Antibody light chain variable domains and their biophysically improved versions for human immunotherapy

We set out to gain deeper insight into the potential of antibody light chain variable domains (V(L)s) as immunotherapeutics. To this end, we generated a naïve human V(L) phage display library and, by using a method previously shown to select for non-aggregating antibody heavy chain variable domains (V(H)s), we isolated a diversity of V(L) domains by panning the library against B cell super-antigen protein L. Eight domains representing different germline origins were shown to be non-aggregating at concentrations as high as 450 µM, indicating V(L) repertoires are a rich source of non-aggregating domains. In addition, the V(L)s demonstrated high expression yields in E. coli, protein L binding and high reversibility of thermal unfolding. A side-by-side comparison with a set of non-aggregating human V(H)s revealed that the V(L)s had similar overall profiles with respect to melting temperature (T(m)), reversibility of thermal unfolding and resistance to gastrointestinal proteases. Successful engineering of a non-canonical disulfide linkage in the core of V(L)s did not compromise the non-aggregation state or protein L binding properties. Furthermore, the introduced disulfide bond significantly increased their T(m)s, by 5.5–17.5 °C, and pepsin resistance, although it somewhat reduced expression yields and subtly changed the structure of V(L)s. Human V(L)s and engineered versions may make suitable therapeutics due to their desirable biophysical features. The disulfide linkage-engineered V(L)s may be the preferred therapeutic format because of their higher stability, especially for oral therapy applications that necessitate high resistance to the stomach’s acidic pH and pepsin.