Kinetics of change in the eotaxin concentration in serum and cerebrospinal fluid of mice infected with Angiostrongylus cantonensis

Cytokines in the Brain and Neuroinflammation: We Didn’t Starve the Fire!

In spite of the brain-protecting tissues of the skull, meninges, and blood-brain barrier, some forms of injury to or infection of the CNS can give rise to cerebral cytokine production and action and result in drastic changes in brain function and behavior. Interestingly, peripheral infection-induced systemic inflammation can also be accompanied by increased cerebral cytokine production. Furthermore, it has been recently proposed that some forms of psychological stress may have similar CNS effects. Different conditions of cerebral cytokine production and action will be reviewed here against the background of neuroinflammation. Within this context, it is important to both deepen our understanding along already taken paths as well as to explore new ways in which neural functioning can be modified by cytokines. This, in turn, should enable us to put forward different modes of cerebral cytokine production and action in relation to distinct forms of neuroinflammation.

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.

Preliminary expression profile of cytokines in brain tissue of BALB/c mice with Angiostrongylus cantonensis infection

Background

Angiostrongylus cantonensis (A. cantonensis) infection can result in increased risk of eosinophilic meningitis. Accumulation of eosinophils and inflammation can result in the A. cantonensis infection playing an important role in brain tissue injury during this pathological process. However, underlying mechanisms regarding the transcriptomic responses during brain tissue injury caused by A. cantonensis infection are yet to be elucidated. This study is aimed at identifying some genomic and transcriptomic factors influencing the accumulation of eosinophils and inflammation in the mouse brain infected with A. cantonensis.

Methods

An infected mouse model was prepared based on our laboratory experimental process, and then the mouse brain RNA Libraries were constructed for deep Sequencing with Illumina Genome Analyzer. The raw data was processed with a bioinformatics’ pipeline including Refseq genes expression analysis using cufflinks, annotation and classification of RNAs, lncRNA prediction as well as analysis of co-expression network. The analysis of Refseq data provides the measure of the presence and prevalence of transcripts from known and previously unknown genes.

Results

This study showed that Cys-Cys (CC) type chemokines such as CCL2, CCL8, CCL1, CCL24, CCL11, CCL7, CCL12 and CCL5 were elevated significantly at the late phase of infection. The up-regulation of CCL2 indicated that the worm of A. cantonensis had migrated into the mouse brain at an early infection phase. CCL2 could be induced in the brain injury during migration and CCL2 might play a major role in the neuropathic pain caused by A. cantonensis infection. The up-regulated expression of IL-4, IL-5, IL-10, and IL-13 showed Th2 cell predominance in immunopathological reactions at late infection phase in response to infection by A. cantonensis. These different cytokines can modulate and inhibit each other and function as a network with the specific potential to drive brain eosinophilic inflammation. The increase of ATF-3 expression at 21 dpi suggested the injury of neuronal cells at late phase of infection. 1217 new potential lncRNA were candidates of interest for further research.

Conclusions

These cytokine networks play an important role in the development of central nervous system inflammation caused by A. cantonensis infection.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-015-0939-6) contains supplementary material, which is available to authorized users.

AcCystatin, an immunoregulatory molecule from Angiostrongylus cantonensis, ameliorates the asthmatic response in an aluminium hydroxide/ovalbumin-induced rat model of asthma

