Cutting Edge: Dendritic Cells Copulsed with Microbial and Helminth Antigens Undergo Modified Maturation, Segregate the Antigens to Distinct Intracellular Compartments, and Concurrently Induce Microbe-Specific Th1 and Helminth-Specific Th2 Responses

Immunological mechanisms involved in macrophage activation and polarization in schistosomiasis

Human schistosomiasis is caused by helminths of the genus Schistosoma. Macrophages play a crucial role in the immune regulation of this disease. These cells acquire different phenotypes depending on the type of stimulus they receive. M1 macrophages can be ‘classically activated’ and can display a proinflammatory phenotype. M2 or ‘alternatively activated’ macrophages are considered anti-inflammatory cells. Despite the relevance of macrophages in controlling infections, the role of the functional types of these cells in schistosomiasis is unclear. This review highlights different molecules and/or macrophage activation and polarization pathways during Schistosoma mansoni and Schistosoma japonicum infection. This review is based on original and review articles obtained through searches in major databases, including Scopus, Google Scholar, ACS, PubMed, Wiley, Scielo, Web of Science, LILACS and ScienceDirect. Our findings emphasize the importance of S. mansoni and S. japonicum antigens in macrophage polarization, as they exert immunomodulatory effects in different stages of the disease and are therefore important as therapeutic targets for schistosomiasis and in vaccine development. A combination of different antigens can provide greater protection, as it possibly stimulates an adequate immune response for an M1 or M2 profile and leads to host resistance; however, this warrants in vitro and in vivo studies.

The α-Gal Syndrome and Potential Mechanisms

The α-Gal syndrome is a complex allergic disease characterized by the development of specific IgE antibodies against the carbohydrate galactose-α-1,3-galactose (α-Gal), an oligosaccharide present in cells and tissues of non-primate mammals. Individuals with IgE antibodies to α-Gal suffer from a delayed form of anaphylaxis following red meat consumption. There are several features that make the α-Gal syndrome such a unique allergic disease and distinguish it from other food allergies: (1) symptoms causing IgE antibodies are directed against a carbohydrate moiety, (2) the unusual delay between the consumption of the food and the onset of the symptoms, and (3) the fact that primary sensitization to α-Gal occurs via tick bites. This review takes a closer look at the immune response against α-Gal, in healthy and in α-Gal allergic individuals. Furthermore, the similarities and differences between immune response against α-Gal and against the other important glycan moieties associated with allergies, namely cross-reactive carbohydrate determinants (CCDs), are discussed. Then different mechanisms are discussed that could contribute to the delayed onset of symptoms after consumption of mammalian meat. Moreover, our current knowledge on the role of tick bites in the sensitization process is summarized. The tick saliva has been shown to contain proteins carrying α-Gal, but also bioactive molecules, such as prostaglandin E2, which is capable of stimulating an increased expression of anti-inflammatory cytokines while promoting a decrease in the production of proinflammatory mediators. Together these components might promote Th2-related immunity and trigger a class switch to IgE antibodies directed against the oligosaccharide α-Gal. The review also points to open research questions that remain to be answered and proposes future research directions, which will help to get a better understanding and lead to a better management of the disease.

Effect of O-linked glycosylation on the antigenicity, cellular uptake and trafficking in dendritic cells of recombinant Ber e 1

Ber e 1, a major Brazil nut allergen, has been successfully produced in the yeast Pichia pastoris expression system as homogenous recombinant Ber e 1 (rBer e 1) with similar physicochemical properties and identical immunoreactivity to its native counterpart, nBer e 1. However, O-linked glycans was detected on the P.pastoris-derived rBer e 1, which is not naturally present in nBer e 1, and may contribute to the allergic sensitisation. In this study, we addressed the glycosylation differences between P. pastoris-derived recombinant Ber e 1 and its native counterparts. We also determined whether this fungal glycosylation could affect the antigenicity and immunogenicity of the rBer e 1 by using dendritic cells (DC) as an immune cell model due to their role in modulating the immune response. We identified that the glycosylation occurs at Ser96, Ser101 and Ser110 on the large chain and Ser19 on the small polypeptide chain of rBer e 1 only. The glycosylation on rBer e 1 was shown to elicit varying degree of antigenicity by binding to different combination of human leukocyte antigens (HLA) at different frequencies compared to nBer e 1 when tested using human DC-T cell assay. However, both forms of Ber e 1 are weak immunogens based from their low response indexes (RI). Glycans present on rBer e 1 were shown to increase the efficiency of the protein recognition and internalization by murine bone marrow-derived dendritic cells (bmDC) via C-type lectin receptors, particularly the mannose receptor (MR), compared to the non-glycosylated nBer e 1 and SFA8, a weak allergenic 2S albumin protein from sunflower seed. Binding of glycosylated rBer e 1 to MR alone was found to not induce the production of IL-10 that modulates bmDC to polarise Th2 cell response by suppressing IL-12 production and DC maturation. Our findings suggest that the O-linked glycosylation by P. pastoris has a small but measurable effect on the in vitro antigenicity of the rBer e 1 compared to its non-glycosylated counterpart, nBer e 1, and thus may influence its applications in diagnostics and immunotherapy.

Sequential Co-infection of Heligmosomoides polygyrus and Mycobacterium tuberculosis Determine Lung Macrophage Polarization and Histopathological Changes

BACKGROUND

Tuberculosis is a chronic infection caused by Mycobacterium tuberculosis (M.tb), which needs proper macrophage activation for control. It has been debated whether the co-infection with helminth will affect the immune response to mycobacterial infection.

OBJECTIVE

To determine the effect of sequential co-infection of Heligmosomoides polygyrus (H.pg) nematodes and M.tb on T cell responses, macrophages polarization and lung histopathological changes.

METHOD

This study used 49 mice divided into 7 treatment groups, with different sequence of infection of M.tb via inhalation and H.pg via oral ingestion for 8 and 16 weeks. T cells response in the lung, intestine, and peripheral blood were determined by flow cytometry. Cytokines (IL-4, IFN-γ, TGB-β1, and IL-10) were measured in peripheral blood using ELISA. Lung macrophage polarization were determined by the expression of iNOS (M1) or Arginase 1 (M2). Mycobacterial count were done in lung tissue. Lung histopathology were measured using Dorman's semiquantitative score assessing peribronchiolitis, perivasculitis, alveolitis, and granuloma formation.

RESULT

M.tb infection induced Th1 response and M1 macrophage polarization, while H.pg infection induced Th2 and M2 polarization. In sequential co-infection, the final polarization of macrophage was dictated by the sequence of co-infection. However, all groups with M.tb infection showed the same degree of mycobacterial count in lung tissues and lung tissue histopathological changes.

