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Abstract
Helminth parasites infect almost one-third of the world's population, primarily in tropical regions. However, regions where helminth parasites are endemic record much lower prevalences of allergies and autoimmune diseases, suggesting that parasites may protect against immunopathological syndromes. Most helminth diseases are spectral in nature, with a large proportion of relatively asymptomatic cases and a subset of patients who develop severe pathologies. The maintenance of the asymptomatic state is now recognized as reflecting an immunoregulatory environment, which may be promoted by parasites, and involves multiple levels of host regulatory cells and cytokines; a breakdown of this regulation is observed in pathological disease. Currently, there is much interest in whether helminth-associated immune regulation may ameliorate allergy and autoimmunity, with investigations in both laboratory models and human trials. Understanding and exploiting the interactions between these parasites and the host regulatory network are therefore likely to highlight new strategies to control both infectious and immunological diseases.
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102
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Rujeni N, Taylor DW, Mutapi F. Human schistosome infection and allergic sensitisation. J Parasitol Res 2012; 2012:154743. [PMID: 22970345 PMCID: PMC3434398 DOI: 10.1155/2012/154743] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2012] [Accepted: 06/28/2012] [Indexed: 12/24/2022] Open
Abstract
Several field studies have reported an inverse relationship between the prevalence of helminth infections and that of allergic sensitisation/atopy. Recent studies show that immune responses induced by helminth parasites are, to an extent, comparable to allergic sensitisation. However, helminth products induce regulatory responses capable of inhibiting not only antiparasite immune responses, but also allergic sensitisation. The relative effects of this immunomodulation on the development of protective schistosome-specific responses in humans has yet to be demonstrated at population level, and the clinical significance of immunomodulation of allergic disease is still controversial. Nonetheless, similarities in immune responses against helminths and allergens pose interesting mechanistic and evolutionary questions. This paper examines the epidemiology, biology and immunology of allergic sensitisation/atopy, and schistosome infection in human populations.
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Affiliation(s)
- Nadine Rujeni
- Institute of Immunology and Infection Research, Centre for Immunity, Infection, and Evolution, School of Biological Sciences, University of Edinburgh, Ashworth Laboratories, King's Buildings, West Mains Rd, Edinburgh EH9 3JT, UK
| | - David W. Taylor
- Institute of Immunology and Infection Research, Centre for Immunity, Infection, and Evolution, School of Biological Sciences, University of Edinburgh, Ashworth Laboratories, King's Buildings, West Mains Rd, Edinburgh EH9 3JT, UK
| | - Francisca Mutapi
- Institute of Immunology and Infection Research, Centre for Immunity, Infection, and Evolution, School of Biological Sciences, University of Edinburgh, Ashworth Laboratories, King's Buildings, West Mains Rd, Edinburgh EH9 3JT, UK
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103
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Babayan SA, Allen JE, Taylor DW. Future prospects and challenges of vaccines against filariasis. Parasite Immunol 2012; 34:243-53. [PMID: 22150082 DOI: 10.1111/j.1365-3024.2011.01350.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Filarial infections remain a major public health and socio-economic problem across the tropics, despite considerable effort to reduce disease burden or regionally eliminate the infection with mass drug administration programmes. The sustainability of these programmes is now open to question owing to a range of issues, not least of which is emerging evidence for drug resistance. Vaccination, if developed appropriately, remains the most cost-effective means of long-term disease control. The rationale for the feasibility of vaccination against filarial parasites including onchocerciasis (river blindness, Onchocerca volvulus) and lymphatic filariasis (Wuchereria bancrofti or Brugia malayi) is founded on evidence from both humans and animal models for the development of protective immunity. Nonetheless, enormous challenges need to be faced in terms of overcoming parasite-induced suppression without inducing pathology as well as the need to both recognize and tackle evolutionary and ecological obstacles to successful vaccine development. Nonetheless, new technological advances in addition to systems biology approaches offer hope that optimal immune responses can be induced that will prevent infection, disease and/or transmission.
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Affiliation(s)
- Simon A Babayan
- Institute of Immunology and Infection Research, and Centre for Immunity, Infection & Evolution, University of Edinburgh, Edinburgh, UK.
