Peptide Sequence of Pili Subunit Protein 49.8 kDa Shigella flexneri as Antigenic Epitope for Shigellosis Vaccine Development.

Objectives: This study investigates the amino acid sequence and identifies antigenic epitopes of 49.8 kilodalton (kDa) pili protein Shigella flexneri, which will be used as candidates for the shigellosis vaccine.

Materials and methods: Our study is a prospectively descriptive laboratory. We used bacterial isolate of S. flexneri pili isolation was performed using a pili cutter and sodium dodecyl-sulfate polyacrylamide gel electrophoresis. The amino acid sequences were analyzed using liquid chromatography dual mass spectrometry (LC-MS/MS) method in the proteomic laboratory. The target epitope antigenicity analysis was tested using Kolaskar and Tongaonkar Antigenicity software. The Bepired Linear Epitope Prediction software is used for epitope mapping. PymOL software was used for the visualization of proteins and molecular docking. Peptides and antibodies were applied to hemagglutination test and immune response was tested using the dot blot method.

Results: LC-MS/MS analysis results from the mascot server showed that the 49.8 kDa pili protein is S. flexneri similar to the flagellin protein of S. flexneri 1235-66 (ID I6H2T2). The results of antigenicity analysis and epitope mapping showed that areas of protein that has the most potential and antigenic epitopes are the regions 98-111 and 263-290 with the amino acid sequences, QSSTGTNSQSDLDS (Q-S) and DTTITKAETKTVTKNQVVDTPVTTDAAK (D-K). The results of the molecular docking interaction test between the peptide and the B-cell receptor have a low binding energy. Peptide Q-S and peptide D-K antigens are hemagglutinin molecules because they can agglutinate erythrocytes. The immune response between peptide antigens and anti-peptide antibodies can react based on color gradations in the dotblot method.

Conclusion: The amino acid sequences Q-S and D-K are potentially antigenic epitopes. These peptides can be used to develop candidates for shigellosis vaccine.