Synthetic mycobacterial diacyl trehalose lipids reveal differential recognition by human T cell receptors and the innate immune receptor Mincle
Authors: Josephine F. Reijneveld1,2,3, Mira Holzheimer3, Kattya Lopez1,4, Sara Suliman1, Megan B. Murray5, Eri Ishikawa6,7, Sho Yamasaki6,7, Adriaan J. Minnaard3, D. Branch Moody1, Ildiko Van Rhijn1,2

1 Division of Rheumatology, Inflammation, and Immunity, Brigham and Women’s Hospital and Harvard Medical School, Boston, MA, United States
2 Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands.
3 Stratingh Institute for Chemistry, University of Groningen, Groningen, The Netherlands
4 Socios En Salud, Lima, Peru
5 Division of Global Health Equity, Department of Global Health and Social Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston, MA, United States
6 Department of Molecular Immunology, Research Institute for Microbial Diseases, Osaka University, Suita, Osaka, Japan.
7 Laboratory of Molecular Immunology, Immunology Frontier Research Center, Osaka University, Suita, Osaka, Japan

The cell wall of Mycobacterium tuberculosis is composed of diverse glycolipids which potentially interact with the human immune system. One of these lipids is diacyl trehalose (DAT). Purified DAT is known to be a ligand for the innate immune receptor Mincle, but it is unknown whether it can function as a foreign antigen for human T cells that are part of the adaptive immune system. Cell wall lipids of Mtb can be presented to T cell receptors by the antigen presenting molecules CD1a, CD1b, CD1c, and CD1d. The non-polymorphic nature of CD1 molecules makes lipids presented by CD1 proteins ideal targets for vaccine approaches and diagnostic purposes. To overcome difficulties in obtaining pure compounds from bacterial extracts, we synthesized and tested three forms of DAT that differ in their fatty acid composition: DAT1, DAT2, and DAT3. To study the potential recognition of DATs by human T cells, we loaded the lipid-binding antigen presenting molecule CD1b with DATs and looked for T cells that bound the complex in both healthy donors from Boston and participants of a Peruvian tuberculosis cohort. CD1b presenting DAT1 and DAT2 was recognized by T cells, but CD1b presenting DAT3 was not. In addition, we derived a T cell line from human peripheral blood mononuclear cells using CD1b-DAT2 complexes and showed that there is no cross-reactivity between DATs, suggesting that the chemical structure of the fatty acid determines recognition by T cells. In contrast with the lack of recognition of DAT3 by human T cells, we found that DAT3, but not DAT1 or DAT2, was able to activate the Mincle receptor. Thus, we show that the mycobacterial lipid DAT can be both an antigen for T cells and an agonist for the innate Mincle receptor, and that small chemical differences determine recognition by different parts of the immune system.

Josephine Reijneveld MSc

Brigham and Women's Hospital/Groningen University/Utrecht University

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