Vaccine building 'kit': combining peptide bricks to elicit a desired immune response without adding an adjuvant.

Protein nanoparticles (NPs) can be used as vaccine platforms for target antigen presentation. Aim: To conduct a proof-of-concept study to demonstrate that an effective NP platform can be built based on a short self-assembling peptide (SAP) rather than a large self-assembling protein. Materials & methods: SUMO-based protein fusions (SFs) containing an N-terminal SAP and a C-terminal antigen were designed, expressed in Escherichia coli and purified. The structure was investigated by electron microscopy. The antibody response was tested in mice after two adjuvant-free immunizations. Results: Renatured SFs form fiber-like NPs with the antigen exposed on the surface and induce a significant antibody response with a remarkably high target-to-platform ratio. Conclusion: The platform is effective and has considerable potential for modification toward various applications, including vaccine development.

We aimed to extend the arsenal of protein platforms used for vaccine development. To this end, in this proof-of-concept study we constructed new self-assembling fusion proteins consisting of three modules. Module 1 is responsible for the self-assembly, while modules 2 and 3 are responsible for the immune response. Modules 1 and 2 form the platform, while module 3 represents the target antigen exposed on the surface of the self-assembled nanoparticles. After conventional biosynthesis in Escherichia coli, the proteins undergo efficient self-assembly during purification, and the resulting nanoparticles elicit a strong immune response without using an enhancing agent (adjuvant). The simple modular design and a high target-to-platform ratio of the immune response make our system a promising approach for practical applications, including vaccine development.

Gene cloning, expression and characterization of novel phytase from Obesumbacterium proteus.

The gene phyA encoding phytase was isolated from Obesumbacterium proteus genomic library and sequenced. The cleavage site of the PhyA signal peptide was predicted and experimentally proved. The PhyA protein shows maximum identity of 53% and 47% to phosphoanhydride phosphorylase from Yersinia pestis and phytase AppA from Escherichia coli, respectively. Based on protein sequence similarity of PhyA and its homologs, the phytases form a novel subclass of the histidine acid phosphatase family. To characterize properties of the PhyA protein, we expressed the phyA gene in E. coli. The specific activity of the purified recombinant PhyA was 310 U mg(-1) of protein. Recombinant PhyA showed activity at pH values from 1.5 through 6.5 with the optimum at 4.9. The temperature optimum was 40-45 degrees C at pH 4.9. The Km value for sodium phytate was 0.34 mM with a Vmax of 435 U mg(-1).