"A sufficiently stereochemically alien pathogen could, in principle, place essentially all of its important antigenic determinants outside the effective recognition repertoire of a conventional adaptive immune system."

With perfect knowledge of the immune system and the capability to create the pathogens of our dreams it would most likely be possible to create this pathogen of our dreams.

Making an entire self replicating mirror organism that would both have this property of "being invisible to the specific immune system" and AND being an effective pathogen is far from a solved problem though. It's further away as useful quantum computing!

We don't even have self replicating mirror cells, just some synthetic Frankensteins.