The Journal of Medical Microbiology, Vol 46, Issue 2 122-128, Copyright © 1997 by Society for General Microbiology

JOURNAL ARTICLE

Characterisation and protective capacity of monoclonal antibodies elicited in mice against protein epitopes of antibiotic-exposed Escherichia coli

M. T. Lun, G. Raponi, A. M. Amatucci, P. G. Natali, R. Fraioli and C. Mancini
Institute of Microbiology, University of Rome La Sapienza, Italy.

The binding capacity and the protective activity of three monoclonal antibodies (MAbs)-ARM 1-4, ARM 1-7 and ARM 2-2-obtained from spleen cells of mice immunised with Escherichia coli O6:K-pre-treated with sub-MIC of aztreonam were studied. The MAbs belonged to IgG1 isotype and showed different reactivity toward protein epitopes of E. coli in an immunoblotting assay. ARM 1-4 recognised epitopes on molecules of 30 kDa and 40 kDa. ARM 1-7 identified an epitope of a molecule of 41 kDa, and ARM 2-2 recognised epitopes of molecules of 15 kDa and 41 kDa. In ELISA the MAbs cross-reacted with E. coli O7:K-, E. coli O111:B4 and E. coli O128:K- with different binding affinity. Furthermore, the MAbs showed complement-dependent bactericidal activity. The MAbs displayed different protective capacities when given to mice 90 min before lethal challenges with 2 x LD50, 4 x LD50 and 8 x LD50 of E. coli strains. In all but one instance (ARM 1-4 versus E. coli O7:K-) it was not possible to correlate protective capacity with binding affinity of a MAb to a given bacterial cell. Therefore, the epitopes recognised by the MAb may be more closely associated with bacterial virulence than in binding to the bacterial cell.

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