Angiostrongylus cantonensis: efficacy of albendazole-dexamethasone co-therapy against infection-induced plasminogen activators and eosinophilic meningitis

Increased expression of the kynurenine pathway in mice with eosinophilic meningitis caused by Angiostrongylus cantonensis infection

Angiostrongylus cantonensis is the major cause of eosinophilic meningitis worldwide. The imbalance of neurotoxic and neuroprotective metabolites in the kynurenine pathway (KP) have been suggested to contribute to the pathogenesis of central nervous system (CNS) infection. We hypothesized that KP may also be involved in parasitic eosinophilic meningitis. BALB/c mice were orally infected with 40 A. cantonensis L3, intraperitoneal dexamethasone at a dose of 500 µg/kg/day was administered from the seventh day of infection until the end of the study. The Evans blue method was used to analyze blood-brain barrier (BBB) dysfunction, and indoleamine 2,3-dioxygenase (IDO) proteins levels was measured by Western blot, immunohistochemistry (IHC), and immunofluorescence. Tryptophan and kynurenine concentrations were analyzed by IHC and liquid chromatography-tandem mass spectrometry (LC-MS/MS). The concentrations of Evans blue, IDO, tryptophan and kynurenine in the different groups of mice were compared using the nonparametric Kruskal-Wallis test. BBB dysfunction was found in mice with eosinophilic meningitis. The administration of dexamethasone significantly decreased the amount of Evans blue. An increased IDO expression was shown in Western blot, IHC and immunofluorescence following 2-3 weeks infection. Increased tryptophan and kynurenine expressions in the brain and cerebrospinal fluid (CSF) were also found in IHC and LC-MS/MS studies. The administration of dexamethasone significantly decreased the amount of IDO, tryptophan and kynurenine. In conclusion, A. cantonensis infection inducing BBB damage, then increased the influx of tryptophan into CSF. The administration of dexamethasone significantly decreased the amount of IDO, tryptophan and kynurenine.

Improvements of cognitive functions in mice heavily infected by Angiostrongylus cantonensis after treatment with albendazole, dexamethasone, or co-therapy

Angiostrongylus cantonensis, the causative agent of human eosinophilic meningitis and eosinophilic meningoencepalitis, has been reported to cause cognitive impairments in the host. To determine whether drug treatment improves the cognitive functions, BALB/c mice infected with 50 third-stage larvae were treated with albendazole, dexamethasone, or co-therapy since day 7 or 14 post-infection for one or two weeks. Abilities of spatial memory and learning of these animals were assessed with the Morris water maze. Our results showed that body weight was significant higher then infected group in the albendazole and combined therapy groups. Significantly lower worm recovery rates were found in mice treated with the same groups. The mice treated with dexamethasone since day 7 for 14 day had significant longer time in the remaining groups were found in forced swimming test. The animals treated with albendazole and combined therapy since day 7 for 14 days was demonstrated to have significantly shorter latencies to the platform in learning memory on day 3 and 4. Mice in these two groups were demonstrated to have significantly higher sores in spatial memory tests. These results indicate that treatment with albendazole or combined therapy may be more efficient in preventing brain damages and depression as well as preserving their capabilities in learning and memory. Therefore, administration of albendazole alone or combined with dexamethasone should have higher efficacies than dexamethasone alone in treatment of BALB/c mice infected with a heavy dose of 50 third-stage larvae of A. cantonensis.

Heme oxygenase-1 modulates brain inflammation and apoptosis in mice with angiostrongyliasis

