The role of the liver in the migration of parasites of global significance

Descriptive study on risk of increased morbidity of schistosomiasis and graft loss after liver transplantation

Solid-organ transplantation procedures have witnessed a surge in frequency. Consequently, increased attention to associated infections and their impact on graft success is warranted. The liver is the principal target for infection by the flatworm Schistosoma mansoni. Hence, rigorous screening protocols for this parasite should be implemented for liver transplantation donors and recipients. This study investigated the risks posed by schistosomiasis-infected liver tissues for successful liver transplantation (LT), considering donors and recipients, by analyzing reported cases. Among the 43 patients undergoing LT (donors = 19; recipients = 24), 32 were infected with S. mansoni, five were infected with other Schistosoma species, and no identification was made in four patients. Reported follow-up periods ranged from 1 to 132 months, and all patients achieved successful recovery. As these helminths do not replicate in their vertebrate hosts, immunosuppressive treatment is not expected to promote increased morbidity or reactivation. Moreover, suspected or confirmed schistosomiasis infections often have a benign course, and generally, should not prevent LT. The available literature was reviewed and a provisional screening protocol has been proposed.

Anthelmintic and Hepatoprotective Activities of the Green-Synthesized Zinc Oxide Nanoparticles Against Parascaris equorum Infection in Rats

MAIN CONCLUSIONS

Green-synthesized zinc oxide nanoparticle is a promising treatment modality against parasitic infection through its powerful anthelmintic, antioxidant, healing promotion, and anti-inflammation effects.

BACKGROUND

Nanoparticles have many properties, depending on their size, shape, and morphology, allowing them to interact with microorganisms, plants, and animals.

OBJECTIVES

Investigation of the therapeutic effects of green-synthesized zinc oxide nanoparticles (ZnO NPs) on Parascaris equorum infection in rats.

METHODS

Thirty-six rats were divided into two divisions: the first division is noninfected groups were allocated into three groups. Group 1: Control, group 2: ZnO NPs (30 mg/kg), and group 3: ZnO NPs (60 mg/kg). The second division is infected groups were allocated into three groups. Group 1: vehicle, group 2: ZnO NPs (30 mg/kg), and group 3: ZnO NPs (60 mg/kg).

FINDINGS

Ten days post-infection, two larvae per gram of liver tissue were present in the vehicle group compared to the control group. No larvae were recovered from ZnO NPs (30 mg/kg), and one larva/g.tissue from ZnO NPs (60 mg/kg)-treated groups compared to untreated infected animals. Green-synthesized ZnO NPs caused a significant decrease in liver functions, low-density lipoprotein (LDL), cholesterol, triglycerides, malondialdehyde (MDA), and nitric oxide (NO). While it caused a significant increase in hemoglobin (HB), high-density lipoprotein (HDL), butyrylcholinesterase (BCHE), glutathione (GSH), catalase (CAT), and glutathione S-transferase (GST) in infected treated rats. The histological inflammation and fibroplasia scores showed a significant enhancement during the treatment with ZnO NPs (30, 60 mg/kg) compared to the infected untreated animals that scored the highest pathological destruction score. Immunohistochemical markers of NF-κB showed a significant decrease during the treatment with ZnO NPs (30, 60 mg/kg) compared to the infected untreated animals.

From the discovery of helminths to the discovery of their carcinogenic potential

Cancer involves a major aberration in the normal behaviour of cells, making them divide continuously, which interferes with the normal physiology of the body. The link between helminths and their cancer-inducing potential has been proposed in the last century. The exact pathway is still not clear but chronic inflammation in response to the deposited eggs, immune response against soluble egg antigens, and co-infection with a third party (a bacteria, a virus, or infection leading to a change in microbiome) seems to be the reasons for cancer induction. This review looks into the historical outlook on helminths along with their epidemiology, morphology, and life cycle. It then focuses on providing correlations between helminth infection and molecular mechanism of carcinogenesis by elaborating upon epidemiological, clinical, and surgical studies. While the cancer-inducing potential has been convincingly established only for a few helminths and studies point out towards possible cancer-inducing ability of the rest of the helminths elucidated in this work, however, more insights into the immunobiology of helminths as well as infected patients are required to conclusively comment upon this ability of the latter.

