For antivirals, the hypothesis is a viral infection that the amyloids and tau are responses to. A study in Taiwan showed promising results.

For TDAP, nobody knows. All we have is a flabbergastingly strong signal from statistical analysis of the US Veterans' Administration entire cohort from 2012-2018. Is it the tetanus, the diphtheria, the pertussis vaccine? An "inactive" ingredient? Something else very, very strongly correlated with administration of booster, such as a more active lifestyle? If it is anything at all, it seems to be the only thing that works, other than maybe herpes treatment.