CONCLUSION

Sequential co-infection of H.pg and M.tb induces different T cell response which leads to different macrophage polarization in lung tissue. Helminth infection induced M2 lung macrophage polarization, but did not cause different mycobacterial count nor lung histopathological changes.

Clinical Use of Schistosoma mansoni Antigens as Novel Immunotherapies for Autoimmune Disorders

The hygiene hypothesis states that improved hygiene and the resulting disappearance of once endemic diseases is at the origin of the enormous increase in immune related disorders such as autoimmune diseases seen in the industrialized world. Helminths, such as Schistosoma mansoni, are thought to provide protection against the development of autoimmune diseases by regulating the host's immune response. This modulation primarily involves induction of regulatory immune responses, such as generation of tolerogenic dendritic cells and alternatively activated macrophages. This points toward the potential of employing helminths or their products/metabolites as therapeutics for autoimmune diseases that are characterized by an excessive inflammatory state, such as multiple sclerosis (MS), type I diabetes (T1D) and inflammatory bowel disease (IBD). In this review, we examine the known mechanisms of immune modulation by S. mansoni, explore preclinical and clinical studies that investigated the use of an array helminthic products in these diseases, and propose that helminthic therapy opens opportunities in the treatment of chronic inflammatory disorders.

The long-standing history of Corynebacterium parvum, immunity, and viruses

We report a review of all the experimental and clinical studies performed in the last 60 years on the antiviral activity of inactivated Corynebacterium parvum (Cutibacterium acnes). This bacterium has been originally investigated and used for its oncolytic properties linked to immunomodulating activity, but the interest to successfully prevent and treat bacterial, fungal, and viral infections and lethality, uprising the innate immunity barriers produced many experimental models and very few clinical studies. The dramatic defenseless situation due to impending CoViD‐19 pandemic claims to exhume and highlight this aspecific strategy in preventive and therapeutic settings; as a matter of fact, no new or mutated virus can potentially escape to this strong innate immune surveillance strengthened by adequate C. parvum protocols.

Training the Fetal Immune System Through Maternal Inflammation-A Layered Hygiene Hypothesis

Over the last century, the alarming surge in allergy and autoimmune disease has led to the hypothesis that decreasing exposure to microbes, which has accompanied industrialization and modern life in the Western world, has fundamentally altered the immune response. In its current iteration, the “hygiene hypothesis” suggests that reduced microbial exposures during early life restricts the production and differentiation of immune cells suited for immune regulation. Although it is now well-appreciated that the increase in hypersensitivity disorders represents a “perfect storm” of many contributing factors, we argue here that two important considerations have rarely been explored. First, the window of microbial exposure that impacts immune development is not limited to early childhood, but likely extends into the womb. Second, restricted microbial interactions by an expectant mother will bias the fetal immune system toward hypersensitivity. Here, we extend this discussion to hypothesize that the cell types sensing microbial exposures include fetal hematopoietic stem cells, which drive long-lasting changes to immunity.

Peptides from allergenic lipocalins bind to formyl peptide receptor 3 in human dendritic cells to mediate TH2 immunity

BACKGROUND

How TH2-mediated allergic immune responses are induced is still under investigation.

OBJECTIVE

In an in vitro system we compared the effect of lipocalin allergens and nonallergenic homologues on human monocyte-derived dendritic cells (DCs) to investigate how they polarize naive CD4+ TH cells. Microarray data gained with these DCs showed a significant difference in expression of formyl peptide receptors (FPRs). Activation of FPR3 in human monocyte-derived DCs leads to inhibition of IL-12 production. Low concentrations of IL-12 during T-cell priming biases immune responses toward TH2. We hypothesize that binding of allergenic lipocalins to FPR3 might be a mechanism for induction of allergic immune responses.

METHODS

We examined whether lipocalins and FPR3 colocalize within the cells by using confocal microscopy. With calcium mobilization assays of FPR3-transfected HEK 293 cells, we measured FPR3 signaling in response to allergenic and nonallergenic lipocalins. Silencing of FPR3 in DCs and pretreatment with an antagonistic peptide were used to assess the function of FPR3 in TH2 induction.

RESULTS

FPR3 and lipocalins colocalize in the same vesicles in DCs. Cathepsin S-digested allergenic lipocalins, but not digestion products of nonallergenic homologues, activate FPR3 signaling. FPR3 silencing in DCs or pretreatment with an antagonistic peptide restores IL-12 and induces IL-10 expression by DCs treated with lipocalin allergens, attenuating the TH2 bias and inducing IL-10 production in cocultured TH cells.

CONCLUSION

We describe a novel molecular mechanism for induction of TH2-mediated allergic immune responses.

Trichinella spiralis Excretory-Secretory Products Stimulate Host Regulatory T Cell Differentiation through Activating Dendritic Cells

Trichinella spiralis maintains chronic infections within its host, involving a variety of immunomodulatory properties, the mechanisms of which have not been completely elucidated. In this study, we found that T. spiralis infection induced strong regulatory T cell responses through parasite excretory-secretory (ES) products, characterized by increase of CD4⁺CD25⁺Foxp3⁺ and CD4⁺CD25^-Foxp3⁺ Treg cells accompanied by high levels of IL-10 and TGF-β. T. spiralis adult worm excretory-secretory products (AES) and muscle larvae excretory-secretory products (MES) were both able to activate BMDCs in vitro to facilitate their maturation and to create regulatory cytokines IL-10 and TGF-β. The T. spiralis AES- and MES-pulsed dendritic cells (DCs) possessed abilities not only to present antigens to sensitized CD4⁺ T cell to stimulate their proliferation but also to induce naive CD4⁺ T cells to differentiate to Treg cells secreting IL-10 and TGF-β. The passive transfer of T. spiralis AES- and MES-pulsed bone marrow-derived dendritic cells (BMDCs) conferred the naive mice to acquire the differentiation of Treg cells. T. spiralis AES possesses a better ability to induce Treg cells than did MES, although the latter has the ability to induce CD4⁺CD25^-Foxp3⁺ Treg cells. The results obtained in this study suggested that T. spiralis ES products stimulate the differentiation of host Treg cells possibly through activating dendritic cells to create a regulatory environment that benefits the survival of the parasite in the host.

