After Lady Sif (who had the hobby of hunting monsters) joined the Avengers Academy, she asked Director Fury if there were any monsters that she could hunt in Midgard, Fury told her that yes, they had many monsters, Dracula was one of the monsters Fury mentioned.
Worried about the eminent extinction of his race, Dracula allied himself with Mephisto in an attack against the Avengers Academy. Mephisto promised him he could turn the students into vampires if he helped him with his plan.
Just like Mephisto's other ally Satana, Dracula eventually defected him after learning that he was just using them, and wasn't going to give either of them what he had promised. Nick Fury took this opportunity to ask Dracula to ally himself with Avengers Academy, Fury promised they would try to help him restore the vampire nation, as long as he stopped with his plans to bite people to turn them into vampires. Dracula agreed to Fury proposition, and helped the students defeat Mephisto.
Avengers Under Siege
Dracula was one of the Avengers Academy students that helped defeat and recapture the villains that were freed from their cages by Baron Zemo after he was manipulated by Mephisto into believing they would serve him if he freed them.