Effect of specific chemotherapy on the immune response and resistance to reinfection in experimental Schistosomiasis mansoni

Abstract

Mice infected for 45 days with 120 Schistosoma mansoni cercariae and treated with praziquantel in a dose of 500 mg/kg for two consecutive days had a significant lower resistance to reinfection when challenged two weeks after treatment (45% compared to 88% in infected challenged untreated mice). In praziquantel-treated mice, the reduction in the per cent resistance was accompanied by a diminution in the size of hepatic granulomata and its in vivo correlate the delayed foot pad swelling. Moreover, the granuloma proportionate T-cell subset enumeration revealed a significant reduction in the number of T-helper cells. The humoral immune response as measured by the immediate foot pad swelling was not affected by praziquantel. Results reveal besides the diminution of the state in resistance to reinfection after praziquantel, possible involvement of egg-related pathology as a T-cell mediated reaction and as a mechanical obstacle in maintenance of this resistance.