Suppression of the growth and metastasis of mouse melanoma by Taenia crassiceps and Mesocestoides corti tapeworms.

Cancer is still one of the leading causes of death, with an estimated 19.3 million new cases every year. Our paper presents the tumor-suppressing effect of Taenia crassiceps and Mesocestoides corti on B16F10 melanoma, the intraperitoneal application of which followed the experimental infection with these tapeworms, resulting in varying degrees of effectiveness in two strains of mice. In the case of M. corti-infected ICR mice, a strong tumor growth suppression occurred, which was accompanied by a significant reduction in the formation of distant metastases in the liver and lung. Tapeworm-infected C57BL/6J mice also showed a suppression of tumor growth and, in addition, the overall survival of infected C57BL/6J mice was significantly improved. Experiments with potential cross-reaction of melanoma and tapeworm antigens with respective specific antibodies, restimulation of spleen T cells, or the direct effect of tapeworm excretory-secretory products on melanoma cells in vitro could not explain the phenomenon. However, infections with T. crassiceps and M. corti increased the number of leukocytes possibly involved in anti-tumor immunity in the peritoneal cavity of both ICR and C57BL/6J mice. This study unveils the complex interplay between tapeworm infections, immune responses, and melanoma progression, emphasizing the need for further exploration of the mechanisms driving observed tumor-suppressive effects.

Tegument Ultrastructure and Morphology of the Capsule Surrounding the Tetrathyridia of the Genus Mesocestoides Vaillant, 1863 in the Liver of the Root Vole.

The ultrastructure of the tegument of encapsulated tetrathyridia of the genus Mesocestoides Vaillant, 1863 (Cestoda, Cyclophyllidea, Mesocestoididae) from the liver of root voles Microtus oeconomus (Pallas, 1776) and the structure of the three-layered capsule surrounding them were studied for the first time. Several types of extracellular structures were noted on the surface of the tetrathyridia tegument: vesicles, fine granular material, and vacuoles. In addition, the phenomenon of shedding microtriches, which have expanded parts, was found. Host cells in contact with extracellular material show signs of destruction. A characteristic feature of the capsules surrounding the tetrathyridia is the reticular structure of the fibrous layer containing both native and degenerating inflammatory cells.

microRNA silencing in a whole worm cestode model provides insight into miR-71 function.

Parasites belonging to the class Cestoda include zoonotic species such as Echinococcus spp. and Taenia spp. that cause morbidity and mortality in endemic areas, mainly affecting pastoral and rural communities in low income countries but also upper middle income countries. Cestodes show remarkable developmental plasticity, implying tight regulation of gene expression throughout their complex life cycles. Despite the recent availability of genomic data for cestodes, little progress was made on postgenomic functional studies. MicroRNAs (miRNAs) are key components of gene regulatory systems that guide diverse developmental processes in multicellular organisms. miR-71 is a highly expressed miRNA in cestodes, which is absent in vertebrates and targets essential parasite genes, representing a potential key player in understanding the role of miRNAs in cestodes biology. Here we used transfection with antisense oligonucleotides to perform whole worm miRNA knockdown in tetrathyridia of Mesocestoides vogae (syn. Mesocestoides corti), a laboratory model of cestodes. We believe this is the first report of miRNA knockdown at the organism level in these parasites. Our results showed that M. vogae miR-71 is involved in the control of strobilation in vitro and in the establishment of murine infection. In addition, we identified miR-71 targets in M. vogae, several of them being de-repressed upon miR-71 knockdown. This study provides new knowledge on gene expression regulation in cestodes and suggests that miRNAs could be evaluated as new selective therapeutic targets for treating Neglected Tropical Diseases prioritised by the World Health Organization.

Wood mouse (Apodemus sylvaticus L.) as intermediate host for Mesocestoides canislagopodis (Rudolphi, 1810) (Krabbe 1865) in Iceland.

