Angiostrongylus cantonensis: role of eosinophils in the neurotoxic syndrome (Gordon-like phenomenon)

Magnetic resonance imaging in dogs with neuroangiostrongyliasis (rat lungworm disease)

The magnetic resonance imaging (MRI) appearance of the brain and spinal cord in humans with neuroangiostrongyliasis (NA) due to Angiostrongylus cantonensis infection has been well reported. Equivalent studies in animals are lacking. This case series describes clinical and MRI findings in 11 dogs with presumptively or definitively diagnosed NA. MRI of the brain and/or spinal cord was performed using high-field (1.5 T) or low-field (0.25 T) scanners using various combinations of transverse, sagittal, dorsal and three-dimensional (3D) T1-weighted (T1W), transverse, sagittal and dorsal T2-weighted (T2W), T2W fluid-attenuated inversion recovery (FLAIR) and T2*-weighted (T2*W) gradient echo (GRE), dorsal T2W short tau inversion recovery (STIR) and post-gadolinium transverse, sagittal, dorsal and 3D T1W and transverse T2W FLAIR sequences. In 4/6 cases where the brain was imaged, changes consistent with diffuse meningoencephalitis were observed. Evidence of meningeal involvement was evident even when not clinically apparent. The spinal cord was imaged in 9 dogs, with evidence of meningitis and myelitis detected in regions consistent with the observed neuroanatomical localization. Pathognomonic changes of neural larva migrans, as described in some human patients with NA, were not detected. NA should be considered in the differential diagnosis of dogs with MRI evidence of focal or diffuse meningitis, myelitis and/or encephalitis, especially in areas where A. cantonensis is endemic. If not precluded by imaging findings suggestive of brain herniation, cerebrospinal fluid (CSF) collection for cytology, fluid analysis, real-time polymerase chain reaction (qPCR) and enzyme-linked immunosorbent assay (ELISA) testing should be considered mandatory in such cases after the MRI studies.

Neuronal Apoptosis: Pathological Basis of Behavioral Dysfunctions Induced by Angiostrongylus cantonensis in Rodents Model

Angiostrongylus cantonensis invades the central nervous system (CNS) of humans to induce eosinophilic meningitis and meningoencephalitis and leads to persistent headache, cognitive dysfunction, and ataxic gait. Infected mice (nonpermissive host), admittedly, suffer more serious pathological injuries than rats (permissive host). However, the pathological basis of these manifestations is incompletely elucidated. In this study, the behavioral test, histological and immunohistochemical techniques, and analysis of apoptotic gene expression, especially caspase-3, were conducted. The movement and motor coordination were investigated at week 2 post infection (PI) and week 3 PI in mice and rats, respectively. The cognitive impairs could be found in mice at week 2 PI but not in rats. The plaque-like lesion, perivascular cuffing of inflammatory cells, and dilated vessels within the cerebral cortex and hippocampus were more serious in mice than in rats at week 3 PI. Transcriptomic analysis showed activated extrinsic apoptotic pathway through increased expression of TNFR1 and caspase-8 in mice CNS. Immunohistochemical and double-labeling for NeuN and caspase-3 indicated the dramatically increased expression of caspase-3 in neuron of the cerebral cortex and hippocampus in mice but not in rats. Furthermore, western-blotting results showed high expression of cleaved caspase-3 proteins in mice but relatively low expression in rats. Thus, extrinsic apoptotic pathway participated in neuronal apoptosis might be the pathological basis of distinct behavioral dysfunctions in rodents with A. cantonensis infection. It provides the evidences of a primary molecular mechanism for the behavioral dysfunction and paves the ways to clinical diagnosis and therapy for A. cantonensis infection.

Comparative pathogenesis of eosinophilic meningitis caused by Angiostrongylus mackerrasae and Angiostrongylus cantonensis in murine and guinea pig models of human infection

This study investigated comparatively the pathogenicity of experimental infection of mice and guinea pigs, with Angiostrongylus mackerrasae and the closely related species A. cantonensis. Time course analyses showed that A. mackerrasae causes eosinophilic meningitis in these hosts, which suggests that the species has the potential to cause meningitis in humans and domestic animals. Both A. mackerrasae and the genetically similar A. cantonensis caused eosinophilic meningitis in mice at two time points of 14 and 21 days post infection (dpi). The brain lesions in mice infected with A. mackerrasae were more granulomatous in nature and the parasites were more likely to appear degenerate compared with lesions caused by A. cantonensis. This may indicate that the mouse immune system eliminates A. mackerrasae infection more effectively. The immunologic responses of mice infected with the two Angiostrongylus species was compared by assessing ex vivo stimulated spleen derived T cells and cytokines including interferon-gamma, interleukin 4 and interleukin 17 on 14 and 21 dpi. The results were similar for mice infected with A. cantonensis and A. mackerrasae. Serum from the infected animals with either A. cantonensis or A. mackerrasae recognized total soluble antigen of A. cantonensis female worms on Western blot.

