Effect of lipopolysaccharide injection on worm load in mice infected with S, mansoni

ABSTRACT

Salmonellosis bacteriemia in patients with hepatosplenic schistosomiasis is common in endemic areas of Schistosoma and Salmonella infection [Rocha and Brito, 1982]. Bacterial lipopolysaccharide [LPS] which is rich in walls of gram negative bacilli [eg. Salmonella species] causes potyclonal B lymphocyte activation resulting in hyper-grammaglobulinemia and immunecomplex [1C] formation [Rose et al, 1982]. The aim of this work was to study the effect of LPS on the worm load [worm count] in mice infected with S, mansoni Fourteen Swiss albino mice [10-12 weeks old and 25 g weight] [Control group] were infected with S.mansoni using paddling technique [Azim and Watson, 1984], Each mouse was exposed to about 150 cercariae for a period of one hour. Another 20 age- and sex-matched mice [experimental group] were simultaneously infected with S0mansoni and infected intraperitoneally with 150 microg LPS/mouse [LPSphenol extract from S. typhimurium; Sigma, USA] Six weeks after infection, mice were killed and the hepatic and the mesenteric blood vessels were perfused with citrated saline from the hepatic vein and the descending aorta, respectively. The adult worms were collected from the cut portal vein and counted [Duvall and BeWitt 1967]. In the experimental group [S. mansoni and LPS], the mean count of adult S. mansoni worm couples was significantly lower than that of the control group [S. mansoni only] [P<0.001] [Table 1]. The significant decrease of worm load in mice infected with LPS may suggest a protective role of LPS in this group of mice. The exact mechanism of this protection is not clear, but it could be speculated First, LPS might act as an adjuvant [Parant, 1983] leading to augmentation of immune response against S. mansoni Second, antiidiotype antibodies produced by LPS [Rose et al, 1982] may have immunomodulatory effect. In fact these antidodies were found able to protect rats from a challenge with S. mansoni [Grzych et al, 1985]. Third, IC's produced in response to LPS in the experimental group were found to be higher than those in the control group [data not presented]. A protective role of IC's has been previously suggested [Bout et al., 1977]. Whatever the mechanism, the decrease in worm load will lead to decrease in egg deposition and other harmful effects of these worms on different organs resulting in changes in immunopathological and clinical