The rat nematode lungworm Angiostrongylus cantonensis undergoes obligatory intracerebral migration in its hosts and causes eosinophilic meningitis or meningoencephalitis. Heme oxygenase 1 (HO-1) has several cytoprotective properties such as anti-oxidative, anti-inflammatory, and anti-apoptotic effects. HO-1 in brain tissues was induced in A. cantonensis-infected group and showed positive modulation in cobalt protoporphyrin (CoPP)-treated groups. Assay methods for the therapeutic effect include western blot analysis, enzyme-linked immunosorbent assay, gelatin zymography, blood-brain barrier permeability evaluation and eosinophil count in cerebrospinal fluid. The combination of albendazole (ABZ) and CoPP significantly decreased pro-inflammatory cytokines, tumor necrosis factor-α, interleukin (IL)-1β, IL-5, and IL-33 but significantly increased anti-inflammatory cytokines IL-10 and transforming growth factor-β. In addition, worm recovery, matrix metalloproteinase-9, BBB permeability, and eosinophil counts were decreased in the ABZ and CoPP co-treated groups. Induction of HO-1 with CoPP strongly inhibited the protein levels of caspase-3 and increased the induction of annexin-V and B-cell leukemia 2. Thus, co-treatment with ABZ and CoPP prevented A. cantonensis-induced eosinophilic meningoencephalitis and its anti-apoptotic effect by promoting HO-1 signaling prior to BBB dysfunction. HO-1 induction might be a therapeutic modality for eosinophilic meningoencephalitis.

Clinical Efficacy and Safety of Albendazole and Other Benzimidazole Anthelmintics for Rat Lungworm Disease (Neuroangiostrongyliasis): A Systematic Analysis of Clinical Reports and Animal Studies

The safety and efficacy of benzimidazole anthelmintics for the treatment of rat lungworm disease (neuroangiostrongyliasis) have been questioned regardless of numerous experimental animal studies and clinical reports. In this review, 40 of these experimental animal studies and 104 clinical reports are compiled with a focus on albendazole. Among the 144 articles involving an estimated 1034 patients and 2561 animals, 4.1% were inconclusive or vague regarding the use of benzimidazoles. Of the remaining 138 articles, 90.5% found benzimidazoles to be safe and effective (885 patients, 2530 animals), 4.3% as safe but ineffective (73 patients, 3 animals), and 5.0% caused adverse reactions (7 patients, 28 animals). Among those clinical reports that described a confirmed diagnosis of neuroangiostrongyliasis in which albendazole monotherapy was used, 100% reported high efficacy (743 patients, 479 animals). In those where albendazole-corticosteroid co-therapy was used, 97.87% reported it to be effective (323 patients, 130 animals).

Co-Therapy of Albendazole and Dexamethasone Reduces Pathological Changes in the Cerebral Parenchyma of Th-1 and Th-2 Dominant Mice Heavily Infected with Angiostrongylus cantonensis: Histopathological and RNA-seq Analyses

Administration of albendazole alone was not very suitable for the treatment of cerebral angiostrongyliasis. This study was designed to evaluate the effects of the co-therapy of this drug and dexamethasone in Th-1 and Th-2 dominant mice infected with Angiostrongylus cantonensis. Each of BALB/c and C57BL/6 mice infected with 50 A. cantonensis third-stage larvae were administered albendazole (10 mg/kg/day) alone, dexamethasone (0.5 mg/kg/day) alone, or co-therapy of the two drugs from day 7 or 14 post-infection for 7 or 14 days. After sacrifice, coronal slices were prepared from five brain regions and stained with hematoxylin and eosin. Eight pathological changes were employed to determine the therapeutic effectiveness using a scoring system. RNA-seq analysis was performed to confirm the histopathological findings. The infected BALB/c and C57BL/6 mice had similar patterns in the pathological changes. Meningitis, hemorrhage, size of worms, and encephalitis in the cerebral parenchyma were slighter in the mice treated with co-therapy than the remaining groups. Mice treated from day 14 had more severe changes than those from day 7. The histopathological findings were found to be consistent to immune responses determined by RNA-seq analysis. Co-therapy was determined to reduce pathological changes after administration to mice infected with A. cantonensis.

In vitro efficacy of anthelmintics on Angiostrongylus cantonensis L3 larvae

Angiostrongylus cantonensis is the leading cause of eosinophilic meningitis worldwide, with life-threatening complications if not managed correctly. Previous in vitro studies have utilized change in motility patterns of adult female worms to assess the efficacy of anthelmintics qualitatively. However, it is the third stage larvae (L3) that are infectious to humans. With differential staining using propidium iodide penetration as the indicator of death, we can distinguish between dead and live larvae. This assay has enabled us to quantify the in vitro efficacy of nine clinically established anthelmintics on A. cantonensis L3. All drugs were tested at a 1 mm concentration. Piperazine and niclosamide were ineffective in inducing larval death; however, albendazole sulfoxide, pyrantel pamoate, diethylcarbamazine, levamisole and praziquantel were effective as compared to unexposed controls (P < 0.05). Ivermectin and moxidectin did not induce significant levels of mortality, but they considerably reduced larval motility almost immediately. This study indicates the need for further in vivo studies to determine the optimal dose and time frame for post-infection treatment with anthelmintics that demonstrated efficacy.