Cathepsin L3 From Fasciola hepatica Induces NLRP3 Inflammasome Alternative Activation in Murine Dendritic Cells

The production of IL-1-family cytokines such as IL-1β and IL-18 is finely regulated by inflammasome activation after the recognition of pathogens associated molecular pattern (PAMPs) and danger associated molecular patterns (DAMPs). However, little is known about the helminth-derived molecules capable of activating the inflammasome. In the case of the helminth trematode Fasciola hepatica, the secretion of different cathepsin L cysteine peptidases (FhCL) is crucial for the parasite survival. Among these enzymes, cathepsin L3 (FhCL3) is expressed mainly in the juvenile or invasive stage. The ability of FhCL3 to digest collagen has demonstrated to be critical for intestinal tissue invasion during juvenile larvae migration. However, there is no information about the interaction of FhCL3 with the immune system. It has been shown here that FhCL3 induces a non-canonical inflammasome activation in dendritic cells (DCs), leading to IL-1β and IL-18 production without a previous microbial priming. Interestingly, this activation was depending on the cysteine protease activity of FhCL3 and the NLRP3 receptor, but independent of caspase activation. We also show that FhCL3 is internalized by DCs, promoting pro-IL-1β cleavage to its mature and biologically active form IL-1β, which is released to the extracellular environment. The FhCL3-induced NLRP3 inflammasome activation conditions DCs to promote a singular adaptive immune response, characterized by increased production of IFN-γ and IL-13. These data reveal an unexpected ability of FhCL3, a helminth-derived molecule, to activate the NLRP3 inflammasome, which is independent of the classical mechanism involving caspase activation.

Host-Parasite Interactions Promote Disease Tolerance to Intestinal Helminth Infection

Parasitic helminths are among the most pervasive pathogens of the animal kingdom. To complete their life cycle, these intestinal worms migrate through host tissues causing significant damage in their wake. As a result, infection can lead to malnutrition, anemia and increased susceptibility to co-infection. Despite repeated deworming treatment, individuals living in endemic regions remain highly susceptible to re-infection by helminths, but rarely succumb to excessive tissue damage. The chronicity of infection and inability to resist numerous species of parasitic helminths that have co-evolved with their hosts over millenia suggests that mammals have developed mechanisms to tolerate this infectious disease. Distinct from resistance where the goal is to destroy and eliminate the pathogen, disease tolerance is an active process whereby immune and structural cells restrict tissue damage to maintain host fitness without directly affecting pathogen burden. Although disease tolerance is evolutionary conserved and has been well-described in plant systems, only recently has this mode of host defense, in its strictest sense, begun to be explored in mammals. In this review, we will examine the inter- and intracellular networks that support disease tolerance during enteric stages of parasitic helminth infection and why this alternative host defense strategy may have evolved to endure the presence of non-replicating pathogens and maintain the essential functions of the intestine.

Clonorchis sinensis adult-derived proteins elicit Th2 immune responses by regulating dendritic cells via mannose receptor

BACKGROUND

Clonorchis sinensis (C. sinensis) is the most widespread human liver fluke in East Asia including China and Korea. Clonorchiasis as a neglected tropical zoonosis, leads to serious economic and public health burden in China. There are considerable evidences for an etiological relation between chronic clonorchiasis and liver fibrosis in human beings. Liver fibrosis is a highly conserved and over-protected response to hepatic tissue injury. Immune cells including CD4+ T cell as well as dendritic cell (DC), and pro-fibrogenic cytokines like interleukin 4 (IL-4), IL-13 have been identified as vital manipulators in liver fibrogenesis. Our previous studies had a mere glimpse of T helper type 2 (Th2) dominant immune responses as key players in liver fibrosis induced by C. sinensis infection, but little is known about the involved mechanisms in this pathological process.

METHODOLOGY/PRINCIPAL FINDINGS

By flow cytometry (FACS), adult-derived total proteins of C. sinensis (CsTPs) down-regulated the expression of surface markers CD80, CD86 and major histocompatibility complex class II (MHC-II) on lipopolysaccharide (LPS) induced DC. ELISA results demonstrated that CsTPs inhibited IL-12p70 release from LPS-treated bone marrow-derived dendritic cells (BMDC). IL-10 level increased in a time-dependent manner in LPS-treated BMDCs after incubation with CsTPs. CD4+ T cells incubated with LPS-treated BMDCs plus CsTPs could significantly elevate IL-4 level by ELISA. Meanwhile, elevated expression of pro-fibrogenic mediators including IL-13 and IL-4 were detected in a co-culture system of LPS-activated BMDCs and naive T cells containing CsTPs. In vivo, CsTPs-immunized mice enhanced expression of type 2 cytokines IL-13, IL-10 and IL-4 in both splenocytes and hepatic tissue. Exposure of BMDCs to CsTPs activated expression of mannose receptor (MR) but not toll like receptor 2 (TLR2), TLR4, C-type lectin receptor DC-SIGN and Dectin-2 on the cell surface by RT-PCR and FACS. Blockade of MR almost completely reversed the capacity of CsTPs to suppress LPS-induced BMDCs surface markers CD80, CD86 and MHC-II expression, and further made these BMDCs fail to induce a Th2-skewed response as well as Th2 cell-associated cytokines IL-13 and IL-4 release in vitro.

CONCLUSIONS/SIGNIFICANCE

Collectively, we validated that CsTPs could suppress the maturation of BMDCs in the presence of LPS via binding MR, and showed that the CsTPs-pulsed BMDCs actively polarized naive T helper cells to Th2 cells though the production of IL-10 instead of IL-12. CsTPs endowed host with the capacity to facilitate Th2 cytokines production including IL-13 and IL-4 in vitro and vivo. The study might provide useful information for developing potential therapeutic targets against the disease.

Propionibacterium acnes Enhances the Immunogenicity of HIVBr18 Human Immunodeficiency Virus-1 Vaccine

Immunization of BALB/c mice with HIVBr18, a DNA vaccine containing 18 CD4⁺ T cell epitopes from human immunodeficiency virus (HIV), induced specific CD4⁺ and CD8⁺ T cell responses in a broad, polyfunctional and persistent manner. With the aim of increasing the immunogenicity of this vaccine, the effect of Propionibacterium acnes as an adjuvant was evaluated. The adjuvant effects of this bacterium have been extensively demonstrated in both experimental and clinical settings. Herein, administration of two doses of HIVBr18, in the presence of P. acnes, increased the proliferation of HIV-1-specific CD4⁺ and CD8⁺ T lymphocytes, the polyfunctional profile of CD4⁺ T cells, the production of IFN-γ, and the number of recognized vaccine-encoded peptides. One of the bacterial components responsible for most of the adjuvant effects observed was a soluble polysaccharide extracted from the P. acnes cell wall. Furthermore, within 10 weeks after immunization, the proliferation of specific T cells and production of IFN-γ were maintained when the whole bacterium was administered, demonstrating a greater effect on the longevity of the immune response by P. acnes. Even with fewer immunization doses, P. acnes was found to be a potent adjuvant capable of potentiating the effects of the HIVBr18 vaccine. Therefore, P. acnes may be a potential adjuvant to aid this vaccine in inducing immunity or for therapeutic use.

