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. Author manuscript; available in PMC: 2020 Apr 1.
Published in final edited form as: Cell Immunol. 2019 Mar 19;338:32–42. doi: 10.1016/j.cellimm.2019.03.003

Table 1.

Endotoxin Levels in Purified CTB-INS Protein Preparations

Vaccine Samples Triton X-114 Endotrap Resin Purification conditions CTB-INS protein recovery (%) Endotoxin levels (EU/mL)
CTB-INS − − D 100 66,700
CTB-INS − + D 77.9 1.3
CTB-INS + − D 86.1 1.1
CTB-INS + + D 55.6 0.01

Removal of residual LPS endotoxin from CTB-INS protein isolated from E. coli. Partially purified recombinant CTB-INS fusion protein was isolated from sonicated E. coli BL-21 cells by nickel – agarose (Ni-NTA) affinity column chromatography under denaturing conditions of 8.0 M urea (D). Residual LPS was removed from the partially purified CTB-INS protein by treatment with 0.1% Triton X-114 or by passage of the protein over an Endotrap resin column. For maximum endotoxin removal, CTB-INS protein was purified by treatment with Triton X-114 followed by treatment with Endotrap resin.