Table 1.

Pathogen-Based Biomarkers in AD. Numerous pathogens have been associated with AD pathogenesis and the onset of cognitive decline. Biomarkers are listed along with their source and relationship to AD.

	Biomarker	Source	Description	Reference
Antimicrobial Peptides
	⍺-Defensin 1	Blood	Increased in blood of AD patients.	[39]
	⍺-Defensin 2	Blood	Increased in blood of AD patients.	[39]
	Lactoferrin	Saliva	Decreased with AD and aMCI.	[40]
	Lipocalin-1	Tears	Decreased in AD.	[41]
	Dermcidin	Tears	Increased in AD.	[41]
	Lysozyme-C	Tears	Decreased in AD.	[41]
	Lacritin	Tears	Decreased in AD.	[41]
Antibodies
	IgG against Epstein-Barr Virus	Blood	Correlates with development of aMCI.	[42]
	IgG and IgA against C. pneumoniae	Blood	Detectable in patients with vascular dementia.	[43]
	IgG against HSV-2	Blood	Correlates with cognitive decline.	[25]
	IgG against CMV	Blood	Correlates with cognitive decline.	[25]
	IgG against T. gondii	Blood	Correlates with cognitive decline.	[25]
	IgM against HSV-1	Blood	Associated with increased risk of AD.	[44,45]
	IgG against H. Pylori	Blood	Associated with lower MMSE scores.	[35]
Other
	Fungal Proteins and DNA	CSF, Blood	Detectable in AD patients.	[36,46]
	Gut Microbiome composition	fecal matter	Correlates to gut dysbiosis and cognitive decline.	[6,47]
	Porphyromonas gingivalis	CSF	Identified in 96% of postmortem brain tissue samples of AD patients.	[30]