Dexamethasone downregulates the expressions of MMP-9 and oxidative stress in mice with eosinophilic meningitis caused by Angiostrongylus cantonensis infection

Steroids have been shown to be beneficial in patients and mice with eosinophilic meningitis caused by Angiostrongylus cantonensis infection; however, the mechanism for this beneficial effect is unknown. We speculated that the effect of steroids in eosinophilic meningitis caused by A. cantonensis infection may be mediated by the downregulation of matrix metallopeptidase-9 (MMP-9) and oxidative stress pathways via glucocorticoid receptors (GRs). We found blood-brain barrier (BBB) dysfunction in mice with eosinophilic meningitis 2-3 weeks after infection as evidenced by increased extravasation of Evans blue and cerebrospinal fluid (CSF) albumin levels. The administration of dexamethasone significantly decreased the amount of Evans blue and CSF albumin. The effect of dexamethasone was mediated by GRs and heat shock protein 70, resulting in subsequent decreases in the expressions of nuclear factor kappa B (NF-κB), c-Jun N-terminal kinase (JNK), and extracellular signal-regulated kinase (ERK) in the CSF and brain parenchymal after 2 weeks of steroid administration. Steroid treatment also decreased CSF/brain homogenate MMP-9 concentrations, but had no effect on CSF MMP-2 levels, indicating that MMP-9 rather than MMP-2 played a major role in BBB dysfunction in mice with eosinophilic meningitis. The concentration of 8-hydroxy-2'-deoxyguanosine (8-OHdG) gradually increased after 1-3 weeks of infection, and the administration of dexamethasone significantly downregulated the concentration of oxidized derivative 8-OHdG in CSF. In conclusion, increased 8-OHdG and MMP-9 concentrations were found in mice with eosinophilic meningitis caused by A. cantonensis infection. The effect of dexamethasone was mediated by GRs and significantly decreased not only the levels of 8-OHdG and MMP-9 but also NF-κB, JNK and ERK.

3-Hydroxybenzaldehyde and 4-Hydroxybenzaldehyde enhance survival of mouse astrocytes treated with Angiostrongylus cantonensis young adults excretory/secretory products

Background

Methods

Results

Conclusions

Angiostrongylus spp. (Nematoda; Metastrongyloidea) of global public health importance

Human angiostrongyliasis is an important foodborne zoonosis, caused by the infection with Angiostrongylus costaricensis and Angiostrongylus cantonensis. These two species have a significant public health impact in different areas of the world. Angiostrongyliasis is re-emerging and expanding to urban settings rising significant concerns regarding the control of these infections. This review focuses on aspects such as life cycle, epidemiology, clinical manifestations, diagnostics, food safety and control of illness caused especially by A. cantonensis.

Albendazole-Schisandrin B Co-Therapy on Angiostrongylus cantonensis-Induced Meningoencephalitis in Mice

Currently, Angiostrongylus cantonensis infections are predominantly treated with albendazole. However, the use of albendazole can provoke certain neurological symptoms as a result of the immune response triggered by the dead worms. Therefore, treatment usually involves co-administration of corticosteroids to limit the inflammatory reaction. Corticosteroids play a useful role in suppressing inflammation in the brain; however, long-term usage or high dosage may make it problematic.Schisandrin B, an active ingredient from Schisandra chinensis, has been shown to have anti-inflammatory effects on the brain. This study aimed to investigate the effects and potential of schisandrin B in combination with albendazole to treat Angiostrongylus-induced meningoencephalitis. Here, we show that albendazole-schisandrin B co-treatment suppressed neuroinflammation in Angiostrongylus-infected mice and increased the survival of the mice. Accordingly, albendazole-schisandrin B co-treatment significantly inhibited inflammasome activation, pyroptosis, and apoptosis. The sensorimotor functions of the mice were also repaired after albendazole-schisandrin B treatment. Immune response was shown to shift from Th2 to Th1, which reduces inflammation and enhances immunity against A. cantonensis. Collectively, our study showed that albendazole-schisandrin B co-therapy may be used as an encouraging treatment for Angiostrongylus-induced meningoencephalitis.

