Human Extraparenchymal Neurocysticercosis: The Control of Inflammation Favors the Host…but Also the Parasite

Oxfendazole Nitazoxanide combination in experimental neurocysticercosis - Anti-inflammatory and cysticidal effects

Neurocysticercosis (NCC) is a parasitic infection caused by the larval stage of the pork tapeworm, Taenia solium. The complications of NCC include seizures, headaches, cognitive impairment, and focal neurological deficits. In addition to antiparasitic drugs and surgery, the management of NCC includes the use of corticosteroids to reduce inflammation and control symptoms. The traditional treatment with albendazole and praziquantel has not been altered over 30 years and present several side effects. There are other anti-helminthic drugs such as oxfendazole and nitazoxanide that may show efficacy in NCC treatment. The aim of this study was to determine the histopathologic aspects of experimental NCC after in vivo treatment with the combination of oxfendazole and nitazoxanide. Balb/c mice were infected with T. crassiceps cysticerci and divided into groups of 10 animals each that received a single dose through gavage as follows: group treated with NaCl 0.9% (control group); group treated by monotherapy of the anti-helminthic drugs, 30 mg/kg in single dose of oxfendazole (OXF) or nitazoxanide (NTZ); and groups treated with the combination of the drugs (OXF/NTZ group). Macroscopic and microscopic analysis were performed. There was greater presence of final stage cysticerci after treatment. The microscopic analysis of the general pathological processes showed that the monotherapy with all treatment groups induced higher perivasculitis than what was observed in the control group. In contrast, the combination treatment showed a lower observation of PMN and MN inflammatory infiltration in comparison to the other treatments and to the control one. These results show that indeed the association of benzimidazole derivatives which present both anti-helminthic and anti-inflammatory properties with other cysticidal drugs are beneficial for the NCC treatment in which the aim is to destroy parasite without inducing inflammatory damage in the brain tissue.

Sexual dimorphism in the murine model of extraparenchymal neurocysticercosis

Neurocysticercosis is a heterogeneous disease, and the patient's sex seems to play a role in this heterogeneity. Hosts' sexual dimorphism in cysticercosis has been largely explored in the murine model of intraperitoneal Taenia crassiceps cysticercosis. In this study, we investigated the sexual dimorphism of inflammatory responses in a rat model of extraparenchymal neurocysticercosis caused by T. crassiceps. T. crassiceps cysticerci were inoculated in the subarachnoid space of Wistar rats (25 females, 22 males). Ninety days later, the rats were euthanized for histologic, immunohistochemistry, and cytokines studies. Ten animals also underwent a 7-T magnetic resonance imaging (MRI). Female rats presented a higher concentration of immune cells in the arachnoid-brain interface, reactive astrogliosis in the periventricular region, in situ pro-inflammatory cytokine (interleukin [IL]-6) and anti-inflammatory cytokine (IL-10), and more intense hydrocephalus on MRI than males. Intracranial hypertension signals were not observed during the observational period. Overall, these results suggest sexual dimorphism in the intracranial inflammatory response that accompanied T. crassiceps extraparenchymal neurocysticercosis.

Report of three patients with extensive neurocysticercosis in rural southern Tanzania: neurological, serological and neuroradiological findings

BACKGROUND

Neurocysticercosis (NCC) is common in eastern Africa, but disease presentation varies considerably. Most patients have single or few NCC-typical lesions in their brain but some present with a large number of lesions. We present three patients with positive antibody-based serology for Taenia solium cysticercosis screened at the Vwawa district hospital, Mbozi district, southern Tanzania, in whom extensive NCC was confirmed by neuroimaging.

CASE PRESENTATIONS

Patient 1 was a 55-year-old female from the tribe Malila smallholder farmer who has had four generalized tonic-clonic epileptic seizures over a period of 11 years and one episode of transient left hemiparesis one year before seizure onset. The patient also reported monthly to weekly episodes of severe, progressive, unilateral headache. The computed tomography (CT) scan of the brain showed 25 NCC lesions of which 15 were in the vesicular stage. Patient 2 was a 30-year-old male from tribe Nyha mechanic who reported monthly episodes of moderate to severe, progressive, bilateral headache, but no epileptic seizures. The CT scan showed 63 NCC lesions of which 50 were in the vesicular stage. Patient 3 was a 54-year-old female from the tribe Malila smallholder farmer who suffered from frequent generalized tonic-clonic epileptic seizures with potential signs of focal seizure onset. She also reported weekly to daily episodes of severe, progressive, unilateral headache. The CT scan showed 29 NCC lesions of which 28 were in the vesicular stage.

