A Comparative Study of Peripheral Immune Responses to Taenia solium in Individuals with Parenchymal and Subarachnoid Neurocysticercosis

Transcriptomic analysis of subarachnoid cysts of Taenia solium reveals mechanisms for uncontrolled proliferation and adaptations to the microenvironment

Subarachnoid neurocysticercosis (SANCC) is caused by an abnormally transformed form of the metacestode or larval form of the tapeworm Taenia solium. In contrast to vesicular parenchymal and ventricular located cysts that contain a viable scolex and are anlage of the adult tapeworm, the subarachnoid cyst proliferates to form aberrant membranous cystic masses within the subarachnoid spaces that cause mass effects and acute and chronic arachnoiditis. How subarachnoid cyst proliferates and interacts with the human host is poorly understood, but parasite stem cells (germinative cells) likely participate. RNA-seq analysis of the subarachnoid cyst bladder wall compared to the bladder wall and scolex of the vesicular cyst revealed that the subarachnoid form exhibits activation of signaling pathways that promote proliferation and increased lipid metabolism. These adaptions allow growth in a nutrient-limited cerebral spinal fluid. In addition, we identified therapeutic drug targets that would inhibit growth of the parasite, potentially increase effectiveness of treatment, and shorten its duration.

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.

Analysis of immune response in BALB/c mice immunized with recombinant plasmids pMZ-X3-Ts14-3-3.3 and pMZ-X3-sp-Ts14-3-3.3 of Taenia solium

There is a lack of vaccine against human cysticercosis, thus making a huge population at the risk of infection. In this study, we chose a novel potential antigen molecule Taenia solium 14-3-3.3 (Ts14-3-3.3) and optimized it as sp-Ts14-3-3.3 (sp is immunoglobulin H chain V-region precursor, partial) in order to construct recombinant plasmids pMZ-X3-Ts14-3-3.3 and pMZ-X3-sp-Ts14-3-3.3. BALB/c mice were divided into four groups for immunization: pMZ-X3-Ts14-3-3.3, pMZ-X3-sp-Ts14-3-3.3, pMZ-X3 plasmid control group and PBS control group. Compared with two control groups, the proliferation level of splenic lymphocytes increased significantly in pMZ-X3-Ts14-3-3.3 and pMZ-X3-sp-Ts14-3-3.3 groups and reached the maximum in week 6. And the same case arose as cytokines associated with Th1 response, IFN-γ, and IL-2 while those with Th2 response, IL-4, IL-10 went up and reached the maximum in week 4. The levels of serum specific IgG, IgG1 and IgG2a rose and reached the maximum in week 6, 4 and 6, respectively. Meanwhile, the proportion of CD4⁺/CD8⁺ splenic T lymphocytes increased and reached the peak in week 6. The results indicated that the recombinant plasmids pMZ-X3-Ts14-3-3.3 and pMZ-X3-sp-Ts14-3-3.3 can induce specific cellular and humoral immune responses in BALB/c mice with immunization. Notably, the recombinant plasmid pMZ-X3-sp-Ts14-3-3.3 has a better immune effect, which proves that Ts14-3-3.3 enjoys a higher possibility as a potential antigen molecule to T. solium vaccine.

The Local Inflammatory Profile and Predictors of Treatment Success in Subarachnoid Neurocysticercosis

BACKGROUND

Subarachnoid neurocysticercosis (SANCC) represents the most severe and difficult to treat form of neurocysticercosis. The inflammatory response contributes significantly to the morbidity and mortality of the disease. This study sought to understand the nature and evolution of the inflammation associated with SANCC, and evaluate for predictors of time to cure.

METHODS

There were 16 subjects with SANCC (basilar cistern, sylvian fissure, and/or spinal involvement) during active infection who had cerebrospinal fluid (CSF) cytokine and chemokine profiling, of whom 9 had a second CSF sample at (or following) the time of cure. The relationships between clinical parameters and cytokine/chemokine results were assessed.

