Improved experimental model of hepatic cystic hydatid disease resembling natural infection route with stable growing dynamics and immune reaction

Usefulness of a murine model of hepatic cystic echinococcosis for preclinical drug trials: Efficacy of albendazole vs albendazole nanocrystals

Cystic echinococcosis is a zoonotic infection caused by the larval stage of Echinococcus granulosus sensu lato. The disease is characterized by the long-term growth of cysts, most commonly in the liver and lungs. Although an ideal model of cystic echinococcosis should induce the development of cysts in the liver and imitate the natural infection route, the murine model of intraperitoneal is still widely used in the field of experimental theraphy. The aim of the present work was to evaluate the usefulness of the murine model of hepatic CE for preclinical drug trials. The effectiveness of albendazole could also be assessed by measuring the diameter of the hepatic cyst. The albendazole significantly reduced the size of the cysts. The ultrastructural alterations of the germinal layer of hepatic cysts provoked by albendazole coincided with those observed in the intraperitoneal model. Similar results were obtained with both albendazole doses. Therefore, the efficacy of albendazole nanocrystals in the murine model of hepatic cystic echinococcosis was carried out at albendazole doses of 25 mg/kg. The abdominal ultrasound allows us to assess the response of cysts to drugs only in a qualitative manner. Although the size of cysts in the albendazole nanocrystal group was not significantly lower than that observed with albendazole, at the ultrastructural level, a greater extent of damage was observed. The murine model of hepatic cystic echinococcosis can be effectively used for assessing the effect of novel formulations or compounds. The main advantage of this model is that cysts are located in the orthotopic organ, which resembles the location most commonly found in human cases. In future studies, the usefulness of the model for pharmacokinetics studies in hepatic cysts will be evaluated.

Mouse model of secondary cystic echinococcosis

Cystic echinococcosis (CE) is a parasitic zoonosis caused by the larval stage of the cestode Echinococcus granulosus sensu lato (s. l.), a genetic complex composed of five species: E. granulosus sensu stricto (s. s.), E. equinus, E. ortleppi, E. canadensis, and E. felidis. The parasite requires two mammalian hosts to complete its life cycle: a definitive host (mainly dogs) harboring the adult parasite in its intestines, and an intermediate host (mostly farm and wild ungulates) where hydatid cysts develop mainly in the liver and lungs. Humans are accidental intermediate hosts, being susceptible to either primary or secondary forms of CE; the first one due to the ingestion of oncospheres, and the second one because of the spillage of protoscoleces (PSC) contained within a primary cyst. Secondary CE is a serious medical problem, and can be modeled in immunocompetent mice (a non-natural intermediate host) through the intraperitoneal inoculation of viable PSC from E. granulosus s. l. This model is useful to study not only the immunobiology of CE, but also to test new chemotherapeutics or therapeutical protocols, to explore novel vaccine candidates, and to evaluate alternative diagnostic and/or follow-up tools. The mouse model of secondary CE involves two sequential stages: an early stage of parasite pre-encystment (PSC develop into hydatid cysts in the peritoneal cavity of mice), and a late or chronic stage of parasite post-encystment (already differentiated cysts slowly grow during the whole host lifespan). This model is a time-consuming infection, whose outcome depends on several factors like the parasite infective dose, the mouse strain, and the parasite species/genotype. Thus, such variables should always be adjusted according to the research objectives. Herein, the general materials and procedures needed to establish secondary CE in mice are described, as well as several useful tips and recommendations.

