Alveolar echinococcosis in immunocompromised hosts

Narrowing the region of candidate genes that control the development of protoscoleces of Echinococcus multilocularis in the mouse liver

Alveolar echinococcosis is a zoonosis caused by the larval stage of Echinococcus multilocularis. In previous studies, QTL analysis using C57BL/6 N (B6) and DBA/2 (D2) which differ in susceptibility suggested the presence of genes on chromosome 1 that control protoscolex development. In this study, we constructed several congenic mice with different chromosome 1 regions substituted to confirm the presence of responsible genes and to narrow down the regions where the responsible genes exist. Five lines of third-generation congenic strain were constructed and infection experiments were conducted. The results showed that the development of protoscolex was seen in the two lines, resulting to narrow-down the responsible region between 69.4 cM and 70.67 cM. There were 18 genes having different SNPs and 10 genes having amino acid substitutions between B6 and D2 within this region. Infection experiments with third-generation of congenic mice succeeded in narrowing down the chromosomal region determining protoscolex development, resulting to reduce the number of candidate genes. The identification of the gene responsible for protoscolex development will contribute to the control of E. multilocularis infection.

PLGA-PEG-COOH nanoparticles are efficient systems for delivery of mefloquine to Echinococcus multilocularis metacestodes

Alveolar echinococcosis (AE) is a severe disease caused by the infection with the larval stage of Echinococcus multilocularis, the metacestode. As there is no actual curative drug therapy, recommendations to manage AE patients are based on radical surgery and prophylactic administration of albendazole or mebendazole during 2 years to prevent relapses. There is an urgent need for new therapeutic strategies for the management of AE, as the drugs in use are only parasitostatic, and can induce toxicity. This study aimed at developing a drug delivery system for mefloquine, an antiparasitic compound which is highly active against E. multilocularis in vitro and in experimentally infected mice. We formulated mefloquine-loaded PLGA-PEG-COOH (poly-(lactic-co-glycolic acid)) nanoparticles that exhibit stable physical properties and mefloquine content. These nanoparticles crossed the outer acellular laminated layer of metacestodes in vitro and delivered their content to the inner germinal layer within less than 5 min. The in vitro anti-echinococcal activity of mefloquine was not altered during the formulation process. However, toxicity against hepatocytes was not reduced when compared to free mefloquine. Altogether, this study shows that mefloquine-loaded PLGA-PEG-COOH nanoparticles are promising candidates for drug delivery during AE treatment. However, strategies for direct parasite-specific targeting of these particles should be developed.

Chemotherapy for the treatment of alveolar echinococcosis: Where are we?

Alveolar echinococcosis (AE) is a severe liver disease due to infection with the Echinococcus multilocularis larval stage, called the metacestode. Management of AE is based on benzimidazole chemotherapy (albendazole or mebendazole), associated with surgery when possible. Benzimidazoles are the only compounds recommended for the treatment of AE; however, these are parasitostatic, which means that the parasite can resume growth when treatment is interrupted. Also, benzimidazoles can cause liver dysfunction which may prevent their use. Numerous drugs have been reported to have in vitro activity against E. multilocularis, but few had satisfactory in vivo activity, and none were clearly more effective than benzimidazoles. These drugs belong to various therapeutic categories including anti-infective agents (e.g. amphotericin B, mefloquine, pentamidine derivatives), anti-neoplastic compounds (e.g. imatinib, nilotinib, bortezomib), plant-extracted compounds (e.g. thymol, crocin, carvacrol) and others (e.g. metformin, verapamil, thiaclopride). These treatments are generally of limited interest due to their toxicity, their unfavorable pharmacokinetics, or the scarcity of studies involving humans. Apart from benzimidazoles, only amphotericin B, mefloquine and nitazoxanide have been reported to be used for human AE treatment, with unsatisfactory results. Few studies have aimed at developing innovative strategies for AE drug therapy, such as vectorization of drugs using nanoparticles. Altogether, this review emphasizes the urgent need for new therapeutic strategies in AE management, for which there is currently no curative chemotherapy.

