Participation of cell-free haemolymph of Biomphalaria tenagophila in the defence mechanism against Schistosoma mansoni sporocysts.

Biomphalaria tenagophila of Taim strain is able to completely destroy Schistosoma mansoni sporocyst few hours after parasite penetration, although the mechanism is still not well known. In this experimental work we show that passive transference of cell-free haemolymph, especially from B. tenagophila Taim, resulted in higher resistance of B. tenagophila Cabo Frio to S. mansoni infection. This effect was demonstrated in vivo, by the reduction in the infection rate, and the significantly lower production of sporocysts and cercariae of the parasite in snails treated with Taim cell-free haemolymph compared to CBSS-inoculated snails. The protective effect of Taim cell-free haemolymph was also observed during the in vitro interaction between haemocytes and sporocysts. In this system, addition of B. tenagophila cell-free haemolymph, especially from Taim strain, was responsible for significant increase in sporocyst mortality compared to B. glabrata cell-free haemolymph or culture medium. Moreover, the combination of Taim cell-free haemolymph and Cabo Frio haemocytes increased significantly the mortality of sporocysts. The results show that Taim cell-free haemolymph would act direct and indirectly on destruction of S. mansoni sporocysts. The results also suggest that cell-free haemolymph indirectly increases parasite recognition by the circulating granulocytes and it is species specific.