Chemical and immunological characterization of a low molecular weight outer membrane protein of Salmonella typhi.
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, 1% 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.
de Andrade
C M
CM
Departamento de Ciências Biológicas, Escola Nacional de Saúde Pública/FIOCRUZ, Brasil.
Ferreira
A G
AG
da Silva
J D
JD
Nascimento
H J
HJ
da Silva
J G
JG
D000595:Amino Acid Sequence; D000818:Animals; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry / Q000276:immunology* / Q000302:isolation & purification*; D015153:Blotting, Western; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D007114:Immunization; D051379:Mice; D008969:Molecular Sequence Data; D012485:Salmonella typhi / Q000737:chemistry / Q000276:immunology*; D014435:Typhoid Fever / Q000276:immunology
D001425:Bacterial Outer Membrane Proteins; C116185:OMP-28 protein, Salmonella typhi