Fellowship for David Henson: Modulation of Antibodies Targeting ApoA-I in a Mouse Model of Atherosclerosis

Auto-antibodies targeting Apolipoprotein A-I (ApoA-I), the major protein of high density lipoprotein, are found in patients. Some data indicates that free anti-ApoA-I IgG predicts cardiovascular disease events in patients. Our lab has identified a novel biomarker, ApoA-I/IgG immune complexes (ICs) in which ApoA-I and IgG are associated in patient plasma. Elevation in ApoA-I/IgG ICs predicts protection from cardiovascular events. In a population with coronary artery disease patients with a below median level of ApoA-I/IgG ICs have a hazard ratio of 1.50 (95% CI: 1.03-2.18) for Major Adverse Cardiovascular Events (MACE) after adjustment for 11 common cardiovascular risk factors. Studies in mice support our human work. We find that mice immunized with an ApoA-I peptide in an immunostimulatory liposome develop increased free anti-ApoA-I IgG and increased atherosclerosis. These immunized mice also lack ApoA-I IgG ICs. This corroborates the dichotomy seen in patients that anti-ApoA-I IgG increases cardiovascular risk while ApoA-I/IgG ICs decrease cardiovascular risk. Based on this data we hypothesize that by modulating the immune response to either increase ApoA-I/IgG ICs or decrease free anti-ApoA-I IgG in an atherosusceptible mouse model we will decrease atherosclerosis development. Our goal in aim 1 is to induce ApoA-I/IgG ICs. To complete this we propose to test multiple adjuvants to alter the induced IgG subclass ratio. Studies of ApoA-I/IgG ICs in patients indicates that IgG4 antibodies are enriched within the immune complexes as compared to total plasma. Human IgG4 has anti-inflammatory effects and is similar in function to IgG1 in mice. Our current strategy utilizes MPL-A which induces a 2:1 ratio of IgG1 to IgG2a. We propose to test alum and CpG in addition to MPL-A. Alum induces a highly IgG1 response while CpG will induce an IgG2a response. The induction of immune complexes will be measured in mice following immunization, and the development of atherosclerosis will be determined via en face quantification. In aim 2 we propose to utilize immunomodulatory liposomes to deplete free anti-ApoA-I IgG in mice. Previous work in our lab has shown that doxorubicin containing liposomes coated with antigen can suppress a preexisting immune response to the antigen. We will further this work to determine if suppression of anti-ApoA-I IgG using doxorubicin or azithromycin containing liposomes can decrease the development of atherosclerosis in mice. The data generated in these aims will provide details about the impact of antibodies targeting ApoA-I and the initial development of therapeutics to modulate free anti-ApoA-I IgG and ApoA-I/IgG ICs with a long term goal of decreasing the burden of cardiovascular disease in patients.