Composition of the Schistosoma mansoni worm secretome: Identification of immune modulatory Cyclophilin A

The helminth Schistosoma mansoni modulates the infected host's immune system to facilitate its own survival, by producing excretory/secretory molecules that interact with a variety of the host's cell types including those of the immune system. Herein, we characterise the S. mansoni adult male worm secretome and identify 111 proteins, including 7 vaccine candidates and several molecules with potential immunomodulatory activity. Amongst the molecules present in the secretome, a 17-19kDa protein analogous to human cyclophilin A was identified. Given the ability of cyclophilin A to modulate the immune system by regulating antigen presenting cell activity, we sought to determine whether recombinant S. mansoni Cyclophilin A (rSmCypA) is capable of modulating bone-marrow derived dendritic cell (BMDC) and T cell responses under in vitro conditions. rSmCypA was enzymatically active and able to alter the pro-inflammatory cytokine profile of LPS-activated dendritic cells. rSmCypA also modulated DC function in the induction of CD4+ T cell proliferation with a preferential expansion of Treg cells. This work demonstrates the unique protein composition of the S. mansoni male worm secretome and immunomodulatory activity of S. mansoni Cyclophilin A.

Anisakis - immunology of a foodborne parasitosis

Anisakis species are marine nematodes which can cause zoonotic infection in humans if consumed in raw, pickled or undercooked fish and seafood. Infection with Anisakis is associated with abdominal pain, nausea and diarrhoea and can lead to massive infiltration of eosinophils and formation of granulomas in the gastrointestinal tract if the larvae are not removed. Re-infection leads to systemic allergic reactions such as urticarial or anaphylaxis in some individuals, making Anisakis an important source of hidden allergens in seafood. This review summarizes the immunopathology associated with Anisakis infection. Anisakiasis and gastroallergic reactions can be prevented by consuming only fish that has been frozen to -20°C to the core for at least 24 hours before preparation. Sensitization to Anisakis proteins can also occur, primarily due to occupational exposure to infested fish, and can lead to dermatitis, rhinoconjunctivitis or asthma. In this case, exposure to fish should be avoided.

Myeloid Cell Phenotypes in Susceptibility and Resistance to Helminth Parasite Infections

Many major tropical diseases are caused by long-lived helminth parasites that are able to survive by modulation of the host immune system, including the innate compartment of myeloid cells. In particular, dendritic cells and macrophages show markedly altered phenotypes during parasite infections. In addition, many specialized subsets such as eosinophils and basophils expand dramatically in response to these pathogens. The changes in phenotype and function, and their effects on both immunity to infection and reactivity to bystander antigens such as allergens, are discussed.

Parasitic infection as a potential therapeutic tool against rheumatoid arthritis

Parasites, which are a recently discovered yet ancient dweller in human hosts, remain a great public health burden in underdeveloped countries, despite preventative efforts. Rheumatoid arthritis is a predominantly cosmopolitan health problem with drastic morbidity rates, although encouraging progress has been achieved regarding treatment. However, although various types of methods and agents have been applied clinically, their broad usage has been limited by their adverse effects and/or high costs. Sustained efforts have been exerted on the 'hygiene hypothesis' since the 1870s. The immunosuppressive nature of parasitic infections may offer potential insight into therapeutic strategies for rheumatoid arthritis, in which the immune system is overactivated. An increasing number of published papers are focusing on the preventive and/or curative effect of various parasitic infection on rheumatoid arthritis from experimental studies to large-scale epidemiological studies and clinical trials. Therefore, the present review aimed to provide a general literature review on the possible beneficial role of parasitic infection on rheumatoid arthritis.

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.

Molecular events by which dendritic cells promote Th2 immune protection in helmith infection

Helminth parasites are a major cause of global infectious diseases, affecting nearly one quarter of the world's population. The common feature of helminth infections is to skew the immune system towards a T-helper 2 (Th2) response that helps to control disease. Dendritic cells (DCs), which are professional antigen-presenting cells, play a critical role for Th2 skewing against helminth parasites. However, the molecular mechanisms by which helminth antigens activate DCs for Th2 polarization have not yet been clearly defined. This review provides a focused update on the major role of DCs for inducing and/or enhancing Th2 immune responses in helminthic infection and will discuss the main signalling-dependent and independent mechanisms by which helminth antigens activate DCs for Th2 skewing.

Host parasite communications-Messages from helminths for the immune system: Parasite communication and cell-cell interactions

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Helminth parasites release a spectrum of mediators to dampen host immunity.

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Secreted proteins can act on host receptors and intracellular signalling.

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Parasites also produce exosome-like extracellular vesicles containing microRNAs.

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Exosomes can enter host cells and modulate host gene expression.

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Extracellular vesicles may be a more general mode of host-parasite interaction.

Helminths are metazoan organisms many of which have evolved parasitic life styles dependent on sophisticated manipulation of the host environment. Most notably, they down-regulate host immune responses to ensure their own survival, by exporting a range of immuno-modulatory mediators that interact with host cells and tissues. While a number of secreted immunoregulatory parasite proteins have been defined, new work also points to the release of extracellular vesicles, or exosomes, that interact with and manipulate host gene expression. These recent results are discussed in the overall context of how helminths communicate effectively with the host organism.

MGL Receptor and Immunity: When the Ligand Can Make the Difference

C-type lectin receptors (CLRs) on antigen-presenting cells (APCs) facilitate uptake of carbohydrate antigens for antigen presentation, modulating the immune response in infection, homeostasis, autoimmunity, allergy, and cancer. In this review, we focus on the role of the macrophage galactose type C-type lectin (MGL) in the immune response against self-antigens, pathogens, and tumor associated antigens (TAA). MGL is a CLR exclusively expressed by dendritic cells (DCs) and activated macrophages (MØs), able to recognize terminal GalNAc residues, including the sialylated and nonsialylated Tn antigens. We discuss the effects on DC function induced throughout the engagement of MGL, highlighting the importance of the antigen structure in the modulation of immune response. Indeed modifying Tn-density, the length, and steric structure of the Tn-antigens can result in generating immunogens that can efficiently bind to MGL, strongly activate DCs, mimic the effects of a danger signal, and achieve an efficient presentation in HLA classes I and II compartments.

