This is an interesting paper. Two thoughts occur to me about it.

(1) The authors used polyclonal antibodies raised against various kinds of whole fungi. They used these, using immunochemistry, to detect unknown antigens, presumably proteins, in the brains of subjects with various neurological disorders but not in the brains of healthy subjects.

It does not follow from this that the unknown antigens are of fungal origin. In my view it is far more likely that they detected unknown human proteins (presumably involved in the pathology of some neurological disorders) which share epitopes with some fungal proteins. This is the problem with using polyclonal rather than monoclonal antibodies in such studies - at best they are a "blunt probe".

(2) Generally the blood-brain barrier does not allow entry of proteins from peripheral sources into the brain. If the authors wish to argue that the antigens that they have detected are of fungal origin then they need to show what is special about the blood-brain barrier in people with neurological disorders - letting fungal antigens into their brains but not for normal subjects who happen to have had an opportunistic fungal infection.

Pending more data, this paper is in my large "very inconclusive" basket.