Targeting melanoma associated antigens with antigen-specific antibodies: An examination of mechanisms and strategies in two antigen systems
Hsu, Jeff Chi-Feng
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The overall objectives of this thesis are (i) to investigate the mechanisms underlying anti-GD3 ganglioside monoclonal antibody (mAb)-, and anti-high molecular weight-melanoma associated antigen (HMW-MAA) mAb-mediated direct effects on the biology of melanoma cells; and (ii) to develop an active specific immunotherapeutic strategy which can generate antibodies against GD3 and HMW-MAA in hosts which bear these self melanoma associated antigens (MAA). Chapter one summarizes the pre-clinical and clinical results and the potential mechanisms of action, of mAb targeting these two MAA, after having described these antigens' structure, expression and potential functions. This is followed by a review of the use of antigen mimics for the development of antibody-based active specific immunotherapy. Chapters two and three utilize in vitro assays to investigate the first objective of this thesis, which includes a detailed characterization of anti-GD3 mAb R24-mediated inhibitory effects on the growth of melanoma cells (Chapter two), and an examination of the role of HMW-MAA in melanoma cell migration, and the inhibition of this function by anti-HMW-MAA mAb 763.74 (Chapter three). Chapters four, five, and six investigate the second objective of this thesis via panning phage display peptide libraries with GD3- or HMW-MAA-specific mAb to isolate peptide mimics of these antigens. Specifically, GD3 peptide mimic isolation, peptide binding characteristics, and immunogenicity in mice are presented (Chapter four). A comparative analysis of the immunogenicity of peptides isolated with HMW-MAA-specific Ab1 (mAb 763.74) and Ab3 (anti-anti-id mAb GH786) is also presented (Chapter five), and the functional effects of antibodies elicited by mAb 763.74-isolated peptide is evaluated (Chapter six). Finally, chapter seven is dedicated to discussing future research directions with respect to (i) further elucidation of mechanisms underlying mAb-mediated effects on melanoma cells; and (ii) strategies to improve the immune responses induced by the isolated peptide mimics. Collectively, the studies described in this thesis extend the current understanding of non-immunological mechanisms mediated by GD3- and HMW-MAA-specific mAb; furthermore, the results obtained from these studies will also represent a useful background to design strategies to implement active, specific immunotherapy of melanoma with novel immunogens represented by peptide mimics of GD3 ganglioside and HMW-MAA.