MicroRNA expressions associated with eosinophilic meningitis caused by Angiostrongylus cantonensis infection in a mouse model

Angiostrongylus cantonensis (A. cantonensis) infection is the major cause of eosinophilic meningitis (EM). Severe cases or infant and child cases have poor prognosis. MicroRNAs (miRNAs) play important roles in inflammation; however, little is known about the roles in brain inflammation caused by A. cantonensis. In this study, Illumina deep sequencing and bioinformatics were used to determine the abundance and differential expression of miRNAs in the brain tissues of a mouse model. A total of 648 conserved miRNAs were identified, 157 of which were significantly differentially expressed between infected mice and normal mice. The five most fold-changed miRNAs were miR-511-5p, miR-511-3p, miR-223-3p, miR-155-5p and miR-206-3p. These expressions of miR-511, miR-223, miR-155, miR-206, miR-142 and miR-21a were validated by quantitative reverse transcription polymerase chain reaction (RT-PCR). The analysis of these miRNAs showed that miR-511-3p was more abundant than the miR-511-5p strand, and increased to a peak in 21 days after A. cantonensis infection, miR-223 might be a potential indicator of disease severity and the upregulation of miR-155-5p after stimulation with the somatic antigen of phase IV A. cantonensis implied its involvement in the central nervous system (CNS) inflammation induced by A. cantonensis infection. These observations suggest that miRNAs may play important roles in the regulation of EM caused by A. cantonensis infection.

Anti-ST2 monoclonal antibody inhibits eosinophil infiltration in Angiostrongylus cantonensis-infected mice

BACKGROUND/PURPOSE

Interleukin-33 (IL-33) could play an important role in the pathogenesis of angiostrongylosis. However, the role of IL-33/ST2 pathway in this parasitic infection is uncertain.

METHODS

C57BL/six mice were each infected with 35 Angiostrongylus cantonensis larvae. One group of mice received an intraperitoneal injection of anti-ST2 monoclonal antibody (mAb; 50 μg) 3 days postinfection and subsequent booster shots of the same dose at 5-day intervals. Blood samples from each group were collected every week for assays.

RESULTS

The level of IL-5 significantly decreased in the mAb-treated group, and the infiltration of eosinophils in the meninges was also significantly reduced.

CONCLUSION

The IL-33/ST2 axis may play a crucial role in the pathogenesis of angiostrongylosis and the results of this study could be useful for the development of strategies to reduce the neurological damage caused by this parasitic infection.

A RAB family antigen of Angiostrongylus cantonensis induces a Th1-type immune response in vitro and in vivo

A cDNA library was constructed from an Angiostrongylus cantonensis young adult and the encoded proteins were expressed in Escherichia coli. One reactive antigen, a RAB-2 protein, was selected using an immunoscreening technique. The expression of the Th1-type cytokine IFN-γ was elicited in mouse splenic cells that were co-cultured with the recombinant RAB-2 protein and in the sera of mice that were immunised with this protein and adjuvant (50 μg at 2-week intervals). In the A. cantonensis-infected groups, the mice were orally infected with 35 infective larvae, and a subset of the infected mice were immunised with the recombinant RAB-2 protein in adjuvant. Serum samples were collected every week for ELISA, and the pathological examinations were performed at 14 days post infection (dpi). An increase in IFN-γ expression was noted in the blood, and the brain sections revealed moderate eosinophilic meningitis in the immunised mice. The RAB-2 antigen of A. cantonensis induced a Th1-type immune response both in vitro and in vivo.

