Double hit viral parasitism, polymicrobial CNS residency and perturbed proteostasis in Alzheimer's disease: A data driven, in silico analysis of gene expression data.

The aim of this study was to determine the interaction of peripheral immunity vs. the CNS in the setting of AD pathogenesis at the transcriptomic level in a data driven manner. For this purpose, publicly available gene expression data from the GEO Datasets repository. We performed differential gene expression and functional enrichment analyses were performed on the five retrieved studies: (a) three hippocampal cortex (HC) studies (b) one study of peripheral blood mononuclear cells (PBMC) and (c) one involving neurofibrillary tangle - containing neurons of the entorhinal cortex (NFT EC). Subsequently, BLAST was used to determine protein conservation between human proteins vs. microbial, whereas putative protein / oligopeptide antigenicity were determined via RANKPep. Gene ontology and pathway analyses revealed significantly enriched viral parasitism pathways in both PBMC and NFT - EC datasets, mediated by ribosomal protein families and epigenetic regulators. Among these, a salient viral pathway referred to Influenza A infection. NFT - EC annotations included leukocyte chemotaxis and immune response pathways. All datasets were significantly enriched for infectious pathways, as well as pathways involved in impaired proteostasis and non - phagocytic cell phagosomal cascades. In conclusion, our in silico analysis outlined an ad hoc model of AD pathophysiology in which double hit (PBMC and NFT-EC) viral parasitism is mediated by eukaryotic translational hijacking, and may be further implicated by impaired immune responses. Overall, our results overlap with the antimicrobial protection hypothesis of AD pathogenesis and support the notion of a pathogen - driven etiology.