Angiostrongylus cantonensis in travelers: clinical manifestations, diagnosis, and treatment

PURPOSE OF REVIEW

Angiostrongylus cantonensis eosinophilic meningitis is a neglected, yet important emerging disease, which has been increasingly recognized in travelers. In this review, we describe the occurrence of the disease in travelers, sources of infection, clinical manifestations, diagnosis, and currently recommended treatment.

RECENT FINDINGS

Various intermediate hosts and/or paratenic hosts can be the source of infection in humans. Serological tests for antibody may be negative early in the course of the disease but PCR for antigen detection in the CSF has recently been developed and may help to make the diagnosis at an earlier stage. High-dose corticosteroids (e.g. prednisolone 60 mg per day for at least 1-2 weeks) are currently the recommended treatment. Efficacy and safety of antihelminthic drugs for treatment remains controversial because of theoretical concerns that they may worsen the inflammatory response to dead and dying worms. Previous clinical trials were conducted with small numbers of participants and were underpowered. Further well designed clinical trials are urgently needed.

SUMMARY

Awareness about increasing numbers of A. cantonensis eosinophilic meningitis in travelers is very important. Travelers should be advised about possible sources of infection. Diagnosis should be confirmed by antigen or antibody detection in blood or CSF. High-dose corticosteroids are the recommended treatment. The efficacy of various antihelminthic drugs is unproven. A large-scale, double-blind, randomized, controlled trial of antihelminthic drug involving antihelminthic drugs such as albendazole is necessary to prove the efficacy before formally advocating their use on a regular basis.

Dexamethasone Downregulates Expressions of 14-3-3β and γ-Isoforms in Mice with Eosinophilic Meningitis Caused by Angiostrongylus cantonensis Infection

Steroids are commonly used in patients with eosinophilic meningitis caused by A. cantonensis infections. The mechanism steroids act on eosinophilic meningitis remains unclear. In this mouse experiments, expressions of 14-3-3 isoform β and γ proteins significantly increased in the CSF 2–3 weeks after the infection, but not increasedin the dexamethasone-treated group. Expression of 14-3-3 β, γ, ɛ, and θ isoforms increased in brain meninges over the 3-week period after infection and decreased due to dexamethasone treatment. In conclusion, administration of dexamethasone in mice with eosinophilic meningitis decreased expressions of 14-3-3 isoform proteins in the CSF and in brain meninges.

Proteomic Analysis of Differentially Expressed Proteins in Intracranial Angiostrongylus cantonensis Larvae in Permissive and Non-Permissive Hosts

Angiostrongylus cantonensis infection can lead to severe neuropathological damage caused by the development of these nematodes in the central nervous system after penetrating the blood-brain barrier. They commonly cause eosinophilic meningitis or meningoencephalitis in non-permissive hosts (e.g., mice). It has been shown that differences exist in the brains of permissive and non-permissive hosts during the larval development of A. cantonensis; however, the mechanism underlying the difference is not completely understood. This study analyzed and characterized the differentially expressed proteins in the intracranial A. cantonensis larvae in rat (ILR) and mouse (ILM) brains by using proteomics. We found that 29 proteins were differentially expressed: 12 of these proteins were highly expressed in ILR, whereas the remaining 17 proteins were highly expressed in ILM. Three protein spots were homologous to the actin-2, actin-1, and disorganized muscle protein 1 (dim-1) of Caenorhabditis elegans. In addition, proteomic analyses revealed that act-1 and act-2 were up-regulated in ILM compared to ILR, whereas dim-1 was down-regulated in ILM. Annotation using gene ontology revealed that act-1, act-2, and dim-1 were mainly associated with adenosine triphosphate (ATP) catabolic processes and ATP binding. Quantitative real-time polymerase chain reaction analyses of act-1 and dim-1 using the first internal transcribed spacers of A. cantonensis 18S ribosomal RNA (rRNA) was consistent with 2-dimensional gel electrophoresis (2-DE) and the sizes of these parasites; ILR was longer and wider than ILM. These results indicate that the differentially expressed proteins dim-1 and act-1 could be related to the development and pathogenicity of A. cantonensis in different hosts.

