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Wei Y, Wahome N, Kumar P, Whitaker N, Picking WL, Middaugh CR. Effect of Phosphate Ion on the Structure of Lumazine Synthase, an Antigen Presentation System From Bacillus anthracis. J Pharm Sci 2017; 107:814-823. [PMID: 29045884 DOI: 10.1016/j.xphs.2017.10.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Revised: 10/06/2017] [Accepted: 10/09/2017] [Indexed: 12/20/2022]
Abstract
Lumazine synthase (LS) is an oligomeric enzyme involved in the biosynthesis of riboflavin in microorganisms, fungi, and plants. LS has become of significant interest to biomedical science because of its critical biological role and attractive structural properties for antigen presentation in vaccines. LS derived from Bacillus anthracis (BaLS) consists of 60 identical subunits forming an icosahedron. Its crystal structure has been solved, but its dynamic conformational properties have not yet been studied. We investigated the conformation of BaLS in response to different stress conditions (e.g., chemical denaturants, pH, and temperature) using a variety of biophysical techniques. The physical basis for these thermal transitions was studied, indicating that a molten globular state was present during chemical unfolding by guanidine HCl. In addition, BaLS showed 2 distinct thermal transitions in phosphate-containing buffers. The first transition was due to the dissociation of phosphate ions from BaLS and the second one came from the dissociation and conformational alteration of its icosahedral structure. A small conformational alteration was induced by the binding/dissociation of phosphate ions to BaLS. This work provides a closer view of the conformational behavior of BaLS and provides important information for the formulation of vaccines which use this protein.
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Affiliation(s)
- Yangjie Wei
- Macromolecule and Vaccine Stabilization Center, Department of Pharmaceutical Chemistry, University of Kansas, 2030 Becker Drive, Lawrence, Kansas 66047; Department of Pharmaceutical Chemistry, University of Kansas, 2030 Becker Drive, Lawrence, Kansas 66047
| | - Newton Wahome
- Macromolecule and Vaccine Stabilization Center, Department of Pharmaceutical Chemistry, University of Kansas, 2030 Becker Drive, Lawrence, Kansas 66047; Department of Pharmaceutical Chemistry, University of Kansas, 2030 Becker Drive, Lawrence, Kansas 66047
| | - Prashant Kumar
- Macromolecule and Vaccine Stabilization Center, Department of Pharmaceutical Chemistry, University of Kansas, 2030 Becker Drive, Lawrence, Kansas 66047; Department of Pharmaceutical Chemistry, University of Kansas, 2030 Becker Drive, Lawrence, Kansas 66047
| | - Neal Whitaker
- Macromolecule and Vaccine Stabilization Center, Department of Pharmaceutical Chemistry, University of Kansas, 2030 Becker Drive, Lawrence, Kansas 66047; Department of Pharmaceutical Chemistry, University of Kansas, 2030 Becker Drive, Lawrence, Kansas 66047
| | - Wendy L Picking
- Department of Pharmaceutical Chemistry, University of Kansas, 2030 Becker Drive, Lawrence, Kansas 66047
| | - C Russell Middaugh
- Macromolecule and Vaccine Stabilization Center, Department of Pharmaceutical Chemistry, University of Kansas, 2030 Becker Drive, Lawrence, Kansas 66047; Department of Pharmaceutical Chemistry, University of Kansas, 2030 Becker Drive, Lawrence, Kansas 66047.
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Wei Y, Wahome N, VanSlyke G, Whitaker N, Kumar P, Barta ML, Picking WL, Volkin DB, Mantis NJ, Middaugh CR. Evaluation of lumazine synthase from Bacillus anthracis as a presentation platform for polyvalent antigen display. Protein Sci 2017; 26:2059-2072. [PMID: 28736824 DOI: 10.1002/pro.3243] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2017] [Revised: 07/08/2017] [Accepted: 07/19/2017] [Indexed: 12/31/2022]
Abstract
Polyvalent antigen display is an effective strategy to enhance the immunogenicity of subunit vaccines by clustering them in an array-like manner on a scaffold system. This strategy results in a higher local density of antigens, increased high avidity interactions with B cells and other antigen presenting cells, and therefore a more effective presentation of vaccine antigens. In this study, we used lumazine synthase (LS), an icosahedral symmetry capsid derived from Bacillus anthracis, as a scaffold to present 60 copies of a linear B cell epitope (PB10) from the ricin toxin fused to the C terminus of LS via four different linkers. We then investigated the effects of linker length, linker rigidity and formaldehyde crosslinking on the protein assembly, conformational integrity, thermal stability, in vitro antibody binding, and immunogenicity in mice. Fusion of the PB10 peptide onto LS, with varying linker lengths, did not affect protein assembly, thermal stability or exposure of the epitope, but had a minor impact on protein conformation. Formaldehyde crosslinking considerably improved protein thermal stability with only minor impact on protein conformation. All LS_PB10 constructs, when administered to mice by injection without adjuvant, elicited measurable anti-ricin serum IgG titers, although the titers were not sufficient to confer protection against a 10× lethal dose ricin challenge. This work sheds light on the biophysical properties, immunogenicity and potential feasibility of LS from B. anthracis as a scaffold system for polyvalent antigen display.
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Affiliation(s)
- Yangjie Wei
- Macromolecule and Vaccine Stabilization Center, Department of Pharmaceutical Chemistry, University of Kansas, Lawrence, Kansas, 66047.,Department of Pharmaceutical Chemistry, University of Kansas, Lawrence, Kansas, 66047
| | - Newton Wahome
- Macromolecule and Vaccine Stabilization Center, Department of Pharmaceutical Chemistry, University of Kansas, Lawrence, Kansas, 66047.,Department of Pharmaceutical Chemistry, University of Kansas, Lawrence, Kansas, 66047
| | - Greta VanSlyke
- Division of Infectious Disease, Wadsworth Center, New York State Department of Health, Albany, New York, 12208
| | - Neal Whitaker
- Macromolecule and Vaccine Stabilization Center, Department of Pharmaceutical Chemistry, University of Kansas, Lawrence, Kansas, 66047.,Department of Pharmaceutical Chemistry, University of Kansas, Lawrence, Kansas, 66047
| | - Prashant Kumar
- Macromolecule and Vaccine Stabilization Center, Department of Pharmaceutical Chemistry, University of Kansas, Lawrence, Kansas, 66047.,Division of Infectious Disease, Wadsworth Center, New York State Department of Health, Albany, New York, 12208
| | - Michael L Barta
- Department of Pharmaceutical Chemistry, University of Kansas, Lawrence, Kansas, 66047
| | - Wendy L Picking
- Department of Pharmaceutical Chemistry, University of Kansas, Lawrence, Kansas, 66047
| | - David B Volkin
- Macromolecule and Vaccine Stabilization Center, Department of Pharmaceutical Chemistry, University of Kansas, Lawrence, Kansas, 66047.,Department of Pharmaceutical Chemistry, University of Kansas, Lawrence, Kansas, 66047
| | - Nicholas J Mantis
- Division of Infectious Disease, Wadsworth Center, New York State Department of Health, Albany, New York, 12208
| | - C Russell Middaugh
- Macromolecule and Vaccine Stabilization Center, Department of Pharmaceutical Chemistry, University of Kansas, Lawrence, Kansas, 66047.,Department of Pharmaceutical Chemistry, University of Kansas, Lawrence, Kansas, 66047
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