CONCLUSIONS

Clinical presentation of NCC with multiple brain lesions varies considerably ranging from few epileptic seizures and severe headache to severe epilepsy with frequent epileptic seizures. Individuals with neurological signs/symptoms that may be due to NCC, based for example on epidemiological criteria or serological evidence of cysticercosis, are recommended to undergo neuroimaging before anthelminthic treatment is considered.

Standardizing an Experimental Murine Model of Extraparenchymal Neurocysticercosis That Immunologically Resembles Human Infection

BACKGROUND

Neurocysticercosis (NCC) is endemic in non-developed regions of the world. Two forms of NCC have been described, for which neurological morbidity depends on the location of the lesion, which can be either within the cerebral parenchyma or in extraparenchymal spaces. The extraparenchymal form (EXP-NCC) is considered the most severe form of NCC. EXP-NCC often requires several cycles of cysticidal treatment and the concomitant use of glucocorticoids to prevent increased inflammation, which could lead to intracranial hypertension and, in rare cases, to death. Thus, the improvement of EXP-NCC treatment is greatly needed.

METHODS

An experimental murine model of EXP-NCC, as an adequate model to evaluate new therapeutic approaches, and the parameters that support it are described. EXP-NCC was established by injecting 30 Taenia crassiceps cysticerci, which are less than 0.5 mm in diameter, into the cisterna magna of male and female Wistar rats.

RESULTS

Cyst implantation and infection progression were monitored by detecting the HP10 antigen and anti-cysticercal antibodies in the serum and cerebral spinal fluid (CSF) of infected rats and by magnetic resonance imaging. Higher HP10 levels were observed in CSF than in the sera, as in the case of human EXP-NCC. Low cell recruitment levels were observed surrounding established cysticerci in histological analysis, with a modest increase in GFAP and Iba1 expression in the parenchyma of female animals. Low cellularity in CSF and low levels of C-reactive protein are consistent with a weak inflammatory response to this infection. After 150 days of infection, EXP-NCC is accompanied by reduced levels of mononuclear cell proliferation, resembling the human disease. EXP-NCC does not affect the behavior or general status of the rats.

CONCLUSIONS

This model will allow the evaluation of new approaches to control neuroinflammation and immunomodulatory treatments to restore and improve the specific anti-cysticercal immunity in EXP-NCC.

Albendazole - Ivermectin combination decreases inflammation in experimental neurocysticercosis

Neurocysticercosis (NCC) is a public health issue in endemic regions and is considered the main preventable cause of neurologic disease. It is caused by the presence of Taenia solium cysticercus in the central nervous system. The current treatment is performed with anthelminthic drugs - albendazole (ABZ) or praziquantel - associated with anti-inflammatory and corticosteroids in order to prevent the negative effects of the inflammatory reaction to the parasite's death. Ivermectin (IVM) is an anthelminthic drug that has been shown to present an anti-inflammatory effect. The aim of this study was to was to evaluate the histopathologic aspects of experimental NCC after in vivo treatment with a combination of ABZ-IVM. Balb/c mice were intracranially inoculated with T. crassiceps cysticerci and after 30 days of infection were treated with a single dose of NaCl 0.9% (control group), ABZ monotherapy (40 mg/kg), IVM monotherapy (0.2 mg/kg) or a combination of ABZ-IVM. 24h after the treatment the animals were euthanized and the brain was removed for histopathologic analysis. The IVM monotherapy and ABZ-IVM combination showed more degenerated cysticerci, less inflammatory infiltration, meningitis and hyperemia than the other groups. Therefore, it is possible to recommend the combination of albendazole and ivermectin as alternative chemotherapy for NCC due to its antiparasitic and anti-inflammatory effects, with potential to decrease the negative effects of the inflammatory burst when the parasite is killed within the CNS.

