Lipopolysaccaride Detoxification by Endotoxin Neutralizing Protein
NAVAL MEDICAL RESEARCH INST BETHESDA MD
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Endotoxin neutralizing protein ENP, a recombinant form of the anti- lipopolysaccharide factor that was isolated from amebocytes of the American horseshoe crab, Limulus polyphemus, detoxifies lipopolysaccharide LPS both in vitro and in vivo. Using the Limulus amebocyte lysate assay, LPS was detoxified by ENP at a 1 to 1 weight ratio 11. When isolated rat aortic rings were preincubated for 16 hr with either LPS or LPSENP 15, only aortas in the LPS ENP group contracted normally under norepinephrine stimulation. To show that detoxification of a lethal amount of LPS 18 mgkg, LD50 at 48 hr persists in vivo, LPSalbumin 11 or LPSENP 11 mixtures were preincubated 30 min, 37 deg C and then injected intravenously into rats. In the 8 hr after injection, LPSENP challenged rats, in contrast to their LPSalbumin injected counterparts, had significantly fewer physical signs of acute LPS toxicity p0.001. At 48 hr after challenge, all LPSENP treated rats survived p0.01 vs LPSalbumin, and with significantly less weight loss p0.001 vs LPSalbumin challenged survivors. At necropsy, the LPSENP group was free of typical LPS-induced gross organ lesions, notably in the liver, spleen, gut-associated lymphoid tissue GALT, and small intestine. By microscopic examination, lymphocytic necrosis in the spleen and GALT of the LPSENP treated survivors was significantly milder than that in the LPSalbumin challenged survivors, although the degree of hepatocellular necrosis and small intestinal enteritis was similar. LPS- neutralizing proteins such as ENP may be useful in treating LPS toxicity.