[ABetaMale]

[1] is probably the study you're thinking of. There's also [2] regarding herpesviridae, among others.

In short, there are good reasons at this point to believe that amyloid-β's primary function is as antimicrobial peptide, and thus various infections may cause the seeding of amyloid-β deposits. These deposits may then persist for years beyond any useful benefit, especially if the brain's clearance mechanisms are impaired.

Note that, per [2]:

Importantly, in the antimicrobial protection model, neurodegeneration is not mediated by pathogen activities that directly kill neurons. Rather, Aβ innate immune pathways targeting pathogens mediate the AD [Alzheimer's Disease] neuropathogenesis that leads to widespread neurodegeneration. Thus, our model is consistent with the amyloid cascade hypothesis and overwhelming data showing the primacy of Aβ in AD pathology.

[1]. Dominy et al (2019). Porphyromonas gingivalis in Alzheimer’s disease brains: Evidence for disease causation and treatment with small-molecule inhibitors. https://doi.org/10.1126/sciadv.aau3333

[2]. Eimer et al (2018). Alzheimer’s Disease-Associated β-Amyloid Is Rapidly Seeded by Herpesviridae to Protect against Brain Infection. https://doi.org/10.1016/j.neuron.2018.06.030

[tdeck]

This is such a great reply, thank you!