High-Level Periplasmic Expression and Purification of scFvs

In the past few years, some of the limitations of monoclonal antibodies (MAbs) as therapeutic agents have been addressed by genetic engineering. Such an approach is particularly suitable because of the domain structure of the Ab molecule, where functional domains carrying antigen (Ag)-binding activities (Fabs or Fvs) or effector functions (Fcs) can be exchanged between Abs. Furthermore, genetically truncated versions of Ab can be produced, ranging in size from the smallest Ag-binding unit or Fv, to Fab′ and F(ab′)₂ s. To stabilize the association of recombinant V_H and V_L domains, they have been joined in scFv constructs with a short peptide linker (1 2)). These small scFvs are particularly interesting for clinical applications (3 ). They are only one half the size of Fabs and thus have lower retention times in nontarget tissues, more rapid blood clearance, and better tumor penetration. They are also less immunogenic and are amenable to fusions with proteins and peptides.