Schistosoma japonicum Associated Colorectal Cancer and Its Management

BACKGROUND

An association between Schistosoma japonicum and colorectal cancer in humans has been known since a long time; however, this association remains understudied and lacks comprehensive experimentation support.

OBJECTIVE

Various epidemiological and pathological studies have established the role of chronic inflammation as a major factor behind the induction of colorectal cancer. The aim of this review is to present the current knowledge on the association of Schistosoma japonicum with colorectal cancer.

RESULT

Mechanisms which lead to induction and progression of colorectal cancer are highlighted along with diagnosis and treatment for the same. Further, various methodologies, including mass drug administration, use of new drugs and vaccines, role of apoptosis, and histone-modifying enzymes, have been described which can either prevent the schistosomal infection itself or can check it from reaching an advanced stage.

CONCLUSIONS

Epidemiological, clinical, pathological and surgical studies suggest that Schistosoma japonicum is responsible for induction of colorectal cancer. However, thorough clinical studies are required to support and globally accept this notion. Further, methodologies highlighted in this work can be employed in order to take care of schistosomal infection or address the cancer induction and progression.

Escaping the enemy's bullets: an update on how malaria parasites evade host immune response

Malaria continues to cause untold hardship to inhabitants of malaria-endemic regions, causing significant morbidity and mortality that severely impact global health and the economy. Considering the complex life cycle of malaria parasites (MPs) and malaria biology, continued research efforts are ongoing to improve our understanding of the pathogenesis of the diseases. Female Anopheles mosquito injects MPs into its hosts during a blood meal, and MPs invade the host skin and the hepatocytes without causing any serious symptoms. Symptomatic infections occur only during the erythrocytic stage. In most cases, the host's innate immunity (for malaria-naïve individuals) and adaptive immunity (for pre-exposed individuals) mount severe attacks and destroy most MPs. It is increasingly understood that MPs have developed several mechanisms to escape from the host's immune destruction. This review presents recent knowledge on how the host's immune system destroys invading MPs as well as MPs survival or host immune evasion mechanisms. On the invasion of host cells, MPs release molecules that bind to cell surface receptors to reprogram the host in a way to lose the capacity to destroy them. MPs also hide from the host immune cells by inducing the clustering of both infected and uninfected erythrocytes (rosettes), as well as inducing endothelial activation. We hope this review will inspire more research to provide a complete understanding of malaria biology and promote interventions to eradicate the notorious disease.

Range of metastrongylids (superfamily Metastrongyloidea) of public health and veterinary concern present in livers of the endemic lizard Gallotia galloti of Tenerife, Canary Islands, Spain

BACKGROUND

Endemic lizards of the genus Gallotia are of high ecological value to the terrestrial ecosystem of the archipelago of the Canary Islands, being potent seed spreaders as well as an important component of the diet of other vertebrates. The endemic lizard Gallotia galloti in Tenerife has recently been reported to be a paratenic host of Angiostrongylus cantonensis, an invasive metastrongylid with zoonotic potential that is associated with rats as definitive hosts. However, microscopic examination of G. galloti tissue samples also revealed the presence of other metastrongylid larvae inside granulomas on the liver of this reptile. The aim of this study was to investigate the presence of helminths other than A. cantonensis in tissues of G. galloti from Tenerife.

METHODS

A multiplex-nested PCR targeting the internal transcribed spacer 1 was designed that enabled the species-specific detection of A. cantonensis, Angiostrongylus vasorum, Aelurostrongylus abstrusus, Crenosoma striatum and Crenosoma vulpis. Liver samples from 39 G. galloti were analysed.

RESULTS

Five metastrongylids were detected: A. cantonensis (15.4% of samples analysed), A. vasorum (5.1%), Ae. abstrusus (30.8%), C. striatum (30.8%) and undetermined metastrongylid sequences (12.8%). Co-infection was highly prevalent among the lizards which tested positive.

CONCLUSIONS

The study provides a new specific tool for the simultaneous detection of a range of metastrongylids of veterinary importance as well as new data on the circulation of metastrongylids in an ecosystem dominated by lizards.

