Expression and Purification of Brucella spp. Lumazine Synthase Decameric Carrier in Fusion to Extracellular Domain of Influenza M2E Protein

Brucella spp. Lumazine synthase enzyme is a decameric protein carrier that displays foreign antigens effectively in a polyvalent manner. The applied strategy using this molecule results in a higher density of antigens and enhances the immunogenicity of peptide vaccines. In the current study, Brucella lumazine synthase (BLS) was applied for fusion with influenza matrix protein 2 ectodomain (M2E) as a foreign peptide. The primary studies were based on bioinformatics tools and the fusion was expressed and purified in the following levels. Forming of the decamer was confirmed by electrophoresis and western blotting techniques. Influenza matrix protein 2 was stably expressed at the 10 amino terminals of lumazine synthase. The purified fusion was injected into mice and immune responses were evaluated with the indirect enzyme-linked immunosorbent assay (ELISA) technique. According to ELISA results yield of the purification process was 41% with the ion-exchange method and the protein was as a single band in Sodium Dodecyl Sulfate PolyAcrylamide Gel Electrophoresis (SDS-PAGE). The titer of immunized mice serum with a decameric fusion of lumazine synthase and matrix protein (M2BL) was determined to be more than 1:32000 by indirect ELISA. The level of responses against matrix protein in the decameric state of M2BL, was about 20% higher than monomer M2BL. Anti M2BL was cross-reacted effectively with influenza M2E and in comparison with samples injected with adjuvant, the level of antiM2E was similar. The results in this study confirm the role of multi-copy presentation systems and the applicability of BLS as an antigen carrier and adjuvant in designing peptide vaccines.