Comparison of early and late treatment with a recombinant endotoxin neutralizing protein in a rat model of Escherichia coli sepsis

Objective: To test the efficacy of a recombinant endotoxin neutralizing protein as compared with saline in rats with Escherichia coli sepsis. Design: Prospective, controlled animal trial. Setting: Hospital animal research laboratory. Subjects: Male Wistar rats challenged with intraperitoneal E. coli, O18ac K1, and treated 1 hr later with ceftriaxone and gentamicin. Interventions: Recombinant endotoxin neutralizing protein, 50 mg/kg, was administered to rats 1, 2, or 3 hrs after E. coli challenge; saline was administered to control animals, Measurements and Main Results: Quantitative bacteremia, 1 hr after challenge and before antibiotic administration, was not significantly different between treatment groups (range geometric mean 451 to 621 colony-forming units [cfu]/mL). The endotoxin concentration, measured immediately before recombinant endotoxin neutralizing protein administration, was significantly higher in animals sampled and treated at 2 hrs (geometric mean 260 EU/mL; 95% confidence interval 140 to 480 EU/mL), or 3 hrs (geometric mean 697 EU/mL; 95% confidence interval 307 to 1585 EU/mL) after E. coli challenge, compared with animals sampled and treated at 1 hr (geometric mean 17 EU/mL; 95% confidence interval 7 to 69 EU/mL). Survival rate was significantly greater in rats treated with recombinant endotoxin neutralizing protein at 1 hr (23/27; p<.001) or 2 hrs (8/30; p <.01) after E. coli challenge than in controls (1/32). Conclusion: Administration of recombinant endotoxin neutralizing protein delayed up to 2 hrs after challenge with E. coli improves survival in antibiotic-treated rats with Gram-negative sepsis.