MAMMALIAN-CELL EXPRESSION OF DIMERIC SMALL IMMUNE PROTEINS (SIP)

We have designed and expressed bivalent small immune proteins (SIP) ba sed on scFv fragments connected through a short linker of four amino a cids to the CH3 domain of the human immunoglobulin gamma 1 H-chain. Th ree different versions have been designed and expressed in mammalian c ells. In one construct a cysteine residue was included in the last ami no acid of the flexible 15-amino acid long linker connecting the V-L a nd V-H domains, thus creating a disulphide bond stabilized molecule. A version with a shorter (five amino acids) V-L/V-H linker was also pro duced and shown to be efficiently assembled and secreted. All three SI Ps form dimers retaining their antigenic specificity in Western blotti ng and having a comparable functional affinity (avidity) as determined by ELISA.