Bioengineering to harness the immune adjuvanting properties of reactive carbonyls

点击翻译按钮获取中文摘要

Protein oxidation is widespread and serves physiological functions such as during bacterial killing by leukocytes undergoing oxidative burst, but can also result in pathology when unchecked, such as the unwanted immune responses seen in diabetes and atherosclerosis. Although the immune enhancing effects of protein oxidation are well described, their underlying mechanism remains unknown. Our group is among the first to suggest a chemical hallmark of protein oxidation, a reactive chemical group termed a reactive carbonyl (RC), as a common immune enhancing agent when introduced into to protein. We have demonstrated that addition of RC groups to various proteins under different oxidative conditions enhances their immune stimulating activity, showing that this applies to many common proteins. We have recently demonstrated that RC addition activates an important type of immune cell called a helper T cell (Th). Th are activated when they encounter protein presented to them by an antigen presenting cell (APC). APCs interact with Th cells via a molecule called MHC class II, which contains a peptide fragment of the protein that is 'seen' by the T cell. Our results show that the addition of an RC group to a peptide allows the peptide to bind more tightly to MHC class II, which results in increased Th cell activation and enhanced antibody responses. The purpose of this proposal is to investigate the mechanistic basis of how proteins that bear RC as a consequent of their oxidation, are more immunogenic. We set out to examine the biochemical nature of this interaction using a combination of chemical modification of proteins and peptides, immunological assays, peptide-MHC class II binding assays and X-ray crystallography to solve the atomic structure of the peptide-MHC class II complex. This information will then be used to attempt to modify the immune activating properties of a whole protein rather than a peptide. If successful we will then apply this technology to the design of an experimental vaccine based on influenza haemagglutinin (HA), the target protein on the virus of protective neutralizing antibodies. This will provide proof of principle for the design of vaccines that target the adaptive immune response to specific epitopes in the absence of inflammatory adjuvants. The characterization of a major mechanism underlying protein oxidation-mediated immune enhancement coupled with a novel concept for vaccine adjuvantation makes this a highly original proposal with the potential for high impact in the fields of biochemistry and immunology. The project benefits from an established collaborative consortium of chemists, proteomics experts, crystallographers and immunologists that will ensure the highest chance of success within the proposed timescale.