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Infection and Immunity, September 1999, p. 4668-4672, Vol. 67, No. 9
Department of Clinical Medicine,
Received 18 March 1999/Returned for modification 28 May
1999/Accepted 15 June 1999
Lactoferrin (LF) is a glycoprotein that exerts both bacteriostatic
and bactericidal activities. The interaction of LF with lipopolysaccharide (LPS) of gram-negative bacteria seems to play a
crucial role in the bactericidal effect. In this study, we evaluated, by means of an enzyme-linked immunosorbent assay, the binding of
biotinylated LF to the S (smooth) and R (rough) (Ra, Rb, Rc, Rd1, Rd2,
and Re) forms of LPS and different lipid A preparations. In addition,
the effects of two monoclonal antibodies (AGM 10.14, an immunoglobulin
G1 [IgG1] antibody, and AGM 2.29, an IgG2b antibody), directed
against spatially distant epitopes of human LF, on the LF-lipid A or
LF-LPS interaction were evaluated. The results showed that biotinylated
LF specifically binds to solid-phase lipid A, as this interaction was
prevented in a dose-dependent fashion by either soluble uncoupled LF or
lipid A. The binding of LF to S-form LPS was markedly weaker than that
to lipid A. Moreover, the rate of LF binding to R-form LPS was
inversely related to core length. The results suggest that the
polysaccharide O chain as well as oligosaccharide core structures may
interfere with the LF-lipid A interaction. In addition, we found that
soluble lipid A also inhibited LF binding to immobilized LPS,
demonstrating that, in the whole LPS structure, the lipid A region
contains the major determinant recognized by LF. AGM 10.14 inhibited LF binding to lipid A and LPS in a dose-dependent fashion, indicating that
this monoclonal antibody recognizes an epitope involved in the binding
of LF to lipid A or some epitope in its close vicinity. In contrast,
AGM 2.29, even in a molar excess, did not prevent the binding of LF to
lipid A or LPS. Therefore, AGM 10.14 may represent a useful tool for
neutralizing selectively the binding of LF to lipid A. In addition, the
use of such a monoclonal antibody could allow better elucidation of the
consequences of the LF-lipid A interaction.
0019-9567/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Lactoferrin-Lipid A-Lipopolysaccharide Interaction: Inhibition
by Anti-Human Lactoferrin Monoclonal Antibody AGM 10.14
*
Corresponding author. Mailing address: Immunologia,
Policlinico, Piazza G. Cesare, 4-70124 Bari, Italy. Phone: 39 080 5478492. Fax: 39 080 5478537. E-mail:
Jirillo{at}midim.uniba.it.
Infection and Immunity, September 1999, p. 4668-4672, Vol. 67, No. 9
0019-9567/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
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