Mesocestoides canislagopodis is a common parasite of the arctic fox (Vulpes lagopus) in Iceland. In the past, household dogs (Canis familiaris) and cats (Felis catus) were also reported in Iceland to be infected. Recently, scolices of a non-maturing Mesocestoides sp. were detected in the intestines of the gyrfalcon (Falco rusticolus), and tetrathyridia were isolated in the body cavity of rock ptarmigan (Lagopus muta) and subsequently described. All stages were confirmed, using both morphological and molecular methods, to belong to the same species, M. canislagopodis. In the present study, post-mortem examination of wood mice (Apodemus sylvaticus), sampled in autumn 2014 on a farm in Northeast Iceland, revealed the presence of tetrathyridia in the peritoneal cavity and in the liver. Most tetrathyridia in the peritoneal cavity were free, but some were encapsulated in a thin connective tissue stroma and loosely attached to the inner organs. They appear as whitish, heart-shaped, flattened, unsegmented bodies with a slightly pointed posterior end. In the liver, tetrathyridia were seen as pale-tanned nodules embedded in the parenchyma. Comparative molecular analysis, both at the generic level (D1 domain LSU ribosomal DNA), and at the specific level (cytochrome c oxidase subunit I (cox1) and 12S mitochondrial DNA), revealed that the tetrathyridia belonged to M. canislagopodis. A. sylvaticus represents a new second intermediate host record in Iceland, and the first description of a rodent as intermediate host for this species, thus participating in the life cycle of the parasite.

Squamata reptiles as a potential source of helminth infections when preyed on by companion animals.

BACKGROUND: Squamate reptiles cohabiting with companion animals may represent a source of helminth infections, especially through predation by dogs and cats with an outdoor lifestyle. METHODS: In order to assess the role of reptiles as intermediate/paratenic hosts of trophically transmitted helminths, synanthropic reptiles (n = 245) captured from different ecological settings (i.e., households, dog shelters, urban, peri-urban and rural areas or natural parks) of southern Italy were examined for endoparasites. Parasitic cysts (i.e., larval forms of acanthocephalans, cestodes and nematodes) and free helminths (i.e., adult nematodes and digeneans) were morphologically and molecularly identified, and statistical analysis was carried out to evaluate the correlations between reptiles, infections, and ecological settings. RESULTS: Overall, 31% of reptiles were positive for at least one helminth, with Podarcis siculus (18.7%) and Tarentola mauritanica (8.1%) being the most frequently infected species. Among the parasites of medical interest, Joyeuxiella echinorhyncoides showed the highest prevalence (19.7%), followed by Diplopylidium acanthotetra (10.5%), Joyeuxiella pasqualei, Mesocestoides lineatus (5.6%) and Physaloptera sp. (3.9%). Macracanthorhynchus hirudinaceus was detected once. Podarcis siculus and T. mauritanica were associated with cestode infections. CONCLUSIONS: The wide range of helminths detected here in reptiles living in sympatry with pets and the fact that many of these helminth species are parasitic and may infect companion animals (e.g., J. pasqualei, J. echinorhyncoides, D. acanthotetra, Physaloptera sp.) and humans (i.e., Macracanthorhynchus hirudinaceus, Mesocestoides lineatus) indicate the potential health risk associated with pets preying on these small vertebrates. Our results indicate the need for complementary investigations of trophically transmitted parasites in dogs and cats living in sympatry with reptiles.

Molecular Characterization of Mesocestoides litteratus (Cestoda: Cyclophyllidea: Mesocestoididae) Tetrathyridium Isolated from Two Species of Rodents from Iran.

PURPOSE: Mesocestoides spp. are Cyclophyllidean tapeworms with zoonotic importance. The current study aimed to investigate the molecular characteristics of Mesocestoides larvae (tetrathyridium) isolated from the abdominal cavity of persion jird, Meriones persicus, and from the liver of grey hamster, Cricetulus migratorius, in Ardabil Province, northwest Iran. METHODS: Genomic DNA of the isolates of Mesocestoides tetrathyridium were extracted, and mitochondrial gene of cytochrome-c oxidase subunit1 (cox1) was amplified. Sequencing of PCR products were performed and phylogenic analysis was run using MEGA 6.0 software. RESULTS: Both isolates were identified as Mesocestoides litteratus, showing high identity with M. litteratus sequences available in GenBank. Also, they had 100% homology to each other. Intra-species variation within isolates of M. litteratus were 0-2.4%. The phylogenetic reconstruction based on the partial sequence of the cox1 gene showed that our sequences of M. litteratus were clustered with M. litteratus isolates from Slovakia, Netherlands, Germany and Italy. CONCLUSION: This is the first molecular description of M. litteratus from M. persicus and C. migratorius. Phylogenetic analysis illustrated that M. litteratus isolates of the current study had very high identities with the isolates of this species from other countries.