RESULTS

Compared to pools of healthy donor CSF, those with active SANCC showed a significant (P < .05) increase in chemokines and cytokines associated with Type 1 immunity (interferon [IFN] γ, interleukin [IL] 12p70, C-X-C Motif Ligand 10 CXCL-10); Type 2 immunity (IL-10, IL-13); IFNα2; and the chemokines Macrophage inflammatory protein MIP-1α/CCL3, MIP-1ß/CCL4, and Vascular Endothelial Growth Factor VEGF that appears to be locally (central nervous system [CNS]) produced. Compared to those with active disease, those with CSF taken at the time of cure showed a significant decrease in most of these chemokines and cytokines. Despite this, CSF from cured SANCC patients had levels of IL-10 (P = .039), CXCL-10 (P = .039), and IL-12p70 (P = .044) above those seen in CSF from uninfected subjects. High ratios of IL-12p70/IL-10 early in infections were associated with a shorter time to cure (r = -0.559; P = .027), and a high Taenia solium burden (by quantitative polymerase chain reaction) was associated with longer times to cure (r = 0.84; P = .003).

CONCLUSIONS

SANCC is associated with a marked, CNS-localized cytokine-/chemokine-driven inflammatory response that largely decreases with curative therapy, though some analytes persisted above the normal range. The relative balance between proinflammatory and regulatory cytokines may be an important determinant for a cure in SANCC.

Changes in inflammatory gene expression in brain tissue adjacent and distant to a viable cyst in a rat model for neurocysticercosis

BACKGROUND

The parasite Taenia solium causes neurocysticercosis (NCC) in humans and is a common cause of adult-onset epilepsy in the developing world. Hippocampal atrophy, which occurs far from the cyst, is an emerging new complication of NCC. Evaluation of molecular pathways in brain regions close to and distant from the cyst could offer insight into this pathology.

METHODS

Rats were inoculated intracranially with T. solium oncospheres. After 4 months, RNA was extracted from brain tissue samples in rats with NCC and uninfected controls, and cDNA was generated. Expression of 38 genes related to different molecular pathways involved in the inflammatory response and healing was assessed by RT-PCR array.

RESULTS

Inflammatory cytokines IFN-γ, TNF-α, and IL-1, together with TGF-β and ARG-1, were overexpressed in tissue close to the parasite compared to non-infected tissue. Genes for IL-1A, CSF-1, FN-1, COL-3A1, and MMP-2 were overexpressed in contralateral tissue compared to non-infected tissue.

CONCLUSIONS

The viable cysticerci in the rat model for NCC is characterized by increased expression of genes associated with a proinflammatory response and fibrosis-related proteins, which may mediate the chronic state of infection. These pathways appear to influence regions far from the cyst, which may explain the emerging association between NCC and hippocampal atrophy.

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.

Old friends meet a new foe: A potential role for immune-priming parasites in mitigating COVID-19 morbidity and mortality

The novel virus, Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), and the associated Coronavirus Disease 2019 (COVID-19) represent a pathogen to which human beings have limited to no evolved immune response. The most severe symptoms are associated with overactive inflammatory immune responses, leading to a cytokine storm, tissue damage, and death, if not balanced and controlled. Hypotheses within Evolutionary Medicine, including the Hygiene/Old Friends Hypothesis, provide an important lens through which to understand and possibly control this overactive immune response. In this article, we explore the role that infection with soil-transmitted helminths (STHs; i.e. intestinal parasitic worms) may play in dampening SARS-CoV-2 symptoms and mitigating the worst COVID-19 outcomes. Specifically, STHs stimulate the immunosuppressive and regulatory T-helper 2 (TH2) branch of the immune system, which decreases ACE2-receptor expression (i.e. receptors SARS-CoV-2 uses to infect host cells), balances the inflammatory TH1/TH17 branches of the immune system triggered by SARS-CoV-2 infection, and reduces inflammation through the release of anti-inflammatory/regulatory cytokines. Because STHs are common and affect the most vulnerable and marginalized members of society, it is especially important to consider how these parasites may impact COVID-19 outcomes. Areas experiencing endemic STH infections are often characterized by a lack of preventative infrastructure and medical care, which may further exacerbate risk of SARS-CoV-2 infection and COVID-19 development. For this reason, we also explore biocultural factors that contribute to disease outcomes for both SARS-CoV-2 and STH infections. Biocultural and Evolutionary Medicine perspectives on COVID-19 are crucial for understanding the global impact of the disease. Lay summary: An evolutionary perspective is required to understand the global impact and various presentations of COVID-19. We consider how coinfection with soil-transmitted helminths (common parasitic worms that coevolved with humans) may suppress inflammatory immune activity, thereby potentially reducing COVID-19 disease severity. Structural and lifestyle factors shaping coinfection patterns are also discussed.

