Chemical and Immunological Characterization of a Low Molecular Weight Outer Membrane Protein of Salmonella typhi

Abstract

A new immunogenic outer membrane protein, Omp-28 (MW 28,000 and pI 4.6), was isolated from smooth Salmonella typhi cells by the use of an extracting medium containing 6 M urea, I% deoxycholate and 5 mM EDTA. The purification of Omp-28 was performed by gel filtration and fast ion exchange chromatography. This protein showed to be the prevalent component isolated by the latter methodology. Omp-28 is formed by three identical subunits (MW 9,000), not linked by disulfide bonds. The partial N-terminal amino acid sequence of Omp-28 presented great homology with part of the sequence of an Escherichia coli protein found in a precursor whose sequence was predicted by c-DNA. ELISA and Western blotting identified Omp-28 as the major antigenic protein present in the outer membrane protein fraction, isolated by gel filtration. Antibodies against Omp-28 were detected by ELISA in 43 % of 28 sera from typhoid fever convalescent patients. The antisera from mice immunized with Omp-28 and the highest positive typhoid fever convalescent serum gave a positive bactericidal test, killing 50% of Salmonella typhi cells in serum dilutions of 1/80 and 1/320, respectively. These results indicate the immunogenic importance of Omp-28 isolated from Salmonella typhi outer membrane and strongly suggest it should be used in further studies of animal protection against the disease caused by this pathogenic bacteria.

Cloning, sequencing, and in silico characterization of Omp 28 of Salmonella Typhi (strain MTCC 733) to develop r-DNA vaccine for typhoid fever

“…Typhi cells in serum dilution of 1/80 and 1/320. [17] Complete amino acid sequence and location of Omp 28 of S .Typhi has also been analysed. [18] As it is difficult to isolate Omp(s) in bulk for vaccine purpose, this study was undertaken to clone and sequence and in silico analysis of Omp 28 gene of S .Typhi to further explore the possibility of r-DNA vaccine of S .Typhi.…”

Vaccination with Salmonella Typhi recombinant outer membrane protein 28 induces humoral but non-protective immune response in rabbit

“…The findings indicated that though the mortality was reduced after the vaccination with Omp 28 but Omp 28 could not provide complete protective immunity. First report on Omp 28 indicated that the level of antibodies against Omp 28 was very high in serum of collected from patients of typhoid [ 13 ]. Further, mice antibody raised against Omp 28 in mice showed anti-salmonella activity [ 14 ] in vitro .…”

“…Omp 28 is which had been purified from Salmonella Typhi. It was further sequenced, and few tests had been conducted to assess its immune potential in which it had exhibited promising potential [ 13 , 14 ]. Therefore, in our earlier study, we targeted Omp 28 as rDNA vaccine against S .…”