Epidemiological surveys have demonstrated that helminth infections are negatively related to atopic diseases, including asthma. Defining and characterising specific helminth molecules that have excellent immunomodulatory capacities as potential therapeutics for the treatment or prophylaxis of allergic manifestations are of great interest. AcCystatin, a cystatin protease inhibitor of Angiostrongylus cantonensis, is a homologue of other nematode cystatins with immunoregulatory properties. Here, we aim to determine the effects of AcCystatin on an ovalbumin/aluminium hydroxide (OVA/Al[OH]3)-induced rat model of asthma. Wistar rats were randomly divided into four groups, including a control group, an OVA/Al[OH]3-induced asthma group, a group receiving AcCystatin immunisation prior to OVA/Al[OH]3-induced asthma and a group receiving AcCystatin treatment after OVA/Al[OH]3-induced asthma. The numbers of eosinophils, basophils, neutrophils, lymphocytes and monocytes in the peripheral blood and of eosinophils in the bronchoalveolar lavage fluid (BALF) were counted for each animal. The expression levels of the cytokines interferon-γ, interleukin (IL) 4, IL-5, IL-6, IL-10, IL17A and tumour necrosis factor receptor-α in BALF, of OVA-specific immunoglobulin E in BALF and serum and of the chemokines eotaxin-1, eotaxin-2, eotaxin-3, MCP-1 and MCP-3 in lung tissue were measured. In addition, the degree of peribronchial and perivascular inflammation and the intensity of goblet cell metaplasia were qualitatively evaluated. The sensitised/challenged rats developed an extensive cell inflammatory response of the airways. AcCystatin administration significantly reduced the cellular infiltrate in the perivascular and peribronchial lung tissues and reduced both goblet mucous production and eosinophil infiltration. The rats that were treated with AcCystatin before or after sensitisation with OVA showed significant decreases in eotaxin-1, eotaxin-3 and MCP-1 expression in the lung tissue. The production of IL-4, IL-5, IL-6 and IL-17A and of OVA-specific IgE antibodies was also significantly reduced in AcCystatin-treated rats compared with untreated asthmatic rats. The AcCystatin treatment was associated with a significant increase in IL-10 levels. Our present findings provide the first demonstration that AcCystatin is an effective agent in the prevention and treatment of the airway inflammation associated with asthma.

Eosinophil chemotactic chemokine profilings of the brain from permissive and non-permissive hosts infected with Angiostrongylus cantonenis

Angiostrongylus cantonensis invasion primarily cause heavy or negligible eosinophic meningitis and meningoencephalitis in the brain of non-permissive and permissive hosts, respectively. Chemokines are effective leukocyte chemoattractants and may play an essential role in mediating eosinophil recruitment in angiostrongyliasis. In the present study, we comparatively analyzed changes in peripheral and CSF eosinophil counts, and expression profilings of eosinophil chemotactic chemokines in A. cantonensis-infected mice (CCL 2, CCL 3, CCL 5, CCL7, CCL 8, CCL 11, CCL 12, CCL 24 and CCL 28) and rats (CCL 2, CCL 3, CCL 5, CCL 11 and CCL 12) were explored at 1, 2, 5, 7, 14, and 21 days post-infection (dpi), and found significantly elevated numbers of eosinophils in blood and CSF of infected mice after 5 dpi, while significant increases of eosinophils in blood and CSF of infected rats were detected after 5 and 14 dpi, respectively. The kinetics of CSF eosinophilia is basically correlated with eosinophil chemotactic chemokine levels in brains of infected animals at each time point. Interestingly, less CSF eosinophils and infiltration of eosinophils in the brain were noted in rats than in mice, though extremely high levels of chemokines were also maintained in the brains of infected rats at 21 dpi. We further described CCL 11 (eotaxin), a previously reported eosinophil chemotactic factor in angiostrongyliasis, was mainly released from activated microglia in mice and rats infected with A. cantonensis. Our results reveal that different complicated chemokine networks mediate recruitment of eosinophils between permissive and non-permissive hosts during A. cantonensis infection, and provide promising targets for clinical treatment of angiostrongyliasis.

