Guided selection of antibody fragments specific for human interferon γ receptor 1 from a human VH- and VL-gene repertoire

Abstract

Objective: The guided selection strategy for isolation of human antibody (Ab) fragments specific for human interferon γ receptor 1 (IFNGR-1) from a cloned Ab VH and VL repertoire has been investigated. In order to identify recombinant Abs binding to soluble antigen, a novel method termed affinity sedimentation was introduced here. Results and conclusions: The VH region of murine monoclonal Ab (IRγ-1) against human IFNGR-1 was combined with human VL repertoire and used for selection of human VL regions. One of these human VL regions (κ2) possesses high homology to the murine template VL region, also in CDR3 (77%). A chimeric Fab consisting of κ2 and the murine IRγ-1 VH region was highly IFNGR-1 specific and exerted the same epitope specificity and a comparable binding affinity as the parental murine Fab. In a further step, the selected human VL region κ2 was combined with a human VH repertoire and led by guided selection to the generation of a completely human Fab (1b5) specific for human IFNGR-1. The overall VH region homology of 1b5 compared to the parental antibody IRγ-1 was 81%, with a rather low homology in CDR3. Binding competition studies revealed that the epitope recognized by 1b5 differs from the parental Ab IRγ-1.