Historical changes in surgical strategy and complication management for hepatic cystic echinococcosis

Echinococcosis is a zoonotic parasitic disease caused by Escherichia larvae. It frequently involves the liver (70%-75%), followed by the lungs (15%-20%), and occasionally the brain, heart, spleen, bone, and other organs. The main pathogenic forms of human echinococcosis currently include cystic echinococcosis (CE) and alveolar echinococcosis (AE). CE is globally distributed, while the distribution of AE is generally restricted to the northern hemisphere. In China, CE accounts for 75% of all echinococcosis cases. With rapid advances in surgical techniques in recent decades, the surgical strategy for CE has changed, especially with the continuous improvement of surgical methods and the expansion of surgical contraindications. To further understand the changes in surgical treatment strategies for hepatic CE, we interpreted and analyzed the existing literature addressing the surgical treatment of hepatic CE both domestically and abroad and briefly summarized them in chronological order. This review aims to provide a deeper understanding of the progress in the surgical treatment of hepatic CE to provide clearer avenues for its clinical diagnosis and treatment.

Establishment of a secondary infection laboratory model of Echinococcus shiquicus metacestode using BALB/c mice and Mongolian jirds (Meriones unguiculatus)

Echinococcus shiquicus is peculiar to the Qinghai–Tibet plateau of China. Research on this parasite has mainly focused on epidemiological surveys and life cycle studies. So far, limited laboratory studies have been reported. Here, experimental infection of E. shiquicus metacestode in BALB/c mice and Mongolian jirds (Meriones unguiculatus) was carried out to establish alternative laboratory animal models. Intraperitoneal inoculation of metacestode material containing protoscoleces (PSCs) obtained from infected plateau pikas were conducted on BALB/c mice. Furthermore, metacestode material without PSCs deriving from infected BALB/c mice was intraperitoneally inoculated to Mongolian jirds. Experimental animals were dissected for macroscopic and histopathological examination. The growth of cysts in BALB/c mice was infiltrative, and they invaded the murine entire body. Most of the metacestode cysts were multicystic, but a few were unilocular. The cysts contained sterile vesicles, which had no PSCs. The metacestode materials were able to successfully infect new mice. In the jirds model, E. shiquicus cysts were typically formed freely in the peritoneal cavity; the majority of these cysts were free while a small portion adhered loosely to nearby organs. The proportion of fertile cysts was high, and contained many PSCs. The PSCs produced in Mongolian jirds also successfully infected new ones, which confirms that jirds can serve as an alternative experimental intermediate host. In conclusion, a laboratory animal infection was successfully established for E. shiquicus using BALB/c mice and Mongolian jirds. These results provide new models for the in-depth study of Echinococcus metacestode survival strategy, host interactions and immune escape mechanism.

Echinococcus multilocularis and Other Taeniid Metacestodes of Muskrats in Luxembourg: Prevalence, Risk Factors, Parasite Reproduction, and Genetic Diversity

Muskrats (Ondatra zibethicus) are competent intermediate hosts for Echinococcus multilocularis, are frequently infected with this zoonotic cestode, and have even been proposed as a target species to monitor endemicity levels of this parasite. However, their contribution to maintaining the parasitic lifecycle is still unclear. To obtain data on infection frequency and reproductive potential, 280 muskrats from the Grand Duchy of Luxembourg were examined for cestode larvae in the years 2013−2017. Based on morphological and molecular identification, Echinococcus multilocularis was found at a prevalence of 14.6%. Other metacestodes were Hydatigera kamiyai, with a prevalence of 45.7%, Taenia martis with 8.9%, Taenia polyacantha with 5.0%, and Versteria mustelae, which was found in 0.7% of all muskrats. More than 80% of E. multilocularis-infected muskrats contained fertile metacestodes with a mean number of >300,000 (and up to 1,609,816) protoscoleces, which is by far the highest reproductive potential known from any intermediate host species in Europe. Temporal analysis of E. multilocularis prevalence within the study period (and in comparison with earlier data) strongly indicates a robust increase in the studied area. Host age seemed to be an important risk factor for infection, as well as co-infections with Hydatigera kamiyai. A preference for the right medial lobe of the liver as the location of E. multilocularis metacestode was observed. Intraspecific genetic variation among 89 discrete E. multilocularis metacestodes was non-existent based on 300−1590 bp sections of cox1. This is a stark contrast to H. kamiyai, of which nine haplotypes were found on a short 318 bp section of cox1, resulting in genetic diversity in the small country of Luxembourg at a similar level than previously reported from large stretches of Europe and northern Asia.

