
What was done
Narrative review evaluating literature on the infectious hypothesis of Alzheimer's disease (AD). The authors reviewed evidence concerning the role of bacteria, viruses, fungi, and eukaryotic parasites as triggers for AD pathology, as well as the proposed physiological role of amyloid beta as an antimicrobial peptide.
What was found
The abstract reports no primary experimental or statistical findings. It notes a 99.6% failure rate in AD clinical trials to support the argument that the amyloid cascade hypothesis does not address the root etiology of sporadic AD, and summarizes published literature proposing that amyloid beta and alpha-synuclein participate in innate immune defense before becoming pathologically dysregulated.
Why it matters
Reframes amyloid accumulation as a downstream consequence of innate immune activation against pathogens rather than the sole initiating cause of Alzheimer's disease.
Limits
As a narrative review, it introduces no new clinical or experimental data. The abstract does not specify literature search criteria, study counts, or systematic quality assessments of the cited studies. Direct causality between infection and sporadic AD remains unestablished.
Cited by
- supports Beta-amyloid, phosphorylated tau, and alpha-synuclein are antimicrobial peptides.