EFFICACY OF A RECOMBINANT ENDOTOXIN NEUTRALIZING PROTEIN IN RABBITS WITH ESCHERICHIA-COLI SEPSIS

Gram-negative bacterial sepsis is associated with endotoxemia and a hi gh mortality rate. In previous studies, we demonstrated the therapeuti c benefit of an anti-lipopolysaccharide factor isolated from amebocyte s of Limulus polyphemus, and of a recombinant version of this protein, termed endotoxin neutralizing protein (ENP), in rabbits challenged wi th purified lipopolysaccharides. To assess the benefit of ENP in treat ing a live bacterial infection, we established a rabbit model of Esche richia coil (E. coli) peritonitis and bacteremia with high mortality d espite gentamicin treatment. Twenty-four pairs of New Zealand white ra bbits were challenged intraperitoneally (IP) with E. coli O18ac K1 in 5% porcine mucin (mean bacteria per dose = 2.5 x 10(8)). The animals w ere treated with intravenous (IV) gentamicin (2.5 mg/kg), and with eit her ENP (5 mg/kg) or saline IV at 1 hr after E. coil challenge. All ra bbits were bacteremic 1 hr after challenge (geometric mean 4.1 +/- 1.2 x 10(4) cfu/ml). Peak geometric mean serum endotoxin (2.62 v 10.54 EU /mL, P =.013) and tumor necrosis factor (TNF) (2540 v 6438 TNF units/m L, P =.046) concentrations were lower in ENP-treated animals as compar ed to control animals. Seven of 24 animals treated with ENP survived 2 4 hr compared with 4 of 24 controls (Kaplan-Meier analysis, P =.19). H owever, in the subgroup of 13 paired animals in whom bacteremia was el iminated by gentamicin treatment, 5 of 13 ENP-treated animals survived 24 hr, compared with 1 of 13 controls (Kaplan-Meier analysis, P =.032 ). We conclude that ENP treatment of rabbits with E. coli peritonitis and bacteremia lowers serum endotoxin and TNF concentrations, and impr oves survival, but only when bacteremia is eliminated by antibiotic th erapy. (C) 1994 Wiley-Liss, Inc.