Spleen atrophy related immune system changes attributed to infection of Angiostrongylus cantonensis in mouse model

The spleen is one of the most important peripheral immune organs, which is frequently affected in infectious diseases. Infectious diseases can induce splenic alterations including splenic atrophy and functional alteration, while splenic atrophy may in turn interferes with recovery of infectious diseases. Angiostrongyliasis is an infectious disease by Angiostrongylus cantonensis (A. cantonensis), which invade non-permissive hosts, such as humans and mice, to cause severe damage to the central nervous system (CNS) and acute inflammatory response. A. cantonensis infection-induced CNS injury has been confirmed to be due to profound immunopathology derived from peripheral immune components. However, the mechanism of immunopathology remains largely unknown. Here, we found that A. cantonensis invaded non-permissive hosts such as mice in the brain, but not in the other peripheral organs. However, this infection induced severe spleen atrophy. We further recognized that this atrophy is associated with a decrease of total splenocyte number and disruption of splenic structure due to reduced proliferation and increased apoptotosis. These also resulted in deterioration of T cell profile in the periphery with a low CD4/CD8 ratio and B/T cell ratio, and increased ratio of CD4⁺CD25⁺Foxp3⁺ Treg, CD8⁺CD28^- T, and CD38⁺T lymphocyte of spleen. Albendazole treatment can alleviate spleen atrophy and set T cell immune reconstitution in some extend. Our data showed that A. cantonensis infection can cause splenic atrophy. These results are suggested to put more emphasis to improve the function of immune system. Meanwhile, infection and treatment model will be useful to evaluate new therapeutic approaches which can prevent or reverse immunosuppression and infectious complications.

Angiostrongylus cantonensis: a review of its distribution, molecular biology and clinical significance as a human pathogen

Angiostrongylus cantonensis is a metastrongyloid nematode found widely in the Asia-Pacific region, and the aetiological agent of angiostrongyliasis; a disease characterized by eosinophilic meningitis. Rattus rats are definitive hosts of A. cantonensis, while intermediate hosts include terrestrial and aquatic molluscs. Humans are dead-end hosts that usually become infected upon ingestion of infected molluscs. A presumptive diagnosis is often made based on clinical features, a history of mollusc consumption, eosinophilic pleocytosis in cerebral spinal fluid, and advanced imaging such as computed tomography. Serological tests are available for angiostrongyliasis, though many tests are still under development. While there is no treatment consensus, therapy often includes a combination of anthelmintics and corticosteroids. Angiostrongyliasis is relatively rare, but is often associated with morbidity and sometimes mortality. Recent reports suggest the parasites' range is increasing, leading to fatalities in regions previously considered Angiostrongylus-free, and sometimes, delayed diagnosis in newly invaded regions. Increased awareness of angiostrongyliasis would facilitate rapid diagnosis and improved clinical outcomes. This paper summarizes knowledge on the parasites' life cycle, clinical aspects and epidemiology. The molecular biology of Angiostrongylus spp. is also discussed. Attention is paid to the significance of angiostrongyliasis in Australia, given the recent severe cases reported from the Sydney region.

Microglia activation: one of the checkpoints in the CNS inflammation caused by Angiostrongylus cantonensis infection in rodent model

Angiostrongylus cantonensis (A. cantonensis) is a rodent nematode. Adult worms of A. cantonensis live in the pulmonary arteries of rats; humans are non-permissive hosts like the mice. The larva cannot develop into an adult worm and only causes serious eosinophilic meningitis or meningo-encephalitis if humans or mice eat food containing larva of A. cantonensis in the third stage. The differing consequences largely depend on differing immune responses of hosts to parasite during A. cantonensis invasion and development. To further understand the reasons why mice and rats attain different outcomes in A. cantonensis infection, we used the HE staining to observe the pathological changes of infected mice and rats. In addition, we measured mRNA levels of some cytokines (IL-5, IL-6, IL-13, Eotaxin, IL-4, IL-10, TGF-β, IFN-γ, IL-17A, TNF-α, IL-1β, and iNOS) in brain tissues of mice and rats by real-time PCR. The result showed that brain inflammation in mice was more serious than in rats. Meanwhile, mRNA expression levels of IL-6, IL-1β, TNF-α, and iNOS increased after mice were infected. In contrast, mRNA levels of these cytokines in rats brain tissues decreased at post- infection 21 days. These cytokines mostly were secreted by activated microglia in central nervous system. Microglia of mice and rats were showed by Iba-1 (microglia marker) staining. In micee brains, microglia got together and had more significant activation than in rats brains. The results demonstrate that mice and rats have different CNS inflammation after infection by A. cantonensis, and it is in line with other researchers' reported findings. In conclusion, it is suggested that microglia activation is probably to be one of the most important factors in angiostrongyliasis from our study.

