This invention relates to fusion proteins that include a whey acidic protein (WAP) domain-containing polypeptide and a second polypeptide. Additionally, the invention relates to fusion proteins that include a WAP domain-containing polypeptide a second polypeptide, and a third polypeptide. The second and/or third polypeptides of the fusion proteins of the invention are a Fe polypeptide; an albumin polypeptide; a cytokine targeting polypeptide; or a serpin polypeptide. This invention also relates to methods of using such molecules in a variety of therapeutic and diagnostic indications, as well as methods of producing such molecules.