Evaluation of Salmonella enterica serotype typhi Lipopolysaccharide immunization induction in rats
  • Article Type: Research Article
  • Eurasian Journal of Biosciences, 2020 - Volume 14 Issue 2, pp. 3911-3915
  • Published Online: 17 Oct 2020
  • Open Access Full Text (PDF)


Background: Salmonella enterica serotype typhi (SeT) is a bacterium with a gram-negative staining characteristic. This pathogen is globally known for its responsibility of causing typhoid fever. Controlling the disease burden is a great deal especially in the developing countries. According to this, finding a sufficient vaccine against the bacterium may provide a successful tool to prevent detrimental outcomes induced by the disease especially in the health and economic sectors. Objectives: This study was conducted to test if a purified lipopolysaccharide (PLPS) from SeT was able to induce neutralizing antibodies (NAb) against SeT O and H antigens in rats. Materials and methods: First, traditional cultivation and biochemical assays, Api-E20 test, and a 16S rRNA based polymerase chain reaction (PCR) and partial gene sequencing (PGS) analyses were employed to confirm the identity of the bacterium. Then, PLPS was obtained using a modified hot phenol-water extraction method and fractionated by SDS-PAGE electrophoresis. After that, bacterial-protein- and nucleic-acid-based contaminations of the PLPS were tested using silver and coomassie blue staining (SCBS) and ethidium bromide electrophoresis (EBE), respectively. Later, 10 rats were subcutaneously injected with PLPS at week 0 (wk-0) followed by booster doses at wk-2, wk-4, and wk-8. Then, a challenge test was applied to those rats using (3.8×109cells/ml) of SeT. This was followed by slide-agglutination screening of NAb-O and NAb-H complexes. Those complexes also were visualized using SDS-PAGE. Results: The identity of SeT was positively recognized using the confirming tests. The purity tests showed clearly that there were no protein and nucleic acid contaminations accompanied PLPS. The PLPS based immunization revealed successful NAb-O and NAb-H slide agglutination which later was successfully confirmed by SDS-PAGE. Conclusions: LPS induces successful neutralizing antibodies in the serum of the tested rats that show high agglutination activity against the O and H antigens of the S. Typhi. Collectively, LPS may be considered as a vital candidate vaccine against the bacterium.


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