Dexamethasone inhibits brain apoptosis in mice with eosinophilic meningitis caused by Angiostrongylus cantonensis infection

Background

Angiostrongylus cantonensis, the rat lungworm, is the major cause of eosinophilic meningitis worldwide. Rats serve as the definitive host of the nematode, but humans can be infected incidentally, leading to eosinophilic meningitis. A previous BALB/c animal study has demonstrated increased apoptotic proteins and decreased anti-apoptotic proteins in mice infected with A. cantonensis. Steroids may be an effective treatment option for eosinophilic meningitis caused by A. cantonensis, but the involved mechanism is unclear. This study hypothesized that the beneficial effects of steroids on eosinophilic meningitis are mediated by decreased apoptosis.

Methods

In a BALB/c animal model, mice were orally infected with 50 A. cantonensis L3 via an oro-gastric tube and were sacrificed every week for 3 consecutive weeks after infection or until the end of the study. Dexamethasone was injected intra-peritoneally from the 7^th day post-infection until the end of the 21-day study. Evans blue method was used to measure changes in the blood brain barrier, while western blotting, immuno-histochemistry, and TUNEL assay were used to analyze brain homogenates expression of apoptotic and anti-apoptotic proteins.

Results

There were increased amounts of Evans blue, apoptotic proteins (caspase-3, -8, and -9 and cytochrome C), and decreased anti-apoptotic proteins (bcl-2) after 2-3 weeks of infection. Dexamethasone administration significantly decreased Evans blue extravasations and apoptotic protein expressions.

Conclusions

Apoptosis of mice brain homogenates can be repressed by dexamethasone treatment.

Dexamethasone downregulated the expression of CSF 14-3-3β protein in mice with eosinophilic meningitis caused by Angiostrongylus cantonensis infection

Angiostrongylus cantonensis is the main causative agent of human eosinophilic meningitis in Southeast Asia and the Pacific Islands. A previous study demonstrated that the 14-3-3β protein is a neuropathological marker in monitoring neuronal damage in meningitis. Steroids are commonly used in patients with eosinophilic meningitis caused by A. cantonensis infection. However, the mechanism by which steroids act in eosinophilic meningitis is unknown. We hypothesized that the beneficial effect of steroids on eosinophilic meningitis is partially mediated by the down-regulation of 14-3-3β protein expression in the cerebrospinal fluid (CSF). In this animal study, we determined the dynamic changes of 14-3-3β protein in mice with eosinophilic meningitis. The 14-3-3β protein in serum and CSF was increased in week 2 and 3 after infections. Dexamethasone administration significantly decreased the amounts of CSF 14-3-3β protein. By developing an in-house ELISA to measure 14-3-3β protein, it was found that the amounts of 14-3-3β protein in the CSF and serum increased over a three-week period after infection. There was a remarkable reduction of 14-3-3β protein in the CSF after 2 weeks of dexamethasone treatment. In conclusion, the administration of corticosteroids in mice with eosinophilic meningitis decreased the expression of 14-3-3β protein in the CSF.

