The Possibility of an Infectious Etiology of Alzheimer Disease

Mol Neurobiol. 2019 Jun;56(6):4479-4491. doi: 10.1007/s12035-018-1388-y. Epub 2018 Oct 18.


Over the past three decades, there has been constant postulation regarding the infectious etiology of Alzheimer disease (AD), which in turn suggests the vital role of various infectious agents in AD-associated inflammatory pathways. Recent findings indicate anti-microbial properties of Aβ, and suggest that Aβ production and deposition in AD might be induced by infectious agents. Several types of spirochetes have been associated to dementia, cortical atrophy, and pathological and biological hallmarks of AD. A significant association between AD spirochetes and other pathogens like HSV-1 and Chlamydia pneumonia has now become well established. In neurons infected by HSV-1 showed Aβ and hyperphosphorylated Tau accumulation. The expression of pro-inflammatory molecules have been found to be enhanced by specific bacterial ligands, and viral and bacterial DNA and RNA, thus activating the immune system. Aβ has now been established as anti-microbial peptide capable of inducing pore formation, thus justifying their infection-mediated accumulation. Thus, a proper combination of anti-inflammatory, anti-viral, and antibiotic therapeutics might potentially prevent the progression of AD. Here, we discussed the potential role of bacterial, fungi, and viral infections in AD causation and progression, and the potential-associated therapies to counter the AD condition.

Keywords: Alzheimer disease; Microorganism; Neuroinfection; Neuroinflammation; Neurotropic viruses.

Publication types

  • Review

MeSH terms

  • Alzheimer Disease / microbiology*
  • Alzheimer Disease / parasitology
  • Alzheimer Disease / therapy
  • Alzheimer Disease / virology*
  • Animals
  • Humans
  • Inflammation / pathology
  • Models, Biological
  • Nervous System / pathology