Characterization of an Anti-Idiotypic Antibody Blocking the Capacity of the HIV-1 Specific nMAb 2F5

摘要

Recently we were able to show that the murine anti-idiotypic antibody (Ab2) 3H6 (Kunert et al., 2002; Antiidiotypic Antibody Inducing HIV-1 Neutralizing Antibodies Pending) significantly blocked the binding of the human mAb 2F5 to its synthetic epitope ELDKWA as well as to gp160. Furthermore, 3H6 was also capable of decreasing the in vitro neutralisation potency of 2F5 in a dose-related way. Finally, the murine 3H6 Fab fragments were capable to induce Abl-like neutralising immune responses after applying the Ab2 to mice. Thus, Ab2/3H6 successfully mimics a neutralising epitope on gp41, which is either not or only poorly immuno-genic on the native HIV-1 during natural infection. In the present study the murine Ab2/3H6 was partially humanized (the murine variable regions were fused with the corresponding human constant regions) and recombinantly expressed either as whole IgGl (using two different expression strategies) or Fab fragment in CHO cells. Crude Ab2/3H6 IgG 1 and Ab2/3H6 Fab expression supernatants were effectively purified using either protein A for Ab2/3H6 IgGl (up to 90% recovery) or a combination of anion-exchange and size-exclusion chromatography in case of Ab2/3H6 Fab (up to 75% recovery). The purified Ab2/3H6 versions were further characterized by several specificity studies and competition experiments with neutralizing monoclonal antibody nMAb 2F5.