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Barclay TG, Rajapaksha H, Thilagam A, Qian G, Ginic-Markovic M, Cooper PD, Gerson A, Petrovsky N. Physical characterization and in silico modeling of inulin polymer conformation during vaccine adjuvant particle formation. Carbohydr Polym 2016; 143:108-15. [PMID: 27083349 DOI: 10.1016/j.carbpol.2016.01.062] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Revised: 12/28/2015] [Accepted: 01/27/2016] [Indexed: 12/15/2022]
Abstract
This study combined physical data from synchrotron SAXS, FTIR and microscopy with in-silico molecular structure predictions and mathematical modeling to examine inulin adjuvant particle formation and structure. The results show that inulin polymer chains adopt swollen random coil in solution. As precipitation occurs from solution, interactions between the glucose end group of one chain and a fructose group of an adjacent chain help drive organized assembly, initially forming inulin ribbons with helical organization of the chains orthogonal to the long-axis of the ribbon. Subsequent aggregation of the ribbons results in the layered semicrystalline particles previously shown to act as potent vaccine adjuvants. γ-Inulin adjuvant particles consist of crystalline layers 8.5 nm thick comprising helically organized inulin chains orthogonal to the plane of the layer. These crystalline layers alternate with amorphous layers 2.4 nm thick, to give overall particle crystallinity of 78%.
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Affiliation(s)
- Thomas G Barclay
- Future Industries Institute, University of South Australia, Mawson Lakes, SA 5095, Australia.
| | - Harinda Rajapaksha
- Vaxine Pty Ltd, Flinders Medical Centre, Bedford Park, SA 5042, Australia.
| | - Alagu Thilagam
- Future Industries Institute, University of South Australia, Mawson Lakes, SA 5095, Australia.
| | - Gujie Qian
- Future Industries Institute, University of South Australia, Mawson Lakes, SA 5095, Australia.
| | - Milena Ginic-Markovic
- Future Industries Institute, University of South Australia, Mawson Lakes, SA 5095, Australia.
| | - Peter D Cooper
- Vaxine Pty Ltd, Flinders Medical Centre, Bedford Park, SA 5042, Australia; Cancer Research Laboratory, ANU Medical School, Garran, ACT 2605, Australia; John Curtin School of Medical Research, ANU, Acton, ACT 2601, Australia.
| | - Andrea Gerson
- Future Industries Institute, University of South Australia, Mawson Lakes, SA 5095, Australia; Blue Minerals Consultancy, Mill Terrace, Middleton, SA 5213, Australia.
| | - Nikolai Petrovsky
- Vaxine Pty Ltd, Flinders Medical Centre, Bedford Park, SA 5042, Australia; Department of Endocrinology, Flinders Medical Centre/Flinders University, Bedford Park, SA 5042, Australia.
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Petrovsky N, Cooper PD. Advax™, a novel microcrystalline polysaccharide particle engineered from delta inulin, provides robust adjuvant potency together with tolerability and safety. Vaccine 2015; 33:5920-6. [PMID: 26407920 PMCID: PMC4639457 DOI: 10.1016/j.vaccine.2015.09.030] [Citation(s) in RCA: 83] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Revised: 09/06/2015] [Accepted: 09/11/2015] [Indexed: 12/19/2022]
Abstract
There is an ongoing need for new adjuvants to facilitate development of vaccines against HIV, tuberculosis, malaria and cancer, amongst many others. Unfortunately, the most potent adjuvants are often associated with toxicity and safety issues. Inulin, a plant-derived polysaccharide, has no immunological activity in its native soluble form but when crystallized into a stable microcrystalline particulate from (delta inulin) acquires potent adjuvant activity. Delta inulin has been shown to enhance humoral and cellular immune responses against a broad range of co-administered viral, bacterial, parasitic and toxin antigens. Inulin normally crystallizes as large heterogeneous particles with a broad size distribution and variable solubility temperatures. To ensure reproducible delta inulin particles with a consistent size distribution and temperature of solubility, a current Good Manufacturing Practice (cGMP) process was designed to produce Advax™ adjuvant. In its cCMP form, Advax™ adjuvant has proved successful in human trials of vaccines against seasonal and pandemic influenza, hepatitis B and insect sting anaphylaxis, enhancing antibody and T-cell responses while being safe and well tolerated. Advax™ adjuvant represents a novel human adjuvant that enhances both humoral and cellular immunity. This review describes the discovery and development of Advax™ adjuvant and research into its unique mechanism of action.
