INTRODUCTION: The Pathogen Infection Hypothesis proposes that β-Amyloid (Aβ) functions as an antimicrobial peptide, with pathogen-induced aggregation potentially contributing to Alzheimer's disease (AD) pathology. METHODS: We used human iPSC-derived 2D neurons and 3D cerebral organoids from wild-type and familial AD (PSEN1/2 mutant) lines to model acute infections with HSV-1 and TBEV and Aβ aggregation. Transcriptomic and proteomic analyses were conducted to assess molecular responses. RESULTS: HSV-1, but not TBEV, induced robust Aβ clustering, which was, however, dependent on extracellular amyloid peptides. Transcriptomic profiling revealed widespread HSV-1-induced changes, including activation of neurodegeneration-related pathways. Proteomic profiling confirmed enrichment of neurodegeneration- and senescence-associated secretome signatures. PSEN1/2 mutations did not alter the acute infection response. Reanalysis of independent datasets confirmed our findings and revealed a limited protective effect of acyclovir. DISCUSSION: Results directly support the Pathogen Infection Hypothesis and suggest that preventing viral infections via vaccinations may represent a feasible approach to reducing AD risk.

Biomedical Research Centre University Hospital Hradec Kralove Sokolska 581 Hradec Kralove 500 05 Czech Republic

Department of Experimental Biology Faculty of Science Masaryk University Kamenice 5 Brno 625 00 Czech Republic

Department of Histology and Embryology Faculty of Medicine Masaryk University Kamenice 5 Brno 625 00 Czech Republic

Institute of Parasitology Biology Centre of the Czech Academy of Sciences Branisovska 1160 31 Ceske Budejovice 370 05 Czech Republic

International Clinical Research Center St Anne's University Hospital Brno Pekarska 53 Brno 602 00 Czech Republic

Laboratory of Genetics and Genomics National Institute on Aging Intramural Research Program National Institutes of Health Baltimore MD 21224 USA

Veterinary Research Institute Hudcova 296 70 Brno 621 00 Czech Republic

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