Pathological examination of Ym1, a chitinase family protein, in Mesocestoides corti-infected mice.

Mammals express a set of chitinase family proteins, comprising chitinases, which can hydrolyze chitin, and chitinase-like proteins without the chitinase activity but possessing chitin-binding properties. They act as endogenous lectins, regulating various physiological/pathological events. Ym1, originally identified as an eosinophil chemotactic factor or a macrophage-derived protein in parasite-infected mice, is a rodent-specific chitinase-like protein. Ym1 is also purified from eosinophilic crystals formed in the lung and urinary system in various disease models. We previously reported that major cellular sources of murine Ym1 are alveolar macrophages in the lung and neutrophils/monocytes lineage cells of the spleen and bone marrow under normal conditions. We here analyzed the detailed cellular expression of Ym1 in Mesocestoides corti (M. corti)-infected mice. Ym1 was significantly increased in the liver containing the larvae, lung, and peritoneal exudate cells in M. corti-infected mice, where activated macrophages expressed Ym1. Characteristic needle-shaped eosinophilic crystals appeared in the larvae-free lung, and Ym1 was localized to endoplasmic reticulum of activated alveolar macrophages. Moreover, swollen mesothelial cells covering the liver, spleen, and heart expressed Ym1 abundantly. Although the role of Ym1 in parasitic infection remains unclear, our findings focusing on an endogenous lectin may help in better understanding defense mechanism against parasites.

Cell repertoire and proliferation of germinative cells of the model cestode Mesocestoides corti.

The phylum Platyhelminthes shares a unique population of undifferentiated cells responsible for the proliferation capacity needed for cell renewal, growth, tissue repair and regeneration. These cells have been extensively studied in free-living flatworms, whereas in cestodes the presence of a set of undifferentiated cells, known as germinative cells, has been demonstrated in classical morphology studies, but poorly characterized with molecular biology approaches. Furthermore, several genes have been identified as neoblast markers in free-living flatworms that deserve study in cestode models. Here, different cell types of the model cestode Mesocestoides corti were characterized, identifying differentiated and germinative cells. Muscle cells, tegumental cells, calcareous corpuscle precursor cells and excretory system cells were identified, all of which are non-proliferative, differentiated cell types. Besides those, germinative cells were identified as a population of small cells with proliferative capacity in vivo. Primary cell culture experiments in Dulbecco's Modified Eagle Medium (DMEM), Echinococcus hydatid fluid and hepatocyte conditioned media in non-reductive or reductive conditions confirmed that the germinative cells were the only ones with proliferative capacity. Since several genes have been identified as markers of undifferentiated neoblast cells in free-living flatworms, the expression of pumilio and pL10 genes was analysed by qPCR and in situ hybridization, showing that the expression of these genes was stronger in germinative cells but not restricted to this cell type. This study provides the first tools to analyse and further characterise undifferentiated cells in a model cestode.

Contact between Mesocestoides vogae tetrathyridia induces their division.

