The hunger for blood, in my understanding, is more of a supernatural requirement to fuel their undead status as opposed to maintaining metabolism. It seems to me that as long as they fulfill the ritual requirements of the magic keeping them animate, it shouldn't really matter what is in the blood that they ingest. I can see them gaining more spiritual sustenance from sentient beings than from animals, but only because their nature draws more power from such beings, or because they are intended to be a bane on the species they were when they were alive.

But the better point is: would undead creatures have an immune system for AIDS to attack in the first place? That idea of Dracula with a runny nose is a bit too silly :P

Biologically, a creature that was accustomed to consuming blood for survival would have the immune system to tackle potential threats such as AIDS. This, of course, is all in theory.

Technically, if one doesn't have an ulser or open wound in their mouth, they cannot get AIDS from drinking infected blood - this goes for vampires and humans.

does mosquitos gets AIDS from drinking blood?same way for vampires also

Vampires can't get AIDS from sucking infected blood because they are fake.

No, I will refer you to iamdavidh's post.

It seems like a logical response.

Vampires are immune to aids they're invulnerable to diseases, and poison and they don't breathe too.

Vampires are immune from all human diseases and they are immortal.