Understanding the role of anti-apolipoprotein A-I antibodies in atherosclerotic cardiovascular disease

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PROJECT SUMMARY / ABSTRACT – PROJECT 4 The identification of autoantigens in atherosclerotic plaques has prompted investigation of the antibody-mediated pathogenesis of cardiovascular disease (CVD). Detailed characterization of the antigen, epitope specificity, antibody subclass and receptor engagement will enhance the understanding of CVD and guide therapeutic development. One target of IgG antibody induction in patients is apolipoprotein A-I (ApoA-I), the major protein of high density lipoprotein (HDL). Although anti-ApoA-I antibodies have been identified in mice and human subjects, the role of these antibodies have not been elucidated. Furthermore, the immunologic impact of antibodies bound to ApoA-I in an immune complex (ApoA-I/IgG ICs) is unclear. The long-term goal is to develop novel peptide and antibody therapeutics based on mechanistic insight from mice, to reduce the burden of CVD in patients. To achieve this goal, the overall objectives of this proposal build from our observations in human subjects to characterize the molecular components of the anti-ApoA-I antibody response in mice and correlate their characteristics with cellular interactions, functional outcomes and atherosclerosis progression. The hypothesis is that anti-ApoA-I antibodies exhibit both pro- and anti-inflammatory effects depending on the antibody characteristics (i.e. subclass, epitope specificity, Fc receptor interaction) leading to exacerbation or suppression of atherosclerosis. The rationale for this proposed research is that understanding one component of the immune response associated with CVD will promote improved patient outcomes through novel therapeutic strategies. Encouraged by strong preliminary data, this hypothesis will be tested through two specific aims: 1) Elucidate the molecular components and functional implications of antibodies targeting peptide epitopes derived from ApoA-I; and 2) Determine if ApoA-I/IgG ICs mediate an anti-inflammatory phenotype by engaging with the inhibitory Fc receptor using in vitro assays and in vivo studies in atherosusceptible mouse models. In the first aim, a structure immunogenicity relationship will be generated by correlating in silico modeling, biophysical characterization and immunogenicity studies of known peptide epitopes derived from ApoA-I. These data will be correlated with antibody profiles and subclass composition of the antibody response toward ApoA-I. In the second aim, the mechanistic impact of anti-ApoA-I antibodies will be determined by characterizing cell polarization in the presence of specific anti-ApoA-I profiles and inducing antibody profiles in atherosusceptible mice lacking Fc receptors. The innovation and significance of the proposed work is driven by the novel immunomodulation strategies that will improve our understanding of antibody-mediated immune responses, which will guide continued efforts to develop novel immunotherapies through coordination with the CPRI COBRE, to decrease the burden of CVD in patients.