Alteration of T cell subtypes in spleen and antibodies of serum in mice infected with Angiostrongylus cantonensis

The immune responses of Angiostrongylus cantonensis infection are closely relevant to the host's self-protection and the nematode's pathogenesis. In the present study, BALB/c mice were randomly divided into uninfected control group, infection group 1, and infection group 2. The infection group 1 and infection group 2 were infected with 20 and 40 third-stage larvae of A. cantonensis per mouse, respectively. The splenocytes from the mice were collected and cultured on the 19th and 25th days post-infection; the subtypes of T cells in splenocytes were detected by flow cytometry with fluorescence staining method, and the cytokines in cultured supernatants of splenocytes were assayed by the method of ELISA. The specific IgG and IgE antibodies in sera of the mice were periodically detected by ELISA. The results showed that the percentages of CD4(+) and CD4(+) IL-4(+) T cells in splenocytes of infected mice were much higher (P < 0.05) than those in control mice; however, the percentages of CD4(+) IL-17(+) and CD4(+) IFN-γ(+) T cell were much lower(P < 0.01) after the infection. The levels of CD8(+) T cells in infected mice also rose, but differences between control mice and infected mice were not significant. In comparison with control mice, the concentration of IL-4 in the cultured supernatants of splenocytes in infected mice increased significantly (P < 0.05), but that of IL-17 decreased significantly (P < 0.01). In addition, the number of larvae infected and days after infection may influence levels of the T cell subtypes and the cytokines in spleen, too (P > 0.05). On humoral immunity, the levels of specific IgG antibodies in sera rose a bit at the fifth day post-infection, and reached a peak at the 20th day post-infection; the specific IgE antibodies gradually heightened during first 10 days post-infection; then, it showed a downward trend during the 15th to 25th days post-infection. It is evident that the percentages of CD4(+) T lymphocytes of spleen in the mice infected with A. cantonensis markedly increase and polarize to Th2 phenotypes, and the function of Th17 cells is inhibited. In addition, the elevation of specific IgG antibodies in sera of the infected mice is more significant than that of specific IgE antibodies.

Granulocytes in helminth infection -- who is calling the shots?

Helminths are parasitic organisms that can be broadly described as “worms” due to their elongated body plan, but which otherwise differ in shape, development, migratory routes and the predilection site of the adults and larvae. They are divided into three major groups: trematodes (flukes), which are leaf-shaped, hermaphroditic (except for blood flukes) flatworms with oral and ventral suckers; cestodes (tapeworms), which are segmented, hermaphroditic flatworms that inhabit the intestinal lumen; and nematodes (roundworms), which are dioecious, cylindrical parasites that inhabit intestinal and peripheral tissue sites. Helminths exhibit a sublime co-evolution with the host´s immune system that has enabled them to successfully colonize almost all multicellular species present in every geographical environment, including over two billion humans. In the face of this challenge, the host immune system has evolved to strike a delicate balance between attempts to neutralize the infectious assault versus limitation of damage to host tissues. Among the most important cell types during helminthic invasion are granulocytes: eosinophils, neutrophils and basophils. Depending on the specific context, these leukocytes may have pivotal roles in host protection, immunopathology, or facilitation of helminth establishment. This review provides an overview of the function of granulocytes in helminthic infections.

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.

Twenty two cases of canine neural angiostrongylosis in eastern Australia (2002-2005) and a review of the literature

Cases of canine neural angiostrongylosis (NA) with cerebrospinal fluid (CSF) evaluations in the peer-reviewed literature were tabulated. All cases were from Australia. A retrospective cohort of 59 dogs was contrasted with a series of 22 new cases where NA was diagnosed by the presence of both eosinophilic pleocytosis and anti-Angiostrongylus cantonensis immunloglobulins (IgG) in CSF, determined by ELISA or Western blot. Both cohorts were drawn from south east Queensland and Sydney. The retrospective cohort comprised mostly pups presented for hind limb weakness with hyperaesthesia, a mixture of upper motor neurone (UMN) and lower motor neurone (LMN) signs in the hind limbs and urinary incontinence. Signs were attributed to larval migration through peripheral nerves, nerve roots, spinal cord and brain associated with an ascending eosinophilic meningo-encephomyelitis. The contemporary cohort consisted of a mixture of pups, young adult and mature dogs, with a wider range of signs including (i) paraparesis/proprioceptive ataxia (ii) lumbar and tail base hyperaesthesia, (iii) multi-focal central nervous system dysfunction, or (iv) focal disease with neck pain, cranial neuropathy and altered mentation. Cases were seen throughout the year, most between April and July (inclusive). There was a preponderance of large breeds. Often littermates, or multiple animals from the same kennel, were affected simultaneously or sequentially. A presumptive diagnosis was based on consistent signs, proximity to rats, ingestion/chewing of slugs or snails and eosinophilic pleocytosis. NA was diagnosed by demonstrating anti-A. cantonensis IgG in CSF. Detecting anti-A. cantonensis IgG in serum was unhelpful because many normal dogs (20/21 pound dogs; 8/22 of a hospital population) had such antibodies, often at substantial titres. Most NA cases in the contemporary series (19/22) and many pups (16/38) in the retrospective cohort were managed successfully using high doses of prednisolone and opioids. Treatment often included antibiotics administered in case protozoan encephalomyelitis or translocated bacterial meningitis was present. Supportive measures included bladder care and physiotherapy. Several dogs were left with permanent neural deficits. Dogs are an important sentinel species for NA. Human cases and numerous cases in tawny frogmouths were reported from the same regions as affected dogs over the study period.