Antibody Banding Patterns of the Enzyme-Linked Immunoelectrotransfer Blot and Brain Imaging Findings in Patients With Neurocysticercosis

Background

The enzyme-linked immunoelectrotransfer blot (EITB) assay is the reference serological test for neurocysticercosis (NCC). A positive result on EITB does not always correlate with the presence of active infections in the central nervous system (CNS), and patients with a single viable brain cyst may be EITB negative. Nonetheless, EITB antibody banding patterns appears to be related with the expression of 3 protein families of Taenia solium, and in turn with the characteristics of NCC in the CNS (type, stage, and burden of viable cysts).

Methods

We evaluated EITB antibody banding patterns and brain imaging findings of 548 NCC cases. Similar banding patterns were grouped into homogeneous classes using latent class analysis. The association between classes and brain imaging findings was assessed.

Results

Four classes were identified. Class 1 (patients negative or only positive to the GP50 band, related to the protein family of the same name) was associated with nonviable or single viable parenchymal cysticerci; class 2 (patients positive to bands GP42-39 and GP24, related to the T24-42 protein family, with or without anti-GP50 antibodies) was associated with intraparenchymal viable and nonviable infections; classes 3 and 4 (positive to GP50, GP42-39, and GP24 but also responding to low molecular weight bands GP21, GP18, GP14, and GP13, related to the 8 kDa protein family) were associated with extraparenchymal and intraparenchymal multiple viable cysticerci.

Conclusions

EITB antibody banding patterns correlate with brain imaging findings and complement imaging information for the diagnosis of NCC and for staging NCC patients.

In vitro model of postoncosphere development, and in vivo infection abilities of Taenia solium and Taenia saginata

Taenia solium is known to cause human cysticercosis while T. saginata does not. Comparative in vitro and in vivo studies on the oncosphere and the postoncospheral (PO) forms of T. solium and T. saginata may help to elucidate why cysticercosis can occur from one and not the other. The aim of this study was to use in vitro culture assays and in vivo models to study the differences in the development of the T. solium and T. saginata oncosphere. Furthermore, this study aimed to evaluate the expression of cytokines and metalloproteinases (MMPs) in human peripheral blood mononuclear cells (PBMCs), which were stimulated by these oncospheres and PO antigens. T. solium and T. saginata activated oncospheres (AO) were cultured in INT-407 and HCT-8 intestinal cells for 180 days. The T. solium began to die while the T. saginata grew for 180 days and developed to cysticerci in INT-407 cells. Rats were inoculated intracranially with AO and PO forms of either T. saginata or T. solium. Rats infected with T. solium AO and PO forms developed neurocysticercosis (NCC), while those infected with the T. saginata did not. Human PMBCs were stimulated with antigens of AO and PO forms of both species, and the production of cytokines and metalloproteinases (MMPs) was measured. The T. solium AO antigen stimulated a higher production of IL-4, IL-5, IL-13, IFN-γ, and IL-2 cytokines compared to T. saginata AO. In the PO form, the T. saginata PO antigen increased the production of IL-4, IL-5, IL-13, IFN-γ, IL-1β, IL-6, IL-10, TNF-α and IL-12 cytokines compared to T. solium, suggesting that this global immune response stimulated by different forms could permit survival or destruction of the parasite depending of their life-cycle stage. Regarding MMPs, T. solium AO antigen stimulated a higher production of MMP-9 compared to T. saginata AO antigen, which may be responsible for altering the permeability of intestinal cells and facilitating breakdown of the blood-brain barrier during the process of invasion of host tissue.

