Designing and Expression of an Immunogenic Poly-Epitope Protein from Streptococcus pneumoniae:

A well-designed vaccine against Streptococcus pneumonia, a respiratory pathogen, by immunoinformatics approaches can lead to an effective mucosal and local immunity in the upper respiratory tract. In this study, we chose virulence proteins from different strains of S. pneumonia (Pneumolysin, Neuraminidase, Zink-Metalloproteinase, and Hydrolase) and designed a new multi-epitope construct by properly linking the individual predicted T and B cell specific epitopes. Then, the polytope, named PNEU, was expressed in Escherichia coli as a prokaryotic system. Through computational calculations, PNEU polypeptide with 216 aa has the theoretical pI 8.04 and instability index 33.63, which show that it is a stable and soluble protein. Also, the 3D structure of PNEU was predicted by Phyre2 server with 96.0% confidence. In conclusion, PNEU protein can be considered as a stable and soluble immunogenic protein, which may be efficiently used for immunity stimulation in laboratory animals, investigated in future studies. Highlights The poly epitope PNEU protein is a vaccine candidate for Streptococcus pneumonia. PNEU is a stable and soluble protein. PNEU shows a proper folding through in silico 3D structure prediction. PNEU protein expression in prokaryotic systems was confirmed.