Development of the dual-vector system-III (DVS-III), which facilitates affinity maturation of a Fab antibody via light chain shuffling.

Light (L) chain shuffling is routinely used to analyze optimal L chains that pair with a specific heavy (Fd or H) chain, which ultimately leads to in vitro affinity maturation of a particular antibody. One of the major drawbacks to this procedure is that L chain libraries have to be created for each distinct H chain, which involves complicated cloning procedures. Herein, we designed of the dual-vector system-III (DVS-III), which is composed of a set of pLf1T-3 phagemid and pHg3A-3 plasmid, for L chain shuffling of any given human Fab antibody via phage display technology. To demonstrate the feasibility of our system, a human naïve L chain sublibrary, HuNL-D3, constructed in pLf1T-3 phagemid, was combined with the Fd of a human anti-IL-15 Fab, 4H10, subcloned in pHg3A-3 plasmid as a model system. After solution-phase sorting and biopanning the library we obtained eight Fab variants (4H10-LP1-7 and 4H10-LS). Among them, 4H10-LP4 exhibited the highest affinity which is about 36-fold higher than that of the parent molecule 4H10 (K(D)=6 nM versus 200 nM). Our results demonstrate that the DVS-III, along with the HuNL-D3 L chain sublibrary, can be served as a convenient approach for affinity maturation of any given human Fab antibody through L chain optimization.
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