Yes, they're pretty much the same as viruses, except they don't alter the DNA of their host, they just turn everything they touch into more of themselves. How this could be interesting, I don't know, but it could help as a kind of killswitch, as it makes the bots die and turn into more of the prions. With viruses, the bots just turn into a virus factory which makes things really laggy. Prions could be used to just kill stuff off or something. I don't know.