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104
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Regulatory T cells in human lymphatic filariasis: stronger functional activity in microfilaremics. PLoS Negl Trop Dis 2012; 6:e1655. [PMID: 22666510 PMCID: PMC3362610 DOI: 10.1371/journal.pntd.0001655] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2011] [Accepted: 03/09/2012] [Indexed: 11/19/2022] Open
Abstract
Infection with filarial parasites is associated with T cell hyporesponsiveness, which is thought to be partly mediated by their ability to induce regulatory T cells (Tregs) during human infections. This study investigates the functional capacity of Tregs from different groups of filarial patients to suppress filaria-specific immune responses during human filariasis. Microfilaremic (MF), chronic pathology (CP) and uninfected endemic normal (EN) individuals were selected in an area endemic for Brugia timori in Flores island, Indonesia. PBMC were isolated, CD4CD25hi cells were magnetically depleted and in vitro cytokine production and proliferation in response to B. malayi adult worm antigen (BmA) were determined in total and Treg-depleted PBMC. In MF subjects BmA-specific T and B lymphocyte proliferation as well as IFN-gamma, IL-13 and IL-17 responses were lower compared to EN and CP groups. Depletion of Tregs restored T cell as well as B cell proliferation in MF-positives, while proliferative responses in the other groups were not enhanced. BmA-induced IL-13 production was increased after Treg removal in MF-positives only. Thus, filaria-associated Tregs were demonstrated to be functional in suppressing proliferation and possibly Th2 cytokine responses to BmA. These suppressive effects were only observed in the MF group and not in EN or CP. These findings may be important when considering strategies for filarial treatment and the targeted prevention of filaria-induced lymphedema. Lymphatic filariasis is a neglected disease still prominent in low-resource settings and is very disabling when it progresses to chronic pathology caused by lymphedema. Until now, studies on the contribution of Tregs to lymphocyte hyporesponsiveness in human filariasis have focused on frequency and phenotypic characteristics of these cells. We have looked at the functional consequence of the presence of Tregs in filaria-specific immune responses during different stages of human lymphatic filariasis. Proliferation of not only T cells, but also B cells, was decreased in patients with microfilaremia compared to uninfected individuals and chronic pathology (lymphedema) patients. The suppressed lymphocyte proliferative responses were increased after in vitro removal of Tregs in the microfilaria-positive group only, indicating the presence of filaria-specific functional Tregs in microfilaremic patients which are not as active in subjects with chronic pathology or without infection. Th2 cytokine responses were specifically enhanced in microfilaremics as well after Treg depletion, suggesting Treg-associated suppression of filaria-specific Th2 responses. Taken together, filaria-specific Treg contribute to immune modulation during microfilaremia and might need to be considered in therapeutic strategies to prevent chronic pathology induced by filarial infection.
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105
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Arndts K, Deininger S, Specht S, Klarmann U, Mand S, Adjobimey T, Debrah AY, Batsa L, Kwarteng A, Epp C, Taylor M, Adjei O, Layland LE, Hoerauf A. Elevated adaptive immune responses are associated with latent infections of Wuchereria bancrofti. PLoS Negl Trop Dis 2012; 6:e1611. [PMID: 22509424 PMCID: PMC3317915 DOI: 10.1371/journal.pntd.0001611] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2011] [Accepted: 02/28/2012] [Indexed: 12/24/2022] Open
Abstract
In order to guarantee the fulfillment of their complex lifecycle, adult filarial nematodes release millions of microfilariae (MF), which are taken up by mosquito vectors. The current strategy to eliminate lymphatic filariasis as a public health problem focuses upon interrupting this transmission through annual mass drug administration (MDA). It remains unclear however, how many rounds of MDA are required to achieve low enough levels of MF to cease transmission. Interestingly, with the development of further diagnostic tools a relatively neglected cohort of asymptomatic (non-lymphedema) amicrofilaremic (latent) individuals has become apparent. Indeed, epidemiological studies have suggested that there are equal numbers of patent (MF+) and latent individuals. Since the latter represent a roadblock for transmission, we studied differences in immune responses of infected asymptomatic male individuals (n = 159) presenting either patent (n = 92 MF+) or latent (n = 67 MF−) manifestations of Wuchereria bancrofti. These individuals were selected on the basis of MF, circulating filarial antigen in plasma and detectable worm nests. Immunological profiles of either Th1/Th17, Th2, regulatory or innate responses were determined after stimulation of freshly isolated PBMCs with either filarial-specific extract or bystander stimuli. In addition, levels of total and filarial-specific antibodies, both IgG subclasses and IgE, were ascertained from plasma. Results from these individuals were compared with those from 22 healthy volunteers from the same endemic area. Interestingly, we observed that in contrast to MF+ patients, latent infected individuals had lower numbers of worm nests and increased adaptive immune responses including antigen-specific IL-5. These data highlight the immunosuppressive status of MF+ individuals, regardless of age or clinical hydrocele and reveal immunological profiles associated with latency and immune-mediated suppression of parasite transmission. The tropical helminth infection lymphatic filariasis affects more than 120 million people worldwide and is considered a major public health concern. Over 90% of infections are elicited by Wucheria bancrofti and adult worms reside in the lymphatic system releasing millions of microfilariae (MF), which periodically circulate in the blood. New diagnostic tools have provided a method to determine asymptomatic patients that are amicrofilaremic: a subset of individuals that have so far been neglected but are of special interest since these patients represent a dead end in terms of parasite transmission. Therefore, we were interested in determining whether the absence of MF was associated with distinct immunological profiles and observed that indeed responses in MF+ patients were dampened. From the viewpoint of the helminth such overall suppression of immune responses may facilitate MF transmission. Latent individuals however, presented elevated filarial specific responses and extrapolating these findings to the host provides novel insight into possible protective mechanisms which either actively hinders the release of MF from worms or their travel to the periphery. Further research into these aspects may broaden the range of strategies currently employed to reduce transmission and in turn eliminate bancroftian filariasis.
