Antibody Engineering

AbstractAntibodies contain sites in the heavy and light chain variable domains (V domains) with antigen‐binding activity largely independent of their constant domains (C domains). Recombinant antibodies that bind with pathological proteins are used widely as drugs. In addition, antibodies containing V domain nucleophilic sites that bind protein targets irreversibly or catalyse target breakdown. Target‐specific therapeutic antibodies 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, restore the C domain‐dependent catalytic activity and incorporate effector functions residing in the C 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. Uptake of antibodies by internalisation of membrane‐bound antigen forms can render intracellular antigens sensitive to antibody targeting.Key ConceptsAntibodies 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 as complement activation and Fc receptor binding.Monoclonal IgG antibodies that bind protein target reversibly have emerged as a major class of biological drugs for various diseases. The efficacy and safety of antibody drugs depend on their antigen recognition affinity, specificity andin vivopharmacokinetics.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 IgG antibody functions can be attained in the test tube by rational or random mutagenesis coupled with directed selection of the mutants.The new electrophilic immunisation approach has enabled on‐demand production of next‐generation monoclonal IgGs with superior protein target neutralisation capacity made possible by irreversible target binding.Combined innate and adaptive immunity algorithms have been applied to produce monoclonal IgM, IgA and V domains that rapidly and specifically catalyse the degradation of disease‐associated protein targets, making feasible the development of more efficacious and safer therapeutic antibodies.