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

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.

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.

Differences of proteolytic enzymes and pathological changes in permissive and nonpermissive animal hosts for Angiostrongylus cantonensis infection

In this study, mice (nonpermissive hosts) infected with Angiostrongylus cantonensis showed significant worm degeneration and eosinophil degranulation, whereas infected rats (permissive hosts) showed lower worm degeneration and eosinophil degranulation. Pathophysiological changes developed to a lesser extent in rat than in the mouse strains. Neurological evaluation of A. cantonensis-infected mice showed mechanical damage caused by worms migrating to the brain. A significant correlation between the proteolytic enzymes, plasminogen activator (PA) and matrix metalloproteinase-9 (MMP-9), and pathological changes was found in hosts with eosinophilic meningitis or meningoencephalitis. Also, the ratio of cerebrospinal fluid (CSF) to serum albumin was consistently increased in hosts with angiostrongyliasis as compared with control. These data clearly indicate that PA and MMP-9 proteolytic enzymes as well as pathological changes are different in permissive and nonpermissive hosts.

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

Angiostrongyliasis is one of the common causes leading to eosinophilic meningitis. Tissue-type plasminogen activator (tPA) and urokinase-type plasminogen activator (uPA) may play a role in the pathogenesis. Administration of steroid drugs has been reported to possibly relieve the symptoms of eosinophilic meningitis. This study evaluates the curative effects of albendazole-dexamethasone co-therapy on eosinophilic meningitis in BALB/c mice. Assay indicators for the therapeutic effect include worm recovery, histopathological score of meningitis, tPA, uPA, total protein, and leukocyte counts. The results show that the albendazole-dexamethasone co-therapy significantly decreased (P<0.05) these factors after treatment on day 5 post-inoculation (PI), in contrast to treatment on 15 PI. Thus, the timing of medication is important and is closely related to the anthelmintic efficacy of a drug. At the same dosage and days post-infection, the earlier administration shows better results. This study showed that albendazole-dexamethasone co-therapy is an effective approach for the treatment of parasitic meningitis.

Cellular immune responses and cytokine production in BALB/c and C57BL/6 mice during the acute phase of Angiostrongylus costaricensis infection

In our experimental study we were able to show that the contrasting outcome of Angiostrongylus costaricensis infection in C57BL/6 and BALB/c mice, in respect of morbidity and mortality, can be explained by divergent cellular immune responses and a different cytokine pattern in each strain. In BALB/c mice (i.e. those with high mortality), the initial high proliferation of ConA or LPS stimulated spleen cells dropped to very low levels after 2 weeks post-infection (p.i.), whereas in C57BL/6 mice (i.e. those with low mortality), only a minor reduction in lymphoproliferative responses after mitogenic stimulation was observed. The specific proliferation of spleen cells after stimulation with A. costaricensis adult worm antigen remained low in BALB/c mice throughout the experiment, but showed an augmented proliferation in C57BL/6 mice, especially from 2 weeks p.i. onwards. The mitogen-induced production of Th2-type cytokines (IL-4, IL-5, IL-6, IL-10) in spleen cell cultures remained low in BALB/c mice until 4 weeks p.i., but production of Th1-type cytokines (IL-2, IFN-gamma) was highly elevated at 14 and 28 days p.i. In C57BL/6 mice, an upregulated and balanced production of both Th1- and Th2-type cytokines was measured during the course of infection. In summary, a polarization of the immune response towards cellular hyporesponsiveness and a predominantly Th1 cytokine profile was observed in A. costaricensis infected BALB/c mice, which may contribute to pathogenesis and increased morbidity.

Induction of cerebrospinal fluid eosinophilia in rats by the intraventricular injection of Angiostrongylus cantonensis antigen

Resistance to Angiostrongylus cantonensis is contingent upon the generation of an eosinophilic response in the CSF of infected hosts. We have studied the parameters required for the generation of this CSF eosinophilia in normally permissive rats. We initially induced a marked peripheral eosinophilia in rats by infection with either Mesocestoides corti or Angiostrongylus cantonensis or the surgical transfer of A. cantonensis young adult worms (YA) into their pulmonary arteries. Next, we injected various antigens into the ventricles of these rats. A. cantonensis-preinfected rats demonstrated significant CSF eosinophilia following injection of A. cantonensis egg antigen, 1st-stage larval (L1) antigen, or M. corti antigen, but not following YA antigen inoculation. A. cantonensis egg and M. corti antigens were potent chemoattractants for eosinophils in an in vitro chemotaxis assay. These data indicate that peripheral eosinophilia, meningeal stimulation by A. cantonensis infection and the presence of potent chemoattractants, e.g., egg and L1 antigens are prerequisites for CSF eosinophil accumulation in permissive rat hosts.

Mediastinal lymph node cells of Angiostrongylus cantonensis-infected rats respond to antigens and release interleukin-5 in vitro

The kinetics of eosinophil growth and/or survival stimulating factor (Eo-stimulating factor) production in Angiostrongylus cantonensis-infected rats was assessed by in vitro marrow cultures. When lymphocytes, obtained from cervical, mediastinal or mesenteric lymph nodes of infected WKAH rats, were cultured with A. cantonensis antigens, Eo-stimulating factor activity was detected in the conditioned media obtained only from mediastinal lymph node cells at and after 35 days p.i. Eo-stimulating factor activity in the conditioned media was not detected before or at 20 days p.i. The kinetics of the factor was, therefore, almost identical to those of eosinophilia in bone marrow and peripheral blood. This Eo-stimulating factor activity was inhibited (maximum inhibition = 73%) by anti-mouse IL-5 monoclonal antibody in a dose-dependent fashion, indicating that the factor would be, at least in part, identical to IL-5. Similar Eo-stimulating factors were also detected in the conditioned media which were obtained by stimulating spleen cells from Wistar rats at 35-45 days p.i. with Con A. These data suggest that lymphocytes in the mediastinal lymph nodes, local lymph nodes near the adult worm habitat, could play an essential role in induction of eosinophilia in A. cantonensis-infected rats.

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.