Generation of high-affinity human antibodies by combining donor-derived and synthetic complementarity-determining-region diversity

Abstract

Combinatorial libraries of rearranged hypervariable V_H and V_L sequences from nonimmunized human donors contain antigen specificities, including anti-self reactivities, created by random pairing of V_Hs and V_Ls. Somatic hypermutation of immunoglobulin genes, however, is critical in the generation of high-affinity antibodies in vivo and occurs only after immunization. Thus, in combinatorial phage display libraries from nonimmunized donors, high-affinity antibodies are rarely found. Lengthy in vitro affinity maturation is often needed to improve antibodies from such libraries^1,2. We report the construction of human Fab libraries having a unique combination of immunoglobulin sequences captured from human donors and synthetic diversity in key antigen contact sites in heavy-chain complementarity-determining regions 1 and 2. The success of this strategy is demonstrated by identifying many monovalent Fabs against multiple therapeutic targets that show higher affinities than approved therapeutic antibodies^3,4,5,6. This very often circumvents the need for affinity maturation, accelerating discovery of antibody drug candidates.