Liver Proteome Alterations in Red Deer (Cervus elaphus) Infected by the Giant Liver Fluke Fascioloides magna

Liver fluke infections are recognised as diseases with worldwide distribution and considerable veterinary and public health importance. The giant liver fluke, Fascioloides magna, is an important non-native parasite which has been introduced to Europe, posing a threat to the survival of local wildlife populations such as red deer (Cervus elaphus). The aim of the study was to analyse differences in liver proteomes between F. magna-infected and control red deer groups using a label-based high-throughput quantitative proteomics approach. The proteomics analysis identified 234 proteins with differential abundance between the control and infected groups. Our findings showed that F. magna infection in this definitive host is associated with changes in the metabolism of proteins and fatty acids, oxidative stress, fibrosis, and signaling pathways. The identified proteins and associated biological pathways represent a valuable contribution to the understanding of host-parasite interactions and the pathogenesis of liver fluke infection.

Parasites of the liver - epidemiology, diagnosis and clinical management in the European context

Parasites in the liver cause significant global morbidity and mortality, as they can lead to recurrent cholangitis, cirrhosis, liver failure and cancer. Due to climate change and globalisation, their incidence is increasing, especially in Europe. The correct diagnosis of a hepatic parasite is often delayed because clinicians are unfamiliar with respective entities. Therefore, in this review, we aim to provide clinicians with a comprehensive clinical picture of hepatic parasites and to bring these neglected parasitic liver diseases to the wider attention of hepatology stakeholders in Europe and around the world.

Next-Generation Human Liver Models for Antimalarial Drug Assays

Advances in malaria prevention and treatment have significantly reduced the related morbidity and mortality worldwide, however, malaria continues to be a major threat to global public health. Because Plasmodium parasites reside in the liver prior to the appearance of clinical manifestations caused by intraerythrocytic development, the Plasmodium liver stage represents a vulnerable therapeutic target to prevent progression. Currently, a small number of drugs targeting liver-stage parasites are available, but all cause lethal side effects in glucose-6-phosphate dehydrogenase-deficient individuals, emphasizing the necessity for new drug development. Nevertheless, a longstanding hurdle to developing new drugs is the availability of appropriate in vitro cultures, the crucial conventional platform for evaluating the efficacy and toxicity of drugs in the preclinical phase. Most current cell culture systems rely primarily on growing immortalized or cancerous cells in the form of a two-dimensional monolayer, which is not very physiologically relevant to the complex cellular architecture of the human body. Although primary human cells are more relevant to human physiology, they are mainly hindered by batch-to-batch variation, limited supplies, and ethical issues. Advances in stem cell technologies and multidimensional culture have allowed the modelling of human infectious diseases. Here, current in vitro hepatic models and toolboxes for assaying the antimalarial drug activity are summarized. Given the physiological potential of pluripotent and adult stem cells to model liver-stage malaria, the opportunities and challenges in drug development against liver-stage malaria is highlighted, paving the way to assess the efficacy of hepatic plasmodicidal activity.

Distinct hepatic myeloid and lymphoid cell repertoires are associated with susceptibility and resistance to Ascaris infection

The soil-transmitted helminth Ascaris lumbricoides infects ~800 million people worldwide. Some people are heavily infected, harbouring many worms, whereas others are only lightly infected. The mechanisms behind this difference are unknown. We used a mouse model of hepatic resistance to Ascaris, with C57BL/6J mice as a model for heavy infection and CBA/Ca mice as a model for light infection. The mice were infected with the porcine ascarid, Ascaris suum or the human ascarid, A. lumbricoides and immune cells in their livers and spleens were enumerated using flow cytometry. Compared to uninfected C57BL/6J mice, uninfected CBA/Ca mice had higher splenic CD4+ and γδ T cell counts and lower hepatic eosinophil, Kupffer cell and B cell counts. Infection with A. suum led to expansions of eosinophils, Kupffer cells, monocytes and dendritic cells in the livers of both mouse strains and depletions of hepatic natural killer (NK) cells in CBA/Ca mice only. Infection with A. lumbricoides led to expansions of hepatic eosinophils, monocytes and dendritic cells and depletions of CD8+, αβ, NK and NK T cells in CBA/Ca mice, but not in C57BL/6J mice where only monocytes expanded. Thus, susceptibility and resistance to Ascaris infection are governed, in part, by the hepatic immune system.

