Comparative gene analysis of XXXX hemocytes pre- and post-exposure to miracidia of @entity380 .

@entity380 @entity10300 @entity16757
The internal defense mechanism of the snail @entity10300 during a schistosome infection is activated and mediated via the immune effector cells known as hemocytes. Since resistance and susceptibility to schistosome infection is known to be genetically determined, our interest was to use the EST approach as a gene discovery tool to examine transcription profiles in hemocytes of resistant snails pre- and post-exposure to @entity380 . Comparative analysis of the transcripts suggested that parasite exposure caused an active metabolic response in the hemocytes. The most abundant transcripts were those showing 23-74% similarity to known @entity16757 ( @entity16757 ). Further characterization by @entity16757 -PCR indicated the @entity16757 transcripts were expressed in normal snails, parasite exposed snails, and the embryonic cell line Bge. To determine whether the occurrence of @entity16757 transcripts correlates to the presence of functional enzyme activity in the snails, @entity16757 assays were performed from both resistant and susceptible snails, pre- and post-exposure to miracidia, using protein extracts from the head-foot and posterior region tissues. Results indicated that in the resistant snail, @entity16757 activity was greater in the posterior region than in the head-foot. After exposure, however, @entity16757 activity increased dramatically in the head-foot, with peak activity at 24 h post-exposure. The detection of @entity16757 activity in @entity10300 was unexpected and the role of this enzyme in the hemocyte-mediated killing of parasites is not yet known. However, identification of this and other transcripts from these cells by the EST approach provides a useful resource towards elucidating the molecular basis of resistance/susceptibility in this snail-host parasite relationship.