IL-4-Producing Dendritic Cells Induced during Schistosoma japonica Infection Promote Th2 Cells via IL-4-Dependent Pathway

Although dendritic cells (DCs) have been widely demonstrated to play essential roles in initiation of Th2 responses in helminth infections and allergic reactions, the mechanisms remain uncertain largely because DCs do not produce IL-4. In present investigation, we have uncovered a novel subset of DCs from mice infected with Th2-provoking pathogens Schistosoma japonica, which independently promoted Th2 cells via IL-4-dependent pathway. These DCs contained similar levels of IL-4 mRNA and higher levels of IL-12p40 mRNA comparing to basophils, correlating to their Th2-promoting and Th1-promoting dual polarization capacities. Characterized by expression of FcεRI(+), these DCs were induced independent of T cells. Further investigations revealed that Th2-promoting FcεRI(+) DCs were monocyte-derived inflammatory DCs, which were sufficient to induce Th2 cells in vivo. Egg Ags together with GM-CSF or IL-3 alone were able to stimulate the generation of Th2-promoting FcεRI(+) DCs from bone marrow cells in vitro. To our knowledge, our data for the first time demonstrate that IL-4-producing DCs are induced under some Th2-provoking situations, and they should play important roles in initiation of Th2 response.

Development of chitosan-pullulan composite nanoparticles for nasal delivery of vaccines: in vivo studies

Here, we aimed at developing chitosan/pullulan composite nanoparticles and testing their potential as novel systems for the nasal delivery of diphtheria toxoid (DT). All the chitosan derivatives [N-trimethyl (TMC), chloride and glutamate] and carboxymethyl pullulan (CMP) were synthesised and antigen-loaded composites were prepared by polyion complexation of chitosan and pullulan derivatives (particle size: 239-405 nm; surface charge: +18 and +27 mV). Their immunological effects after intranasal administration to mice were compared to intramuscular route. Composite nanoparticles induced higher levels of IgG responses than particles formed with chitosan derivative and antigen. Nasally administered TMC-pullulan composites showed higher DT serum IgG titre when compared with the other composites. Co-encapsulation of CpG ODN within TMC-CMP-DT nanoparticles resulted in a balanced Th1/Th2 response. TMC/pullulan composite nanoparticles also induced highest cytokine levels compared to those of chitosan salts. These findings demonstrated that TMC-CMP-DT composite nanoparticles are promising delivery system for nasal vaccination.

Immunostimulatory Effects Triggered by Enterococcus faecalis CECT7121 Probiotic Strain Involve Activation of Dendritic Cells and Interferon-Gamma Production

Probiotics can modulate the immune system, conferring beneficial effects on the host. Understanding how these microorganisms contribute to improve the health status is still a challenge. Previously, we have demonstrated that Enterococcus faecalis CECT7121 implants itself and persists in the murine gastrointestinal tract, and enhances and skews the profile of cytokines towards the Th1 phenotype in several biological models. Given the importance of dendritic cells (DCs) in the orchestration of immunity, the aim of this work was to elucidate the influence of E. faecalis CECT7121 on DCs and the outcome of the immune responses. In this work we show that E. faecalis CECT7121 induces a strong dose-dependent activation of DCs and secretion of high levels of IL-12, IL-6, TNFα, and IL-10. This stimulation is dependent on TLR signaling, and skews the activation of T cells towards the production of IFNγ. The influence of this activation in the establishment of Th responses in vivo shows the accumulation of specific IFNγ-producing cells. Our findings indicate that the activation exerted by E. faecalis CECT7121 on DCs and its consequence on the cellular adaptive immune response may have broad therapeutic implications in immunomodulation.

Carbohydrates as allergens

Complex carbohydrates are effective inducers of Th2 responses, and carbohydrate antigens can stimulate the production of glycan-specific antibodies. In instances where the antigen exposure occurs through the skin, the resulting antibody production can contain IgE class antibody. The glycan-stimulated IgE may be non-specific but may also be antigen specific. This review focuses on the production of cross-reactive carbohydrate determinants, the recently identified IgE antibody response to a mammalian oligosaccharide epitope, galactose-alpha-1,3-galactose (alpha-gal), as well as discusses practical implications of carbohydrates in allergy. In addition, the biological effects of carbohydrate antigens are reviewed in setting of receptors and host recognition.

Modulation of Th1/Th2 immune responses by killed Propionibacterium acnes and its soluble polysaccharide fraction in a type I hypersensitivity murine model: induction of different activation status of antigen-presenting cells

Propionibacterium acnes (P. acnes) is a gram-positive anaerobic bacillus present in normal human skin microbiota, which exerts important immunomodulatory effects, when used as heat- or phenol-killed suspensions. We previously demonstrated that heat-killed P. acnes or its soluble polysaccharide (PS), extracted from the bacterium cell wall, suppressed or potentiated the Th2 response to ovalbumin (OVA) in an immediate hypersensitivity model, depending on the treatment protocol. Herein, we investigated the mechanisms responsible for these effects, using the same model and focusing on the activation status of antigen-presenting cells (APCs). We verified that higher numbers of APCs expressing costimulatory molecules and higher expression levels of these molecules are probably related to potentiation of the Th2 response to OVA induced by P. acnes or PS, while higher expression of toll-like receptors (TLRs) seems to be related to Th2 suppression. In vitro cytokines production in cocultures of dendritic cells and T lymphocytes indicated that P. acnes and PS seem to perform their effects by acting directly on APCs. Our data suggest that P. acnes and PS directly act on APCs, modulating the expression of costimulatory molecules and TLRs, and these differently activated APCs drive distinct T helper patterns to OVA in our model.

Bacterial skin commensals and their role as host guardians

Recent years' investigations of the co-evolution and functional integration of the human body and its commensal microbiota have disclosed that the microbiome has a major impact on physiological functions including protection against infections, reaction patterns in the immune system, and disposition for inflammation-mediated diseases. Two ubiquitous members of the skin microbiota, the Gram-positive bacteria Staphylococcus epidermidis and Propionibacterium acnes, are predominant on human epithelia and in sebaceous follicles, respectively. Their successful colonisation is a result of a commensal or even mutualistic lifestyle, favouring traits conferring persistency over aggressive host-damaging properties. Some bacterial properties suggest an alliance with the host to keep transient, potential pathogens at bay, such as the ability of S. epidermidis to produce antimicrobials, or the production of short-chain fatty acids by P. acnes. These features can function together with host-derived components of the innate host defence to establish and maintain the composition of a health-associated skin microbiota. However, depending largely on the host status, the relationship between the human host and S. epidermidis/P. acnes can also have parasitic features. Both microorganisms are frequently isolated from opportunistic infections. S. epidermidis is a causative agent of hospital-acquired infections, mostly associated with the use of medical devices. P. acnes is suspected to be of major importance in the pathogenesis of acne and also in a number of other opportunistic infections. In this review we will present bacterial factors and traits of these two key members of our skin microbiota and discuss how they contribute to mutualistic and parasitic properties. The elucidation of their roles in health-promoting or disease-causing processes could lead to new prophylactic and therapeutic strategies against skin disorders and other S. epidermidis/P. acnes-associated diseases, and increase our understanding of the delicate interplay of the skin microbiota with the human host.