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Affiliation(s)
- Kathrin Arndts
- Institute of Medical Microbiology, Immunology and Parasitology, University Hospital Bonn, Bonn, Germany
| | - Susanne Deininger
- Institute of Medical Microbiology, Immunology and Parasitology, University Hospital Bonn, Bonn, Germany
| | - Sabine Specht
- Institute of Medical Microbiology, Immunology and Parasitology, University Hospital Bonn, Bonn, Germany
| | - Ute Klarmann
- Institute of Medical Microbiology, Immunology and Parasitology, University Hospital Bonn, Bonn, Germany
- Institute of Medical Biometry, Informatics and Epidemiology, University Hospital Bonn, Bonn, Germany
| | - Sabine Mand
- Institute of Medical Microbiology, Immunology and Parasitology, University Hospital Bonn, Bonn, Germany
| | - Tomabu Adjobimey
- Institute of Medical Microbiology, Immunology and Parasitology, University Hospital Bonn, Bonn, Germany
| | - Alexander Y. Debrah
- Kumasi Centre for Collaborative Research in Tropical Medicine, Kumasi, Ghana
- Faculty of Allied Health Sciences, Department of Theoretical and Applied Biology, and School of Medical Sciences, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana
| | - Linda Batsa
- Kumasi Centre for Collaborative Research in Tropical Medicine, Kumasi, Ghana
| | - Alexander Kwarteng
- Kumasi Centre for Collaborative Research in Tropical Medicine, Kumasi, Ghana
| | - Christian Epp
- Department für Infektiologie, Parasitologie, Universitätsklinikum Heidelberg, Heidelberg, Germany
| | - Mark Taylor
- Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Ohene Adjei
- Kumasi Centre for Collaborative Research in Tropical Medicine, Kumasi, Ghana
- Faculty of Allied Health Sciences, Department of Theoretical and Applied Biology, and School of Medical Sciences, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana
| | - Laura E. Layland
- Institute of Medical Microbiology, Immunology and Parasitology, University Hospital Bonn, Bonn, Germany
- * E-mail:
| | - Achim Hoerauf
- Institute of Medical Microbiology, Immunology and Parasitology, University Hospital Bonn, Bonn, Germany
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106
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Ek C, Whary MT, Ihrig M, Bravo LE, Correa P, Fox JG. Serologic evidence that ascaris and toxoplasma infections impact inflammatory responses to Helicobacter pylori in Colombians. Helicobacter 2012; 17:107-15. [PMID: 22404440 PMCID: PMC3305284 DOI: 10.1111/j.1523-5378.2011.00916.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
BACKGROUND Helicobacter pylori-infected children from coastal Tumaco, Colombia, have more parasitism, and adults have lower gastric cancer risk compared with high-altitude Pasto/Tuquerres residents. Because helminth and Toxoplasma gondii infections alter helicobacter gastritis in rodent models, we determined whether seropositivity to Ascaris lumbricoides or T. gondii was associated with Th2-IgG1 or Th1-IgG2 responses to H. pylori. METHODS Sera (240) from the two populations were evaluated for A. lumbricoides and T. gondii seropositivity and results correlated with IgE and IgG isotype responses to H. pylori. RESULTS Most Tumaco children and adults were seropositive for A. lumbricoides (89%, 66%), T. gondii (59%, 98%), or both (45%, 66%). In contrast, seropositivity among Pasto/Tuquerres children was much lower (9%A. lumbricoides, 11%T. gondii, and 2% dual positive) but increased in adults (58%A. lumbricoides, 82%T. gondii, and 41% dual positive). A. lumbricoides seropositivity correlated with elevated IgE and anti-inflammatory Th2-IgG1 responses to H. pylori, while T. gondiigondii seropositivity was linked to elevated IgE, pro-inflammatory Th1-IgG2, IgG3, and IgG4 responses to H. pylori. Individuals with high T. gondii titers had reduced Th1-IgG2, IgG3, and IgG4 responses to H. pylori. CONCLUSIONS Results support regional differences for childhood parasitism and indicate A. lumbricoides and T. gondii infections may impact inflammatory responses to H. pylori and partially explain differences in gastric cancer risk in Colombia.