Efficacy of tribendimidine against Angiostrongylus cantonensis infection in the mice

Angiostrongyliasis, also known as eosinophils meningitis, is caused by Angiostrongylus cantonensis parasites in the human central nervous system. Currently, the drug of choice for treatment of angiostrongyliasis is albendazole, but dead worm lysis causes severe inflammatory response, which leads to central nervous system damage. Tribendimidine, a broad-spectrum anti-helmintic drug developed in China, is a derivative of amidantel. This study was designed to test the efficacy of tribendimidine against A. cantonensis in mice. We treated 65 infected female BALB/c mice with tribendimidine or albendazole by oral route. We observed that tribendimidine at doses of 50, 100 and 200 mg/kg/day was effective, and the worm reduction rates were 54.8 %,77.4 %, and 100 % compared with the control group. In addition, the therapeutic effect of early tribendimidine treatment (7 days post-infection [PI]) was better than the late treatment (14 days PI), in comparison with the albendazole group (20 mg/kg/day). The index of therapeutic efficacy included body weight, neurological function, survival time, worm reduction, mRNA levels of proinflammatory cytokines in brain tissue, histopathological examination and electron microscopy scanning. The results showed that tribendimidine could kill the larvae of A. cantonensis in the mice model, and the worm's body wall was observed to be damaged. After treatment with tribendimidine, the survival conditions such as body weight and neurological function were improved, and brain inflammation was reduced in infected mice. This study showed a strong efficacy of tribendimidine against A. cantonensis and provided suitable alternative treatments to further explore its potential use in treatment of human angiostrongyliasis.

The use of albendazole and diammonium glycyrrhizinate in the treatment of eosinophilic meningitis in mice infected with Angiostrongylus cantonensis

Angiostrongylus cantonensis (A. cantonensis) infection causes eosinophilic meningitis in humans. Eosinophilia and a Th2-type immune response are the crucial immune mechanisms for eosinophilic meningitis. CD4+CD25+ regulatory T cells (Treg) are involved in the pathogenesis of A. cantonensis. Diammonium glycyrrhizinate (DG) is a compound related to glycyrrhizin (GL), a triterpene glycoside extracted from liquorice root. We investigated the curative effects and probable mechanisms of therapy involving a combination of albendazole and DG in BALB/c mice infected with A. cantonensis, and compared these with therapy involving albendazole and dexamethasone. We analysed survival time, body weight, signs, eosinophil numbers, immunoglobulin E (IgE), interleukin-5 (IL-5), and eotaxin concentrations, numbers and Foxp3 expression of CD4+CD25+ Treg, worm recovery and histopathology. The present results demonstrated that the combination of albendazole and DG could increase survival time more efficiently and relieve neurological dysfunction; decrease weight loss, eosinophil numbers, concentrations of IgE, IL-5 and eotaxin, the number and expression of Foxp3 of CD4+CD25+ Treg; and improve worm recovery and histopathology changes in treated animals, compared with the combination of albendazole and dexamethasone. The observations presented here suggest that the albendazole and dexamethasone combination could be replaced by the combination of albendazole and DG.

Curcumin alleviates eosinophilic meningitis through reduction of eosinophil count following albendazole treatment against Angiostrongylus cantonensis in mice

Angiostrongylus cantonensis (A. cantonensis) is the most common cause of parasitic eosinophilic meningitis worldwide. By using an animal model of BALB/c mice infected with A. cantonensis, previous studies indicated that the anthelmintic drug, albendazole, could kill A. cantonensis larvae and prevent further infection. However, the dead larvae will induce severe immune responses targeting at brain tissues. To alleviate the detrimental effects caused by the dead larvae, we administered curcumin, a traditional anti-inflammatory agent, as a complementary treatment in addition to albendazole therapy, to determine whether curcumin could be beneficial for treatment. The results showed that although curcumin treatment alone did not reduce worm number, combined treatment by albendazole and curcumin helped to reduce eosinophil count in the cerebrospinal fluid, better than using albendazole alone. This alleviating effect did not affect albendazole treatment alone, since histological analysis showed similar worm eradication with or without addition of curcumin. Nevertheless, curcumin treatment alone and combined albendazole-curcumin treatment did not inhibit MMP-9 expression in the brain tissue. In conclusion, curcumin, when used as a complementary treatment to albendazole, could help to alleviate eosinophilic meningitis through suppression of eosinophil count in the cerebrospinal fluid.

