Abstract: The invention provides single-chain Alphabody library comprising at least 100 different-sequence single-chain Alphabody polypeptides, wherein said Alphabody polypeptides differ from each other in at least one of a defined set of 5 to 20 variegated amino acid residue positions, and wherein at least 70% but not all of said variegated amino acid residue positions are located either in the loop, helix surface or linker region of the Alphabody. The invention further provides methods for use of the Alphabody libraries and Alphabodies obtainable by the methods of the invention.

Abstract: The invention provides single-chain Alphabody library comprising at least 100 different-sequence single-chain Alphabody polypeptides, wherein said Alphabody polypeptides differ from each other in at least one of a defined set of 5 to 20 variegated amino acid residue positions, and wherein at least 70% but not all of said variegated amino acid residue positions are located either in the loop, helix surface or linker region of the Alphabody. The invention further provides methods for use of the Alphabody libraries and Alphabodies obtainable by the methods of the invention.

Abstract: The invention provides methods for the production of single-chain Alphabody polypeptides having detectable binding affinity for, or detectable in vitro activity on, a viral protein of interest, which comprising the step of producing a single-chain Alphabody library comprising at least 100 different-sequence single-chain Alphabody polypeptides, wherein said Alphabody polypeptides differ from each other in at least one of a defined set of 5 to 20 variegated amino acid residue positions, and wherein said variegated amino acid residue positions are located at specific positions in one or more of the alpha-helices of the Alphabody or the linker fragment connecting two consecutive alpha-helices of the Alphabody polypeptides. The invention further provides Alphabodies obtainable by the methods of the invention and uses thereof.

Abstract: Alphabodies that specifically bind to cytokines or growth factor and/or their receptors, as well as polypeptides that comprise or essentially consist of such Alphabodies. Further nucleic acids encoding such Alphabodies; methods for preparing such Alphabodies and polypeptides; host cells expressing or capable of expressing such Alphabodies and polypeptides; compositions, and in particular pharmaceutical compositions, that comprise such Alphabodies, polypeptides, nucleic acids and/or host cells; and uses of such Alphabodies or polypeptides, nucleic acids, host cells and/or compositions, in particular for prophylactic, therapeutic or diagnostic purposes.

Abstract: Single-chain Alphabodies that comprise an alpha-helical binding region which mediates binding to a first fusion-driving region of a class-1 viral fusion protein and which structurally mimics a second fusion-driving region of said class-1 viral fusion protein, wherein said first and second fusion-driving regions of said class-1 viral fusion protein are regions which interact to drive the fusion between a virus displaying said class-1 viral fusion protein and a target cell.