Contents

#### **Preface XI**

Naito


Preface

plied in patients.

rived repertoires.

power and tasks of antibody engineering.

Antibodies are most important molecules for therapy, diagnosis, and biological and medical research. For about 40 years, the hybridoma technology is used to generate mouse antibod‐ ies with high affinities. However, antibodies against nonimmunogenic, toxic, self-antigens and human/mouse cross-reactive epitopes cannot be obtained by this classical technique. Additionally, the mouse monoclonal antibodies elicit a strong immune response when ap‐

A breakthrough to solve these problems was the development of human antibody reper‐ toires and *in vitro* antibody selection methods in the beginning of the nineties. In the follow‐ ing years, it was demonstrated that the generation of specific antibodies by the immune system could be imitated successfully *in vitro*. The development of antibodies, particularly human antibodies, could be dramatically improved. The human antibody repertoires and corresponding *in vitro* selection techniques are now used to generate and modify human an‐ tibodies against virtually every protein and desired epitope or conformation. This is the

The most frequently *in vitro*–selected recombinant antibody format is the scFv, which can be converted into full-length antibodies or scFv-Fc proteins, both of which have similar charac‐ teristics. Engineering of the Fc region increases the half-life and improves the affinity of Fc domains for their receptors on immune effector cells or to complement. For specific applica‐ tions, different antibody formats such as bispecific antibodies, minibodies, or diabodies can be generated. Furthermore, very stable single domain antibodies comprising only the varia‐ ble domain of the heavy chain can be selected by phage display from camel- or shark-de‐

The first approved recombinant therapeutic antibodies were chimeric or humanized variants of mouse hybridoma antibodies. Today, fully human antibodies are selected from human an‐ tibody repertoires mainly against antigens involved in infectious diseases and cancer. How‐ ever, the number of new mAbs validating new therapeutic targets is limited because therapeutic target discovery is very laborious. Affinity maturation of selected clones is impor‐ tant when low-affinity clones are selected from naive or synthetic libraries where the antibody genes have not been subjected to somatic hypermutation in contrast to immune libraries. New promising affinity maturation approaches include mammalian cell surface display of antibod‐ ies coupled with somatic hypermutation mediated by activation-induced cytidine deaminase (AID). Furthermore, affinity maturation based on incorporation of a random repertoire of mi‐ crochip-synthesized CDRs into a known antibody framework has recently been demonstrat‐ ed. However, affinity maturation based on introduction of random or site-directed mutations

can be time-consuming because secondary libraries must be built up and screened.


Lavanya Suneetha, Prasanna Marsakatla, Rachel Supriya Suneetha and Sujai Suneetha
