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Meijlink MA, Chua YC, Chan STS, Anderson RJ, Rosenberg MW, Cozijnsen A, Mollard V, McFadden GI, Draper SL, Holz LE, Hermans IF, Heath WR, Painter GF, Compton BJ. 6″-Modifed α-GalCer-peptide conjugate vaccine candidates protect against liver-stage malaria. RSC Chem Biol 2022; 3:551-560. [PMID: 35656478 PMCID: PMC9092427 DOI: 10.1039/d1cb00251a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2021] [Accepted: 03/02/2022] [Indexed: 11/21/2022] Open
Abstract
Self-adjuvanting vaccines consisting of peptide epitopes conjugated to immune adjuvants are a powerful way of generating antigen-specific immune responses. We previously showed that a Plasmodium-derived peptide conjugated to a rearranged form of α-galactosylceramide (α-GalCer) could stimulate liver-resident memory T (TRM) cells that were effective killers of liver-stage Plasmodium berghei ANKA (Pba)-infected cells. To investigate if similar or even superior TRM responses can be induced by modifying the α-GalCer adjuvant, we created new conjugate vaccine cadidates by attaching an immunogenic Plasmodium-derived peptide antigen to 6″-substituted α-GalCer analogues. Vaccine synthesis involved developing an efficient route to α-galactosylphytosphingosine (α-GalPhs), from which the prototypical iNKT cell agonist, α-GalCer, and its 6″-deoxy-6″-thio and -amino analogues were derived. Attaching a cathepsin B-cleavable linker to the 6″-modified α-GalCer created pro-adjuvants bearing a pendant ketone group available for peptide conjugation. Optimized reaction conditions were developed that allow for the efficient conjugation of peptide antigens to the pro-adjuvants via oxime ligation to create new glycolipid-peptide (GLP) conjugate vaccines. A single dose of the vaccine candidates induced acute NKT and Plasmodium-specific CD8+ T cell responses that generated potent hepatic TRM responses in mice. Our findings demonstrate that attaching antigenic peptides to 6″-modifed α-GalCer generates powerful self-adjuvanting conjugate vaccine candidates that could potentially control hepatotropic infections such as liver-stage malaria. Candidate vaccines comprised of peptide antigen conjugated to 6″-modified α-GalCer analogues generate potent hepatic TRM responses in mice with a single dose inducing protective immunity against malaria in a Plasmodium sporozoite challenge model.![]()
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Affiliation(s)
- Michael A. Meijlink
- Ferrier Research Institute, Victoria University of Wellington, Lower Hutt, New Zealand
| | - Yu Cheng Chua
- Department of Microbiology and Immunology, Doherty Institute for Infection and Immunity, University of Melbourne, Melbourne, VIC, Australia
| | - Susanna T. S. Chan
- Ferrier Research Institute, Victoria University of Wellington, Lower Hutt, New Zealand
| | - Regan J. Anderson
- Ferrier Research Institute, Victoria University of Wellington, Lower Hutt, New Zealand
| | - Matthew W. Rosenberg
- Ferrier Research Institute, Victoria University of Wellington, Lower Hutt, New Zealand
| | - Anton Cozijnsen
- School of BioSciences, University of Melbourntie, Parkville, VIC, Australia
| | - Vanessa Mollard
- School of BioSciences, University of Melbourntie, Parkville, VIC, Australia
| | | | - Sarah L. Draper
- Ferrier Research Institute, Victoria University of Wellington, Lower Hutt, New Zealand
| | - Lauren E. Holz
- Department of Microbiology and Immunology, Doherty Institute for Infection and Immunity, University of Melbourne, Melbourne, VIC, Australia
| | - Ian F. Hermans
- Malaghan Institute of Medical Research, Wellington, New Zealand
- Avalia Immunotherapies Limited, Lower Hutt, New Zealand
| | - William R. Heath
- Department of Microbiology and Immunology, Doherty Institute for Infection and Immunity, University of Melbourne, Melbourne, VIC, Australia
| | - Gavin F. Painter
- Ferrier Research Institute, Victoria University of Wellington, Lower Hutt, New Zealand
- Avalia Immunotherapies Limited, Lower Hutt, New Zealand
| | - Benjamin J. Compton
- Ferrier Research Institute, Victoria University of Wellington, Lower Hutt, New Zealand
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Natural and synthetic carbohydrate-based vaccine adjuvants and their mechanisms of action. Nat Rev Chem 2021; 5:197-216. [PMID: 37117529 PMCID: PMC7829660 DOI: 10.1038/s41570-020-00244-3] [Citation(s) in RCA: 112] [Impact Index Per Article: 37.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/03/2020] [Indexed: 01/31/2023]
Abstract
Modern subunit vaccines based on homogeneous antigens offer more precise targeting and improved safety compared with traditional whole-pathogen vaccines. However, they are also less immunogenic and require an adjuvant to increase the immunogenicity of the antigen and potentiate the immune response. Unfortunately, few adjuvants have sufficient potency and low enough toxicity for clinical use, highlighting the urgent need for new, potent and safe adjuvants. Notably, a number of natural and synthetic carbohydrate structures have been used as adjuvants in clinical trials, and two have recently been approved in human vaccines. However, naturally derived carbohydrate adjuvants are heterogeneous, difficult to obtain and, in some cases, unstable. In addition, their molecular mechanisms of action are generally not fully understood, partly owing to the lack of tools to elucidate their immune-potentiating effects, thus hampering the rational development of optimized adjuvants. To address these challenges, modification of the natural product structure using synthetic chemistry emerges as an attractive approach to develop well-defined, improved carbohydrate-containing adjuvants and chemical probes for mechanistic investigation. This Review describes selected examples of natural and synthetic carbohydrate-based adjuvants and their application in synthetic self-adjuvanting vaccines, while also discussing current understanding of their molecular mechanisms of action.
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