Isolation and characterisation of a human anti-idiotypic scFv used as a surrogate tumour antigen to elicit an anti-HER-2|[sol]|neu humoral response in mice

摘要

HER-2eu is a tumour antigen that is overexpressed in human breast tumours. Among the vaccine strategies developed to overcome immune tolerance to self-proteins, vaccination with anti-idiotypic (anti-Id) antibodies has been described as a promising approach for treatment of several malignant diseases. To develop an active immunotherapy for cancer patients positive for HER-2eu, we investigated immunisation with human anti-Id single-chain fragments (scFv) mimicking the conformation of HER-2eu protein to induce a humoral response in mice. We selected by phage display two human anti-Id scFv (Ab2β) directed against trastuzumab F(ab′)2 fragments (Ab1), a humanised anti-HER-2eu monoclonal antibody. Using competitive ELISA and Biacore biosensor analysis, we showed that anti-Id scFv 40 and scFv 69 could inhibit HER-2eu binding to trastuzumab. Following vaccination of BALB/c mice with the soluble or phage-displayed scFv, Ab3 polyclonal antibodies, and among them Ab1′ antibodies able to bind HER-2eu, were detected in the sera of the immunised mice. These results demonstrate that the human anti-Id scFv could act as a surrogate antigen for HER-2eu. The present study strongly suggests that the novel 30?kDa human mini-antibody could be used as an anti-idiotype-based vaccine formulation to induce an effective humoral response in patients bearing HER-2eu-positive tumours.