Miljenko,
I can only speculate about the possible answers to your questions. And I suspect that your answers stand a much better chance of matching reality than mine.
Familial AD. I'd suspect a gene defect that weakens the blood/brain barrier allowing more pathogens through and/or allows large numbers of pathogens, especially viral, into the brain; or a defective gene which weakens DNA repair, or immune response.
So I suspect that it's unlikely that the pathogen is passed from mother to child but rather the gene defect that facilitates brain attack.
I suspect AD symptoms are an indication of irrevocable brain damage. That is consistent with those Herpes pts who have been aggressively treated with anti-virals showing less than 1/10th of the expected AD occurrence. i.e the disease symptoms can be prevented, but it would be much more difficult if not impossible to treat dementia, lost memories, etc.
Finally,I suspect AD is a family of diseases rather than one disease with a single cause. I have no clue how a clinical trial would be designed to allow an answer to be found at a reasonable cost and in a reasonable number of years.