Priming dendritic cells for th2 polarization: lessons learned from helminths and implications for metabolic disorders

Nearly one quarter of the world's population is infected with helminth parasites. A common feature of helminth infections is the manifestation of a type 2 immune response, characterized by T helper 2 (Th2) cells that mediate anti-helminth immunity. In addition, recent literature describes a close association between type 2 immune responses and wound repair, suggesting that a Th2 response may concurrently mediate repair of parasite-induced damage. The molecular mechanisms that govern Th2 responses are poorly understood, although it is clear that dendritic cells (DCs), which are the most efficient antigen-presenting cells in the immune system, play a central role. Here, we review the molecular mechanisms by which DCs polarize Th2 cells, examining both helminth antigens and helminth-mediated tissue damage as Th2-inducing triggers. Finally, we discuss the implication of these findings in the context of metabolic disorders, as recent literature indicates that various aspects of the Th2-associated inflammatory response contribute to metabolic homeostasis.

The Differentiation of CD4(+) T-Helper Cell Subsets in the Context of Helminth Parasite Infection

Helminths are credited with being the major selective force driving the evolution of the so-called “type 2” immune responses in vertebrate animals, with their size and infection strategies presenting unique challenges to the immune system. Originally, type 2 immune responses were defined by the presence and activities of the CD4⁺ T-helper 2 subset producing the canonical cytokines IL-4, IL-5, and IL-13. This picture is now being challenged by the discovery of a more complex pattern of CD4⁺ T-helper cell subsets that appear during infection, including Tregs, Th17, Tfh, and more recently, Th22, Th9, and ThGM. In addition, a clearer view of the mechanisms by which helminths and their products selectively prime the CD4⁺ T-cell subsets is emerging. In this review, we have focused on recent data concerning the selective priming, differentiation, and functional role of CD4⁺ T-helper cell subsets in the context of helminth infection. We argue for a re-evaluation of the original Th2 paradigm and discuss how the observed plasticity of the T-helper subsets may enable the parasitized host to achieve an appropriate compromise between elimination, tissue repair, containment, and pathology.

Helminths in the hygiene hypothesis: sooner or later?

There is increasing recognition that exposures to infectious agents evoke fundamental effects on the development and behaviour of the immune system. Moreover, where infections (especially parasitic infections) have declined, immune responses appear to be increasingly prone to hyperactivity. For example, epidemiological studies of parasite-endemic areas indicate that prenatal or early-life experience of infections can imprint an individual's immunological reactivity. However, the ability of helminths to dampen pathology in established inflammatory diseases implies that they can have therapeutic effects even if the immune system has developed in a low-infection setting. With recent investigations of how parasites are able to modulate host immune pathology at the level of individual parasite molecules and host cell populations, we are now able to dissect the nature of the host-parasite interaction at both the initiation and recall phases of the immune response. Thus the question remains - is the influence of parasites on immunity one that acts primarily in early life, and at initiation of the immune response, or in adulthood and when recall responses occur? In short, parasite immunosuppression - sooner or later?

Combatting infectious diseases; nanotechnology as a platform for rational vaccine design

Currently, several successful vaccines are available. However, for pathogens with a highly variable genetic composition, and for which serum IgG antibodies are not a useful correlate of protection, effective vaccines are yet to be developed. This is due to a lack of both the understanding of the immunological pathways leading to long-term protection and the ability to translate the available knowledge into a suitable vaccine formulation. Regarding the latter, nanoparticles can be an attractive platform for vaccine development, as they offer multiple options for improving safety and efficacy. For example, side effects might be decreased upon encapsulation of the adjuvant and the concomitant delivery of antigen and adjuvant is a very promising tool for increasing efficacy. In addition to the many promises, the use of nanoparticles as vaccine carriers should be implemented with caution: the more sophisticated a particle, the more parameters need to be controlled during production and storage.

Elongated TCR alpha chain CDR3 favors an altered CD4 cytokine profile

Background

CD4 T lymphocyte activation requires T cell receptor (TCR) engagement by peptide/MHC (major histocompatibility complex) (pMHC). The TCR complementarity-determining region 3 (CDR3) contains variable α and β loops critical for pMHC recognition. During any immune response, tuning of TCR usage through progressive clonal selection occurs. Th1 and Th2 cells operate at different avidities for activation and display distinct transcriptional programs, although polarization may be plastic, influenced by pathogens and cytokines. We therefore hypothesized that CDR3αβ sequence features may intrinsically influence CD4 phenotype during progression of a response.

Results

We show that CD4 polarization involves distinct CDR3α usage: Th1 and Th17 cells favored short TCR CDR3α sequences of 12 and 11 amino acids, respectively, while Th2 cells favored elongated CDR3α loops of 14 amino acids, with lower predicted affinity. The dominant Th2- and Th1-derived TCRα sequences with14 amino acid CDR3 loops and 12 amino acid CDR3 loops, respectively, were expressed in TCR transgenics. The functional impact of these TCRα transgenes was assessed after in vivo priming with a peptide/adjuvant. The short, Th1-derived receptor transgenic T cell lines made IFNγ, but not IL-4, 5 or 13, while the elongated, Th2-derived receptor transgenic T cell lines made little or no IFNγ, but increased IL-4, 5 and 13 with progressive re-stimulations, mirrored by GATA-3 up-regulation. T cells from primed Th2 TCRα transgenics selected dominant TCR Vβ expansions, allowing us to generate TCRαβ transgenics carrying the favored, Th2-derived receptor heterodimer. Primed T cells from TCRαβ transgenics made little or no IL-17 or IFNγ, but favored IL-9 after priming with Complete Freund’s adjuvant and IL-4, 5, 9, 10 and 13 after priming with incomplete Freund’s. In tetramer-binding studies, this transgenic receptor showed low binding avidity for pMHC and polarized T cell lines show TCR avidity for Th17 > Th1 > Th2. While transgenic expression of a Th2-derived, ‘elongated’ TCR-CDR3α and the TCRαβ pair, clearly generated a program shifted away from Th1 immunity and with low binding avidity, cytokine-skewing could be over-ridden by altering peptide challenge dose.

Conclusion

We propose that selection from responding clones with distinctive TCRs on the basis of functional avidity can direct a preference away from Th1 effector responses, favoring Th2 cytokines.

Molecular characterization and immune modulation properties of Clonorchis sinensis-derived RNASET2

BACKGROUND

Clonorchis sinensis (C. sinensis, Cs) is a trematode parasite that often causes chronic cumulative infections in the hepatobiliary ducts of the host and can lead to pathological changes by continuously released excretory/secretory proteins (ESPs). A T2 ribonuclease in trematode ESPs, has been identified as a potent regulator of dendritic cell (DCs) modulation. We wondered whether there was a counterpart present in CsESPs with similar activity. To gain a better understanding of CsESPs associated immune responses, we identified and characterized RNASET2 of C. sinensis (CsRNASET2) in this paper.