Mesocestoides vogae is a cestode of the order Cyclophyllidea, and its second intermediate hosts are mammals, birds, amphibians, and reptiles. The parasite forms a tetrathyridium in the second intermediate host and multiplies asexually, sometimes to the point of filling the host's abdominal cavity. Proliferated tetrathyridium may cause lethal conditions in the host. During the asexual multiplication period, the scolex first replicates into two and then divides into two worms. In this study, to investigate the factors that promote the replication, tetrathyridia were cultured under various in vitro conditions. When several worms which already had two scolexes were cultured together, the division into two worm bodies was complete, but when single worm was cultured, the division hardly proceeded. The result indicates that the division progression of tetrathyridia with two scolexes requires the presence of other worms. In contrast, tetrathyridia with only one scolex did not initiate the division process, whether cultured together or alone. Then, the necessity of direct contact between the bodies of the worms to promote the division of tetrathyridia with two scolexes was assessed. For this, the well of the culture plate was partitioned into upper and lower parts using a mesh, and 20 worms in the upper part and single worm in the lower part were cultured. In all examined wells, worms in the upper part showed complete division, whereas the worms in the lower part rarely completed the division. Thus, direct contact between tetrathyridium promotes the division of tetrathyridia bearing two scolexes.

Identification and characterization of sirtuin enzymes in cestodes and evaluation of sirtuin inhibitors as new cestocidal molecules.

Anti-parasitic treatment of neglected tropical diseases caused by cestodes such as echinococcosis and cysticercosis relies on a small number of approved anthelmintic drugs. Furthermore, the treatment is usually prolonged and often partially effective and not well tolerated by some patients. Therefore, the identification of novel drug targets and their associated compounds is critical. In this study, we identified and characterised sirtuin enzymes in cestodes and evaluated the cestocidal potential of sirtuin inhibitors as new cestocidal molecules. Sirtuins are a highly conserved family of nicotinamide-adenine dinucleotide-lysine deacylases involved in multiple cellular functions. Here, we described the full repertoire of sirtuin-encoding genes in several cestode species. We identified six sirtuin-encoding genes that were classified into sirtuins Class I (SIRT1, SIRT2, and SIRT3), Class III (SIRT5), and Class IV (SIRT6 and SIRT7). In Echinococcus spp., sirtuin genes showed transcriptional expression throughout several developmental stages, sirtuin 2 (SIRT2) being the most expressed. To evaluate the potential of sirtuin inhibitors as new cestocidal molecules, we determined the in vitro effect of several Class I sirtuin inhibitors by motility assay. Of those, the selective SIRT2 inhibitor Mz25 showed a strong cestocidal activity in Mesocestoides vogae (syn. Mesocestoides corti) tetrathyridia at various concentrations. The Mz25 cestocidal activity was time- and dose-dependent with a half-maximal inhibitory concentration value significantly lower than that of albendazole. Additionally, Mz25 induced extensive damage in the general morphology with marked alterations in the tegument and ultrastructural features. By homology modelling, we found that cestode SIRT2s showed a high conservation of the canonical sirtuin structure as well as in the residues related to Mz25 binding. Interestingly, some non-conservative mutations were found on the selectivity pocket (an Mz25-induced structural rearrangement on the active site), which represent a promising lead for developing selective cestode SIRT2 inhibitors derived from Mz25. Nevertheless, the Mz25 molecular target in M. vogae is unknown and remains to be determined. This report provides the basis for further studies of sirtuins to understand their roles in cestode biology and to develop selective sirtuin inhibitors to treat these neglected tropical diseases.

Distribution and prevalence of Taenia hydatigena, Taenia multiceps, and Mesocestoides spp. in Mongolian sheepdogs.

