Total synthesis of effectors for modulating the human immune system

Abstract

Innate immunity is provided by a complex network of cells, soluble factors, and organs that respond immediately or within hours of the appearance of a stimulus in the body. Innate immune processes can involve recognition of metabolites, including those of self or microbial pathogens, by endogenously-expressed pattern recognition receptors. In this thesis, I explored the structure of different antigens that can be recognized by the innate immunity macrophage inducible C-type lectin receptor (Mincle), innate-like natural killer T (NKT) cell, and mucosal-associated invariant T (MAIT) cells.

Chapter 2 describes the synthesis of acyl variants of cholesteryl and ergosteryl alpha-mannoside (CAMs and EAMs), proposed structures for glycolipids from Candida albicans. These glycolipids were synthesized by mannosylation of cholesterol or ergosterol, followed by the introduction of the acyl groups by esterification of the sugar primary alcohol. The synthetic glycolipids were assessed for their ability to agonize signaling by mouse and human Mincle. We showed that both CAMs and EAMs elicited strong signaling through both mouse and human Mincle.

Chapter 3 discloses the total synthesis of an alpha-galactosylceramide originally reported from Bacteroides fragilis: GalCerBf-716, as well as analogs bearing modified lipid side chains to allow exploration of structure-activity relationships for activation of CD1d-restricted iNKT cells. GalCerBf-716 was synthesized by galactosylation of a sphinganine acceptor, followed by an amide coupling with different acid side chains. All synthesized GalCerBf-716 analogs stimulated mouse and human iNKT cells.

In Chapter 4 we proposed a structure for an undefined antigen (5-F-7-RdX) arising from the reaction of 5-A-RU with a dicarbonyl compound. We synthesized a simpler analog, 7-RdX. 7-RdX was shown to act as a weak and selective agonist for MAIT TCR-Tyr94 cell lines, over Tyr95 cell lines. The electron density of 7-RdX from an X-ray structure in complex with the antigen-presenting molecule MR1 is a close match to that for unknown antigen.