Immunomodulatory effect of splenectomy and its reflection on curative efficacy of praziquantel in experimental schistosomiasis mansoni

ABSTRACT

The efficacy of praziquantel [PZQ] treatment was assessed in Schistosomiasis mansoni [S. mansoni] infected splenectomized mice by studying worm burden and distribution, tissue egg load and oogram pattern. Moreover, possible immunomodulation as a result of splenectomy and its reflection on the efficacy of PZQ was assessed as well in this model. Immunomodulation was studied by estimation of immunoglobulin G and M levels and measurement of hepatic granuloma size. Two batches of S. mansoni infected Swiss albino mice were splenectomized 6 weeks post-infection and praziquantel was given at a dose of 500 mg/kg/2 days either 2 days or 2 weeks post splenectomy. Animals were sacrificed 2 days, 1, 2 and 4 weeks post treatment. Unsplenectomized praziquantel treated controls corresponding to the splenectomized groups, were included in the study. PZQ was found to be less effective as an antischistosomal drug when given to splenectomized mice. This has been shown by the increase insignificantly in worm burden and significantly in tissue egg load in splenectomized relative to unsplenectomized animals. Diminution in the efficacy of PZQ was accompanied by a decrease in immunoglobulin profile [IgG and IgM] and a reduction in the mean diameter of hepatic granuloma. These findings may point to the importance of the spleen in the elimination of the active S mansoni infection and to its role in maintenance of humoral and cellular host immune responses