Metabolomics Analysis of Splenic CD19+ B Cells in Mice Chronically Infected With Echinococcus granulosus sensu lato Protoscoleces

Background: The larval stages of Echinococcus granulosus sensu lato (E. granulosus s.l) infection can alter B cell function and affect host anti-infective immunity, but the underlying mechanism remains unclear. The newly emerging immunometabolism highlights that several metabolites are key factors in determining the fate of immune cells, which provides a new insight for exploring how larval E. granulosus s.l. infection remodels B cell function. This study investigated the metabolomic profiles of B cells in mice infected with E. granulosus s.l. protoscoleces (PSC).

Results:Total CD19⁺ B cells, purified from the spleen of infected mice, showed significantly increased production of IL-6, TNF-α, and IL-10 after exposure to LPS in vitro. Moreover, the mRNA expression of metabolism related enzymes in B cells was remarkably disordered post infection. In addition, differential metabolites were identified in B cells after infection. There were 340 differential metabolites (83 upregulated and 257 downregulated metabolites) identified in the positive ion model, and 216 differential metabolites (97 upregulated and 119 downregulated metabolites) identified in the negative ion mode. Among these, 64 differential metabolites were annotated and involved in 68 metabolic pathways, including thyroid hormone synthesis, the metabolic processes of glutathione, fructose, mannose, and glycerophospholipid. Furthermore, several differential metabolites such as glutathione, taurine, and inosine were validated to regulate the cytokine production in LPS stimulated B cells.

Conclusion:Infection with the larval E. granulosus s.l. causes metabolic reprogramming in the intrinsic B cells of mice, which provides the first evidence for understanding the role and mechanism of B cells in parasite anti-infective immunity from the viewpoint of immunometabolism.

Development of an improved anesthesia protocol to increase CF1 mice survival in a portal vein infection with Echinococcus granulosus sensu lato protoscoleces

In order to optimize the survival rate of animals, the purpose of this study was to evaluate an injectable anesthesia protocol for the development of a murine model of hepatic cystic echinococcosis in female CF-1 mice. Three protocols of injectable anesthesia were evaluated during the infection of mice with Echinococcus granulosus sensu lato protoscoleces via the portal vein. The use or not of pre-anesthesia [atropine (0.4 mg/kg) and tramadol (2 mg/kg)] and the incorporation or not of yohimbine (0.5 mg/kg) (a reverser of xylazine) in mice anesthetized with ketamine/xylazine 80/8 mg/kg were evaluated. Most mice treated only with ketamine/xylazine 80/8 mg/kg did not achieve a deep surgical anesthetic plane. All mice treated with pre-anesthetic drugs achieved a deep surgical anesthetic plane after the administration of the anesthetic cocktail. Pre-anesthetic drugs application significantly reduced time induction of animals compared with those that received only anesthetic cocktail. Recovery time was significantly faster in the group that received yohimbine. Mice underwent laparotomy that did not receive yohimbine after surgery had a survival rate of 67%, whereas in the group treated with yohimbine the survival was 100 %. We recommend the protocol that applied pre-anesthetic drugs + ketamine/xylazine 80/8 mg/kg + yohimbine, as safe and reliable for the portal vein infection of mice with protoscoleces of E. granulosus sensu lato.

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.

Neglected tropical diseases, such as echinococcosis and cysticercosis, which are caused by taeniid cestodes (tapeworms), represent serious public health problems in many countries around the world. Given that there is only a small number of approved anthelmintics for the treatment of cestodiases, and that most of them are not highly effective against larval stages, identifying novel drug targets and their associated compounds is critical. Histone deacetylases (HDACs) are enzymes that produce epigenetic modifications of chromatin, thus modifying cellular gene expression. In this study, we evaluate and characterize a number of HDAC inhibitors on the model cestode Mesocestoides vogae and report the anthelmintic profile of these compounds. Some of the HDAC inhibitors tested showed potent anthelmintic effects, particularly entinostat, TH65 and TH92. These compounds were selected as the most promising candidates due to their high potencies, which were superior to the commercially-available anthelmintic drug albendazole. We also evaluated pairwise drug combinations of HDAC inhibitors and albendazole. The findings of this study provide a starting point for the development of new HDAC-based cestocidal compounds.

