The Chemical Synthesis, Stability, and Activity of MAIT Cell Prodrug Agonists That Access MR1 in Recycling Endosomes

  • ACS Chem Biol. 2020 Feb 21;15(2):437-445. doi: 10.1021/acschembio.9b00902.
Joshua Lange  1 ,  Regan J Anderson  2 ,  Andrew J Marshall  2 ,  Susanna T S Chan  2 ,  Timothy S Bilbrough  2 ,  Olivier Gasser  1 ,  Claudia Gonzalez-Lopez  3 ,  Mariolina Salio  3 ,  Vincenzo Cerundolo  3 ,  Ian F Hermans  1  4 ,  Gavin F Painter  2  4
Affiliations
  • 1. Malaghan Institute of Medical Research , Wellington , New Zealand.
  • 2. The Ferrier Research Institute , Victoria University of Wellington , Wellington , New Zealand.
  • 3. Medical Research Council Human Immunology Unit, Weatherall Institute of Molecular Medicine , University of Oxford , Oxford , United Kingdom.
  • 4. Maurice Wilkins Centre for Molecular Biodiscovery , Auckland , New Zealand.
PMID: 31909966 DOI: 10.1021/acschembio.9b00902
Abstract

Mucosal-associated invariant T (MAIT) cells are Antibacterial effector T cells that react to pyrimidines derived from Bacterial riboflavin synthesis presented by the monomorphic molecule MR1. A major challenge in MAIT cell research is that the commonly used MAIT agonist precursor, 5-amino-6-d-ribitylaminouracil (5-A-RU), is labile to autoxidation, resulting in a loss of biological activity. Here, we characterize two independent autoxidation processes by LCMS. To overcome the marked instability, we report the synthesis of a 5-A-RU prodrug generated by modification of the 5-amino group with a cleavable valine-citrulline-p-aminobenzyl carbamate. The compound is stable in prodrug form, with the parent amine (i.e., 5-A-RU) released only after enzymatic cleavage. Analysis of the prodrug in vitro and in vivo showed an enhanced MAIT cell activation profile compared to 5-A-RU, which was associated with preferential loading within recycling endosomes, a route used by some natural agonists. This prodrug design therefore overcomes the difficulties associated with 5-A-RU in biological studies and provides an opportunity to explore different presentation pathways.

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