BackgroundAlthough spargana, which are the plerocercoids of Spirometra erinacei, are of biological and clinical importance, expressed sequence tags (ESTs) from this parasite have not been explored. To understand molecular and biological features of this parasite, sparganum ESTs were examined by large-scale EST sequencing and multiple bioinformatics tools.MethodsTotal RNA was isolated from spargana and then ESTs were generated, assembled and sequenced. Many biological aspects of spargana were investigated using multi-step bioinformatics tools.ResultsA total of 5,634 ESTs were collected from spargana. After clustering and assembly, the functions of 1,794 Sparganum Assembled ESTs (SpAEs) including 934 contigs and 860 singletons were analyzed. A total of 1,351 (75%) SpAEs were annotated using a hybrid of BLASTX and InterProScan. Of these genes, 1,041 (58%) SpAEs had high similarity to tapeworms. In the context of the biology of sparganum, our analyses reveal: (i) a highly expressed fibronectin 1, a ubiquitous and abundant glycoprotein; (ii) up-regulation of enzymes related with glycolysis pathway; (iii) most frequent domains of protein kinase and RNA recognition motif domain; (iv) a set of helminth-parasitic and spargana-specific genes that may offer a number of antigen candidates.ConclusionsOur transcriptomic analysis of S. erinacei spargana demonstrates biological aspects of a parasite that invades and travels through subcutaneous tissue in intermediate hosts. Future studies should include comparative analyses using combinations of transcriptome and proteome data collected from the entire life cycle of S. erinacei.Electronic supplementary materialThe online version of this article (doi:10.1186/1756-3305-7-368) contains supplementary material, which is available to authorized users.
Survival of Clonorchis sinensis, a cause of human clonorchiasis, requires tegument proteins, which are localized to the tegumental outer surface membrane. These proteins play an important role in a host response and parasite survival. Thus, these proteins are interesting molecular targets for vaccine and drug development. Here, we have determined two crystal structures of the calmodulin like domain (amino acid [aa] positions 1–81) and dynein light chain (DLC)-like domain (aa 83–177) of a 20.8-kDa tegumental-allergen-like protein from Clonorchis sinensis (CsTAL3). The calmodulin like domain has two Ca2+-binding sites (named CB1 and CB2), but Ca2+ binds to only one site, CB1. The DLC-like domain has a dimeric conformation; the interface is formed mainly by hydrogen bonds between the main chain atoms. In addition, we have determined full-length structure of CsTAL3 in solution and showed the conformational change of CsTAL3 induced by Ca2+ ion binding using small-angle X-ray scattering analysis and molecular dynamics simulations. The Ca2+-bound form has a more extended conformation than the Ca2+-free from does. These structural and biochemical analyses will advance the understanding of the biology of this liver fluke and may contribute to our understanding of the molecular mechanism of calcium-responsive and tegumental-allergen-like proteins.
Opisthorchis viverrini, a parasitic trematode, was recategorized as a group 1 biological carcinogen because it causes opisthorchiasis, which may result in cholangiocarcinoma. A new strategy for controlling opisthorchiasis is needed because of issues such as drug resistance and reinfection. Triosephosphate isomerase (TIM), a key enzyme in energy metabolism, is regarded as a potential drug target and vaccine candidate against various pathogens. Here, we determined the crystal structures of wild-type and 3 variants of TIMs from O. viverrini (OvTIM) at high resolution. The unique tripeptide of parasite trematodes, the SAD motif, was located on the surface of OvTIM and contributed to forming a 310-helix of the following loop in a sequence-independent manner. Through thermal stability and structural analyses of OvTIM variants, we found that the SAD motif induced local structural alterations of the surface and was involved in the overall stability of OvTIM in a complementary manner with another parasite-specific residue, N115. Comparison of the surface characteristics between OvTIM and Homo sapiens TIM (HsTIM) and structure-based epitope prediction suggested that the SAD motif functions as an epitope.
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