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Endotoxin-binding and -neutralizing properties of recombinant bactericidal/permeability-increasing protein and
M N Marra1, M B Thornton, J L Snable
1Incyte Pharmaceuticals, Palo Alto, CA 94034.
Objective:
To compare the endotoxin-binding and -neutralizing properties of bactericidal/permeability-increasing protein, the human monoclonal antiendotoxin antibody HA-1A, and the murine antiendotoxin antibody E5.
Design:
Prospective, randomized, placebo-controlled laboratory study.
Setting:
Biotechnology company research laboratory.
Subjects:
Female CD-1 mice.
Interventions:
Recombinant bactericidal/permeability-increasing protein, HA-1A, a human immunoglobulin M monoclonal antibody raised against Escherichia coli J5 (Rc) endotoxin, and E5, a murine immunoglobulin M monoclonal antibody raised against E. coli J5 endotoxin, were compared in the following assays: a) binding to rough lipopolysaccharide immobilized onto microtiter plates; b) inhibition of lipopolysaccharide activity in the limulus amebocyte lysate assay; c) inhibition of lipopolysaccharide-induced cytokine release in whole blood; and d) protection against lethal endotoxin challenge in CD-1 mice.
Measurements And Main Results:
The binding affinity of bactericidal/permeability-increasing protein for immobilized lipopolysaccharide is apparently greater than the binding affinity of HA-1A or E5. Bactericidal/permeability-increasing protein neutralized lipopolysaccharide activity in the chromogenic limulus amebocyte lysate assay, while neither monoclonal antibody inhibited lipopolysaccharide activity. Similarly, bactericidal/permeability-increasing protein reduced lipopolysaccharide-mediated tumor necrosis factor production in human whole blood in vitro, whereas monoclonal antibodies had slight (HA-1A) or no (E5) effect on lipopolysaccharide activity in this system. Administration of bactericidal/permeability-increasing protein gave > 90% protection against an LD60 dose of endotoxin in CD-1 mice, while treatment with HA-1A or E5 did not improve survival rate.
Conclusions:
Neither monoclonal antibody was as effective as bactericidal/permeability-increasing protein at binding or neutralizing endotoxin in vitro or in vivo. The potent endotoxin-binding and -neutralizing properties of bactericidal/permeability-increasing protein indicate that it might be useful in the treatment of endotoxin-related disorders in humans.