The authors alone are responsible for the content and writing of the paper and declare no conflicts of interest. “
“Enterohemorrhagic Escherichia coli (EHEC) causes hemorrhagic colitis, and in more severe cases, a serious clinical complication
called hemolytic uremic syndrome (HUS). Shiga toxin (Stx)is one of the factors that cause HUS. Serotypes of Stx produced by EHEC include Stx1 and Stx2. Although some genetically mutated toxoids of Stx have been developed, large-scale preparation of Stx that is practical Selleckchem Silmitasertib for vaccine development has not been reported. Therefore, overexpression methods for Stx2 and mutant Stx2 (mStx2) in E. coli were developed. The expression plasmid pBSK-Stx2(His) was constructed by inserting the full-length Stx2 gene, in which a six-histidine tag gene was fused at the end of the B subunit into the lacZα fragment gene of the pBluescript II SK(+) vector. An E. coli MV1184 strain transformed with pBSK-Stx2(His) overexpressed histidine-tagged Stx2 (Stx2-His) in cells cultured in CAYE broth in the presence of lincomycin. Stx2-His was purified using TALON metal affinity resin followed by hydroxyapatite chromatography. From 1 L of culture, 68.8 mg of Stx2-His and 61.1 mg of mStx2-His, which was generated by site-directed
mutagenesis, were obtained. Stx2-His had a cytotoxic effect on HeLa cells and was lethal to mice. However, the toxicity of mStx2-His was approximately 1000-fold lower than that of Stx2-His. Mice immunized with MLN8237 in vitro mStx2-His produced specific antibodies that neutralized the toxicity of Calpain Stx2 in HeLa cells. Moreover, these mice survived challenge with high doses of Stx2-His. Therefore, the lincomycin-inducible overexpression method is suitable for large-scale preparation of Stx2 vaccine antigens. Enterohemorrhagic Escherichia coli strains cause hemorrhagic colitis and a serious clinical complication called hemolytic uremic syndrome (HUS) that is characterized by hemolytic anemia, thrombocytopenia, and acute
renal failure [1, 2]. Major causative factors of EHEC include two types of Stx, Stx-1 and Stx-2 (also referred to as Vero toxin-1 and Vero toxin-2, respectively), both of which consist of one A subunit (Stx1A and Stx2A) and five B subunits (Stx1B and Stx2B). At the amino acid sequence level, Stx1 is almost identical to Stx produced by Shigella dysenteriae 1, whereas Stx2 shares only 55% and 61% amino acid sequence identity with Stx1 in the A and B subunits, respectively. The B subunits bind to Gb3 on the eukaryotic cell membrane [3-5], whereas the A subunit functions as an RNA N-glycosidase that cleaves off a single adenine in the 28S rRNA component of the 60S ribosomal subunit, leading to cell death by inhibition of protein synthesis [6, 7]. Stx2 toxicity is reportedly greater than that of Stx1, because in mice the LD50 of Stx2 is lower than that of Stx1 , and in humans Stx2-producing strains generate more severe symptoms than do other strains [9-11].