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.

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.

Reibergram of intrathecal synthesis of C4 in patients with eosinophilic meningitis caused by Angiostrongylus cantonensis

Angiostrongylus cantonensis produces eosinophilic meningitis in humans and is endemic in Thailand, Taiwan, China, and the Caribbean region. During infection with this parasite, it is important to know if the complement system may be activated by the classical or lectin pathway. Cerebrospinal fluid and serum samples from 20 patients with meningitic angiostrongyliasis were used to quantify C4 levels and albumin. Results were plotted on a C4 CSF/serum quotient diagram or Reibergram. Twelve patients showed intrathecal synthesis of C4. Antibody-dependent complement cytotoxicity should be considered as a possible mechanism that destroys third-stage larvae of this helminth in cerebrospinal fluid of affected patients.

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.

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.

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.

Angiostrongylus cantonensis: apoptosis of inflammatory cells induced by treatment with mebendazole or/and interleukin 12 in mice

Angiostrongylus cantonensis is the major cause of human eosinophilic meningoencephalitis. ICR mice were infected orally with 35 infective larvae and sacrificed at 4-14 days, 25 days or 32 days post infection (dpi) for pathological and immunocytochemical examinations. In the non-treated group, no apoptosis signal was found in the meninges or parenchyma of the brains (4-14 dpi). Only a few apoptotic cells were noticed at 25 dpi (3%) and 32 dpi (10%). In the groups, the animals were given a single dose of mebendazole (20 mg/kg, per os at various times) or injections of interleukin 12 (IL-12) (10 ng/daily, intraperitoneally), all the animals were sacrificed at 14 dpi; the number of apoptotic cells was increased (17-21%). In the group that received a single dose of mebendazole (4 dpi) in combination with IL-12 injections (4-13 dpi), mild meningitis was observed, and most of the infiltrated inflammatory cells were in the apoptotic program (55%). Taken together, apoptosis of the inflammatory cells (most were eosinophils) could be induced when the infected mice were treated with mebendazole or/and IL-12.

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.

IgG1,IgG2 and IgE intrathecal synthesis in Angiostrongylus cantonensis meningoencephalitis

INTRODUCTION

Angiostrongylus cantonensis meningoencephalitis is an emergent zoonotic disease in the Caribbean basin, characterized by the presence of eosinophils and third stage larva of the helmint.

OBJECTIVE

To analyze the IgG subclasses and IgE intrathecal synthesis patterns obtained by reibergrams in pediatric patients suffering from eosinophilic meningoencephalitis due to A. cantonensis.

PATIENTS AND METHODS

20 pediatric patients with the disease were studied. During the first diagnostic lumbar puncture an eosinophilic pleocytosis was found. Simultaneously a serum sample was taken. Eight days later, a second lumbar and venous puncture was performed. IgA, IgM, IgG, albumin in serum and cerebrospinal fluid samples were quantified by immunodiffusion in addition to a differential cell count in cerebrospinal fluid. IgG subclasses were quantified in 10 patients by immunodiffusion and IgE in four patients by nephelometry.

RESULTS

During the first diagnostic lumbar puncture, all the cases had a blood-cerebrospinal fluid barrier dysfunction with absence of immunoglobulins intrathecal synthesis, a mean of 450 cells/mul and an average of 48% of eosinophils. In the second lumbar puncture 40% of the patients had a dysfunction of the blood-cerebrospinal fluid barrier and an intrathecal synthesis pattern of IgA+IgM+IgG in 50% of the patients. Eight patients had an intrathecal IgA+IgG class response. The synthesis pattern of IgG subclasses was IgG1+IgG2 in six patients, IgG1+IgG2+IgG3 in one patient, IgG1+IgG2+IgG4 in one more patient. Two patients from the second lumbar puncture remained without intrathecal synthesis. IgE intrathecal synthesis was observed in the four analyzed patients in the first diagnostic lumbar puncture.

