Immune libraries

Two types of antibody libraries can be constructed, immune or non-immune. Immune libraries are constructed by immunizing the animal of interest with an antigen(s). In the case of humans, the source can be volunteers with the disease or condition under study (Persson et al., 1991). Human antibodies have also been obtained from severe combined immunodeficiency mice populated with human peripheral blood... 

Non-immune libraries are produced in a similar fashion, but using B-lymphocytes fromnon-im-munized donors as a source of antibody genes. This approach becomes necessary if initial immunization with the antigen of interest is not possible (e.g. due to ethical considerations). Although such... 

Hanes, J.,Jermutus, L., Weber-Bornhauser, S., Bosshard, H. R., and Pluckthun, A. (1998). Ribosome display efficiently selects and evolves high-affinity antibodies in vitro from immune libraries. Proc. Natl. Acad. Sci. USA, 95(24), 14130—14135. 

Immune libraries and evolutionary selection strategies intersect in the area of antibody humanization. Recently, we have extended the repertoire of methods available for the generation of therapeutic human antibodies by developing phage display strategies for the selection and humanization of antibodies from immune animals other than mice. Our aim here was to modify protein sequence, in some cases in a very radical way, and yet retain the function of the parental antibody. In the following discussion, we will focus on these novel approaches. 

Subsequently, it was demonstrated that it is possible to select and evolve scFv antibody fragments from immune libraries using the E. coli system. Only three rounds of ribosome display were necessary to isolate a family of scFv fragments binding to a peptide variant of the GCN4 leucine zipper, which exists as a random coil in solution (Hanes et al.,... 

In general, the affinity of the antibodies selected is proportional to the size of the library, with Kd s ranging from 10 6/7 for the smaller libraries [2,3] to 10-9 for the larger ones [1,4], a finding which is in line with theoretical considerations [12]. Antibodies selected from immunized libraries tend to have higher affinities for the antigen used for immunization from an equivalent library size. 

Nonimmune or naive libraries are constructed in the same manner as an immune library, but B-cells from nonimmunized donors are used as sources for antibody genes. The diversity of isolated antibodies increases with the library size, and... 

Humanized Antibodies. For human immunotherapeutic applications, the optimal antibody should be of human origin. Immune libraries are perhaps the best way to produce neutralizing antibody responses to protective epitopes on infectious pathogens [26]. For therapeutic purposes, the efficacy of nonhuman-derived monoclonal antibodies is limited by the induction of anti-mouse immune response. Using hybridoma methods to immortalize human B-cells for the construction of human monoclonal antibodies would avoid these issues. However, the absence of a suitable fusion partner and other technical issues has made methods that rely on human B-cell immortalization problematic, forcing reliance on nonhuman organisms [6]. 

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