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Infect. Immun., 06 1997, 2160-2167, Vol 65, No. 6
M Ogata, MF Fletcher, M Kloczewiak, PM Loiselle, EM Zanzot, MW Vermeulen and HS Warren
The 18-kDa cationic protein CAP18 is an antimicrobial protein isolated from
rabbit granulocytes that binds lipopolysaccharide (LPS) and inhibits many
of its biological activities. We covalently coupled a synthetic peptide
representing amino acids 106 to 138 of CAP18 to human immunoglobulin G
(IgG) by using the heterobifunctional linker N-
succinimidyl-3-(2-pyridyidithio)propionate. The ability of CAP18(106-
138)-IgG to bind and neutralize LPS in whole blood in the presence and
absence of anticoagulants was studied. Both CAP18(106-138) and
CAP18(106-138)-IgG significantly suppressed LPS-induced tumor necrosis
factor (TNF) production in whole blood in the absence of anticoagulants.
EDTA potentiated the ability of CAP18(106-138) and CAP18(106-138)-IgG to
decrease LPS-induced TNF production in a dose- dependent manner. In
contrast, heparin inhibited the ability of CAP18(106-138) and
CAP18(106-138)-IgG to suppress LPS-induced TNF production. EDTA also
enhanced LPS capture in a fluid-phase binding assay that utilizes magnetic
anti-IgG beads to capture CAP18(106-138)- IgG (and bound [3H]LPS) in whole
blood. In contrast, heparin inhibited the binding dose dependently. We
conclude that CAP18(106-138)-IgG binds to and neutralizes LPS in whole
blood in the absence of anticoagulants. Further studies of its protective
efficacy in animal models are warranted. Caution should be used in
interpreting assays that measure the binding and neutralization of LPS in
whole blood in the presence of calcium-binding anticoagulants or heparin.
Copyright © 1997, American Society for Microbiology
Effect of anticoagulants on binding and neutralization of lipopolysaccharide by the peptide immunoglobulin conjugate CAP18(106- 138)-immunoglobulin G in whole blood
Department of Pediatrics, Massachusetts General Hospital and Harvard Medical School, Boston, USA.
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