A multiepitopic theoretical fusion construct based on in-silico epitope screening of known vaccine candidates for protection against wide range of enterobacterial pathogens.

Enterobacterial pathogens that have acquired antibiotic resistance genes are a leading cause of community and hospital acquired infections. In such a situation vaccination is considered as a better option to prevent such infections. In the current study reverse vaccinology approach has been used to select peptides from already known immunogenic proteins to design a chimeric construct. We selected Yersiniabactin receptor of Escherichia coli UMN026 and Flagellin of Stenotrophomonas maltophila. B-cell linear epitopes were predicted using Bepipred prediction tool. Peptide binding with reference sets of 27 alleles of MHC class I and class II was also analyzed. The predicted peptides-MHC complexes were further validated using simulation dynamics. The in-silico construction of chimera was done by restriction mapping and codon optimization. Chimera was evaluated using the immunoinformatic approach as done for the selected proteins. From the 673 amino acids of FyuA protein, a region from 1 to 492 was selected for containing more linear epitopes and the processing scores obtained were significant for MHC class I and class II binding. Similarly, from Flagellin, a region between 60 and 328 amino acids was selected and the peptides present in the selected region showed lower percentile ranks for binding with MHC molecules. The simulation studies validated the predictions of peptide-MHC complexes. The selected gene fragments accommodating maximum part of these peptides were used to design a chimaeric construct of 2454 bp. From the immunoinformatic analysis, the chimera was found to be more immunogenic in terms of increased number of B-cell and T-cell epitopes along with increased coverage of global populations with allelic variability.

Serological cross-reactivity of environmental isolates of Enterobacter, Escherichia, Stenotrophomonas, and Aerococcus with Shigella spp.-specific antisera.

Using protocols designed for the isolation of Shigella from environmental freshwater samples from different regions of Bangladesh, 11 bacterial strains giving rise to Shigella-like colonies on selective agar plates and showing serological cross-reaction with Shigella-specific antisera were isolated. Phylogenetic analyses revealed that three of the isolates were most closely related to Escherichia coli, four to Enterobacter sp., two to Stenotrophomonas, and two isolates belonged to the Gram-positive genus Aerococcus. The isolates cross-reacted with six different serotypes of Shigella and were, in each case, highly type-specific. Two of the isolates belonging to the Enterobacter and Escherichia genera gave extremely strong cross-reactivity with Shigella dysenteriae and Shigella boydii antisera, respectively. The Aerococcus isolates gave relatively weak but significant cross-reactions with S. dysenteriae. Western blot analysis revealed that a number of antigens from the isolates cross-react with Shigella spp. The results indicate that important Shigella spp. surface antigens are shared by a number of environmental bacteria, which have implications for the use of serological methods in attempts for the detection and recovery of Shigella from aquatic environments.