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The S. aureus 4-oxalocrotonate tautomerase SAR1376 enhances immune responses when fused to several antigens.

ABSTRACT: A persistent goal of vaccine development is the enhancement of the immunogenicity of antigens while maintaining safety. One strategy involves alteration of the presentation of the antigen by combining antigens with a multimeric scaffold. Multi-antigen vaccines are under development, and there are presently far more candidate antigens than antigen scaffolding strategies. This is potentially problematic, since prior immunity to a scaffold may inhibit immune responses to the antigen-scaffold combination. In this study, a series of domains from S. aureus which have been shown to crystallise into multimeric structures have been examined for their scaffolding potential. Of these domains, SAR1376, a 62 amino acid member of the 4-oxalocrotonate tautomerase (4-OT) family, was pro-immunogenic in mice when fused to a range of pathogen antigens from both S. aureus and P. falciparum, and delivered by either DNA vaccination, viral vector vaccines or as protein-in-adjuvant formulations. The adjuvant effect did not depend on enzymatic activity, but was abrogated by mutations disrupting the hexameric structure of the protein. We therefore propose that SAR1376, and perhaps other members of the 4-OT protein family, represent very small domains which can be fused to a wide range of antigens, enhancing immune responses against them.

SUBMITTER: Diemen PMV

PROVIDER: S-EPMC5431793 | biostudies-literature | 2017 May

REPOSITORIES: biostudies-literature

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The S. aureus 4-oxalocrotonate tautomerase SAR1376 enhances immune responses when fused to several antigens.

Diemen Pauline M van PMV Leneghan Darren B DB Brian Iona J IJ Miura Kazutoyo K Long Carole A CA Milicic Anita A Biswas Sumi S Rollier Christine S CS Wyllie David H DH

Scientific reports 20170511 1

A persistent goal of vaccine development is the enhancement of the immunogenicity of antigens while maintaining safety. One strategy involves alteration of the presentation of the antigen by combining antigens with a multimeric scaffold. Multi-antigen vaccines are under development, and there are presently far more candidate antigens than antigen scaffolding strategies. This is potentially problematic, since prior immunity to a scaffold may inhibit immune responses to the antigen-scaffold combin ...[more]

PMID: 28496136

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Project description:4-Oxalocrotonate tautomerase (4-OT) and trans-3-chloroacrylic acid dehalogenase (CaaD) are members of the tautomerase superfamily, a group of structurally homologous proteins that share a beta-alpha-beta fold and a catalytic amino-terminal proline. 4-OT, from Pseudomonas putida mt-2, catalyzes the conversion of 2-oxo-4-hexenedioate to 2-oxo-3-hexenedioate through the dienol intermediate 2-hydroxymuconate in a catabolic pathway for aromatic hydrocarbons. CaaD, from Pseudomonas pavonaceae 170, catalyzes the hydrolytic dehalogenation of trans-3-chloroacrylate in the trans-1,3-dichloropropene degradation pathway. Both reactions may involve an arginine-stabilized enediolate intermediate, a capability that may partially account for the low-level CaaD activity of 4-OT. Two active-site residues in 4-OT, Leu-8 and Ile-52, have now been mutated to the positionally conserved and catalytic ones in CaaD, alphaArg-8, and alphaGlu-52. The L8R and L8R/I52E mutants show improved CaaD activity (50- and 32-fold increases in k(cat)/K(m), respectively) and diminished 4-OT activity (5- and 1700-fold decreases in k(cat)/K(m), respectively). The increased efficiency of L8R-4-OT for the CaaD reaction stems primarily from an 8.8-fold increase in k(cat), whereas that of the L8R/I52E mutant is due largely to a 23-fold decrease in K(m). The presence of the additional arginine residue in the active site of L8R-4-OT does not alter the pK(a) of the Pro-1 amino group from that measured for the wild type (6.5 +/- 0.1 versus 6.4 +/- 0.2). Moreover, the crystal structure of L8R-4-OT is comparable to that of the wild type. Hence, the enhanced CaaD activity of L8R-4-OT is likely due to the additional arginine residue that can participate in substrate binding and/or stabilization of the putative enediolate intermediate. The results also suggest that the evolution of new functions within the tautomerase superfamily could be quite facile, requiring only a few strategically placed active-site mutations.

Dataset Information

The S. aureus 4-oxalocrotonate tautomerase SAR1376 enhances immune responses when fused to several antigens.

Publications

The S. aureus 4-oxalocrotonate tautomerase SAR1376 enhances immune responses when fused to several antigens.

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