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.
Departamento de Ciências Biológicas, Escola Nacional de Saúde Pública/FIOCRUZ, Brasil.
C M
CM
de Andrade
A G
AG
Ferreira
J D
JD
da Silva
H J
HJ
Nascimento
J G
JG
da Silva
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