Construction and characterization of a pseudo-immune human antibody library using yeast surface display

Lymphocytes from eight individuals out of 60 healthy donors, whose plasmas showed relatively higher antibody titer for a target antigen of death receptor 5 (DR5), were selected for the source of antibody genes to construct so called an anti-DR5 pseudo-immune human single-chain fragment variable (scFv) library on the yeast cell surface (∼2 × 106 diversity). Compared with a large nonimmune human scFv library (∼1 × 109 diversity), the repertoire of the pseudo-immune scFv library was significantly biased toward the target antigen, which facilitated rapid enrichments of the target-specific high affinity scFvs during selections by fluorescence activated cell sortings. Isolated scFvs, HW5 and HW6, from the pseudo-immune library showed much higher specificity and affinity for the targeted antigen than those from the nonimmune library. Our results suggest that a pseudo-immune antibody library is very efficient to isolate target-specific high affinity antibody from a relatively small sized library.