Gastrointestinal parasite infections in livestock and companion animals in Mongolia have not been investigated sufficiently. This study aimed to determine the prevalence of cyclophyllid cestodes (Taeniidae and Mesocestoididae) in Mongolian sheepdogs using copro-DNA analysis. Sheepdog fecal samples (n = 1242) were collected from five ecological zones (mountain taiga, forest-steppe, steppe, desert-steppe, and desert) and four geographical regions (Western, Khangai, Central, and Eastern) within 20 of the country's 21 provinces. Among the 1242 samples, 201 (16.2%) tested positive for mitochondrial cytochrome c oxidase subunit 1 (cox1) and ribosomal 12S rRNA encoding genes of cyclophyllid cestodes. Prevalence in the mountain taiga, forest-steppe, steppe, desert-steppe, and desert zones was 29.2%, 15.4%, 15.1%, 20.1%, and 9.1%, respectively. Prevalence in the Western, Khangai, Central, and Eastern regions was 19.9%, 18.6%, 12.1%, and 12.8%, respectively. Taenia hydatigena, Taenia multiceps, and two Mesocestoides species (Mesocestoides sp.1 and Mesocestoides sp.2) were identified. T. hydatigena was found in the samples from all 20 provinces (all five zones and four regions), while T. multiceps was detected in the samples from 19 provinces (all five zones and four regions). Mesocestoides sp.1 infection was detected in the samples from all zones (except desert) and regions; it was detected in 14 provinces. Mesocestoides sp.2 infection was detected in the samples from all zones (except mountain taiga) and regions and found in seven provinces. Cyclophyllidea infection in sheepdogs is highly prevalent across Mongolia, representing a zoonotic risk. Implementation of a surveillance program for sheepdogs and their owners, and the wild animals in all ecological zones should be considered. In addition, control measures, including public awareness campaigns, especially for sheepdog owners, and periodic deworming of sheepdogs are warranted.

Successful treatment of pleural and peritoneal larval mesocestoidosis with fenbendazole in two dogs.

Mesocestoides spp. are common intestinal tapeworms of dogs and cats. The presence of numerous larval stages in the pleural or peritoneal cavities causes larval mesocestoidosis, that is a potentially life-threatening disease in massive infection. In vivo diagnosis of larval mesocestoidosis is challenging and confirmed diagnosis is often made post-mortem. For this reason, therapeutic recommendations are empirical and there is currently no data on the best treatment options in dogs and cats. Both fenbendazole and praziquantel have been used to treat canine larval mesocestoidosis but failure of complete clearance of larvae has been described for both. Treatment with fenbendazole at 100 mg/kg orally twice a day, for 1-3 months has been reported as being effective. However, it is known that administration of high, off-label doses of fenbendazole can lead to adverse reactions. Here, we report the efficacy of fenbendazole at a lower dosage (50 mg/kg twice a day) in two dogs with pleural and peritoneal mesocestoidosis.

Global prevalence of Mesocestoides infections in animals - A systematic review and meta-analysis.

Mesocestoides spp. are zoonotic cestodes found as adults in carnivorous domestic and wild definitive hosts and as metacestodes in several taxa of intermediate hosts. Although several regional studies record its occurrence in different host populations, the global prevalence and patterns of occurrence of Mesocestoides spp. are not fully understood. The objective of this study was to conduct a systematic review and meta-analysis of published literature to estimate the global prevalence of Mesocestoides spp. in major definitive and intermediate host taxa. Records published in English were collected from NCBI PubMed, Science Direct, Web of Science and Google Scholar databases, with 364 papers being included in the meta-analysis. The overall pooled prevalence estimates show that 21.72 % (95 % CI: 18.49-25.14) of terrestrial carnivore definitive hosts and 7.09 % (95 % CI: 5.79-8.51) of intermediate hosts are infected. Among definitive hosts, opossums and foxes were most commonly infected with pooled global prevalence of 48.16 % (95 % CI: 14.62 - 82.69) and 35.97 % (295 % CI: 9.54 - 42.66) respectively. Pooled global prevalence in domestic dogs and cats were 7.97 % (95 % CI: 5.67 - 10.63) and 8.32 % (95 % CI: 3.78 - 14.41) respectively. Among intermediate hosts, birds and snakes were most commonly infected with pooled global prevalence of 16.19 % (95 %CI: 5.9 - 30.31) and 15.74 % (95 % CI: 10.59 - 21.69) respectively. Our analysis demonstrates that prevalence of Mesocestoides spp. is variable across the world. The sylvatic cycle in wild hosts is likely to be more important than the domestic cycle for the maintenance of Mesocestoides spp. globally. Currently available genetic data at the mitochondrial COI locus was also phylogenetically analyzed. The genetic data supports the taxonomic distinctiveness of only a few of the numerous morphologically described Mesocestoides spp.

Helminth derived factors inhibit neutrophil extracellular trap formation and inflammation in bacterial peritonitis.