Sequence analysis in partial genes of five isolates of Angiostrongylus cantonensis from Taiwan and biological comparison in infectivity and pathogenicity between two strains

Angiostrongylus cantonensis is the most common infectious agent causing eosinophilic meningitis and is present in Taiwan, Thailand and the Pacific islands. Clinical symptoms vary within different endemic regions, and their severity is probably dependent on the number of ingested parasites and the diversity among strains. The experimentally definitive host is the rat, and non-permissive hosts are certain mammals such as humans and mice. In this study, the partial gene sequences of two A. cantonensis strains isolated from five different regions in Taiwan were selected and molecularly analyzed. The internal transcribed spacer gene and cytochrome-c oxidase subunit I gene sequences of the Hualien (H) strain of A. cantonensis differed from those of the Pingtung (P) strain and the other three strains by 19% and 11%, respectively. We analyzed the infectivity, fecundity, and development of the H and P strain in rats and host pathogenicity in mice inoculated with both strains. The number of the emerged first-stage larvae, adult recovery, and average length of adults in Sprague-Dawley rats significantly differed between rats inoculated with the H and P strain. Young adult recovery, average length of young adults, eosinophil counts in the cerebrospinal fluid (CSF), glutathione peroxidase concentration, levels of reactive oxygen species as well as malondialdehyde concentration in the CSF, and the survival of mice significantly differed between BALB/c mice inoculated with the H and P strain. The H strain of A. cantonensis had lower infectivity, delayed fecundity, and poor development in rats, and caused milder pathology and lower mortality in mice than the P strain. These data clearly indicate that the H strain of A. cantonensis is a pathogenically distinct strain with lower infectivity to its definitive host, and causing mild pathogenic symptoms to its non-permissive host.

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.

Differences of larval development and pathological changes in permissive and nonpermissive rodent hosts for Angiostrongylus cantonensis infection

Angiostrongylus cantonensis is a neurotrophic and pulmonary parasite which causes severe neuropathological damages by invading and developing in the central nervous system (CNS). Nonpermissive host with A. cantonensis infection appeared to have more serious neurologic symptoms, and there is still not much knowledge about the host-parasite interrelationship in different hosts. We investigated and compared the larval size, recovery rate, distribution, and the severity of pathologic injuries in the CNS of both permissive host (e.g., rats) and nonpermissive hosts (e.g., mice). In present study, mice infected with A. cantonensis showed higher worm recovery rate in late-stage infection and smaller size of intracranial larvae as compared to the infected rats. Intracranial larvae mainly aggregated on cerebral surface of infected rats but on surface of cerebellum and brainstem in mice. Hemorrhage and tissue edema on brain surface caused by worm migration appeared earlier and severer in infected mice than in rats. Neuropathological examination revealed that injuries induced by A. cantonensis in brain parenchyma included hemorrhage, vascular dilatation, focal necrosis with neuronal loss, and infiltration of inflammatory cells. In the comparison of these pathological changes in rats and mice, infected mice suffered more serious injuries and provoked more intense inflammatory response as compared to infected rats. All these morphological evidences indicate that larval development was retardant in the CNS of nonpermissive host, and nonpermissive host experienced more serious pathological injuries than permissive host. It implies that the difference in innate immune response to parasite infection attribute to host specificity.

Monoclonal antibody 12D5 inhibits eosinophil infiltration in the brain of Angiostrongylus cantonensis-infected BALB/c mice

Each of BALB/c mice was infected with 50 Angiostrongylus cantonensis larvae. One group of mice received an intraperitoneal injection of 50 μg 12D5 monoclonal antibody (mAb) against a 98 kDa antigen of adult worms at 10 days post-infection (dpi), with a booster injection of 25 μg at 12 dpi. Five mice from each group were sacrificed at 14 dpi for pathological examination and RNA extraction. The infiltration of eosinophils and severity of eosinophilic meningitis were reduced in 12D5 mAb-treated mice compared with the infected mice without 12D5 treatment. The levels of eotaxin mRNA expression in spleen significantly increased and the expression of the Th2-type cytokine IL-5 significantly decreased. However, the expression of IL-4 was not changed. 12D5 mAb can observably enhance the survival rate of infected mice and reduce symptoms of angiostrongyliasis. A. cantonensis infection is a major cause of eosinophilic meningoencephalitis. The results of this study could be helpful for the development of treatment of human angiostrongylosis.

