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

• Published in: MICROBIOLOGY and IMMUNOLOGY Vol. 42; no. 8; pp. 521 - 526
• Main Authors: De Andrade, Carlos Maurício, Ferreira, Antônio Gomes Pinto, Da Silva, Joana D'Arc Cardoso, Nascimento, Hilton Jorge, Junior, José Godinho Da Silva
• Format: Journal Article
• Language: English
• Published: Tokyo Blackwell Publishing Ltd 01-01-1998; Center For Academic Publications Japan; Center for Academic Publications Japan
• Subjects: Amino Acid Sequence; Animals; Bacterial Outer Membrane Proteins - chemistry; Bacterial Outer Membrane Proteins - immunology; Bacterial Outer Membrane Proteins - isolation & purification; Bacteriology; Biological and medical sciences; Blotting, Western; Characterization; Chromatography, Gel; Chromatography, Ion Exchange; Enzyme-Linked Immunosorbent Assay; Fundamental and applied biological sciences. Psychology; Humans; Immunization; Mice; Microbiology; Molecular Sequence Data; Morphology, structure, chemical composition; Outer membrane protein; Purification; Salmonella typhi; Salmonella typhi - chemistry; Salmonella typhi - immunology; Typhoid Fever - immunology; Antigen; Membrane protein; Purification; Immunogenicity; Molecular structure; Salmonella typhi; Bacteria; External membrane; Enterobacteriaceae
• ISSN: 0385-5600; 1348-0421
• DOI: 10.1111/j.1348-0421.1998.tb02319.x

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 6M urea, 1% deoxycholate and 5mM 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.