Despite their protective antimicrobial function, neutrophil extracellular traps (NETs) have been implicated in propagation of inflammatory responses in several disease conditions including sepsis. Highly diffusible exogenous ROS produced under such inflammatory conditions, can induce exuberant NETs, thus making inhibition of NETs desirable in inflammatory diseases. Here we report that helminth parasite excretory/secretory factors termed as parasitic ligands (PL) inhibit ROS-induced NETs by blocking the activation of nonselective calcium permeable channel Transient Receptor Potential Melastatin 2 (TRPM2). Therapeutic implication of PL mediated blockage of NET formation was tested in preclinical model of septic peritonitis, where PL treatment regulated neutrophil cell death modalities including NET formation and mitigated neutrophil mediated inflammatory response. This translated into improved survival and reduced systemic and local bacterial load in infected mice. Overall, our results posit PL as an important biological regulator of neutrophil functions with implications to a variety of inflammatory diseases including peritonitis.

First description of peritoneal and pleural metacestodosis caused by Mesocestoides vogae in a European wild cat (Felis silvestris silvestris).

Tapeworms of the genus Mesocestoides (Cestoda: Cyclophyllidea: Mesocestoididae) are still enigmatic to scientists, due to their high morphological variability, low host specificity, and unknown details of their life cycle. They are found worldwide, with carnivorous mammals as the main definitive hosts, and the disease is potentially zoonotic. After ingestion by a definitive host, the tetrathyridium can occasionally migrate through the intestinal wall and reach the peritoneal cavity or abdominal organs causing peritoneal metacestodosis. Here, we report on a case of metacestodosis of a European wild cat (Felis silvestris silvestris) found dead in Croatia. At necropsy, a large number of white, rice-like structures were found free in the abdominal and thoracic cavities, as well as along the serous surfaces and in the lungs. DNA isolated from the nodules was genotyped and based on a 320-base pair long 12S fragment classified as Mesocestoides vogae. Although post-mortem changes were advanced, severe emaciation due to the severe parasitic infection and gastrointestinal bleeding was diagnosed as the likely cause of death. Intestinal cestodosis was previously reported in wild cats, but according to our knowledge, this is the first description of peritoneal and pleural metacestodosis caused by M. vogae tetrathyridia (metacestodes) in any wild carnivore species.

Clinical forms of peritoneal larval cestodiasis by Mesocestoides spp. in dogs: diagnosis, treatment and long term follow-up.

Canine peritoneal larval cestodiasis (CPLC) is a little-known parasitological infestation of the peritoneal cavity of wild and domestic carnivores with Mesocestoides spp. larvae. While adult Mesocestoides tapeworms reside within the small intestine, the larvae occasionally penetrate the host's intestinal wall, causing a potentially life-threatening peritonitis. Severity of infection as well as the host response influences the prognosis significantly, and early diagnosis and treatment are essential. However, due to the lack of specific symptoms, this condition is underdiagnosed and, furthermore, no clear effective treatment has yet been described. The aim of this study is therefore to report two clinical cases of CPLC in dogs and to illustrate their clinical presentation and follow-up to serve as a reference for clinicians and researchers alike. Both animals were presented with abdominal distention as their main complaint. They underwent clinical examination, abdominal ultrasonography, abdominocentesis, and laparotomy followed by biochemical, cytological, parasitological, and molecular examination of the collected samples. After surgical lavage, the dogs received anthelmintic treatment with either fenbendazole (FBZ) or praziquantel (PZQ). Overall, timely and prolonged administration of high doses of FBZ seems to be the most effective treatment method. Irrespective, to date, no treatment capable of complete eradication of the infection and prevention of recurrence of disease has been found. In conclusion, further investigation into appropriate treatment plans as well as diagnostic development is needed.

The potential for histone deacetylase (HDAC) inhibitors as cestocidal drugs.