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.

Kinetic change of oxidative stress in cerebrospinal fluid of mice infected with Angiostrongylus cantonensis

The cerebrospinal fluid (CSF) of C57BL/6 mice infected with Angiostrongylus cantonensis was examined for kinetic changes in oxidative stress parameters, including reactive oxygen species (ROS), superoxide dismutase (SOD), catalase, malondialdehyde (MDA), 8-isoprostane, and 8-hydroxy-2'-deoxyguanosine (8-OHdG). The ROS increased gradually in the early stage of infection. During days 12-30 post-infection, the infected mice revealed ROS levels significantly higher than that in uninfected controls (P < 0.001). The ROS levels peaked at day 24 and then returned to that observed in uninfected controls at day 45 post-infection. The kinetics of MDA, 8-isoprostane, and 8-OHdG concentration changes observed in the CSF of the infected mice corresponded with kinetic changes in ROS levels. Thus, the excess ROS caused lipid peroxidation and DNA damage to cells in the central nervous system (CNS) of mice infected with A. cantonensis despite the increased antioxidant SOD and catalase enzyme activities during post-infection days 12-30. The oxidative stress in the CNS of C57BL/6 mice was apparently increased by diseases associated with A. cantonensis infection.

Oxidative stress in mice infected with Angiostrongylus cantonensis coincides with enhanced glutathione-dependent enzymes activity

This study aimed to estimate reactive oxygen species (ROS) production, antioxidants activity, and biomarkers level of oxidative damage to protein and DNA in the cerebrospinal fluid (CSF) of C57BL/6 mice infected with Angiostrongylus cantonensis. The mean ROS concentration in the CSF of infected mice increased gradually, and the increase in ROS in CSF became statistical significance at days 12-30 post-infection compared to that before infection (P<0.001), and then ROS returned to normal level at day 45 after infection. In parallel with the increase in ROS in the CSF, infected mice showed similar of changes in reduced glutathione (GSH), glutathione reductase (GR), glutathione peroxidase (GPx), and glutathione S-transferase (GST) as that in ROS in the CSF. GSH, GR, GPx, and GST in the CSF of infected mice were all significantly higher than they were before infection during days 12-30 post-infection. However, protein carbonyl content and 8-hydroxy-2'-deoxyguanosine, biomarkers of oxidative damage to protein and DNA, respectively, were also significantly higher in the CSF of infected mice during this period. These results suggest that oxidative stress occur in the cells of central nervous system of mice infected with A. cantonensis during days 12-30 after infection due to ROS overproduction in CSF despite the increase in antioxidants during this period.

Anti-CCR3 monoclonal antibody inhibits eosinophil infiltration in Angiostrongylus cantonensis-infected ICR mice

ICR mice were each infected with 35 Angiostrongylus cantonensis larvae. One group of mice received an intraperitoneal injection of anti-CCR3 monoclonal antibody (mAb) (50 microg) at 10 days post-infection (dpi), while another similarly-treated group also received a booster injection (25 microg) at 12 dpi. All the mice were sacrificed at 14 dpi for pathological examination, enzyme-linked immunosorbent assay analysis and RNA extraction. The infiltration of eosinophils and the severity of eosinophilic meningitis were reduced in both the mAb-treated groups, relative to infected but untreated animals. The levels of CCL11 (eotaxin) in the peripheral circulation and the expression of the Th2-type cytokine interleukin-5 in the brains were significantly reduced. A. cantonensis infection is the major cause of eosinophilic meningoencephalitis in Taiwan, and the results of this study could be useful for the development of strategies to reduce the neurological damage caused by this infection.

