Background: Shigella is the causative agent of human shigellosis and its lipopolysaccharide is detected by TLR4. TLR4 belongs to Toll-like receptors family and many immunological pathways are triggered when these receptors are stimulated. Many researches showed increasing in TLR4 expression in mesenchymal stem cells through lipopolysaccharide treatment. The main goal of this study is detecting the optimum lipopolysaccharide between shigella strains through stimulation of immune system for vaccine studies.

Materials and Methods: In this experimental study human bone marrow derived mesenchymal stem cells were treated with three distinct concentrations (0.1, 0.01, and 0.001) of shigella (S. flexneri, S. dysenteriae, S. sonnei) extract containing lipopolysaccharide. Then TLR4 expression in mRNA level was investigated by RT-PCR and Q-PCR. The cells treated with phosphate buffered saline have been considered as a control group.

Results: Expression of TLR4 was shown in all of case groups except treatment with concentration 0.001 of extracts from sonnei and dysenteriae and also control group. The variations in the expression of TLR4 was dose-dependent in all of case groups. The maximum expression of TLR4 related to treatment with extract from shigella flexneri strain and the minimum expression related to treatment with shigella sonnei extract. The use of lipopolysaccharide from E. coli as a positive control indicated that lipopolysaccharide in shigella extracts is responsible for the increased expression of TLR4.

Conclusion: The TLR4 expression level was increasesed by S. flexneri extract, so it could be recommended for increasing vaccine efficiency.