BACKGROUND: Echinococcosis and cysticercosis are neglected tropical diseases caused by cestode parasites (family Taeniidae). Not only there is a small number of approved anthelmintics for the treatment of these cestodiases, but also some of them are not highly effective against larval stages, such that identifying novel drug targets and their associated compounds is critical. Histone deacetylase (HDAC) enzymes are validated drug targets in cancers and other diseases, and have been gaining relevance for developing new potential anti-parasitic treatments in the last years. Here, we present the anthelmintic profile for a panel of recently developed HDAC inhibitors against the model cestode Mesocestoides vogae (syn. M. corti). METHODOLOGY/PRINCIPAL FINDINGS: Phenotypic screening was performed on M. vogae by motility measurements and optical microscopic observations. Some HDAC inhibitors showed potent anthelmintic activities; three of them -entinostat, TH65, and TH92- had pronounced anthelmintic effects, reducing parasite viability by ~100% at concentrations of ≤ 20 µM. These compounds were selected for further characterization and showed anthelmintic effects in the micromolar range and in a time- and dose-dependent manner. Moreover, these compounds induced major alterations on the morphology and ultrastructural features of M. vogae. The potencies of these compounds were higher than albendazole and the anthelmintic effects were irreversible. Additionally, we evaluated pairwise drug combinations of these HDAC inhibitors and albendazole. The results suggested a positive interaction in the anthelmintic effect for individual pairs of compounds. Due to the maximum dose approved for entinostat, adjustments in the dose regime and/or combinations with currently-used anthelmintic drugs are needed, and the selectivity of TH65 and TH92 towards parasite targets should be assessed. CONCLUSION, SIGNIFICANCE: The results presented here suggest that HDAC inhibitors represent novel and potent drug candidates against cestodes and pave the way to understanding the roles of HDACs in these parasites.

Cellular and humoral peritoneal immunity to Mesocestoides vogae metacestode infection in mice.

BACKGROUND: Here, Mesocestoides (M.) vogae infection in mice is proposed as a suitable experimental model for studying the immunity in the peritoneal cavity of mice. METHODS: To investigate the kinetics of immune parameters in M. vogae-infected mice, we detected, using flow cytometry, the expression of selected lymphoid and myeloid markers within the peritoneal cell population at day 0, 3, 6, 10, 14, 19, 25, 30 and 35 post-infection. Then, using ELISA, we analyzed the cytokine IFN-γ, TGF-ß, IL-4 and IL-10 responses and the levels of anti-M. vogae IgG and IgM antibodies in the peritoneal lavage fluid. Cells isolated from the peritoneal cavity were subjected to further molecular analysis. To assess cell activation, peritoneal cells were exposed to LPS, and culture supernatants were collected and assayed for the level of cytokines and production of nitrite. Ly6C+ and Ly6G+ cells were isolated using MACS from the peritoneal cells at day 35 post-infection. Both MACS-isolated subsets were co-cultured with preactivated T cells to measure their suppressive capacity. Next, the role of parasite excretory-secretory antigens in induction of CD11b+ myeloid cells with the suppressive phenotype and the production of IL-10 was examined. RESULTS: In the peritoneal cavity an initial increase of CD11b+Gr-1+F4/80highMHC IIhigh cells, NK, NKT cells and CD8+ cytotoxic T cells was observed in the first week of infection. At day 14 post-infection, an increase in the number of myeloid CD11b+Gr-1+ cells was detected, and most of this cell population expressed low levels of F4/80 and MHC II in later stages of infection, suggesting the impairment of antigen-presenting cell functions, probably through the excretory-secretory molecules. Moreover, we confirmed that peritoneal Gr1+ cells (Ly6C+ and Ly6G+ population) are phenotypically and functionally consistent with myeloid-derived suppressor cells. Metacestode infection elicited high levels of IL-10 and upregulated STAT-3 in peritoneal cells. A higher level of IgM suggests that this isotype may be predominant and is involved in the host protection. CONCLUSIONS: Mesocestoides vogae tetrathyridia induced the recruitment of immunosuppressive cell subsets, which may play a key role in the downregulation of immune response in long-term parasitic diseases, and excretory-secretory antigens seem to be the main regulatory factor.

