Identification of differentially expressed genes in Oncomelania hupensis chronically infected with Schistosoma japonicum.

Oncomelania hupensis is the unique intermediate host of Schistosoma japonicum. The schistosome-snail interaction is biomedically important. To identify differentially expressed transcripts in O. hupensis chronically infected with S. japonicum, suppression subtractive hybridization (SSH) was used to construct a cDNA library in each direction for transcripts that are more abundantly enriched in head-foot part of the infected O. hupensis and for those that are more abundantly enriched in the uninfected, as head-foot part contains hemocytes and hemolymph which are associated with the snail internal defense system. After differential screening, 39 transcripts were identified, including nine and 30 transcripts enriched in infected and uninfected snails, respectively. Some of the transcripts have similar homology to available sequences in current databases, including transposase, caveolin-like protein, pancreatic trypsin inhibitor-like protein, prosaposin, glutathione s-transferase (GST), and several hypothetical proteins, while most of the transcripts do not match with any sequences in available databases. The identified transcripts were involved functionally in cell growth, metabolism, signal transduction, and immune responses. Two forward library transcripts and 11 reverse library transcripts were selected for real-time PCR, and 10 of them were confirmed to be consistent with the SSH results. It is intriguing to continue functional studies for some genes such as pancreatic trypsin inhibitor; a hypothetical protein (HS576367) related to calcium ion binding; GST; and several unknown proteins (HS576353 and HS576355). These identified differentially expressed genes may be key targets for understanding the molecular mechanism of co-existence during which the snail is unable to rid itself of the schistosome in chronic infection stage.