CONCLUSIONS

The IgG1+IgG2 and IgE intrathecal synthesis pattern demonstrated the complexity of the antigenic mosaic of the helmint and it can contribute to diagnosis of eosinophilic meningoencephalitis due to A. cantonensis.

The role of eosinophils in Angiostrongylus cantonensis infection

Angiostrongylus cantonensis is the causative agent of human eosinophilic meningoencephalitis in the Pacific Islands and Southeast Asia. Prominent eosinophilia in the cerebrospinal fluid (CSF) of the patients has been used as one of the diagnostic criteria for the disease but the role(s) of the CSF eosinophils has remained to be elucidated. In this article, Kentaro Yoshimura, Hiroko Sugaya and Kazuto Ishido discuss the involvement of CSF eosinophils in the killing of intracranial worms and the damage of the central nervous system of the hosts, and consider why eosinophils in A. cantonensis infection play a more important role in nonpermissive hosts (including humans) than in the permissive rat host.

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

The kinetics of changes in the eotaxin concentration in the serum and cerebrospinal fluid (CSF) of BALB/c mice after infection with Angiostrongylus cantonensis and the correlation between the concentration of eotaxin and worm recovery were investigated. The mean concentration of eotaxin in serum of infected mice gradually increased from 46.3+/-6.5 pg/ml at week 0 to 104.9+/-44.8 pg/ml at week 3 after infection, while the mean eotaxin level in the CSF of infected mice rapidly increased from 18.7+/-2.1 pg/ml to 193.2+/-23.6 pg/ml 1 week after infection and then increased further to 507.8+/-167.9 pg/ml at week 3. The concentrations of eotaxin in the CSF of infected mice each week after infection were all significantly higher than those in serum ( P<0.0001). In parallel with the increase in eotaxin in the CSF, infected mice showed gradual increases in CSF eosinophilia and a reduction in intracranial worm recovery. The concentration of eotaxin in CSF was higher in infected mice with more worms in the brain, except when the number of worms in the brain was >30. In addition, when the worm counts in the brains of infected mice were <30, eotaxin concentrations in the CSF were positively correlated with worm counts in the brain ( P<0.001). Thus, the release of eotaxin in the CSF of mice infected with A. cantonensis observed in this study was time dependent and worm-load dependent, and in parallel with the increase in eotaxin in the CSF, and gradual decreases in worm counts in the brains of infected mice.

Combined treatment with interleukin-12 and mebendazole lessens the severity of experimental eosinophilic meningitis caused by Angiostrongylus cantonensis in ICR mice

Angiostrongylus cantonensis is the major cause of eosinophilic meningoencephalitis cases in Taiwan. Mice were orally infected with 35 infective larvae. One group of mice were given a single dose of mebendazole (20 mg/kg of body weight) per os at various times and examined at 14 days postinfection (dpi) for worm recovery rate and pathological studies. A 94 to 97% reduction in worm recovery was observed when medication was given at 4 to 5 dpi. Sections of the brains revealed that untreated infected mice developed typical severe eosinophilic meningoencephalitis. Meninges of these mice were thickened by massive infiltration of eosinophils, whereas only moderate pathological change was observed in the brains of mice that were treated with mebendazole at 4 dpi. Infected mice that received daily injections of 10 ng of interleukin-12 (IL-12) only for various numbers of days also exhibited moderate pathological changes in the brain. Eosinophil infiltration in the brains of these mice was low, and severe mechanical injuries in the parenchyma were observed. Treatment with mebendazole in combination with IL-12, however, resulted in low levels of worm recovery and dramatic lessening of the eosinophilic meningitis. A reverse transcriptase PCR assay of mRNA expression in the brain also revealed that the use of IL-12 had shifted the immune response of the mouse from Th2 type to Th1 type. This study could be used in developing strategies for the treatment of human angiostrongylosis.

