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Infect. Immun., Jun 1996, 2047-2055, Vol 64, No. 6
A Cloeckaert, JM Verger, M Grayon, MS Zygmunt and O Grepinet
The nucleotide sequences encoding the major 25-kDa outer membrane protein
(OMP) (omp25 genes) of Brucella ovis 63/290, Brucella melitensis 16M,
Brucella suis 1330, Brucella canis RM6/66, and Brucella neotomae 5K33 (all
reference strains) were determined and compared with that of Brucella
abortus 544 (P. de Wergifosse, P. Lintermans, J. N. Limet, and A.
Cloeckaert, J. Bacteriol. 177:1911-1914, 1995). The major difference found
was between the omp25 gene of B. ovis and those of the other Brucella
species; the B. ovis gene had a 36-bp deletion located at the 3' end of the
gene. The corresponding regions of other Brucella species contain two 8-bp
direct repeats and two 4-bp inverted repeats, which could have been
involved in the genesis of the deletion. The mechanism responsible for the
genesis of the deletion appears to be related to the "slipped mispairing"
mechanism described in the literature. Expression of the 25-kDa outer
membrane protein (Omp25) in Brucella spp. or expression from the cloned
omp25 gene in Escherichia coli cells was studied with a panel of anti-Omp25
monoclonal antibodies (MAbs). As shown by enzyme-linked immunosorbent assay
(ELISA) and immunoelectron microscopy, Omp25 was exported to the outer
membrane in E. coli expressing either the truncated omp25 gene of B. ovis
or the entire omp25 genes of the other Brucella species. Size and antigenic
shifts due to the 36-bp deletion were demonstrated by sodium dodecyl
sulfate-polyacrylamide gel electrophoresis and immunoblotting and by the
differences in binding patterns in ELISA of the anti-Omp25 MAbs at the cell
surface of E. coli cells harboring the appropriate gene and of cells of B.
ovis and other Brucella species. In particular, MAbs directed against
discontinuous epitopes of the entire Omp25 showed the absence of, or a
significant reduction in, antibody reactivity with the B. ovis truncated
Omp25. The results indicated that, as defined by the MAbs, exported Omp25
probably presents similar topologies in the outer membranes of E. coli and
Brucella spp. and that the short deletion found in the omp25 gene of B.
ovis has important consequences for the expression of surface B-cell
epitopes which should be considered for the development of vaccines against
B. ovis infection.
Copyright © 1996, American Society for Microbiology
Nucleotide sequence and expression of the gene encoding the major 25- kilodalton outer membrane protein of Brucella ovis: Evidence for antigenic shift, compared with other Brucella species, due to a deletion in the gene
Laboratoire de Pathologie Infectieuse et Immunologie, Institut National de la Recherche Agronomique, France.
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