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Affiliation(s)
- Courtney Ek
- Division of Comparative Medicine, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Mark T. Whary
- Division of Comparative Medicine, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Melanie Ihrig
- Comparative Medicine Program, The Methodist Hospital Research Institute, Houston, Texas 77030, USA
| | - Luis E. Bravo
- Department of Pathology, Universidad del Valle School of Medicine, Cali, 25360, Colombia
| | - Pelayo Correa
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee 37240, USA
| | - James G. Fox
- Division of Comparative Medicine, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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107
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Ludwig-Portugall I, Layland LE. TLRs, Treg, and B Cells, an Interplay of Regulation during Helminth Infection. Front Immunol 2012; 3:8. [PMID: 22566894 PMCID: PMC3342019 DOI: 10.3389/fimmu.2012.00008] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2011] [Accepted: 01/13/2012] [Indexed: 11/28/2022] Open
Abstract
Commonly described as masters of regulation parasitic helminth infections provide a fascinating insight into the complexity of our immune system. As with many other pathogens helminths have developed complex evasion strategies and the immune response of the host has to find a balance between eliciting severe damage to eliminate the parasite or limiting damage and thereby accepting the infection. Nevertheless, one should not forget that these infections still pose a serious public health problem and can elicit severe disfigurement or death in the individual. An interesting spin-off of helminth manipulation on host responses is the apparent prevention of autoimmune diseases or allergy although the actual mechanisms remain unclear. It is well known that Toll-like-receptors (TLR) and non-TLR PRRs play a critical role in initiating innate immune responses which in turn create appropriate adaptive immune reactions. Helminths comprise of a multitude of (glyco)-proteins and (glyco)-lipids and some have been shown to trigger TLR, or alter TLR-mediated responses. Such reactions of course alter adaptive immunity as well. This review will address the consequences of TLR-triggering by helminth antigens and the downstream effect on B cell and regulatory T cell (Treg) actions.
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Affiliation(s)
- Isis Ludwig-Portugall
- Institutes of Molecular Medicine and Experimental Immunology, University Bonn Bonn, Germany
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108
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Modulation of specific and allergy-related immune responses by helminths. J Biomed Biotechnol 2011; 2011:821578. [PMID: 22219659 PMCID: PMC3248237 DOI: 10.1155/2011/821578] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2011] [Accepted: 09/09/2011] [Indexed: 01/10/2023] Open
Abstract
Helminths are master regulators of host immune responses utilising complex mechanisms to dampen host protective Th2-type responses and favour long-term persistence. Such evasion mechanisms ensure mutual survival of both the parasite and the host. In this paper, we present recent findings on the cells that are targeted by helminths and the molecules and mechanisms that are induced during infection. We discuss the impact of these factors on the host response as well as their effect in preventing the development of aberrant allergic inflammation. We also examine recent findings on helminth-derived molecules that can be used as tools to pinpoint the underlying mechanisms of immune regulation or to determine new anti-inflammatory therapeutics.