Eosinophils in the cerebrospinal fluid of mice infected with Angiostrongylus cantonensis are resistant to apoptosis

Interleukin-5 (IL-5) transgenic mice were used to assess the immunological features of CSF eosinophils from mice infected with Angiostrongylus cantonensis. CSF eosinophils were hypodense by day 14 post infection (p.i.). CSF eosinophils survived longer in vitro than peritoneal eosinophils collected from cadmium sulphate (CdSO(4)) -treated normal IL-5 transgenic mice. Apoptosis was measured by Annexin V binding and the presence of a distinct laddering pattern of DNA fragmentation on agarose electrophoresis. Regardless of the presence or absence of Actinomycin D, CSF eosinophils collected from IL-5 transgenic mice from days 15-36 p.i. exhibited less apoptosis than peritoneal eosinophils collected from uninfected IL-5 transgenic mice. CSF eosinophils collected from A. cantonensis infected C57BL/6 mice at days 15-34 p.i. showed elongation of survival time and less apoptosis during in vitro cultivation. Reduced apoptosis was noted only in CSF eosinophils, but not in peritoneal eosinophils recovered from the same infected IL-5 transgenic mice. CPP32/Caspase 3 activity of cultured peritoneal eosinophils from both infected and uninfected IL-5 transgenic mice was higher than that of cultured CSF eosinophils. Stimulation with A23187 readily induced apoptosis of peritoneal eosinophils, but not CSF eosinophils or peritoneal eosinophils cultured with mouse recombinant IL-5. The latter cells were morphologically identical to hypodense eosinophils. RT-PCR analysis indicated that bcl-2 and bcl-x(L) mRNA expression was higher in CSF eosinophils compared with peritoneal eosinophils and this expression in the latter cells was upregulated after culture with mouse recombinant IL-5. These results suggest that CSF eosinophils, shifting to hypodense status through an accumulation from peripheral blood, are resistant to apoptosis. These changes may explain the long-lasting, helminthotoxic and neurotoxic actions of CSF eosinophils in A. cantonensis infection.

Development of brain injury in mice by Angiostrongylus cantonensis infection is associated with the induction of transcription factor NF-kappaB, nuclear protooncogenes, and protein tyrosine phosphorylation

Eosinophilic meningitis or meningoencephalitis caused by Angiostrongylus cantonensis is endemic to the Pacific area of Asia, especially Taiwan, Thailand, and Japan. Although eosinophilia is an important clinical manifestation of A. cantonensis infection, the role of eosinophils in the progress of the infection remains to be elucidated. In this experiment, we showed that A. cantonensis-caused eosinoplia and inflammation might lead to the induction of NF-kappaB and protooncogene expression via activation of the tyrosine phosphorylation signal pathway. After mice were infected daily with 30 third-stage larvae of A. cantonensis by oral adminstration for 6 weeks, no significant differences PKC-alpha, MEK-1, ERK-2, JNK, and p38 protein expression were found between the control and infected mice. However, the protein tyrosine phosphorylation levels, NF-kappaB, and iNOS protein products were significantly increased by 3.5-, 3.3-, and 6.3-fold, respectively, after 3 weeks of A. cantonensis infection. The same pattern was found for c-Myc, c-Jun, and c-Fos proteins, which were elevated by 3.2-, 2.3-, and 3.4-fold, respectively, compared to control animals after 3 weeks. The expression potency of these proteins started increasing in week 1, reaching maximal induction in week 3, and then declining in week 5 after A. cantonensis infection. Another consistent result was noted in the pathological observations, including eosinophilia, leukocyte infiltration, granulomatous reactions, and time responses in brain tissues of infected mice. These data suggest that the development of brain injury by eosinophlia of A. cantonensis infection is associated with NF-kappaB and/or nuclear protooncogenes expression, which is activated by the tyrosine phosphorylation pathway.

Role of T cell subpopulations in mice infected with Angiostrongylus cantonensis

When C57BL/6 mice were infected with Angiostrongylus cantonensis, the percentage of T helper (CD4+) cells and T supressor (CD8+) cells in peripheral blood increased weekly until the third and seventh week respectively, and then gradually decreased. C57BL/6 mice were depleted of CD4+ and CD8+ T cells by in vivo injection of anti-CD4 and anti-CD8 monoclonal antibodies, respectively, and then infected with A. cantonensis. There were significantly more and less worms recovered in the mice depleted of CD4+ and CD8+ T cells respectively than in undepleted mice. Discrete subpopulations of T cells from mice exposed to A. cantonensis for 3 weeks or 7 weeks were adoptively transferred to syngeneic recipients which were then given a challenge infection. Protection was mediated by a CD4+ T cell population present in mice after 3 weeks of infection but was not demonstrable with cells taken 7 weeks after infection. When CD4+ T cells obtained from 3-week infected mice were mixed with 5% CD8+ T cells obtained from mice infected for 7 weeks, no significant transfer of resistance was observed. Thus, immune responses to A. cantonensis in mice were regulated by discrete subpopulations of T lymphocytes.