The In Vitro Promoting Angiogenesis Roles of Exosomes Derived from the Protoscoleces of Echinococcus multilocularis

Alveolar echinococcosis (AE) is a persistent parasite condition that causes the formation of tumor-like growths. It is a challenge to treat the disease. These growths need neovascularization to get their oxygen and nutrients, and the disease is prolonged and severe. Considerable research has been conducted on exosomes and their interactions with Echinococcus multilocularis in the context of immunological evasion by the host. However, the extent of their involvement in angiogenesis needs to be conducted. The primary objective of this investigation was to preliminarily explore the effect of exosomes produced from E. multilocularis protoscoleces (PSC-exo) on angiogenesis, to elucidate the mechanism of their roles in the regulation of the downstream pathway of VEGFA activation, and to provide ideas for the development of novel treatments for AE. The study evaluated the impact of PSC-exo increases proliferation, migration, invasion, and tube formation of HUVECs at concentrations of up to 50 μg/ml. In addition, the study sought to validate the findings in vivo. This effect involved increased VEGFA expression at gene and protein levels and AKT/mTOR pathway activation. PSC-exo are crucial in promoting angiogenesis through VEGFA upregulation and AKT/mTOR signaling. This research contributes to our knowledge of neovascularization in AE.

Targeting myeloid-derived suppressor cells promotes antiparasitic T-cell immunity and enhances the efficacy of PD-1 blockade (15 words)

Immune exhaustion corresponds to a loss of effector function of T cells that associates with cancer or chronic infection. Here, our objective was to decipher the mechanisms involved in the immune suppression of myeloid-derived suppressor cells (MDSCs) and to explore the potential to target these cells for immunotherapy to enhance checkpoint blockade efficacy in a chronic parasite infection. We demonstrated that programmed cell-death-1 (PD-1) expression was significantly upregulated and associated with T-cell dysfunction in advanced alveolar echinococcosis (AE) patients and in Echinococcus multilocularis-infected mice. PD-1 blockade ex vivo failed to reverse AE patients' peripheral blood T-cell dysfunction. PD-1/PD-L1 blockade or PD-1 deficiency had no significant effects on metacestode in mouse model. This was due to the inhibitory capacities of immunosuppressive granulocytic MDSCs (G-MDSCs), especially in the liver surrounding the parasite pseudotumor. MDSCs suppressed T-cell function in vitro in an indoleamine 2, 3 dioxygenase 1 (IDO1)-dependent manner. Although depleting MDSCs alone restored T-cell effector functions and led to some limitation of disease progression in E. multilocularis-infected mice, combination with PD-1 blockade was better to induce antiparasitic efficacy. Our findings provide preclinical evidence in support of targeting MDSC or combining such an approach with checkpoint blockade in patients with advanced AE. (200 words).

A SIMPLE, QUICK, AND ECONOMICAL METHOD FOR IN VITRO CULTIVATION OF ECHINOCOCCUS MULTILOCULARIS METACESTODE AND GENERATION OF PRIMARY CELLS

Alveolar echinococcosis is considered to be one of the most potentially lethal parasitic zoonotic diseases. However, the molecular mechanisms by which Echinococcus multilocularis interacts with hosts are poorly understood, hindering the prevention and treatment of this disease. Due to the great advantages of cell culture systems for molecular research, numerous attempts have been made to establish primary cell cultures for E. multilocularis. In this study we developed a simple, rapid, and economical method that allows E. multilocularis metacestode tissue blocks to generate daughter vesicles without the continuous presence of host feeder cells in a regular medium. We performed anaerobic, hypoxic (1% O2), normoxic, and semi-anaerobic (in sealed tubes) cultures and found that E. multilocularis metacestode tissues can produce daughter vesicles only in the sealed tubes after 4 wk of incubation. The daughter vesicles cultivated in this system were remarkably enlarged under anaerobic conditions after 8 days of culture, whereas vesicles cultured under hypoxic (1% O2) and normoxic conditions showed only a mild increase in volume. Our in vitro cultivated vesicles showed strong viability and could be used to test antiparasitic drugs, isolate primary cells, and infect animals.

Immunological Characteristics of Hepatic Dendritic Cells in Patients and Mouse Model with Liver Echinococcus multilocularis Infection

