Inverted Fab2s (IFab2s): engineering and expression of novel, dimeric molecules, with a molecular weight of 100 000

The IFab2 molecule described is expressed by a single gene construct that encodes the VH-CH1 and the Vk-Ck modules of a humanized version of the anti-breast cancer antibody BrE-3, joined via a short peptide linker. It can be shown that this basic genetic construct can lead to the expression of monomers, dimers (IFab2s) and other multimer species, depending on the length of the linker. A 21-residue linker promotes the principal formation of the desired dimer IFab2 molecules. It was also shown that in binding competition assays, purified IFab2 completely retained the affinity and specificity of the original monoclonal antibody.