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Affiliation(s)
- Nikolai Petrovsky
- Vaxine Pty Ltd, Flinders Medical Centre, Adelaide, SA 5042, Australia; Department of Endocrinology, Flinders Medical Centre and Flinders University, Adelaide 5042, Australia.
| | - Peter D Cooper
- Vaxine Pty Ltd, Flinders Medical Centre, Adelaide, SA 5042, Australia; John Curtin School of Medical Research, Australian National University, Canberra 2061, Australia
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Cooper PD, Rajapaksha KH, Barclay TG, Ginic-Markovic M, Gerson AR, Petrovsky N. Inulin crystal initiation via a glucose-fructose cross-link of adjacent polymer chains: atomic force microscopy and static molecular modelling. Carbohydr Polym 2014; 117:964-972. [PMID: 25498723 DOI: 10.1016/j.carbpol.2014.10.022] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Revised: 07/07/2014] [Accepted: 10/06/2014] [Indexed: 01/01/2023]
Abstract
Semi-crystalline microparticles of inulin (MPI) have clinical utility as potent human vaccine adjuvants but their relevant surface structure and crystal assembly remain undefined. We show inulin crystal surfaces to resemble multi-layered, discoid radial spherulites resulting from very rapid formation of complex tertiary structures, implying directed crystal initiation. Physical and in silico molecular modelling of unit cells confirm steric feasibility of initiation by hydrogen-bonded cross-linking of terminal glucose to a fructose of another chain, mimicking bonding in sucrose crystals. A strong, chelate-like dual H-bond is proposed to compel the known antiparallel alignment of inulin chains. Such cross-linking would require one extra fructose per chain in the native inulin crystal, as observed. Completion of five H-bonded internal ring-domains would 'lock in' each new 6-fructose structural unit of each antiparallel helix pair to create a new isoform. All known properties of inulin isoforms follow readily from these concepts.
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Affiliation(s)
- Peter D Cooper
- Vaxine Pty Ltd, Flinders Medical Centre, Bedford Park, SA, Australia 5042; Cancer Research Laboratory, Australian National University Medical School at The Canberra Hospital, Garran, ACT, Australia 2605; John Curtin School of Medical Research, Australian National University, Acton, ACT, Australia 2601.
| | | | - Thomas G Barclay
- Mawson Institute, University of South Australia, Mawson Lakes, SA, Australia 5095
| | | | - Andrea R Gerson
- Mawson Institute, University of South Australia, Mawson Lakes, SA, Australia 5095
| | - Nikolai Petrovsky
- Vaxine Pty Ltd, Flinders Medical Centre, Bedford Park, SA, Australia 5042; Department of Endocrinology, Flinders Medical Centre/Flinders University, Bedford Park, SA, Australia, 5042.
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Cooper PD, Barclay TG, Ginic-Markovic M, Gerson AR, Petrovsky N. Inulin isoforms differ by repeated additions of one crystal unit cell. Carbohydr Polym 2013; 103:392-7. [PMID: 24528745 DOI: 10.1016/j.carbpol.2013.12.066] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2013] [Revised: 12/19/2013] [Accepted: 12/20/2013] [Indexed: 12/21/2022]
Abstract
Inulin isoforms, especially delta inulin, are important biologically as immune activators and clinically as vaccine adjuvants. In exploring action mechanisms, we previously found regular increments in thermal properties of the seven-member inulin isoform series that suggested regular additions of some energetic structural unit. Because the previous isolates carried additional longer chains that masked defining ranges, these were contrasted with new isoform isolates comprising only inulin chain lengths defining that isoform. The new series began with 19 fructose units per chain (alpha-1 inulin), increasing regularly by 6 fructose units per isoform. Thus the 'energetic unit' equates to 6 fructose residues per chain. All isoforms showed indistinguishable X-ray diffraction patterns that were also identical with known inulin crystals. We conclude that an 'energetic unit' equates to one helix turn of 6 fructose units per chain as found in one unit cell of the inulin crystal. Each isoform chain comprised progressively more helix turns plus one additional fructose and glucose residues per chain.
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Affiliation(s)
- Peter D Cooper
- Vaxine Pty Ltd, Flinders Medical Centre, Bedford Park, SA 5042, Australia; Cancer Research Laboratory, Australian National University Medical School at The Canberra Hospital, Garran, ACT 2605, Australia; John Curtin School of Medical Research, The Australian National University, Acton, ACT 2601, Australia.
| | - Thomas G Barclay
- The Mawson Institute, University of South Australia, Mawson Lakes, SA 5095, Australia
| | - Milena Ginic-Markovic
- The Mawson Institute, University of South Australia, Mawson Lakes, SA 5095, Australia
| | - Andrea R Gerson
- The Mawson Institute, University of South Australia, Mawson Lakes, SA 5095, Australia
| | - Nikolai Petrovsky
- Vaxine Pty Ltd, Flinders Medical Centre, Bedford Park, SA 5042, Australia; Department of Endocrinology, Flinders Medical Centre/Flinders University, Bedford Park, SA 5042, Australia.
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