Binders based on dimerised immunoglobulin V_H domains

Antibody binding to antigen is mediated by the surface formed by the association of the two variable (V) regions of the L (V_L) and H (V_H) chains. The capacity of V_L to dimerise and the high structural similarity of V_L and V_H domains suggested the possibility that V_H could also associate. We show here that spontaneous formation of V_H dimers (VHD) is in many cases permissive, producing stable molecules with antigen binding specificity. VHD were displayed on filamentous phages for the selection of antigen-specific binders. VHD were expressed and secreted efficiently from both bacteria and mammalian cells in different formats, including single-chain (V _H(1)-linker-V_H(2)), double chain ((V_H) ₂) and IgG analogues having the V_L replaced by V _H. The affinity (K_d,app) achieved with a V_H dimer expressed in the IgG format, specific for a glutenin subunit was around 30nM measured by two different methods, which was about 20 times higher than that corresponding to the V_L/V_H counterpart.