Low responsiveness of peripheral lymphocytes in extraparenchymal neurocysticercosis

BACKGROUND

The morbidity and mortality of extraparenchymal neurocysticercosis (EP-NC) remain high and effectiveness of current medical treatment is suboptimal. Various factors have been implicated in the severity of EP-NC and in the poor response to treatment, but the possible role of host immune and endocrine systems has not yet been examined thoroughly.

METHODOLOGY/PRINCIPAL FINDINGS

42 participants with EP-NC before receiving standard treatment and 25 healthy controls were included in the study. Treatment response was assessed by comparing pre/post treatment parasite volumes from 3D MRI. Prior to treatment among participants with EP-NC, specific stimulation induced an increased specific proliferative response accompanied by a significant increase in IL-4, NK, NKT, Bregs and Tregs cells, whereas in healthy controls, specific stimulation induced a significant increase in IL-1β, IL-5, CCL5, IL-6, TNF-α, NK and Bregs cells. Significant differences between participants with EP-NC and healthy controls in the specific inflammatory response were observed. Participants with EP-NC prior to treatment had significantly weaker responses of proinflammatory cytokines (IL-6, TNF-α) and NK cells, and stronger IL-4 response. Anthelmintic treatment did not promote significant peripheral immunological changes at any time, although inflammation was sustained in the cerebrospinal fluid. Serum estradiol concentration significantly decreased after anthelmintic treatment among males, and cortisol correlated negatively with IL-6 and positively with IFN-γ levels. No pre-treatment immunologic or endocrinologic parameters were significantly associated with response to treatment.

CONCLUSION/SIGNIFICANCE

Prior to anthelmintic treatment, EP-NC was characterized by low lymphocyte reactivity accompanied by a regulatory response, which may be involved in the lack of peripheral immunological changes during and after treatment, although a central inflammatory response was present. This weak specific peripheral response could favor the chronicity of the infection and the poor response to treatment. Our findings highlight the need for new anti-inflammatory treatment focused on the central nervous system with less systemic immunosuppressive effects.

Neurocysticercosis: A Review into Treatment Options, Indications, and Their Efficacy

Neurocysticercosis, due to the localization of Taenia solium larvae in the Central Nervous System, is a neglected tropical disease still endemic in much of Latin America, Asia and sub-Saharan Africa. The therapeutic management of NC has gradually improved with the establishment of neuroimaging studies (CT and MRI) in endemic countries and with the demonstration of the efficacy of albendazole and praziquantel in the 1980s. But the morbidity and mortality of this preventable disease remain an unacceptable fact. In this scoping review, we will revise the different treatment options and their indications.

Pharmacokinetic Study of Intranasal Dexamethasone and Methylprednisolone Compared with Intravenous Administration: Two Open-Label, Single-Dose, Two-Period, Two-Sequence, Cross-Over Study in Healthy Volunteers

Dexamethasone (DXM) and methylprednisolone (MEP) are potent glucocorticoids used to control several inflammatory conditions. Evidence of delayed DXM reaching the central nervous system (CNS) as well as tachyphylaxis and systemic, undesirable side effects are the main limitations of peripheral delivery. Intranasal administration offers direct access to the brain as it bypasses the blood-brain barrier. The Mucosal Atomization Device is an optimal tool that can achieve rapid absorption into the CNS and the bloodstream across mucosal membranes. This study was designed to evaluate and compare the bioavailability of DXM and MEP after intranasal versus intravenous administration. Two open-label, balanced, randomized, two-treatment, two-period, two-sequence, single-dose, crossover studies were conducted, which involved healthy male and female adult volunteers. After intranasal administration, DXM and MEP were detected in plasma after the first sampling time. Mean peak concentrations of DXM and MEP were 86.61 ng/mL at 60 min and 843.2 ng/mL at 1.5 h post-administration, respectively. DXM and MEP showed high absolute bioavailability, with values of 80% and 95%, respectively. No adverse effects were observed. DXM and MEP systemic bioavailability by intranasal administration was comparable with the intravenous one, suggesting that the intranasal route can be used as a non-invasive and appropriate alternative for systemic drug delivery.