Taenia solium and Taenia saginata are two parasites that cause the tissue infection cysticercosis in their intermediate hosts, pigs and cows, respectively. One major difference between them is that T. solium can also cause neurocysticercosis in the human brain, while T. saginata cannot. Neurocysticercosis is thought to be the major cause of adult-onset seizures in developing countries. It is not well understood why only T. solium can survive in human tissue; however, the host inflammatory response likely plays an important role. The authors found that human immune cells stimulated with T. solium in the early stages of the parasite life cycle produced a more robust cytokine response than T. saginata. However, in the mature stage, which occurs once T. solium reaches the brain, T. solium antigens stimulated a lower inflammatory response compared to T. saginata, suggesting the parasite is able to manipulate the host immune response in some way to evade destruction. These findings may support the differences in growth observed by the authors when rat brains were inoculated with either parasite species. This study provides new insights into the different ways T. solium and T. saginata activate the immune response to survive and develop within the host.

Histopathologic aspects of experimental cysticercosis and in situ cytokines profile in C57BL/6 mice

ABSTRACT Neurocysticercosis (NCC) is one of the parasitic infections that most affects the central nervous system. The knowledge regarding its immunopathogenesis and pathophysiology needs broadening. Taenia crassiceps cysticerci are used as the NCC experimental model. The aim of this work was to describe the general pathological processes and the in situ cytokine profile in C57BL/6 mice inoculated intracranially with viable T. crassiceps cysticerci. The histopathology analysis showed cysticerci in the extraparenchymal and intraventricular region, mononuclear inflammatory infiltration surrounding the parasite, microgliosis and meningitis. The analysis of the in situ immune profiles showed a predominance of the Th2 response. The IL-4 and IL-10 dosages were significantly increased in the infected group. The decrease in the INF-gamma dosage reflects the immunomodulation from the cysticerci. In conclusion, a T. crassiceps NCC infection in C57BL/6 mice triggers an inflammatory response, a predominance of Th2 type in situ profile, with mononuclear inflammatory cell infiltration, meningitis and microgliosis.

No association of IL2, IL4, IL6, TNF, and IFNG gene polymorphisms was found with Taenia solium human infection or neurocysticercosis severity in a family-based study

Neurocysticercosis (NC) is caused by the establishment of the metacestode stage of Taenia solium in the human central nervous system. A great heterogeneity in the susceptibility to the infection and to the disease has been reported. While the factors involved in this heterogeneity are not completely understood, clearly different immune-inflammatory profiles have been associated to each condition. This study evaluated the association of cytokine single nucleotide polymorphisms (SNPs) with susceptibility to infection and disease severity in NC patients. Blood samples from 92 NC cases and their parents (trios) were genotyped for SNPs in five cytokines relevant for the immune response: IL4 (-589C/T), IL6 (-174C/G), IFNG (+874T/A), TNF (-238G/A), and IL2 (-330G/T). Specific DNA fragments were amplified by the polymerase chain reaction, using the 5'-nuclease Taqman assay on a 7500 platform, allowing the detection of the polymorphism genotypes. No association between the polymorphisms evaluated neither with susceptibility to infection nor with disease severity was found, although previous studies reported variations in the levels of these cytokines among different NC clinical pictures. These results, nevertheless, add new elements to our understanding of the complex pathogenic mechanisms involved in susceptibility to infection by T. solium cysticerci and the severity of the ensuing disease.

