Utility of binding protein fusions to immunoglobulin heavy chain constant regions from mammalian and avian species.

Antibodies are of central importance as reagents for the localization of proteins and other biomolecules in cells and tissues. To expand the repertoire of antibody-based reagents, we have constructed a series of plasmid vectors that permit expression of amino-terminal fusions to the hinge and Fc regions from goat, guinea pig, human, mouse, and rabbit immunoglobulin Gs, and chicken immunogloblin Y. The resulting fusion proteins can be produced in transfected mammalian cells and detected with commercially available and species-specific secondary antibody reagents. We demonstrate the utility of this platform by constructing and testing Fc fusions with DARPin, single-chain Fv, nanobody, toxin, and chemokine partners. The resulting fusion proteins were used to detect their targets in tissue sections or on the surface of transfected cells by immunofluorescent staining or on the surface of immune cells by flow cytometry. By expanding the range of Fc sequences available for fusion protein production, this platform will expand the repertoire of primary antibody reagents for multiplexed immunostaining and fluorescence-activated cell sorting analyses.