The cestode Echinococcus multilocularis, which mainly dwells in the liver, leads to a serious parasitic liver disease called alveolar echinococcosis (AE). Despite the increased attention drawn to the immunosuppressive microenvironment formed by hepatic AE tissue, the immunological characteristics of hepatic dendritic cells (DCs) in the AE liver microenvironment have not been fully elucidated. Here, we profiled the immunophenotypic characteristics of hepatic DC subsets in both clinical AE patients and a mouse model. Single-cell RNA sequencing (scRNA-Seq) analysis of four AE patient specimens revealed that greater DC numbers were present within perilesional liver tissues and that the distributions of cDC and pDC subsets in the liver and periphery were different. cDCs highly expressed the costimulatory molecule CD86, the immune checkpoint molecule CD244, LAG3, CTLA4, and the checkpoint ligand CD48, while pDCs expressed these genes at low frequencies. Flow cytometric analysis of hepatic DC subsets in an E. multilocularis infection mouse model demonstrated that the number of cDCs significantly increased after parasite infection, and a tolerogenic phenotype characterized by a decrease in CD40 and CD80 expression levels was observed at an early stage, whereas an activated phenotype characterized by an increase in CD86 expression levels was observed at a late stage. Moreover, the expression profiles of major immune checkpoint molecules (CD244 and LAG3) and ligands (CD48) on hepatic DC subsets in a mouse model exhibited the same pattern as those in AE patients. Notably, the cDC and pDC subsets in the E. multilocularis infection group exhibited higher expression levels of PD-L1 and CD155 than those in the control group, suggesting the potential of these subsets to impair T cell function. These findings may provide valuable information for investigating the role of hepatic DC subsets in the AE microenvironment and guiding DC targeting treatments for AE.

[Clinical Features and Surgical Outcomes of 15 Cases of Intracranial Alveolar Echinococcosis]

Objective

To investigate the surgical treatment strategy of intracranial alveolar echinococcosis (AE) and the clinical outcomes.

Methods

The clinical and follow-up data of 15 intracranial AE patients who underwent surgical treatment in the Departments of Neurosurgery of Sichuan Provincial People's Hospital (SPPH) and People's Hospital of Aba Tibetan and Qiang Autonomous Prefecture (a branch hospital of SPPH) between March 2017 and January 2021 were retrospectively analyzed. Full follow-up data were available for each of the 15 cases. The clinical and imaging characteristics, general surgical information, and surgical outcomes were analyzed.

Results

In the 15 patients, there were a total of 50 intracranial lesions, with an average of (3.3±3.1)/case. Four cases had solitary intracranial lesions, while 11 cases had multiple lesions, with the number of intracranial lesions per case ranging from 2 to 13. All patients with solitary intracranial lesions received total resection. In 6 patients with multiple intracranial lesions, only the largest lesion was surgically removed, and in 5 patients, 2 to 3 adjacent lesions were surgically removed. All but one patient had extracranial lesions in their liver, lungs, kidneys, adrenal glands, and thoracic vertebrae. The patients were followed up for 12 to 58 months after surgery, with the mean follow-up time being (28.1±13.4) months. Among the 15 cases, 13 showed stable intracranial condition during postoperative follow-up. Intracranial lesions recurred in 2 patients who had deep lesions accompanied by dissemination to the subarachnoid space. Two patients died during follow-up.

Conclusion

Microsurgical treatment of intracranial AE is effective, but total surgical resection is difficult to accomplish when patients have echinococcosis lesions located at a depth, especially when the lesions are spreading to the subarachnoid space. The prognosis of patients is closely associated with the extent of lesion invasion and the control of systemic hydatid lesions, especially those in the liver.

Watch-and-wait approach for inactive echinococcal cysts: scoping review update since the issue of the WHO-IWGE Expert Consensus and current perspectives

PURPOSE OF REVIEW

This work aims to provide an update of knowledge on the evolution of inactive cystic echinococcosis (CE) cysts (CE4-CE5) managed by 'watch-and-wait', by means of a scoping review of the literature published after the publication of the WHO-IWGE (Informal Working Group on Echinococcosis) Expert Consensus document in 2010.

RECENT FINDINGS

A total of 31 articles were included. Population ultrasound-based studies showed that spontaneously inactivated CE cysts represent 50.2% (95% confidence interval 38.7-61.8) of all detected untreated CE cysts, and that the prevalence of CE4-CE5 cysts tends to increase with age. Four longitudinal population-based studies showed that CE cysts naturally tend to evolve towards inactivation and that spontaneously inactivated cysts reactivate in a minority of cases. This was confirmed by four hospital-based studies, showing that spontaneously inactivated cysts reactivate rarely, while rate of reactivation is higher if inactivity was obtained posttreatment. It was not possible to drive conclusions on any difference in the clinical course of infection in immunocompromised or pregnant patients.

SUMMARY

CE cysts tend to evolve spontaneously to inactivation over time. The published literature supports the safety of the watch-and-wait approach for inactive cysts, sparing treatment to a substantial proportion of asymptomatic patients. A regular follow-up with ultrasound of all inactive cysts is required to detect reactivations.