Proteomic study of activated Taenia solium oncospheres
Graphical abstract
By proteome techniques we identify a set of Taenia solium oncospheral proteins and further characterize the parasite 14-3-3, providing new information about the host–parasite relationship.
Introduction
Taenia solium and Taenia saginata are among the most prevalent human tapeworms in the world. The intermediate host of T. solium is mainly pigs. Humans act as definitive hosts for the parasite. Gravid segments from humans infected with the adult tapeworm are passed in the faeces each containing around 40,000 eggs that resist destruction in the environment for a relatively long period of time. After ingestion by an intermediate host, oncospheres hatch and activate in the intestine, penetrate the gut and reach different organs via the blood stream, developing into cysticerci mainly in striated muscle. Humans are infected when ingesting raw or inadequately cooked pork containing viable cysticerci. The humans may also act as intermediate hosts for the parasite due to the accidental ingestion of T. solium eggs via unwashed hands or contaminated food, giving rise to human cysticercosis. While infection of the intestinal tract by adult worms is not life-threatening, infection with larval tapeworms from T. solium in man can be very serious and can lead to death when these localize in brain tissue.
Oncospheral hatching and activation have been achieved in vitro, showing that activated oncospheres are surrounded by parasite-derived excretory vesicles [1]. Little is known about the molecular cross-talk between taeniid oncospheres and its host when parasites are activated and ready to traverse the intestinal tissue. In this regard, genomic and ESTs studies have been recently reported for adult worms and cysticerci [2], [3], but not for oncospheres. Similarly, no proteomic studies on T. solium have been performed to date, and thus only individual proteins have been identified and characterized, and from those, the majority have been investigated in cysticerci and adult worms. The cellular events occurring within seconds to minutes after oncospheral activation are probably similar to those found in other eukaryotes upon “activation”, and most probably include changes in intracellular physiology, signaling through kinases and secondary messengers, remodelling of the cytoskeleton and an increase in the overall metabolic rate of the organism [e.g. 4]. In addition, molecules present in the penetration glands of oncospheres, and also those related with adhesion, proteolysis, and sorting-folding of proteins in secreted granules, would be expected to play key roles in the mechanism of oncospheral gut invasion. Oncospheres are the parasite stage determining the infection success in their intermediate host, and thus the identification of proteins from activated oncospheres is the key to understand both the parasite biology and the host–parasite relationship. We initiate here the study of the proteome from in vitro activated oncospheres. To achieve this goal, in vitro hatched and activated oncospheres of T. solium were treated with trypsin and the peptides released were analysed by LC–MS/MS for their identification. In addition, we further characterize one of the parasite proteins – the 14-3-3 – found during our proteomic approach.
Section snippets
Parasites
T. solium adult worms fragments (gravid proglottids) were recovered from Peruvian patients’ stools as described previously [5]. The proglottids were collected by sieving, washed thoroughly with distilled water and stored in 25% glycerol supplemented with penicillin (1000 IU/ml) and gentamicin (100 μg/ml) at 4 °C until used. Species identification was made by histology and PCR-RFLP as described before [5], [6]. The eggs were obtained from gravid proglottids by gentle homogenization (using a manual
Appearance and viability of oncospheres after activation
Activated oncospheres (90% of hatched oncospheres) showed a round-shaped appearance, border-located hooks and the absence of the oncospheral membrane (physically disrupted and discarded, as expected), under a microscope at 100× (Fig. 1a). In addition, activated parasites occasionally showed the presence of secretory vesicles around them (Fig. 1b). Around 10% of oncospheres showed the outer envelope and were considered as hatched but non-activated parasites (data not shown). Activated
Discussion
In an attempt to give the first picture of the biology of invasion by T. solium oncospheres, we have performed a proteomic analysis from in vitro activated oncospheres. Our activation approach resulted in a parasite sample consisting of 90% activated oncospheres without oncospheral membrane, together with 10% activated but “unreleased” parasites presenting the oncospheral membrane. Although these were a minority, we cannot rule out that some of the identified proteins are present in the
Acknowledgements
This project was partially funded by the Fogarty International Center/NIH (training grants D43 TW001140, TW007490 and TW006581), and the Bill and Melinda Gates Foundation (training grant #33848). Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the sponsors. AHG acknowledges financial support from the CSIC-Predoctorate JAE Spanish grant programme.
References (45)
- et al.
The genome project of Taenia solium
Parasitol Int
(2006) - et al.
Characterization of a novel Taenia solium oncosphere antigen
Mol Biochem Parasitol
(2007) - et al.
A proteomic approach to the identification of tegumental proteins of male and female Schistosoma bovis worms
Mol Biochem Parasitol
(2008) - et al.
Exponentially Modified Protein Abundance Index (emPAI) for estimation of absolute protein amount in proteomics by the number of sequenced peptides per protein
Mol Cell Proteomics
(2005) - et al.
The Echinococcus multilocularis 14-3-3 protein protects mice against primary but not secondary alveolar echinococcosis
Vaccine
(2003) - et al.
Proteomic analysis of Schistosoma mansoni cercarial secretions
Mol Cell Proteomics
(2005) 14-3-3 proteins: a historic overview
Semin Cancer Biol
(2006)- et al.
Cloning and sequencing of two actin genes from Taenia solium (Cestoda)
Mol Biochem Parasitol
(1990) - et al.
Paramyosin is the Schistosoma mansoni (Trematoda) homologue of antigen B from Taenia solium (Cestoda)
Mol Biochem Parasitol
(1991) - et al.
Comparison of biochemical and immunochemical properties of myosin II in taeniid parasites
Cell Biol Int
(2006)