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109
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Muskardin TW, Gertner E. A 45-year-old man with flank pain and inability to ejaculate. Arthritis Care Res (Hoboken) 2011; 64:616-22. [PMID: 22162419 DOI: 10.1002/acr.21567] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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110
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Chemokines and cytokines in patients with an occult Onchocerca volvulus infection. Microbes Infect 2011; 14:438-46. [PMID: 22202179 DOI: 10.1016/j.micinf.2011.12.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2011] [Revised: 11/26/2011] [Accepted: 12/05/2011] [Indexed: 11/24/2022]
Abstract
Repeated ivermectin treatment will clear microfilaria (Mf) of Onchocerca volvulus from skin and eyes of onchocerciasis patients while adult filaria remains alive and reproductive, and such occult O. volvulus infection may persist for years. To investigate the effect of residual adult filaria on the immune response profile, chemokines and cytokines were quantified 1) in onchocerciasis patients who developed an occult O. volvulus infection (Mf-negative) due to repeated ivermectin treatments, 2) patients who became Mf-negative without ivermectin treatments due to missing re-infection, and 3) endemic and non-endemic O. volvulus Mf-negative controls. With occult O. volvulus infection, serum levels of pro-inflammatory chemokines MCP-1/CCL2, MIP-1α/CCL3, MIP-1β/CCL4, MPIF-1/CCL23 and CXCL8/IL-8 enhanced and approached higher concentrations as determined in infection-free controls, whilst regulatory and Th2-type cytokines and chemokines MCP-4/CCL13, MIP-1δ/CCL15, TARC/CCL17 and IL-13 lessened. Levels of Eotaxin-2/CCL24, MCP-3/CCL7 and BCA-1/CXCL13 remained unchanged. At 3 days post-initial ivermectin treatment, MCP-1/CCL2, MCP-4/CCL13, MPIF-1/CCL23 and Eotaxin-2/CCL24 were strongly enhanced, suggesting that monocytes and eosinophil granulocytes have mediated Mf clearance. In summary, with occult and expiring O. volvulus infections the serum levels of inflammatory chemokines enhanced over time while regulatory and Th2-type-promoting cytokines and chemokines lessened; these changes may reflect a decreasing effector cell activation against Mf of O. volvulus, and in parallel, an enhancing inflammatory immune responsiveness.
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111
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Mekhaiel DNA, Daniel-Ribeiro CT, Cooper PJ, Pleass RJ. Do regulatory antibodies offer an alternative mechanism to explain the hygiene hypothesis? Trends Parasitol 2011; 27:523-9. [PMID: 21943801 DOI: 10.1016/j.pt.2011.08.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2011] [Revised: 08/17/2011] [Accepted: 08/18/2011] [Indexed: 12/24/2022]
Abstract
The 'hygiene hypothesis', or lack of microbial and parasite exposure during early life, is postulated as an explanation for the recent increase in autoimmune and allergic diseases in developed countries. The favored mechanism is that microbial and parasite-derived products interact directly with pathogen recognition receptors to subvert proinflammatory signaling via T regulatory cells, thereby inducing anti-inflammatory effects and control of autoimmune disease. Parasites, such as helminths, are considered to have a major role in the induction of immune regulatory mechanisms among children living in developing countries. Invoking Occam's razor, we believe we can select an alternative mechanism to explain the hygiene hypothesis, based on antibody-mediated inhibition of immune responses that may more simply explain the available evidence.
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Affiliation(s)
- David N A Mekhaiel
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK
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112
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Díaz A, Casaravilla C, Allen JE, Sim RB, Ferreira AM. Understanding the laminated layer of larval Echinococcus II: immunology. Trends Parasitol 2011; 27:264-73. [PMID: 21376669 DOI: 10.1016/j.pt.2011.01.008] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2010] [Revised: 01/27/2011] [Accepted: 01/31/2011] [Indexed: 01/05/2023]
Abstract
The laminated layer (LL) is the massive carbohydrate-rich structure that protects Echinococcus larvae, which cause cystic echinococcosis (hydatid disease) and alveolar echinococcosis. Increased understanding of the biochemistry of the LL is allowing a more informed analysis of its immunology. The LL not only protects the parasite against host attack but also shapes the overall immune response against it. Because of its dense glycosylation, it probably contains few T-cell epitopes, being important instead in T-cell independent antibody responses. Crucially, it is decoded in non-inflammatory fashion by innate immunity, surely contributing to the strong immune-regulation observed in Echinococcus infections. Defining the active LL molecular motifs and corresponding host innate receptors is a feasible and promising goal in the field of helminth-derived immune-regulatory molecules.
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Affiliation(s)
- Alvaro Díaz
- Cátedra de Inmunología. Departamento de Biociencias, Facultad de Química/IQB, Facultad de Ciencias. Universidad de la República, Montevideo CP 11600, Uruguay.
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