Neurocysticercosis research in Mexico: A bibliometric analysis of the Instituto Nacional de Neurología y Neurocirugía Manuel Velasco Suárez

Neurocysticercosis (NCC) is the most common neglected parasitic disease of the central nervous system and leads to many economic and health issues in endemic and non-endemic countries. A bibliometric analysis would shed light on the evolution and development of research in this field, and this is the first study on NCC research. Our institution in Mexico City, the Instituto Nacional de Neurología y Neurocirugía Manuel Velasco Suárez (INNN), has set some milestones in the management of neurocysticercosis and has a decade-long experience and such an analysis in an endemic country like Mexico will be beneficial. We tracked the scientific output in Scopus, from its foundation to March 2021. The studied variables were article type, number of citations, area (clinical/experimental), chronological profile, and preferred journals. In the period from 1964 to 2021, from a total of 3,166 articles from the institution, 232 papers are related to neurocysticercosis with a total of 7,155 citations. The trending topics in the clinical area are pharmacology and pathology in the experimental papers. The number of articles has steadily increased, but NCC is currently a neglected topic that needs further research to better address the disease burden and allow its eradication.

Evolutionary Adaptations of Parasitic Flatworms to Different Oxygen Tensions

During the evolution of the Earth, the increase in the atmospheric concentration of oxygen gave rise to the development of organisms with aerobic metabolism, which utilized this molecule as the ultimate electron acceptor, whereas other organisms maintained an anaerobic metabolism. Platyhelminthes exhibit both aerobic and anaerobic metabolism depending on the availability of oxygen in their environment and/or due to differential oxygen tensions during certain stages of their life cycle. As these organisms do not have a circulatory system, gas exchange occurs by the passive diffusion through their body wall. Consequently, the flatworms developed several adaptations related to the oxygen gradient that is established between the aerobic tegument and the cellular parenchyma that is mostly anaerobic. Because of the aerobic metabolism, hydrogen peroxide (H₂O₂) is produced in abundance. Catalase usually scavenges H₂O₂ in mammals; however, this enzyme is absent in parasitic platyhelminths. Thus, the architecture of the antioxidant systems is different, depending primarily on the superoxide dismutase, glutathione peroxidase, and peroxiredoxin enzymes represented mainly in the tegument. Here, we discuss the adaptations that parasitic flatworms have developed to be able to transit from the different metabolic conditions to those they are exposed to during their life cycle.

Inflammation in neurocysticercosis: clinical relevance and impact on treatment decisions

INTRODUCTION

Neurocysticercosis is caused by the localization of Taenia solium larvae in the central nervous system. The disease remains endemic in most countries of Latin America, Asia and Africa. While major improvements have been made in its diagnosis and treatment, uncertainties persist regarding the clinical implications and treatment of the inflammatory reaction associated with the disease.

AREAS COVERED

In this review, based on PubMed searches, the authors describe the characteristics of the immune-inflammatory response in patients with neurocysticercosis, its clinical implications and the treatment currently administered. The dual role of inflammation (participating in both, the death of the parasite, and the precipitation of serious complications) is discussed. New therapeutic strategies of potential interest are presented.

EXPERT OPINION

Inflammatory reaction is the main pathogenic mechanism associated to neurocysticercosis. Its management is mainly based on corticosteroids administration. This strategy had improved prognostic of patients as it allows for the control of most of the inflammatory complications. On the other side, it might be involved in the persistence of parasites in some patients, despite cysticidal treatment, due to its immunosuppressive properties. New strategies are needed to improve therapeutical management, particularly in the severest presentations.

Natural history of extraparenchymal neurocysticercosis

BACKGROUND

In patients affected by neurocysticercosis (NCC), the extraparenchymal location of the parasites generates the most severe form of the disease. Due to the difficulty in its diagnosis and management, there are still many questions; in particular, the natural history of parasites at this location is not well known.

METHODS

We included 21 patients with vesicular extraparenchymal NCC who had not received treatment for at least 18 months. We collected their demographic and clinical data, compared their imaging studies at the beginning and the end of the period without treatment and classified the patients, taking into account the evolution of their parasitic burden.

