Generation of Chicken Antibody Libraries and Selection of Antigen Binders

Chicken antibodies have been widely used for research and diagnostic purposes. Chicken antibodies are often cross-reactive to epitopes shared by humans, nonhuman primates, and other mammals, and can be tested in many mouse disease models, which provides an advantage for their preclinical study and evaluation. In addition, the variable region of chicken antibodies has unique structural characteristics, including noncanonical cysteine residues in the heavy chain complementarity-determining region (CDR)3 and a long heavy chain CDR3, which together with a short light chain CDR enable the formation of unconventional antibody paratopes. As chickens have single functional copies of the <i>V</i> _<i>H</i> and <i>J</i> _<i>H</i> genes, and the somatic gene conversion process usually involves <i>D</i> _<i>H</i> genes, all functional VDJ gene fragments can be obtained from the B-cell repertoire using a single PCR primer set, without any primer bias. As for the light chain, chickens only have a <i>V</i> _<i>λ</i> light chain, composed of a single <i>V</i> _<i>λ</i> and <i>J</i> _<i>λ</i> gene pair. Therefore, the chicken light chain repertoire can also be accurately amplified using a single primer set. This unbiased reconstitution of the chicken B-cell repertoire provides a great advantage not only in the construction of phage display libraries but also for the in silico selection of antigen binders from a virtual B-cell receptor repertoire. Here, we introduce the use of chicken antibodies in research, diagnostic, and therapeutic fields. In addition, the chromosomal organization of chicken immunoglobulin genes and its diversification mechanisms for shaping the antibody repertoire are also discussed.