In silico identification and characterization of common epitope-based peptide vaccine for Nipah and Hendra viruses.

OBJECTIVE: To explore a common B- and T-cell epitope-based vaccine that can elicit an immune response against encephalitis causing genus Henipaviruses, Hendra virus (HeV) and Nipah virus (NiV). METHODS: Membrane proteins F, G and M of HeV and NiV were retrieved from the protein database and subjected to different bioinformatics tools to predict antigenic B-cell epitopes. Best B-cell epitopes were then analyzed to predict their T-cell antigenic potentiality. Antigenic B- and T-cell epitopes that shared maximum identity with HeV and NiV were selected. Stability of the selected epitopes was predicted. Finally, the selected epitopes were subjected to molecular docking simulation with HLA-DR to confirm their antigenic potentiality in silico. RESULTS: One epitope from G proteins, one from M proteins and none from F proteins were selected based on their antigenic potentiality. The epitope from the G proteins was stable whereas that from M was unstable. The M-epitope was made stable by adding flanking dipeptides. The 15-mer G-epitope (VDPLRVQWRNNSVIS) showed at least 66% identity with all NiV and HeV G protein sequences, while the 15-mer M-epitope (GKLEFRRNNAIAFKG) with the dipeptide flanking residues showed 73% identity with all NiV and HeV M protein sequences available in the database. Molecular docking simulation with most frequent MHC class-II (MHC II) and class-I (MHC I) molecules showed that these epitopes could bind within HLA binding grooves to elicit an immune response. CONCLUSIONS: Data in our present study revealed the notion that the epitopes from G and M proteins might be the target for peptide-based subunit vaccine design against HeV and NiV. However, the biochemical analysis is necessary to experimentally validate the interaction of epitopes individually with the MHC molecules through elucidation of immunity induction.

Purification and Characterization of Elizabethkingia L-Amino Acid Esterase: an Enzyme Useful for Enzymatic Synthesis of the Dipeptide, Valyl-Glycine.

Valyl-glycine (Val-Gly) is useful as a synthetic substrate of γ-glutamyl-valyl-glycine (γ-Glu-Val-Gly), which exhibits a strong taste of "kokumi." For efficient enzymatic synthesis of Val-Gly from valine methylester and glycine using L-amino acid esterase (LAE), we screened microorganisms producing LAE with synthetic activity toward Val-Gly. Among 17 isolates showing LAE activity, Elizabethkingia sp. TT1, which was identified by 16S rDNA sequence analysis, showed the highest synthetic activity toward Val-Gly. LAE from Elizabethkingia sp. TT1 (TT1LAE) was purified approximately 1300 times, resulting in a yield of 2.8% and specific activity of 118.8 µmol/min/mg protein. SDS-PAGE analysis revealed a subunit molecular mass of 78 kDa. The molecular mass of the native enzyme determined by gel filtration was 103 kDa. The purified enzyme showed maximum activity at pH 9.0 and at a temperature of 25 °C, and it was stable over the pH range of 5.0-8.5 and 25 °C-40 °C. No metal ions that were tested had a significant effect on enzyme activity, but the enzyme was slightly inhibited by EDTA.