Triple vector for expressing antibody molecules in full therapeutic format

A triple expression vector is disclosed for expressing an antibody molecule comprising an Fc domain in prokaryotic cells and in eukaryotic cells. The triple expression vector comprises a polynucleotide encoding an Fc domain; a polynucleotide encoding a phage coat protein; a cloning site for cloning genes encoding an antibody molecule or a part thereof wherein the antibody molecule or part thereof does not comprise an Fc domain; a prokaryotic secretion signal sequence and a eukaryotic secretion signal sequence, or a secretion signal sequence that drives efficient secretion in both prokaryotic and eukaryotic cells; a promoter for mediating expression in eukaryotic cells; and a stop codon for preventing expression of the phage coat protein in eukaryotic cells. The triple expression vector can be used for expressing an antibody molecule in a phage display format; for producing the antibody molecule in a prokaryotic cell, for example in the periplasm of a prokaryotic cell; and for producing the antibody molecule in a eukaryotic cell, for example a mammalian cell, more particularly a human cell. The antibody molecule contains an Fc domain, and may be for example a VHH-Fc molecule or an scFv-Fc molecule or a VH-Fc or a VL-Fc. Phage display libraries produced with the vector present the antibody molecule in its therapeutic format. Use of the vector avoids the need for repeated cloning when moving from one expression medium to another.