Effect of bacterial endotoxin on the course of Plasmodium berghei infection

Abstract

The intraperitoneal administration of certain doses of bacterial ( Escherichia coli) endotoxin to mice has been shown to significantly suppress Plasmodium berghei parasitemia levels and to extend survival of the host. Single doses of 20 μg endotoxin given the day before the injection of 10 7 parasitized RBC extended the usual one-week survival period by about one day. Each daily count of parasitized RBC from mice treated with endotoxin was comparable to the previous day's count for the saline-treated controls. Of the various doses tested, the best results from single injections were obtained with the 20-μg doses. Repeated injections of endotoxin were only slightly more effective than single injections. The similar influence of endotoxin on the course of intravenously induced P. berghei infections demonstrated that the action of endotoxin is not simply a matter of inhibition of passage of malarial inoculum from the peritoneal cavity into the bloodstream. The suppressive influence of endotoxin on P. berghei infections could also be produced in rats. This inhibitive effect of endotoxin may be related to nonspecific stimulation of factors of resistance.