Salmonella enterica serovar Typhi (S. Typhi) is a facultative intracellular pathogen that causes typhoid fever in humans. The emergence of multidrug-resistant strains of S. Typhi and certain drawbacks in presently available vaccines against typhoid, has added a sense of urgency to develop more effective typhoid vaccines. Outer membrane protein (OMPs) has been reported to be immunogens for eliciting active/protective immunity against Salmonella and thus, have great potential for use in vaccination. Earlier, in a study done in our laboratory, a protein from an outer membrane protein (OMP) of S. Typhi with apparent molecular weight of 49kDa was identified in S. Typhi. The 1.3 kb gene for this was cloned in pQE60 plasmid, expressed in E. coli SG13009 cells and purification of r49 kDa OMP was done by Ni-NTA affinity chromatography under different pH conditions. The yield of expressed protein of ~26 mg/L was obtained. We now report the expression of this protein in E. coli BL21 cells using the expression vector pET28a. The r-49kDa OMP was purified by Ni-NTA metal chelate affinity chromatography using 150mM imidazole under denaturing conditions and a yield of ~39 mg/L was achieved.
