Antibody Engineering

Abstract

The antigen‐binding site of antibodies is composed of the heavy and light chain variable domains (V domains). Therapeutic human antibodies specific for individual antigen can be obtained by inducing adaptive B cell development in transgenic animal or by test‐tube affinity maturation of cloned antibody V domain repertoires. The V domains are recloned as full‐length antibodies to improve their pharmacokinetic behaviour and incorporate effector functions residing in the constant domains. Assembly of the V domains into multivalent constructs improves the binding avidity. Linkage to enzymes, toxins or delivery proteins imparts novel functions to the constructs. Emerging engineering strategies include the development of antibodies with catalytic activity and antibodies that can target intracellular antigens. Key Concepts: Antibodies are highly adaptive structures. They are encoded by germline genes that have diversified over evolutionary time and then undergo further antigen‐driven adaptive development over the life time of an individual organism. The antigen combining site is composed of the antibody light and heavy chain subunit variable domains. The constant domain contributes effector functions such complement activation and Fc receptor binding. Monoclonal antibodies have emerged as a major class of biological drugs for various diseases. The efficacy and safety of monoclonal antibody drugs depend on their antigen recognition affinity, specificity and in vivo pharmacokinetics. Understanding the natural process underlying adaptive sequence diversification has permitted isolation of monoclonal antibodies meeting the criteria for therapeutic applications. Antibody display and cloning methods have enabled identification of individual antibodies with defined antigenic specificities from vast repertoires. Improvement of antibody functions can be attained in the test tube by rational or random mutagenesis coupled with directed selection of the mutants. Catalytic antibodies combining the specificity of the antigen‐binding site with the turnover capability of enzymatic sites have emerged as a viable second generation technology for novel antibody applications.