Analysis of an expressed sequence tag library from Dicrocoelium dentriticum

Dicrocoeliosis caused by Dicrocoelium dendriticum is an important liver disease, which affects ruminants all around the world. Despite the significant economic losses caused by this trematode, molecular knowledge is very scarce. In fact, there is no information in the expressed sequence tag (EST) database about the parasite. Furthermore, the immunological diagnosis of dicrocoeliosis remains unsatisfactory, and there aren't available recombinant proteins that could be tested in the diagnosis. For this reason a cDNA library was constructed with mRNA extracted from D. dendriticum adults for first time. A random preliminary screening of 230 phage plaques from the library resulted in the identification of 173 new EST. The deduced proteins expressed by these genes have been described as possible vaccine targets in other trematodes, and/or as relevant diagnosis antigens. Then, our goal was to identify D. dentriticum diagnosis genes to be used as recombinant antigens in the specific immunological diagnosis of the trematodoses. A D. dendriticum cDNA encoding an 8-kDa recombinant protein has been cloned, expressed in Escherichia coli and evaluated in dicrocoeliosis diagnosis using both Western Blot and enzyme-linked immunosorbent assay (ELISA). The recombinant expression molecule has demonstrated its value as a diagnosis antigen of dicrocoeliosis, able to discriminate between positive and controls on day 30 post infection. This is the first research conducted for identification and characterization of D. dendriticum ESTs, which can serve as a starting point for future research on immunodiagnosis and immunoprofilaxis of dicrocoeliosis.