The long and winding road of Ascaris larval migration: the role of mouse models

Ascaris lumbricoides and Ascaris suum are helminth parasites of humans and pigs, respectively. The life cycle of Ascaris sets it apart from the other soil-transmitted helminths because of its hepato-tracheal migration. Larval migration contributes to underestimated morbidity in humans and pigs. This migration, coupled with a lack of a murine model in which the Ascaris parasite might complete its life cycle, has undoubtedly contributed to the neglected status of the ascarid. Our knowledge of the epidemiology of adult worm infections had led us to an enhanced understanding of patterns of infection such as aggregation and predisposition; however, the mechanisms underlying these complex phenomena remain elusive. Carefully controlled experiments in defined inbred strains of mice – with enhanced recovery of larvae in tandem with measurements of cellular, histopathological and molecular processes – have greatly enhanced our knowledge of the early phase of infection, a phase crucial to the success or failure of adult worm establishment. Furthermore, the recent development of a mouse model of susceptibility and resistance, with highly consistent and diverging Ascaris larval burdens in the murine lungs, represents the extremes of the host phenotype displayed in the aggregated distribution of worms and provides an opportunity to explore the mechanistic basis that confers predisposition to light and heavy Ascaris infection. Certainly, detailed knowledge of the cellular hepatic and pulmonary responses at the molecular level can be accrued from murine models of infection and, once available, may enhance our ability to develop immunomodulatory therapies to elicit resistance to infection.

Trilateral Relationship: Ascaris, Microbiota, and Host Cells

Ascariasis is a globally spread intestinal nematode infection of humans and a considerable concern in pig husbandry. Ascaris accomplishes a complex body migration from the intestine via the liver and lung before returning to the intestine. Tissue migration and the habitat shared with a complex microbial community pose the question of how the nematode interacts with microbes and host cells from various tissues. This review addresses the current knowledge of the trilateral relationship between Ascaris, its microbial environment, and host cells, and discusses novel approaches targeting these interactions to combat this widespread infection of livestock and man.

Ascaris lumbricoides and Ascaris suum vary in their larval burden in a mouse model

Ascariasis is a neglected tropical disease, caused by Ascaris lumbricoides, affecting 800 million people worldwide. Studies focused on the early stage of parasite infection, occurring in the gut, liver and lungs, require the use of a mouse model. In these models, the porcine ascarid, Ascaris suum, is often used. The results obtained from these studies are then used to draw conclusions about A. lumbricoides infections in humans. In the present study, we sought to compare larval migration of A. suum and A. lumbricoides in mouse models. We used a previously developed mouse model of ascariasis, which consists of two mouse strains, where one mouse strain – C57BL/6J – is a model for relative susceptibility and the other – CBA/Ca – for relative resistance. Mice of both strains were infected with either A. suum or A. lumbricoides. The larval burden was assessed in two key organs, the liver and lungs, starting at 6 h post infection (p.i.) and ending on day 8 p.i. Additionally, we measured the larval size of each species (μm) at days 6, 7 and 8 p.i. in the lungs. We found that larval burden in the liver is significantly higher for A. lumbricoides than for A. suum. However, the inverse is true in the lungs. Additionally, our results showed a reduced larval size for A. lumbricoides compared to A. suum.

Immune responses in liver and spleen against Plasmodium yoelii pre-erythrocytic stages in Swiss mice model

Though the immunity to malaria has been associated with cellular immune responses, the exact function of the phenotypic cell population is still unclear. This study investigated the host immune responses elicited during the pre-erythrocytic stage, post-Plasmodium yoelii sporozoite infection in Swiss mice model. For this purpose, we analyzed the dynamics of different subsets of immune cells population and cytokine levels in the hepatic mononuclear and splenic cells population during pre-erythrocytic liver-stage infection. We observed a significant reduction in the effectors immune cells population including CD8⁺ T cell, F4/80⁺ macrophage and in plasmacytoid dendritic cells (CD11c⁺ B220⁺). Interestingly, substantial down-regulation was also noted in pro-inflammatory cytokines (i.e. IFN-γ, TNF-α, IL-12, IL-2, IL-17 and iNOS), while, up-regulation of anti-inflammatory cytokines (i.e. IL-10, IL-4 and TGF-β) during asymptomatic pre-erythrocytic liver-stage infection. Collectively, this study demonstrated that during pre-erythrocytic development, Plasmodium yoelii sporozoite impaired the host activators of innate and adaptive immune responses by regulating the immune effector cells, gene expression and cytokines levels for the establishment of infection and subsequent development in the liver and spleen. The results in this study provided a better understanding of the events leading to malarial infection and will be helpful in supportive treatment and vaccine development strategy.