Cerebrospinal fluid eotaxin and eotaxin-2 levels in human eosinophilic meningitis associated with angiostrongyliasis

Eosinophilic meningitis associated angiostrongyliasis (EOMA) is a harmful disease of the brain and spinal cord caused by a parasitic helminth, Angiostrongylus cantonensis, presenting with severe headaches and cerebrospinal fluid (CSF) eosinophilia. However, the immunologic pathophysiology especially in relation to the eosinophilic inflammation is still unknown. We measured the CSF concentrations of eotaxin and eotaxin-2 of 30 patients and 10 controls. The CSF eotaxin and eotaxin-2 levels of the EOMA patients were significantly higher than those of the controls (p<0.001). The positive detection values were 83.3% (25/30) and 93.3% (28/30) for eotaxin and eotaxin-2, respectively. CSF eotaxin-2 levels also correlated with CSF eosinophilia (p=0.002). These results might indicate that the recruitment of eosinophils to the brain and spinal cord in EOMA patients could be related to elevated eotaxin-2 levels.

The role of Th2 cytokines, chemokines and parasite products in eosinophil recruitment to the gastrointestinal mucosa during helminth infection

Trichinella spiralis and Trichuris muris are nematode parasites of the mouse, dwelling in the small and large intestines, respectively: worm expulsion requires development of a Th2 immune response. The chemokine CCL11 is agonist for the chemokine receptor CCR3 and acts in synergy with IL-5 to recruit eosinophils to inflammatory sites. The role of CCL11 in gastrointestinal helminth infection has not been previously studied. We challenged wild-type (WT) BALB/c, CCL11 single knockout (SKO) and CCL11 IL-5 double knockout (DKO) mice with either T. spiralis muscle larvae or T. muris eggs in order to examine eosinophil recruitment to the small and large intestine during helminth infection. A peripheral eosinophilia was seen in WT and SKO mice during T. spiralis infection but not with T. muris. Gastrointestinal eosinophilia was markedly reduced but not ablated in SKO mice -- and negligible in DKO mice -- infected with either nematode. The residual eosinophilia and up-regulation of CCL24 mRNA in the gastrointestinal tract of SKO mice infected with either nematode, together with the presence of an eosinophil-active factor in T. spiralis and T. muris products, suggest that CCL11 is the salient but not the sole eosinophil chemoattractant of biological significance during gastrointestinal helminth infection.

Blood-brain barrier dysfunction occurring in mice infected with Angiostrongylus cantonensis

Several indices were used to assess whether blood-brain barrier (BBB) damage occurs in neurological disorders. Dysfunction of the BBB was surmised to be involved in the pathological changes of eosinophilic meningitis caused by the infection of Angiostrongylus cantonensis. The mean concentration of protein and albumin in the cerebrospinal fluid (CSF) of infected mice gradually increased from days 0 to 18 after infection and then rapidly increased 21 days after infection. The concentrations of protein and albumin in the CSF of infected mice 15 days after infection were all significantly higher than those in uninfected mice (all P-values at least <0.05). Parallel with the increase in protein and albumin in the CSF, infected mice showed a gradual increase in their CSF/serum protein and albumin ratios. The increase became significant at days 21 and 18 after infection, respectively (P<0.01 and P<0.05, respectively). The higher the worm counts in the brain, the higher the CSF/serum albumin ratio was observed in infected mice at day 21 after infection (P<0.001). In addition, the ratios of the CSF/serum albumin were positively correlated with the worm counts in the brain (P<0.001). The total leukocyte and eosinophil counts were also positively correlated with ratios of CSF/serum albumin (P<0.01). The amount of Evans blue in the brain of mice 21 days after infection from peripheral blood via BBB became significantly increased than those in uninfected mice (P<0.001). Thus, the evidence of high concentrations of protein and albumin, high leukocyte counts in CSF, high ratio of CSF/serum protein and albumin, and high permeability of BBB show that dysfunction of the BBB occurred in mice infected with A. cantonensis.