Suppression of inflammatory genes expression in the injured host intestinal wall during Mesocestoides vogae tetrathyridium larvae migration.

Mesocestoides vogae is a cestode parasite of the family Mesocestoididae (order Cyclophyllidea). Its larvae, tetrathyridium, are approximately 1 mm long and 300 µm wide and infect a wide range of host species including humans. Tetrathyridium migrate through the intestinal wall to invade the peritoneal cavity. Despite intestinal penetration by such a large-sized parasite, symptomatic intestinal disorders are not common during the migration period. In this study, the dynamics of tetrathyridia migration and their pathogenicity towards intestinal tissues were examined in mice infected orally with these parasites. Most tetrathyridia were found to migrate through the intestinal wall, moving into the peritoneal cavity or liver 24 to 48 hours after the oral infections. Next, the pathogenicity of tetrathyridium in the intestinal wall was histopathologically evaluated, and tissue injury from tetrathyridium migration was confirmed. Inflammatory foci were observed as tetrathyridium migration tracks from 48 hours after oral infection; however, the number of inflammatory foci had decreased by half more than 48 hours later. Therefore, we examined the gene expression levels of the macrophage driving cytokine, IL-1ß, and the eosinophil recruiting chemokine, CCL11, by quantitative reverse-transcriptase PCR. The expression levels of these genes in the infected group were significantly lower than those of the non-infected group at 48 hours post-infection. Although the immunomodulating ability of the excretory-secretory products released from tetrathyridium has been previously shown by in vitro assays, the significance of this ability in their lifecycle has remained unclear. In this study, we discovered that tetrathyridium causes temporal inflammation in the intestinal wall during penetration and large-scale migration in this organ, but tetrathyridium simultaneously suppresses the host's inflammatory gene expression, might to be a strategy that reduces inflammatory responses and increases survival of the parasite.

Dynamics of protein synthesis in the initial steps of strobilation in the model cestode parasite Mesocestoides corti (syn. vogae).

Mesocestoides corti (syn. vogae) is a useful model for developmental studies of platyhelminth parasites of the Cestoda class, such as Taenia spp. or Echinococcus spp. It has been used in studies to characterize cestode strobilation, i.e. the development of larvae into adult worms. So far, little is known about the initial molecular events involved in cestode strobilation and, therefore, we carried out a study to characterize newly synthesized (NS) proteins upon strobilation induction. An approach based on bioorthogonal noncanonical amino acid tagging and mass spectrometry was used to label, isolate, identify, and quantify NS proteins in the initial steps of M. corti strobilation. Overall, 121 NS proteins were detected exclusively after induction of strobilation, including proteins related to development pathways, such as insulin and notch signaling. Metabolic changes that take place in the transition from the larval stage to adult worm were noted in special NS protein subsets related to developmental processes, such as focal adhesion, cell leading edge, and maintenance of location. The data shed light on mechanisms underlying early steps of cestode strobilation and enabled identification of possible developmental markers. We also consider the use of developmental responsive proteins as potential drug targets for developing novel anthelmintics. BIOLOGICAL SIGNIFICANCE: Larval cestodiases are life-threatening parasitic diseases that affect both man and domestic animals worldwide. Cestode parasites present complex life cycles, in which they undergo major morphological and physiological changes in the transition from one life-stage to the next. One of these transitions occurs during cestode strobilation, when the mostly undifferentiated and non-segmented larval or pre-adult form develops into a fully segmented and sexually differentiated (strobilated) adult worm. Although the proteomes of bona fide larvae and strobialted adults have been previously characterized for a few cestode species, little is still known about the dynamic of protein synthesis during the early steps of cestode strobilation. Now, the assessment of newly synthesized (NS) proteins within the first 48 h of strobilation the model cestode M. corti allowed to shed light on molecular mechanisms that are triggered by strobilation induction. The functional analyses of this repertoire of over a hundred NS proteins pointed out to changes in metabolism and activation of classical developmental signaling pathways in early strobilation. Many of the identified NS proteins may become valuable cestode developmental markers and their involvement in vital processes make them also good candidate targets for novel anthelmintic drugs.