Approaches for Humanization of an Anti-idiotypic Murine Monoclonal Antibody

Abstract

The anti-idiotypic antibody (Ab) Ab2/3H6 (Kunert et al. 2002) is directed against the human monoclonal Ab (mAb) 2F5, which broadly and potently neutralizes primary HIV-1 isolates (Wolbank et al. 2003). Ab2/3H6 is able to mimic the antigen recognition site of the mAb2F5 making it an attractive candidate antigen for HIV-1 vaccine purposes. In this study the mouse variable regions of Ab2/3H6 were subjected to various humanizing approaches using three different methods. For the CDR-grafted variants, an “aggressive” graft harboring less backmutations and a “conservative” graft with more backmutations were designed. In the Superhumanization approach we grafted the murine CDRs to a human framework (FR) which was most related concerning the canonical structure class. The Resurfacing method substitutes mouse amino acids (aa) that are surface exposed in the murine FR by residues usually found in equivalent positions in human Abs. The different Ab2/3H6 variants were characterized by competition experiments with mAb 2F5. The resurfaced and the “conservative” grafted variants showed similar binding properties to mAb 2F5 when compared to the murine Ab2/3H6 version, while the “aggressive” grafted Ab showed less affinity and the superhumanized type lost the ability to bind to mAb 2F5.