Efficacy of albendazole combined with a marine fungal extract (m2-9) against Angiostrongylus cantonensis-induced meningitis in mice

The pathogenesis of angiostrongyliasis, resulting from Angiostrongylus cantonensis invasion of the human central nervous system, remains elusive. Anthelmintics are usually used to kill worms, although dead worms in the brain may cause severe inflammation which will lead to central nervous system damage. Therefore, combination therapy with anthelmintics and anti-inflammatory drugs in the treatment of human angiostrongyliasis needs further study. To evaluate the efficacy of albendazole combined with a marine fungal extract (m2-9) in A. cantonensis infection, BALB/c mice infected by the third-stage larvae of A. cantonensis were divided into three groups: mice treated with albendazole or m2-9 alone or in combination from day 5 post-inoculation (PI). Several efficacy parameters were recorded, including weight change, worm recovery, neurological function, behavioural analysis, eosinophil and leucocyte counts. The results showed that combination therapy increased body weight, reduced worm burden, improved learning ability, memory and action, decreased neurological dysfunction and leucocyte response in these mice. The combination of albendazole and m2-9 treatment significantly decreased leucocyte response and increased the frequency of rearing, compared to infected mice treated with either drug alone. Therefore, m2-9 is a natural product with potentially significant therapeutic value for angiostrongyliasis and is worthy of further study.

Encephalitis caused by Angiostrongylus cantonensis after eating raw frogs mixed with wine as a health supplement

Angiostrongylus cantonensis also known as the rat lungworm, is prevalent in the Pacific Islands and southeast Asia and is the most common cause of eosinophilic meningitis in humans. Although frogs and toads are known as paratenic hosts of A. cantonensis, they are rarely reported as the infectious source of human angiostrongyliasis. We report a case of encephalitis caused by Angiostrongylus cantonensis after eating raw frogs mixed with wine as a health supplement. Prednisolone at a dose of 1 mg/kg/day was prescribed for 14 days successfully. We advise that travelers and residents of endemic areas should avoid eating raw frogs and a public caution on the danger of eating raw wild animal products or the whole animal is recommended to alleviate such accidental infection.

Efficacy of combined treatment with albendazole and baicalein against eosinophilic meningitis induced by Angiostrongylus cantonensis in mice

Angiostrongylus cantonensis infection causes eosinophilic meningitis in humans. Baicalein is a flavonoid originally isolated from the roots of Scutellaria baicalensis Georgi. In this study we evaluated the efficacy of the combination of albendazole and baicalein for treating eosinophilic meningitis in BALB/c mice. Therapeutic efficacy included the survival time, body weight, neurological function, leucocyte and eosinophil counts, eotaxin concentration, matrix metalloproteinase-9 (MMP-9) activity, larval recovery and histopathological examination. The results showed that the combination of albendazole and baicalein was more effective than either drug administered singly. Combination therapy increased the survival time, decreased body weight loss, neurological dysfunction, leucocyte response, eotaxin concentration and MMP-9 activity. Our results suggest that the combination of albendazole and baicalein may exhibit synergistic beneficial effects in the treatment of eosinophilic meningitis induced by A. cantonensis.

Angiostrongylus cantonensis: effect of combination therapy with albendazole and dexamethasone on Th cytokine gene expression in PBMC from patients with eosinophilic meningitis

To determine how combination therapy with albendazole and dexamethasone changed cytokine responses in peripheral blood mononuclear cells (PBMC) in patients with eosinophilic meningitis caused by Angiostrongylus cantonensis (EOMA), we measured mRNA levels of Th2 (IL-5, IL-4 and IL-10) and Th1 (IL-2 and IFN-gamma) cytokines with reverse transcription polymerase chain reaction (RT-PCR). Forty-three patients were divided into three groups: group 1 (pre-treatment, 13 patients), group 2 (7 days post-treatment, 14 patients), and group 3 (30 days post-treatment, 16 patients). Peripheral eosinophil counts were also measured. EOMA patients showed higher levels of Th2 cytokines, including IL-5 and IL-10, and peripheral eosinophil counts, but no changes in IL-4 or Th1 cytokines. Combination therapy reduced IL-5 mRNA expression and peripheral eosinophil counts to control levels, but increased IL-10, IL-2, and IFN-gamma mRNA expression, and did not change IL-4 levels. These data suggest that systemic Th2 cytokine responses, especially IL-5, and peripheral eosinophil counts increased in EOMA patients. Combination therapy with albendazole and dexamethasone can shift the cytokine responses from Th2 to Th1 dominance, which may be a therapeutic mechanism.