1Heat oven to 350°F. Cook and drain pasta shells as directed on package, using minimum cook time. Meanwhile, in 12-inch skillet, cook sausage, garlic and 1 tablespoon of the chopped sage over medium heat 8 to 10 minutes, stirring occasionally, until sausage is no longer pink; drain.
2In medium bowl, beat egg. Stir in ricotta cheese, pumpkin, Parmesan cheese, pepper, 1 cup of the Italian cheese, remaining 1 tablespoon chopped sage and the sausage.
3Spread 1 cup of the Alfredo sauce in ungreased 13x9-inch (3-quart) glass baking dish. Fill pasta shells with sausage mixture. Arrange stuffed shells over sauce in dish. Pour remaining 2 cups of the Alfredo sauce evenly over shells.
4Cover; bake 30 to 35 minutes or until hot. Uncover; top with remaining 1 cup Italian cheese. Bake 5 to 10 minutes longer or until cheese is melted. Garnish with sage leaves.