Abstract
We report the design, construction, and use of the first very large non-immunized phage antibody library in Fab format, which allows the rapid isolation and affinity analysis of antigen-specific human antibody fragments. Individually cloned heavy and light chain variable region libraries were combined in an efficient two-step cloning procedure, permitting the cloning of a total of 3.7 x 10(10) independent Fab clones. The performance of the library was determined by the successful selection of on average 14 different Fabs against 6 antigens tested. These include tetanus toxoid, the hapten phenyl-oxazolone, the breast cancer-associated MUC1 antigen, and three highly related glycoprotein hormones: human chorionic gonadotropin, human luteinizing hormone, and human follicle-stimulating hormone. In the latter category, a panel of either homone-specific or cross-reactive antibodies were identified. The design of the library permits the monitoring of selections with polyclonal phage preparations and to carry out large scale screening of antibody off-rates with unpurified Fab fragments on BIAcore. Antibodies with off-rates in the order of 10(-2) to 10(-4) s-1 and affinities up to 2.7 nM were recovered. The kinetics of these phage antibodies are of the same order of magnitude as antibodies associated with a secondary immune response. This new phage antibody library is set to become a valuable source of antibodies to many different targets, and to play a vital role in target discovery and validation in the area of functional genomics.
Highlights
Display on filamentous phage in combination with selection forms a powerful tool for the identification of peptide- or protein-based drugs [1, 2]
The natural primary antibody repertoire within B cells contains a large array of antibodies that recognize a variety of antigens; this array can be cloned as a “naıve” repertoire of rearranged genes, by harvesting the V-genes from the IgM mRNA of B cells of unimmunized human donors, isolated from peripheral blood lymphocytes [4], from bone marrow or tonsils [7], or from similar animal sources [16]
Design of the Non-immunized Phage Antibody Library—We considered a number of variables to address in the construction of a novel, very large phage antibody library: (i) the primer design was optimized for amplification of variable gene pools to maintain maximum diversity; (ii) a highly efficient two-step cloning method was developed to obtain a very large nonimmunized library; (iii) an antibody format and compatible cloning vector were chosen, which should permit the rapid downstream analysis of selected clones
Summary
Display on filamentous phage in combination with selection forms a powerful tool for the identification of peptide- or protein-based drugs [1, 2]. The natural primary (unselected) antibody repertoire within B cells contains a large array of antibodies that recognize a variety of antigens; this array can be cloned as a “naıve” repertoire of rearranged genes, by harvesting the V-genes from the IgM mRNA of B cells of unimmunized human donors, isolated from peripheral blood lymphocytes [4], from bone marrow or tonsils [7], or from similar animal sources [16] This procedure provides access to antibodies that have not yet encountered antigen, the frequency of those genuine “germline” antibodies will depend heavily on the source of B cells [17]. Over the last few years, more efficient techniques have been developed to build larger libraries of antibody fragments, using sophisticated in vivo recombination methods [6] or brute force cloning procedures [7, 19] Such large libraries have yielded a greater number of human antibodies per antigen tested, with on average much higher affinity (up to subnanomolar). The Fab format permitted the rapid screening and a reliable ranking of individual clones on off-rate using crude antibody fractions
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