RESULTS

A total of 10 men and 11 women were included. Patients had undergone a period of 63±48 months without treatment. During this period, 8 patients (38.1%) showed an increase, 7 (33.3%) a decrease and 6 (28.6%) showed no change in parasite burden.

CONCLUSION

The natural history of extraparenchymal cysticerci is heterogeneous. The results show the ability of parasites to survive for a long time in the extraparenchymal location and explain the chronicity of the disease in some patients. The links between these findings and the difficulties in the therapeutic management of extraparenchymal NCC patients should be studied.

Zoonotic Taenia infections with focus on cysticercosis due to Taenia solium in swine and humans

Zoonotic taeniasis caused by the adult stage of Taenia solium, Taenia saginata or Taenia asiatica are considered neglected tropical diseases by the World Health Organization. The life cycle of these 3 metazoan species is very similar and includes an intermediate host: pigs in the case of T. solium and T. asiatica, and cattle in the case of T. saginata. By eating meat (pork/T. solium, T. asiatica; beef/T. saginata) containing live cysticerci, humans develop taeniasis, which is practically asymptomatic but is the main risk factor for intermediate hosts to become infected. T. saginata causes bovine cysticercosis, while T. solium and T. asiatica cause swine cysticercosis, of veterinary and economic importance. T. solium cysticerci cause neurological disease in humans: neurocysticercosis. Cysticerci develop after ingesting microscopic eggs released from a human tapeworm carrier. Here we describe the life stages of the parasites, diagnosis, pathogenesis, symptomatology of neurocysticercosis, and prevention and control measures. Highlighting the need to validate diagnostic tools, treatments and vaccination in endemic areas, with the challenge of addressing the most vulnerable populations that lack resources. If people understand the transmission route, avoid eating uncooked or insufficiently cooked meat and have adequate hygienic habits, the life cycle of the 3 zoonotic Taenia species may be interrupted. In addition, we describe the growing field of immune response and immunomodulation elicited by the parasites, which may provide essential tools for diagnosis, treatment, control of taeniasis/cysticercosis, as well as for identification of parasite-derived immunomodulators that could aid in the treatment of emerging inflammatory diseases worldwide.

You Talking to Me? Says the Enteric Nervous System (ENS) to the Microbe. How Intestinal Microbes Interact with the ENS

Mammalian organisms form intimate interfaces with commensal and pathogenic gut microorganisms. Increasing evidence suggests a close interaction between gut microorganisms and the enteric nervous system (ENS), as the first interface to the central nervous system. Each microorganism can exert a different effect on the ENS, including phenotypical neuronal changes or the induction of chemical transmitters that interact with ENS neurons. Some pathogenic bacteria take advantage of the ENS to create a more suitable environment for their growth or to promote the effects of their toxins. In addition, some commensal bacteria can affect the central nervous system (CNS) by locally interacting with the ENS. From the current knowledge emerges an interesting field that may shape future concepts on the pathogen-host synergic interaction. The aim of this narrative review is to report the current findings regarding the inter-relationships between bacteria, viruses, and parasites and the ENS.

Neurocisticercosis extraparenquimatosa: reto terapéutico A propósito de un caso de la glándula parótida

Introduction:Neurocysticercosis is a parasitosis of the central nervous system, caused by the intake of eggs from taenia solium. It has a high prevalence in certain regions of Latin America, the southeast of Asia, and sub-Saharan Africa, where unhealthy situations still prevail. Clinical case: A 55-year-old woman with clinical symptoms of 2 years of evolution, such as recurrent headaches that had increased recently in addition to tonic-clonic seizures. In these conditions she was admitted to the hospital’s emergency department. Neuroimaging studies (tomography and magnetic resonance imaging) showed the presence of subarachnoid vesicular structures compatible with neurocysticercosis. Therefore, a cestocidal treatment was administered but the patient did not return to her follow-up appointments for 4 years. When she finally went to her appointment, she was very symptomatic and required the administration of 8 cycles of treatment to eradicate the parasites. Discussion: The great heterogeneity and the non-specificity of the signs and symptoms difficult making a diagnosis of neurocysticercosis. Therefore, it is important to look for complementary laboratory and imaging evidence to confirm it. The treatment of neurocysticercosis represents a challenge for the physician. Particularly, when the parasite is located outside the brain parenchyma, subarachnoid cisterns and ventricular system. In less than a third of these patients the parasites disappear with a single cycle of cestocidal treatment. Conclusion: Neurocysticercosis is a disease closely related to poverty, but it is preventable. Research focused on treatments for neurocysticercosis is still necessary. Key words:Neurocysticercosis; taenia solium; seizures; magnetic resonance; cestocidal.

