Anti-HER2/neu IgG3-(IL-2) and anti-HER2/neu IgG3-(GM-CSF) promote HER2/neu processing and presentation by dendritic cells:: Implications in immunotherapy and vaccination strategies

HER2/neu, a transmembrane glycoprotein overexpressed in several types of human cancers, is a potential target for active immunotherapy. However, this protein and especially its extracellular domain (ECDHER2), is weakly immunogenic and is poorly processed by dendritic cells (DCs). Previously, we showed that anti-HER2/neu IgG3-(IL-2) and anti-HER2/neu lgG3-(GM-CSF) fusion proteins can enhance the immunogenicity of ECD HER2 in mice, and that the non-covalent physical association between each antibody fusion proteins and ECDHFR2 was critical to elicit optimal protective immunity against HER2/neu expressing tumors. We now use the professional antigen-presenting DCs to investigate the effect of the antibody fusion protein binding to ECD HER2 on its trafficking and presentation. We found that when the extracellular domain of HER2/neu fused to ovalbumin (OVA-ECDHER2) is bound by HER2/neu-specific antibody-(IL-2) or antibody-(GM-CSF) fusion proteins, the bound antigen is more efficiently processed by murine bone-marrow-derived dendritic cells (BMDCs) and presented to OVA-specific T-cells than the unbound OVA-ECDHER2. We also found that ECDHER2 bound by anti-HER2/nett IgG3-(IL-2) is very efficiently internalized and that the internalized ECD HER2 is not retained in the early endosomal compartments but traffics to the antigen-processing compartments. These results are consistent with our earlier in vivo studies and suggest that both antibody-(IL-2) and antibody-(GM-CSF) fusion proteins can be used to enhance the immune response to poorly immunogenic antigens including tumor-associated antigens (TAAs). (C) 2005 Elsevier Ltd. All rights reserved.