TNF-α blockade suppresses pericystic inflammation following anthelmintic treatment in porcine neurocysticercosis

Background

Neurocysticercosis (NCC) is an infection of the brain with the larval cyst of the tapeworm, Taenia solium. Cysticidal treatment induces parasite killing resulting in a post inflammatory response and seizures, which generally requires corticosteroid treatment to control inflammation. The nature of this response and how to best control it is unclear. We investigated the anti-inflammatory effects of pretreatment with etanercept (ETN), an anti-tumor necrosis factor agent, or dexamethasone (DEX), a high potency corticosteroid, on the post treatment inflammatory response in naturally infected pigs with neurocysticercosis after a single dose of the cysticidal drug praziquantel (PZQ).

Methodology/Principal findings

We followed the methods from a previously developed treatment model of NCC in naturally infected swine. The four study groups of infected pigs included 3 groups treated with PZQ on day 0: PZQ-treated alone (100 mg/kg PO; n = 9), pretreated with dexamethasone (DEX, 0.2 mg/kg IM administered on days -1, +1 and +3; n = 6), and pretreated with etanercept (ETN, 25 mg IM per animal on days -7 and 0; n = 6). The fourth group remained untreated (n = 3). As measured by quantitative RT-PCR, ETN pretreatment depressed transcription of a wide range of proinflammatory, regulatory and matrix protease encoding genes at 120 hr post PZQ treatment in capsules of cysts that demonstrated extravasated Evans Blue (EB) (a measure of blood brain barrier dysfunction) compared to animals not receiving ETN. Transcription was significantly depressed for the proinflammatory genes tumor necrosis factor (TNF)-α, and interferon (IFN)-γ; the inflammation regulating genes cytotoxic T-lymphocyte-associated protein (CTLA)4, interleukin (IL)-13 and transforming growth factor (TGF)-β; the tissue remodeling genes matrix metalloprotease (MMP)1 and 9, tissue inhibitors of metalloproteases (TIMP)1 and 2, and the genes regulating endothelial function vascular endothelial growth factor (VEGF)1, angiopoietin (Ang)1, Ang 2, and platelet endothelial cell adhesion molecule (PECAM)-1. In contrast, transcription was only modestly decreased in the DEX pretreated pigs compared to PZQ alone, and only for TNF-α, IL-6, IFN-γ, TGF-β and Ang1. IL-10 was not affected by either ETN or DEX pretreatments. The degree of inflammation, assessed by semi-quantitative inflammatory scores, was modestly decreased in both ETN and DEX pretreated animals compared to PZQ treated pigs whereas cyst damage scores were moderately decreased only in cysts from DEX pretreated pigs. However, the proportion of cysts with EB extravasation was not significantly changed in ETN and DEX pretreated groups.

Conclusions/Significance

Overall, TNF-α blockade using ETN treatment modulated expression of a large variety of genes that play a role in induction and control of inflammation and structural changes. In contrast the number of inflammatory cells was only moderately decreased suggesting weaker effects on cell migration into the inflammatory capsules surrounding cysts than on release of modulatory molecules. Taken together, these data suggest that TNF-α blockade may provide a viable strategy to manage post-treatment pericystic inflammation that follows antiparasitic therapy for neurocysticercosis.

Infection of the brain with larvae of the tapeworm Taenia solium is called neurocysticercosis (NCC), a disease with varied and serious neurological symptoms. Therapy requires antiparasitic drugs and corticosteroids to prevent seizures caused by treatment due to inflammation around dying parasites. The gene expression of the proinflammatory molecule tumor necrosis factor alpha (TNF-α) is increased in NCC. We treated three groups of naturally infected pigs with an antiparasitic drug: one group was also pretreated with an anti-TNF-α inhibitor, the second one with a corticosteroid, and the third was not pretreated. All pigs were infused with Evans blue dye (EB), which leaks where the blood brain barrier is damaged by inflammation around cysts. We compared the expression of several genes involved in inflammation, healing and fibrosis and regulation of vascular function in tissues surrounding cysts. In inflamed samples showing leaked EB, the inhibition of TNF-α suppressed nearly all the genes assessed, and this suppression was significantly stronger than the moderate decrease caused by corticosteroid pretreatment on most of the genes. On microscopic examination, the inflammation observed was slightly decreased with both pretreatments in relation to the group that was not pretreated. We believe that the inflammatory route that includes TNF-α should be further explored in the search for better management of inflammation directed to degenerating cysts.