METHODS

We expressed CsRNASET2 in Pichia pastoris and identified its molecular characteristics using bioinformatic analysis and experimental approaches. The immune modulation activities of CsRNASET2 were confirmed by evaluating cytokine production and surface markers of recombinant CsRNASET2 (rCsRNASET2) co-cultured DCs, and monitoring levels of IgG isotypes from rCsRNASET2 administered BALB/c mice.

RESULTS

CsRNASET2 appeared to be a glycoprotein of T2 ribonuclease family harboring conserved CAS motifs and rich in B-cell epitopes. Furthermore, CsRNASET2 was present in CsESPs and was able to modulate cytokine production of DCs. In addition, rCsRNASET2 could significantly suppress the expression of lipopolysaccharide-induced DCs maturation markers. In addition, when subcutaneously administered with rCsRNASET2 there was a marked effect on IgG isotypes in mouse sera.

CONCLUSION

Collectively, we revealed that CsRNASET2, a T2 ribonuclease present in CsESPs, could modulate DCs maturation and might play an important role in C. sinensis associated immune regulation in the host.

Effect of helminth-induced immunity on infections with microbial pathogens

Helminth infections are ubiquitous worldwide and can trigger potent immune responses that differ from and potentially antagonize host protective responses to microbial pathogens. In this Review we focus on the three main killers in infectious disease-AIDS, tuberculosis and malaria-and critically assesses whether helminths adversely influence host control of these diseases. We also discuss emerging concepts for how M2 macrophages and helminth-modulated dendritic cells can potentially influence the protective immune response to concurrent infections. Finally, we present evidence advocating for more efforts to determine how and to what extent helminths interfere with the successful control of specific concurrent coinfections.

Patterns and processes in parasite co-infection

Co-infection of individual hosts by multiple parasite species is a pattern that is very commonly observed in natural populations. Understanding the processes that generate these patterns poses a challenge. For example, it is difficult to discern the relative roles of exposure and susceptibility in generating the mixture and density of parasites within hosts. Yet discern them we must, if we are to design and deliver successful medical interventions for co-infected populations. Here, we synthesise an emergent understanding of how processes operate and interact to generate patterns of co-infection. We consider within-host communities (or infracommunities) generally, that is including not only classical parasites but also the microbiota that are so abundant on mucosal surfaces and which are increasingly understood to be so influential on host biology. We focus on communities that include a helminth, but we expect similar inferences to pertain to other taxa. We suggest that, thanks to recent research at both the within-host (e.g. immunological) and between-host (e.g. epidemiological) scales, researchers are poised to reveal the processes that generate the observed distribution of parasite communities among hosts. Progress will be facilitated by using new technologies as well as statistical and experimental tools to test competing hypotheses about processes that might generate patterns in co-infection data. By understanding the multiple interactions that underlie patterns of co-infection, we will be able to understand and intelligently predict how a suite of co-infections (and thus the host that bears them) will together respond to medical interventions as well as other environmental changes. The challenge for us all is to become scholars of co-infections.

Dendritic cells and other innate determinants of T helper cell polarisation

Adaptive immunity plays a crucial role in natural host defence against pathogens and tumours, and is central to the long-term protective effect of vaccines. It is mediated by T and B cells that are activated through antigen-specific receptors. By contrast, innate immunity responds immediately to infection and damage, and is activated through binding of conserved pathogen or damage-associated molecules to pattern recognition receptors (PRRs) on dendritic cells (DCs) and other innate immunity cell types. Recent studies have demonstrated that the innate immune system also functions to direct the adaptive immune response, not only through antigen presentation but also by providing the key signals for the differentiation of naive CD4+ T cells into functionally distinct T helper (Th) cell subtypes.

Propionibacterium acnes-killed attenuates the inflammatory response and protects mice from sepsis by modulating inflammatory factors

Background

Sepsis is a systemic inflammation associated with infection caused by pathogenic micro-organisms with high mortality rates.

Objective

In this study, we investigated the protective effect of Propionibacterium acnes-killed against polymicrobial sepsis induced by cecal ligation and puncture.

Methods

The mice were treated by intramuscular route in 1, 3, 5, and 7 days before the cecal ligation and puncture induction. The control group animals received vehicle (saline solution 0.9%) and the animals of the treated group received the P. acnes-killed (0.4 mg/animal). After anesthesia, midline laparotomy was performed with exposure of cecum followed by ligature and one transverse perforation of the same, with a 18 G needle, for induction of lethal sepsis. After surgery, the cecum of the animals was replaced into the peritoneal cavity, and it was closed with a 4.0 nylon suture. The survival of animals subjected to lethal sepsis was evaluated after cecal ligation and puncture induction. Six hours after the induction of sepsis, neutrophil migration, the number of bacteria, TNF-α, MCP-1, IL-6, and IL-10 were performed in the peritoneal lavage.

Results

Prophylactic treatment with P. acnes-killed increased the survival of the animals, followed by a significant decrease in the TNF-α, IL-10, and MCP-1 levels, 6 h after cecal ligation and puncture. Furthermore, P. acnes-killed administration reduced the number of bacteria in the peritoneal cavity with increased migration of leukocytes, especially neutrophils.

Conclusion

P. acnes-killed promoted increased survival rate of animals with sepsis, in part attributed to its immunomodulatory properties against pathogenic microorganisms, as well as better control of infection by reducing bacterial counts.

Memory CD8 T cells specific for plasmodia liver-stage antigens maintain protracted protection against malaria

Immunologic memory induced by pathogenic agents or vaccinations is inextricably linked to long-lasting protection. Adequately maintained memory T and B cell pools assure a fast, effective, and specific response against re-infections. Studies of immune responses amongst residents of malaria endemic areas suggest that memory responses to Plasmodia antigens appear to be neither adequately developed nor maintained, because persons who survive episodes of childhood malaria remain vulnerable to persistent or intermittent malaria infections. By contrast, multiple exposures of humans and laboratory rodents to radiation-attenuated Plasmodia sporozoites (γ-spz) induces sterile and long-lasting protection against experimental sporozoite challenge. Protection is associated with MHC-class I-dependent CD8 T cells, the key effectors against pre-erythrocytic stage infection. We have adopted the P. berghei γ-spz mouse model to study memory CD8 T cells that are specific for antigens expressed by Pb liver-stage (LS) parasites and are found predominantly in the liver. On the basis of phenotypic and functional characteristics, we have demonstrated that liver CD8 T cells form two subsets: CD44^hiCD62L^loKLRG-1⁺CD107⁺CD127⁻CD122^loCD8 T effector/effector memory (T_E/EM) cells that are the dominant IFN-γ producers and CD44^hiCD62L^hiKLRG-1⁻CD107⁻CD127⁺CD122^hiCD8 T central memory (T_CM) cells. In this review, we discuss our observations concerning the role of CD8 T_E/EM and CD8 T_CM cells in the maintenance of protracted protective immunity against experimental malaria infection. Finally, we present a hypothesis consistent with a model whereby intrahepatic CD8 T_CM cells, that are maintained in part by LS-Ag depot and by IL-15-mediated survival and homeostatic proliferation, form a reservoir of cells ready for conscription to CD8 T_E/EM cells needed to prevent re-infections.

