Fishing for vaccines against Vibrio cholerae using in silico pan-proteomic reverse vaccinology approach

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Bioinformatics and Genomics

Main article text

 

Introduction

Methodology

  1. Pre-Screening of primary data

    The steps involved pre-screening of primary data include retrieval of the V. cholerae O1 (biovar eltr str. N16961) proteome from UniProt (Bairoch & Apweiler, 2000). Subcellular localization was predicted using the primary sequences of the V. cholerae proteome PSORTb V3.0 (Yu et al., 2010) and CELLO v2.5 (Yu, Lin & Hwang, 2004). Database of Essential Genes (DEG) (http://tubic.tju.edu.cn/deg/) version 10.4 provided the essentiality information of the proteins (Luo et al., 2014). The virulence check was performed using the virulence factor database (VFdb) for identification of potential virulence proteins (Chen et al., 2011). These steps were adopted to identify vital virulence proteins and respective epitopes to be subjected to peptide vaccine discovery.

  2. Screening of selected proteins

    Screening of selected proteins was performed for their suitability of prospective immuno-protective potential. The criteria included appropriate molecular weight (<110 kDa estimated via ExPASy Compute pI / Mw Tool (Gasteiger et al., 2005)), prediction of antigenic and virulence potentials, protein structural details and human homologue search. The crystalline structures for these proteins were obtained from structural database Protein Data Bank (PDB) (Bernstein et al., 1977) or developed using the SWISS-MODEL server (Schwede et al., 2003) and interactions within the pathogen, and with host proteins and cluster of orthologous groups COG were studied using STRING (Search Tool for the Retrieval of Interacting Genes/Proteins) (Szklarczyk et al., 2011).

  3. Epitope Selection

    In third step epitopes were predicted using multiple approaches via different algorithms in order to obtain broad spectrum epitopes. The predicted epitopes were screened to obtain epitopes capable of efficient binding to higher numbers of MHC alleles (Naz et al., 2015). Continuous B-Cell Epitopes were predicted using BcePred server  (Saha & Raghava, 2006). The BCPreds server was employed for prediction of 20-mer B-cell epitopes (EL-Manzalawy, Dobbs & Honavar, 2008). ABCpred, an artificial neural network based B-cell epitope prediction server, was also used for predicting B-cell epitopes  (Saha & Raghava, 2006). Default threshold values were used for each server. Propred and PropredI servers were used to investigate epitope interactions with MHC I and II alleles (Singh & Raghava, 2003), while antigenicity and IC50 calculations were performed with the help of MHCPred (Guan et al., 2003). Using proteins’ three dimensional epitopes were visualized using Discovery studio v4.1 (BIOVIA, 2015). Finally sequences of selected proteins from other virulent strains were obtained from members of V. cholerae NCBI Taxonomic group (TAXID: 666). The predicted antigenic regions were analyzed via BioEdit Sequence Alignment Editor, for sequence divergence against V. cholerae representative strains and consensus sequences were obtained for respective vaccine candidate for inter-strain immune-protection against V. cholerae.

Results

Primary data retrieval

Subcellular localization of screened targets

PPI interactions and COG analysis

3D structures of prioritized vaccine candidates

Predicted prioritized vaccine targets

Epitope mapping

Discussion

Conclusion

Supplemental Information

Screening of prioritized vaccine candidates for V. cholerae

Each sheet contains step by step prioritizatition of the selected vaccine candidates.

DOI: 10.7717/peerj.6223/supp-1

Genome: Vibrio cholerae O1 biovar El tor str. N16961

DOI: 10.7717/peerj.6223/supp-2

Additional Information and Declarations

Competing Interests

The authors declare there are no competing interests.

Author Contributions

Muhammad I. Rashid conceived and designed the experiments, performed the experiments, analyzed the data, contributed reagents/materials/analysis tools, prepared figures and/or tables, authored or reviewed drafts of the paper.

Sammia Rehman performed the experiments, analyzed the data, prepared figures and/or tables, authored or reviewed drafts of the paper.

Amjad Ali conceived and designed the experiments, authored or reviewed drafts of the paper.

Saadia Andleeb conceived and designed the experiments, analyzed the data, authored or reviewed drafts of the paper, approved the final draft.

Data Availability

The following information was supplied regarding data availability:

Raw data are provided in the Supplemental Files.

Funding

The authors received no funding for this work.

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