Host Th1/Th2 immune response to Taenia solium cyst antigens in relation to cyst burden of neurocysticercosis

Neurocysticercosis (NCC), Taenia solium larval infection of the brain, is an important cause of acquired seizures in endemic countries, which relate to number, location and degenerating cysts in the brain. Multicyst infections are common in endemic countries although single-cyst infection prevails in India. Single-cyst infections in an endemic country suggest a role for host immunity limiting the infection. This study examined ex vivo CD4(+) T cells and in vitro Th1 and Th2 cytokine responses to T. solium cyst antigens of peripheral blood mononuclear cells of healthy subjects from endemic and nonendemic regions and of single- and multicyst-infected patients for association with cyst burden of NCC. T. solium cyst antigens elicited a Th1 cytokine response in healthy subjects of T. solium-endemic and T. solium-non-endemic regions and those with single-cyst infections and a Th2 cytokine response from subjects with multicyst neurocysticercosis. Multicyst neurocysticercosis subjects also exhibited low levels of effector memory CD4(+) T cells. Th1 cytokine response of T. solium exposure and low infectious loads may aid in limiting cyst number. Th2 cytokines and low effector T cells may enable multiple-cyst infections to establish and persist.

Neurocysticercosis infection and disease-A review

Neurocysticercosis (NCC) is the most common parasitic disease of the human central nervous system (CNS), a pleomorphic disease with a diverse array of clinical manifestations. The infection is pleomorphic and dependent on a complex range of interconnecting factors, including number and size of the cysticerci, their stage of development and localisation within the brain with resulting difficulties in accurate diagnosis and staging of the disease. This review examines the factors that contribute to the accurate assessment of NCC distribution and transmission that are critical to achieving robust disease burden calculations. Control and prevention of T. solium transmission should be a key priority in global health as intervention can reduce the substantial healthcare and economic burdens inflicted by both NCC and taeniasis. Surveillance systems need to be better established, including implementing obligatory notification of cases. In the absence of reliable estimates of its global burden, NCC will remain-along with other endemic zoonoses, of low priority in the eyes of funding agencies-a truly neglected disease.

Pathogenesis of Taenia solium taeniasis and cysticercosis

Taenia solium infections (taeniasis/cysticercosis) are a major scourge to most developing countries. Neurocysticercosis, the infection of the human nervous system by the cystic larvae of this parasite, has a protean array of clinical manifestations varying from entirely asymptomatic infections to aggressive, lethal courses. The diversity of clinical manifestations reflects a series of contributing factors which include the number, size and location of the invading parasites, and particularly the inflammatory response of the host. This manuscript reviews the different presentations of T. solium infections in the human host with a focus on the mechanisms or processes responsible for their clinical expression.

Regulation of the host immune system by helminth parasites

Helminth parasite infections are associated with a battery of immunomodulatory mechanisms that affect all facets of the host immune response to ensure their persistence within the host. This broad-spectrum modulation of host immunity has intended and unintended consequences, both advantageous and disadvantageous. Thus the host can benefit from suppression of collateral damage during parasite infection and from reduced allergic, autoimmune, and inflammatory reactions. However, helminth infection can also be detrimental in reducing vaccine responses, increasing susceptibility to coinfection and potentially reducing tumor immunosurveillance. In this review we will summarize the panoply of immunomodulatory mechanisms used by helminths, their potential utility in human disease, and prospective areas of future research.