Avengers Assemble Season 1 5 "Blood Feud"

Synopsis
The Avengers are able to capture a squad of Vampires, and there leader turns out to be Black Widow, who was bitten. Black Widow had traced Red Skull to Transylvania, where she was bitten, and sent her with a message for the Avengers, Captain America for Black Widow. On the way to Transylvania, Captain America prepares for Vampires, while recounting that Dracula and him were uneasy allies during WWII. When they get to the castle, Hulk and Thor guarded the entrance, Iron Man insisted that there was a scientific cure, and the rest of the team went to confront Dracula. Dracula captures Hawkeye and Falcon, and trades them for Cap, revealing that the Red Skull told him that Cap's Super-Soldier blood will make him immune to sunlight. The other Avengers intervene, but Hulk gets bitten. Before Captain America can be bitten, Dracula becomes incapacitated by Hulk's Gamma blood. Iron Man realizes that the Hulk's blood has a similar effect on Dracula as sunlight. The Avengers then try to make Hulk angry that he will become rid of the vampirization. Dracula escapes to heal, and Black Widow is cured.