The local immune response during Echinococcus granulosus growth in a quantitative hepatic experimental model

The local immune mechanisms responsible for the establishment and development of Echinococcus granulosus sensu stricto infection in the liver, have been little explored. We developed a suitable experimental model that mimics naturally infected livers using portal injection of protoscoleces. Opposite to Echinococcus multilocularis infection which is dose-dependent, fully mature hydatid cysts can be established in the liver whatever the injection dose; although most of the infection sites were seen at the establishment phase as inflammatory granulomas associated with fibrosis, they never matured into cysts. At the establishment phase, a strong immune response was composed of T and B cells, with T1-type, T2-type cells and cytokines and IL-10-secreting CD8⁺ T cells in the liver. At the established phase, results suggested a local production of antibodies by B cells, and an involvement of NK and NKT cells. Infection outcome and local immune response in the liver, were different in the mouse models of Echinococcus granulosus sensu stricto and Echinococcus multilocularis respectively; however, only early specificities at the microenvironment level might explain the major differences found between the lesions induced by the two species. Our quantitative experimental model appears fully appropriate to further study this microenvironment and its relationship with each cestode species.

Bone marrow-derived mesenchymal stem cell (BM-MSC): A tool of cell therapy in hydatid experimentally infected rats

This study aimed to clarify the potentiality of bone marrow mesenchymal stem cells (BM-MSC) transplantation with albendazole (ABZ) on the modulation of immune responses against hydatid cyst antigens and the regeneration of injured livers in experimentally infected rats. Three different antigens of hydatid cyst fluid (HCF), hydatid cyst protoscolex (HCP) and hydatid cyst germinal layer (HCG) were isolated and their antigenic potencies were determined. The ultrasound, immunological and pathological criteria were investigated. Counting of 80% confluence BM-MSC was 4.68 × 104 cells/cm2 with 92.24% viability. Final population doublings score was 65.31 that indicated proliferation and self-renewability. Phenotyping of BM-MSC showed expression of CD73 and CD29 without exhibition of CD34 and CD14. Ultrasound examination showed multiple hydatid cysts in liver with low blood flow and spleenomegaly 8 weeks' post infection. No significant differences were noted in cystic diameter in uni-cyst liver at 2nd and 4th weeks following ABZ treatment while it was significantly decreased (P < 0.05) following transplantation of BM-MSC + ABZ treatment comparing to experimentally infected untreated group. Igs and IgG responses to the three antigens were significantly elevated while elevation in IgM response was only to HCG (P < 0.05). ABZ treatment accompanied with significant decrease in Igs and IgG titers against HCF and HCG only at 4th week post treatment (P < 0.05). However, Igs titer against HCF, HCP and HCG was significantly decreased at the 4th week following transplantation of BM-MSC + ABZ. Interestingly, the combination of BM-MSC + ABZ treatment resulted in reduction of Igs response to HCP to normal level as that of healthy control. Experimental infection resulted in elevation of TNF-α and IL-6 (P < 0.05) while, IL-4 and IL-10 decreased (P < 0.01). After transplantation of BM-MSC + ABZ treatment, serum TNF-α and IL-6 concentrations were reduced (P < 0.05) at both the 2nd and 4th weeks. However, IL-4 and IL-10 concentrations were significantly elevated (P < 0.05) only at 4th week following transplantation of BM-MSC + ABZ treatment. In conclusion, BM-MSC transplantation following ABZ administration can regenerate injured liver tissue without complete disappearance of hydatid cyst. In addition, it can modulate host protective humeral and cell mediated immune responses against hydatid cyst antigens. Therefore, the current study encourages to move to the step of performing clinical trials in humans.