The effect of cyclosporin A on Angiostrongylus cantonensis infection and eosinophilia in mice

Male BALB/c mice were infected with Angiostrongylus cantonensis and at various times p.i. treated with cyclosporin A (CsA) either for 5 days continuously or intermittently, or for 12-16 days on alternate days. They were monitored for peripheral blood eosinophilia and at necropsy examined for CSF and bone marrow eosinophilia, and worm recovery. CsA treatment provoked a transient inhibition of peripheral blood eosinophilia in all groups examined, followed by rebounding eosinophilia. There was no significant difference in bone marrow and CSF eosinophilia between CsA- and vehicle-treated groups. Mice treated with CsA on alternate days yielded lower intracranial worm recovery with small-sized worms at days 7, 21 and 30 p.i. than vehicle-treated groups did. No significant reduction in worm recovery was noted in mice treated for 5 days either continuously or intermittently, although worms, especially female ones, harvested from groups treated with CsA from days--1 to 3 or from days 13 to 17 were significantly smaller than those from vehicle-treated groups. CsA-treatment suppressed blastogenic responses of spleen cells against Con A or worm antigen at days 7 and 21 p.i. In vitro treatment of the 3rd stage larvae with CsA did not adversely influence survival of A. cantonensis in mice. These data indicate that CsA exerts anti-parasitic effects against A. cantonensis in mice.

Antigen dependent release of interleukin 5 in vitro from spleen cells of mice infected with Angiostrongylus cantonensis

The kinetics of eosinophil growth and/or survival stimulating factors (Eo-stimulating factors) released by spleen cells from A. cantonensis-infected mice were assessed by in vitro marrow cultures. When spleen cells from C57BL/6 mice 8 to 20 days p.i. were cultured with young adult A. cantonensis worm antigen or Con A, almost equal amounts of Eo-stimulating factors were detected in the conditioned media obtained from both stimulations. No Eo-stimulating factor activity was detected in cultures from spleen cells without stimulation or from normal spleen cells with stimulation. Production of Eo-stimulating factors was inhibited by the pretreatment of the spleen cells with anti-Thy1.2 or anti-L3T4 antibodies plus complement but not with anti-Lyt2.2 antibody. In the presence of anti-mouse IL-5 monoclonal antibody, the activity of Eo-stimulating factors was inhibited by up to 99%. IL-5, therefore, appears to play a principal role in induction of eosinophilia in mice infected with A. cantonensis.

Ablation of eosinophils with anti-IL-5 antibody enhances the survival of intracranial worms of Angiostrongylus cantonensis in the mouse

Effects of depressed eosinophilia on the development of Angiostrongylus cantonensis in the mouse were studied using monoclonal rat anti-mouse-interleukin-5 antibody (anti-IL-5). The administration of anti-IL-5 strongly depressed peripheral, cerebrospinal fluid (CSF) and medullary eosinophilic responses in mice infected with A. cantonensis, when compared with groups treated with phosphate-buffered saline solution (PBS) alone or isotype-matched rat IgG. There was no significant difference in A. cantonensis antigen specific IgG and IgE antibody responses between rat IgG treated and anti-IL-5 treated mice. Intracranial worm recovery in anti-IL-5 treated mice was consistently high throughout the course of the study and some worms migrated from the brain to the lungs. By contrast, almost all the intracranial worms in the mouse groups treated with PBS alone or rat IgG died before day 32. These data clearly indicate that IL-5 is essential for eosinophil responses in A. cantonensis infected mice and also that eosinophils serve as a potential effector cell in the killing of the intracranial worms in mice.