Host immune responses during Taenia solium Neurocysticercosis infection and treatment

Taenia solium cysticercosis and taeniasis (TSCT), caused by the tapeworm T. solium, is a foodborne and zoonotic disease classified since 2010 by WHO as a neglected tropical isease. It causes considerable impact on health and economy and is one of the leading causes of acquired epilepsy in most endemic countries of Latin America, Sub-Saharan Africa, and Asia. There is some evidence that the prevalence of TSCT in high-income countries has recently increased, mainly due to immigration from endemic areas. In regions endemic for TSCT, human cysticercosis can manifest clinically as neurocysticercosis (NCC), resulting in epileptic seizures and severe progressive headaches, amongst other neurological signs and/or symptoms. The development of these symptoms results from a complex interplay between anatomical cyst localization, environmental factors, parasite's infective potential, host genetics, and, especially, host immune responses. Treatment of individuals with active NCC (presence of viable cerebral cysts) with anthelmintic drugs together with steroids is usually effective and, in the majority, reduces the number and/or size of cerebral lesions as well as the neurological symptoms. However, in some cases, treatment may profoundly enhance anthelmintic inflammatory responses with ensuing symptoms, which, otherwise, would have remained silent as long as the cysts are viable. This intriguing silencing process is not yet fully understood but may involve active modulation of host responses by cyst-derived immunomodulatory components released directly into the surrounding brain tissue or by the induction of regulatory networks including regulatory T cells (Treg) or regulatory B cells (Breg). These processes might be disturbed once the cysts undergo treatment-induced apoptosis and necrosis or in a coinfection setting such as HIV. Herein, we review the current literature regarding the immunology and pathogenesis of NCC with a highlight on the mobilization of immune cells during human NCC and their interaction with viable and degenerating cysticerci. Moreover, the immunological parameters associated with NCC in people living with HIV/AIDS and treatments are discussed. Eventually, we propose open questions to understand the role of the immune system and its impact in this intriguing host-parasite crosstalk.

Effect of dexamethasone on albendazole cysticidal activity in experimental cysticercosis by Taenia crassiceps in BALB/c mice: In vitro and in vivo evaluation

Taenia solium is a parasite whose larvae (cysticerci) can locate in the central nervous system of humans and cause neurocysticercosis (NC). The introduction of cysticidal drugs such as albendazole (ABZ) for the treatment of NC has significantly improved its prognosis. However, treatment is not always effective, and the high levels of corticosteroids used to prevent inflammatory complications in this disease could be, partly, the cause of this observation. In this context, this study investigated, using the experimental mouse model of intraperitoneal infection with Taenia crassiceps, the influence of corticosteroid administration on the therapeutic efficacy of ABZ. We evaluated and compared the effects of ABZ, dexamethasone (DXM) and their combination (ABZ + DXM) on cyst viability, both in vitro and in vivo. Serum levels of IL-4, IFN-gamma, IL-6 and IL-10 were evaluated in the in vivo study. Results showed that the treatment with ABZ, in vitro and in vivo, was associated with a high number of parasites deaths. Concomitant treatment with DXM did not alter ABZ in vitro cysticidal activity but reduced its effectiveness significantly in the in vivo experimental model. Cytokine serum levels did not change significantly in treated mice compared to the controls. The results of this study are relevant as they indicate a negative effect of corticosteroids on the efficacy of cysticidal therapy. In human neurocysticercosis, control of inflammation is of great importance to most patients in order to avoid complications. Corticosteroids are generally used for this purpose and the results of this study demonstrate the need to find other therapeutic strategies. Further studies are needed to better understand the mechanisms involved.