Immunological mechanisms by which concomitant helminth infections predispose to the development of human tuberculosis

Helminthic infections afflict over 1.5 billion people worldwide, while Mycobacterium tuberculosis infects one third of the world's population, resulting in 2 million deaths per year. Although tuberculosis and helminthic infections coexist in many parts of the world, and it has been demonstrated that the T-helper 2 and T-regulatory cell responses elicited by helminths can affect the ability of the host to control mycobacterial infection, it is still unclear whether helminth infections in fact affect tuberculosis disease. In this review article, current progress in the knowledge about the immunomodulation induced by helminths to diminish the protective immune responses to bacille Calmette-Guerin vaccination is reviewed, and the knowledge about the types of immune responses modulated by helminths and the consequences for tuberculosis are summarized. In addition, recent data supporting the significant reduction of both M. tuberculosis antigen-specific Toll-like receptor (TLR) 2 and TLR9 expression, and pro-inflammatory cytokine responses to TLR2 and TLR9 ligands in individuals with M. tuberculosis and helminth co-infection were discussed. This examination will allow to improve understanding of the immune responses to mycobacterial infection and also be of great relevance in combating human tuberculosis.

Type 2 innate immunity in helminth infection is induced redundantly and acts autonomously following CD11c(+) cell depletion

Infection with gastrointestinal helminths generates a dominant type 2 response among both adaptive (Th2) and innate (macrophage, eosinophil, and innate lymphoid) immune cell types. Two additional innate cell types, CD11c(high) dendritic cells (DCs) and basophils, have been implicated in the genesis of type 2 immunity. Investigating the type 2 response to intestinal nematode parasites, including Heligmosomoides polygyrus and Nippostrongylus brasiliensis, we first confirmed the requirement for DCs in stimulating Th2 adaptive immunity against these helminths through depletion of CD11c(high) cells by administration of diphtheria toxin to CD11c.DOG mice. In contrast, responsiveness was intact in mice depleted of basophils by antibody treatment. Th2 responses can be induced by adoptive transfer of DCs, but not basophils, exposed to soluble excretory-secretory products from these helminths. However, innate type 2 responses arose equally strongly in the presence or absence of CD11c(high) cells or basophils; thus, in CD11c.DOG mice, the alternative activation of macrophages, as measured by expression of arginase-1, RELM-α, and Ym-1 (Chi3L3) in the intestine following H. polygyrus infection or in the lung following N. brasiliensis infection, was unaltered by depletion of CD11c-expressing DCs and alveolar macrophages or by antibody-mediated basophil depletion. Similarly, goblet cell-associated RELM-β in lung and intestinal tissues, lung eosinophilia, and expansion of innate lymphoid ("nuocyte") populations all proceeded irrespective of depletion of CD11c(high) cells or basophils. Thus, while CD11c(high) DCs initiate helminth-specific adaptive immunity, innate type 2 cells are able to mount an autonomous response to the challenge of parasite infection.

Trichinella spiralis: shaping the immune response

The co-evolution of a wide range of helminth parasites and vertebrates represented a constant pressure on the host's immune system and a selective force for shaping the immune response. Modulation of the immune system by parasites is accomplished partly by dendritic cells. When exposed to helminth parasites or their products, dendritic cells do not become classically mature and are potent inducers of Th2 and regulatory responses. Treating animals with helminths (eggs, larvae, extracts) causes dampening or in some cases prevention of allergic or autoimmune diseases. Trichinella spiralis (T. spiralis) possess a capacity to retune the immune cell repertoire, acting as a moderator of the host response not only to itself but also to third party antigens. In this review, we will focus on the ability of T. spiralis-stimulated dendritic cells to polarize the immune response toward Th2 and regulatory mode in vitro and in vivo and also on the capacity of this parasite to modulate autoimmune disease--such as experimental autoimmune encephalomyelitis.

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

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

Helminth infections: therapeutic potential in autoimmune disorders

Knowledge of immunity enables us to predict that the reactions set in response to infection with helminth would prevent concomitant disease driven by an opposing spectrum of immune events. In another way, the immune response generated to combat the helminth infection could counteract the immunopathological reactions that drive autoimmune diseases. Rodent model systems recapitulate many aspects of human autoimmune diseases and have been enormously useful in defining mechanisms of immunopathology after infection. From this theoretical perspective, many researchers have proved that infection with a variety of helminth can ameliorate disease in murine model systems. Thus, helminth-evoked Th2 events were shown to improve disorders in which Th1 events predominated. This raised the question, 'Can this information be translated into therapies for autoimmune diseases in humans via actual infection, cell delivery or drug intervention?' In this review, we will present some experimental trails to treat autoimmune disorders through establishment of some parasitic infections.

Concurrent bacterial stimulation alters the function of helminth-activated dendritic cells, resulting in IL-17 induction

Infection with schistosome helminths is associated with granulomatous inflammation that forms around parasite eggs trapped in host tissues. In severe cases, the resulting fibrosis can lead to organ failure, portal hypertension, and fatal bleeding. Murine studies identified IL-17 as a critical mediator of this immunopathology, and mouse strains that produce high levels of IL-17 in response to schistosome infection show increased mortality. In this article, we demonstrate that schistosome-specific IL-17 induction by dendritic cells from low-pathology C57BL/6 mice is normally regulated by their concomitant induction of IL-10. Simultaneous stimulation of schistosome-exposed C57BL/6 dendritic cells with a heat-killed bacterium enabled these cells to overcome IL-10 regulation and induce IL-17, even in wild-type C57BL/6 recipients. This schistosome-specific IL-17 was dependent on IL-6 production by the copulsed dendritic cells. Coimmunization of C57BL/6 animals with bacterial and schistosome Ags also resulted in schistosome-specific IL-17, and this response was enhanced in the absence of IL-10-mediated immune regulation. Together, our data suggest that the balance of pro- and anti-inflammatory cytokines that determines the severity of pathology during schistosome infection can be influenced not only by host and parasite, but also by concurrent bacterial stimulation.