Characterization of monoclonal antibodies against eosinophil chemotactic factors from young adult worms of Angiostrongylus cantonensis

Two kinds of IgG1 monoclonal antibodies against eosinophil chemotactic factors (ECFs) derived from Angiostrongylus cantonensis young adult worms (YA) were established. Western blot analyses demonstrated that one monoclonal antibody recognized a 16.1 kD component of YA-whole worm extract, and the other an 85 kD component. These antibodies did not show any cross reactions against several helminth antigens, as assessed by ELISA. The chemotactic activity of YA-whole worm extract for guinea-pig-eosinophils was significantly inhibited by previous incubation of the extract with these monoclonal antibodies; the monoclonal antibody recognizing the 16.1 kD component inhibited 56-61% of the ECF activity whilst the antibody recognizing the 85 kD component inhibited 20-34% of the activity. The combination of both monoclonal antibodies showed a stronger inhibitory effect (71-81%) than either antibody alone. Similar magnitudes of inhibition were noted when the chemotactic activity for human eosinophils was measured using YA-whole worm extract preincubated with these monoclonal antibodies. Neither monoclonal antibodies inhibited the chemotactic activity of whole worm extracts of A. cantonensis first stage larvae, Metastrongylus apri adult worms, Spirometra erinacei plerocercoids and Fasciola sp. adult worms. These data suggest that the two monoclonal antibodies will be useful for the isolation and purification of ECF-YA as well as for elucidating the possible in vivo role of ECF-YA.

The influence of Mesocestoides corti on subsequent Angiostrongylus cantonensis infections in mice

The influence of Mesocestoides corti on subsequent Angiostrongylus cantonensis infection in mice (C57BL/6 and BALB/c) was assessed. Both strains of mice infected with M. corti demonstrated a peak blood eosinophilia at around 3 weeks post-infection (p.i.). C57BL/6 and BALB/c mice primarily infected with M. corti were given A. cantonensis infection 18 days later, but pre-existing M. corti infection did not affect the recovery of intracranial worms of A. cantonensis at day 21 p.i. BALB/c mice with mixed parasite infections showed low morbidity and mortality as compared with mice singly infected with A. cantonensis and some mice demonstrated a pulmonary migration of intracranial worms. In C57BL/6 mice, intracranial worms were killed and thus all mice survived. C57BL/6 mice with mixed parasite infections failed to resist A. cantonensis reinfection. The blastogenic responses of spleen cells against A. cantonensis antigen were lower in BALB/c than in C57BL/6 mice and mixed parasite infections also resulted in less blastogenic responses against both concanavalin A and A. cantonensis antigen than monoinfection. The recovery of M. corti biomass was significantly higher in mice with mixed parasite infections than mice with monoinfection with M. corti. These data suggest a distinct difference in response to A. cantonensis infection between C57BL/6 and BALB/c mice, and the induction of immunosuppression in both mouse strains following M. corti infection. Blood eosinophilia provoked by M. corti infection is not directly associated with the killing of worms in subsequent A. cantonensis infection.

Alteration in density of eosinophils in the cerebrospinal fluid of mice infected with Angiostrongylus cantonensis

The density of eosinophils in the cerebrospinal fluid (CSF) and blood of male ddY mice infected with Angiostrongylus cantonensis was examined on days 14, 20 and 27 post-infection (p.i.) with discontinuous Percoll gradient centrifugation. Normal blood eosinophils had a density of between 1.070 and 1.080 g ml-1. No significant changes in density in blood eosinophils were noted during the course of the observations. CSF eosinophils began to become hypodense (defined as density less than 1.070 g ml-1) on day 20 p.i., and 88% of eosinophils were hypodense on day 27. Our results suggest therefore that eosinophils probably become hypodense in the CSF and brain tissues, but not in the blood.

Total and specific IgE in serum and cerebrospinal fluid of rats and guinea pigs infected with Angiostrongylus cantonensis

The total and specific IgE response to Angiostrongylus cantonensis infection was evaluated according to host permissiveness. Total IgE levels measured by a double antibody radioimmunoassay (RIA) increased slowly in the permissive host (the rat), reaching a maximum between 4 and 8 weeks after infection. This maximum was earlier but significantly lower in the non-permissive host (the guinea pig). IgE antibodies specific for adult worms or L1 or L3 larvae of A. cantonensis were measured by a radioallergosorbent test (RAST). In the case of adult worms and L1 antigens, specific IgE antibody levels showed large variations in relation to the duration of infection in rats. In contrast to total IgE levels, the specific IgE response to L3 larvae was lower in rats than in guinea pigs in both the serum and cerebrospinal fluid (CSF). These results suggest variations in the total vs specific IgE response according to host permissiveness or non-permissiveness to A. cantonensis infection. These results are discussed in the context of the possible participation of IgE antibodies in immune defence.