The interesting thing about viruses and prions is that as far as I know, no-one can decide if they are alive or not.
Prions definitely aren't alive, they are simply large molecules and meet few if any of the definitions of life. They don't really do anything themselves, and rely entirely on the mechanisms of host organisms. They are the biological equivalent of audio feedback.
Viruses can do a few things - they latch onto the correct receptor on a cell and can inject their core into it. That could be called movement (sort of) and sensitivity.
Beyond that all they really do is corrupt the protein synthesis system of their host organism. They are a complex chemical construct.
I don't viruses them as a life-form any more than I see a computer virus as a computer.
Some researchers think all life descended from something like a viruses. But viruses can't survive long outside a cell and they lack the mechanisms to reproduce themselves without a cellular host.