The present invention relates, in one aspect, to a vector comprising (a) a first polynucleotide capable of encoding a first (poly)peptide comprising at least one cysteine residue, and (b) a second polynucleotide capable of encoding a second (poly)peptide which is a cell surface anchor comprising at least one cysteine residue, wherein the vector is operable in a eukaryotic host cell to express and to cause or allow the attachment of said first (poly)peptide to said second (poly)peptide by formation of a disulfide bond between said cysteine residues comprised within said first (polypeptide and said second (poly)peptide, respectively, wherein said first (poly)peptide is exhibited at the surface of a eukaryotic host cell.