Human bactericidal/permeability-increasing protein and a recombinant NH2-terminal fragment cause killing of serum-resistant gram-negative bacteria in whole blood and inhibit tumor necrosis factor release induced by the bacteria.

Abstract

The bactericidal/ permeability-increasing protein (BPI) ofneutrophils and BPI fragments neutralize the effects of isolated Gram-negative bacterial lipopolysaccharides both in vitro and in vivo. Since endotoxin most commonly enters the host as constituents of invading Gram-negative bacteria, we raised the question: Can BPI and its bioactive fragments also protect against whole bacteria? To determine whether the bactericidal and endotoxin-neutralizing activities of BPI / fragments are expressed when Gram-negative bacteria are introduced to the complex environment of whole blood we examined the effects of added BPI and proteolytically prepared and recombinant NH2-terminal fragments on: (a) the fate of serum-resistant encapsulated Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa that survive the antibacterial actions of whole blood and (b) the ability of these bacteria to trigger cytokine release. Added BPI in nanomolar concentrations killed each ofthree encapsulated strains ofE. coli and in closely parallel fashion inhibited tumor necrosis factor (TNF) release. Holo-BPI and its NH2-terminal fragment were equipotent toward a rough LPS chemotype Kl-encapsulated strain, but the fragment was substantially more potent than holo-BPI toward two encapsulated smooth LPS chemotype strains. TNF release induced by K. pneumoniae and P. aeruginosa was also inhibited by both holo-BPI and fragment but, at the protein concentrations tested, P. aeruginosa was killed only by the fragment and K. pneumoniae was not killed by either protein. The bactericidal action of BPI/fragment toward E. coli is inhibited by C7-depleted serum, but accelerated by normal serum, indicating that BPI, acting in synergy with late complement components, enhances extracellular killing of serum-resistant bacteria. Thus, BPI and an even more potent NH2-terminal fragment may protect against Gram-negative bacteria in the host by blocking bacterial proliferation as well as endotoxin-mediated

Competition between Bactericidal/Permeability-Increasing Protein and Lipopolysaccharide-Binding Protein for Lipopolysaccharide Binding to Monocytes

“…rBPI 23 [2], a human recombinant NlIj-terminal fragment of BPI possessing LPS-neutralizing activity [14], was obtained from XOMA (Berkeley, CA). Thaumatin (XOMA), used as a control protein, has a molecular weight and isoelectric point similar to rBPI 23 [2].…”

“…By both flow cytometry and confocal microscopy, we observed that rBPI 2 3 • a recombinant Nl-ly-rerminal fragment of BPI [2,14], reduced LPS binding to monocytes when added to normal plasma containing LBP. Low residual LPS binding was observed.…”

Lipopolysaccharide (LPS)-binding Proteins BPI and LBP Form Different Types of Complexes with LPS

“…Because low concentrations of BPI can inhibit LBP-promoted LPS signaling (23)(24)(25), we investigated whether low (substoichiometric) concentrations of BPI can block the enhancing effects of LBP on the fluorescence of FITC-LPS. To this end, the fluorescence of FITC-LPS was monitored both after preincubation for 30 min with increasing amounts of BPI to permit formation of LPS-BPI complexes and after subsequent addition of LBP.…”

Protection of Immuno-Compromised Mice from Lethal Infection of Klebsiella Pneumonia by rAAV2-BPI23-Fcγ1 Gene Transfer

“…(5). BPI has the effect of neutralizing endotoxin and directly killing GNB, but has no adverse effect on eukaryotic cells (6,7). The phase II/III trial of rBPI 23 and rBPI 21 demonstrated that administration of rBPI has effect on GNB infected patient (8,9).…”