Randal W. Scott

Human neutrophil bactericidal/permeability-increasing protein reduces mortality rate from endotoxin challenge: a placebo-controlled study.

ObjectivesTo study the toxicology and pharmacology of the endotoxin-neutralizing agent, bactericidal/permeability-increasing protein. DesignProspective, randomized, placebo-controlled laboratory study. SettingAcademic research laboratory. SubjectsCD-1 mice (n = 259); Sprague Dawley rats (n = 26); New Zealand White rabbits (n = 19). InterventionsPharmacokinetics of intravenously injected bactericidal/permeability-increasing protein was assessed in mice. Toxicology was tested in mice and rats. Efficacy of intravenously administered bactericidal/permeability-increasing protein as an endotoxin-neutralizing agent was tested in mice, rats, and rabbits. Measurements and Main ResultsAdministration of a single 10-mg/kg bolus injection of bactericidal/permeability-increasing protein resulted in no alterations in hematologic, renal, or hepatic function, activity level, or weight gain in animals observed over a 7-day study period. A single bolus injection (10 mg/kg) of bactericidal/permeability-increasing protein protected 15 of 16 mice from a lethal endotoxin challenge (mortality rate 1/16 [6.25%]) compared with a 100% (16/16) mortality rate in the saline-treated controls (p < .001). Bactericidal/permeability-increasing protein administered up to 1 hr after endotoxin provided significant protection against lethal endotoxin challenge. Furthermore, bactericidal/permeability-increasing protein reduced the induration and dermal necrosis observed in the localized dermal Shwartzman reaction. ConclusionsBactericidal/permeability-increasing protein is a potent antiendotoxin that neutralizes endotoxin in vivo and prevents mortality in animal models of lethal endotoxemia. (Crit Care Med 1994; 22:553–558)

Relative concentrations of endotoxin-binding proteins in body fluids during infection

Endotoxin initiates the systemic inflammatory response, haemodynamic changes, and multi-organ failure that may occur as a consequence of systemic gram-negative bacterial infection. The serum protein lipopolysaccharide-binding protein (LBP) binds to the lipid A component of bacterial endotoxin and facilitates its delivery to the CD14 antigen on the macrophage, where inflammatory cytokines are released and a cascade of host mediators is initiated. The neutrophil granular protein bactericidal/permeability-increasing protein (BPI) competes with LBP for endotoxin binding and functions as a molecular antagonist of LBP-endotoxin interactions. We have measured concentrations of both proteins in body fluids from 49 consecutive patients. In 16 of 17 samples of fluid from closed-space infections, BPI was present in greater concentration than LBP (median BPI/LBP ratio 7.6 [95% CI 2.32-22.1]). The ratio of BPI and LBP was not significantly different from 1.0 in abdominal fluid from 10 patients with peritonitis (ratio 0.235 [0.18-0.47]), whereas the BPI/LBP ratio was low in 22 non-infected body fluids (0.01 [0.001-0.04]) and concentrations of both proteins approached those in normal human plasma. BPI concentrations were directly correlated with the quantity of neutrophils within clinical samples (rs = 0.81, p < 0.0001). Thus, within abscess cavities BPI is available in sufficient quantities for effective competition with LBP for endotoxin. BPI may attenuate the local inflammatory response and the systemic toxicity of endotoxin release during gram-negative infections.

From expressed sequence tags to ‘epigenomics’: an understanding of disease processes

Expressed sequence tags (ESTs) are at the forefront of technological change that is sweeping the biomedical research community. ESTs provide a high throughput means for identifying gene transcripts and monitoring complex gene expression patterns. EST-based technologies coupled with sophisticated computer analysis tools enable the informational content and output of the genome to be accessed and evaluated on a scale immensely larger than previously possible. EST-based technologies are being used to understand disease processes and to find better disease treatments, and will allow biology to move from single gene to multigene, or even more complex epigenetic, explanations for disease.

A novel LBP-BPI fusion protein with in vivo efficacy and longer half life

Bactericidal/permeability-increasing protein (BPI) is a neutrophil azurophilic granule protein which binds to and neutralizes the biological activity of Gram-negative bacterial endotoxin both in vitro and in vivo. The therapeutic utility of BPI is hampered by its remarkably short circulating half life. BPI shares 44% sequence identity with lipopolysaccharide binding protein (LBP), an acute phase protein which facilitates endotoxin-mediated cellular responses and has a long circulating half-life. BPI and LBP are members of a family of proteins which regulate LPS activity in vivo. Genetically engineered variants of BPI and LBP were designed to maintain the endotoxin neutralizing properties of BPI but to have an extended circulating half life. One of these, LBP-BPI, is comprised of the N-terminal half of LBP, linked to the C-terminal half of BPI. Like BPI, LBP-BPI had endotoxin neutralizing activity in vitro and in vivo and gave a significant protective effect against lethal endotoxin challenge in mice (90% survival in treated group vs 10% survival in untreated controls P < 0.001). Neither LBP nor the 25 kDa N-terminal fragments of BPI and LBP were protective in this model of lethal endotoxin challenge. Pharmacokinetic studies in CD-1 mice showed that the LBP-BPI variant is cleared 74 times more slowly than BPI. Longer half-life versions of BPI have a broader window of protection and require lower overall doses to maintain therapeutically effective circulating concentrations. Molecules such as the LBP-BPI variant will have greater therapeutic utility than the native BPI molecule by virtue of these properties.