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Evaluation of lumazine synthase from Bacillus anthracis as a presentation platform for polyvalent antigen display.

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.

SUBMITTER: Wei Y

PROVIDER: S-EPMC5606532 | biostudies-literature | 2017 Oct

REPOSITORIES: biostudies-literature

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Evaluation of lumazine synthase from Bacillus anthracis as a presentation platform for polyvalent antigen display.

Wei Yangjie Y Wahome Newton N VanSlyke Greta G Whitaker Neal N Kumar Prashant P Barta Michael L ML Picking Wendy L WL Volkin David B DB Mantis Nicholas J NJ Middaugh C Russell CR

Protein science : a publication of the Protein Society 20170913 10

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 scaffo ...[more]

PMID: 28736824

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Project description:BackgroundAnthrax is caused by Bacillus anthracis that produce two exotoxins, lethal toxin and edema toxin. The lethal toxin is composed of the lethal factor (LF) complexed with the cell binding protective antigen (PA83, 83 kDa). Likewise, the edema factor (EF) binds to the PA83 to form the edema toxin. Once PA83 is bound to the host cell surface, a furin-like protease cleaves the full-length, inactive protein into 63 kDa and 20 kDa antigens (PA63 and PA20). PA63 forms a heptamer and is internalized via receptor mediated endocytosis forming a protease-stable pore, which allows EF and LF to enter the cell and exert their toxic effects.Both proteolytically cleaved protective antigens (PA63 and PA20 fragments) are found in the blood of infected animals. The 63 kDa protective antigen PA63 fragment has been thoroughly studied while little is known about the PA20.MethodsIn this study we examined the role of PA20 using high throughput gene expression analysis of human peripheral blood mononuclear cells (PBMC) exposed to the PA20. We constructed a PA mutant in which a Factor Xa proteolytic recognition site was genetically engineered into the protective antigen PA83 to obtain PA20 using limited digestion of this recombinant PA83 with trypsin.ResultsGlobal gene expression response studies indicated modulation of various immune functions and showed gene patterns indicative of apoptosis via the Fas pathway in a subset of the lymphoid cells. This finding was extended to include observations of increased Caspase-3 enzymatic activity and the identification of increases in the population of apoptotic, but not necrotic cells, based on differential staining methods. We identified a list of approximately 40 inflammatory mediators and heat-shock proteins that were altered similarly upon exposure of PBMC to either rPA20 or B. anthracis spores/vegetative cells.ConclusionThis study shows that the PA20 has an effect on human peripheral blood leukocytes and can induce apoptosis in the absence of other PA components.

Dataset Information

Evaluation of lumazine synthase from Bacillus anthracis as a presentation platform for polyvalent antigen display.

Publications

Evaluation of lumazine synthase from Bacillus anthracis as a presentation platform for polyvalent antigen display.

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