  Background: Shigella is one of the major cause of dysenteric diarrhea, which
is known shigelosis. Shigelosis causes 160,000 deaths annually of diarrheal
disease in a global scale especially children less than 5 years old. No
licensed vaccine is available against shigelosis, therefore, efforts for
develop an effective and safe vaccine against shigella as before needed. The
reverse vaccinology (RV) is a novel strategy that evaluate genome or proteome
of an organism to find a new promising vaccine candidate. In this study,
immunogenicity of a designed-recombinant antigen is evaluated through the
insilico studies and animal experiments to predict a new immunogenic candidate
against Shigella. Methods: In the first step, proteome of shigella flexneri was
obtained from UniProtKB and then the outer membrane and extracellular were
predicted. TolC as an outer membrane protein was selected and confirmed. In
next steps, pre-selected protein was evaluated for transmembrane domains,
homology, conservation, antigenicity, solubility, and B- and T-cell prediction
by different online servers. Result: TolC as a conserved outer membrane
protein, using different immunoinformatics tools had acceptable scores and was
selected as an immunogenic antigen for animal experimenta studies. Recombinant
TolC protein after expression and purification, was administered to BALB/c mice
intraperitoneally over three routes. The sera of mice was used to evaluate the
IgG1 production assay by indirect-ELISA. The immunized mice depicted effective
protection against 2 LD50 of shigella flexneri ATCC12022 (challenge study).
Conclusion: Therefore, the reverse vaccinology approach and experimental test
results demonstrated that TolC as a novel effective and immunogenic antigen is
capable for protection against shigellosis.
