Schistosome infection intensity is inversely related to auto-reactive antibody levels

Regulatory T-cells in helminth infection: induction, function and therapeutic potential

Helminth parasites infect an alarmingly large proportion of the world's population, primarily within tropical regions, and their ability to down‐modulate host immunity is key to their persistence. Helminths have developed multiple mechanisms that induce a state of hyporesponsiveness or immune suppression within the host; of particular interest are mechanisms that drive the induction of regulatory T‐cells (Tregs). Helminths actively induce Tregs either directly by secreting factors, such as the TGF‐β mimic Hp‐TGM, or indirectly by interacting with bystander cell types such as dendritic cells and macrophages that then induce Tregs. Expansion of Tregs not only enhances parasite survival but, in cases such as filarial infection, Tregs also play a role in preventing parasite‐associated pathologies. Furthermore, Tregs generated during helminth infection have been associated with suppression of bystander immunopathologies in a range of inflammatory conditions such as allergy and autoimmune disease. In this review, we discuss evidence from natural and experimental infections that point to the pathways and molecules involved in helminth Treg induction, and postulate how parasite‐derived molecules and/or Tregs might be applied as anti‐inflammatory therapies in the future.

Regulation of immunity and allergy by helminth parasites

There is increasing interest in helminth parasite modulation of the immune system, both from the fundamental perspective of the "arms race" between host and parasite, and equally importantly, to understand if parasites offer new pathways to abate and control untoward immune responses in humans. This article reviews the epidemiological and experimental evidence for parasite down-regulation of host immunity and immunopathology, in allergy and other immune disorders, and recent progress towards defining the mechanisms and molecular mediators which parasites exploit in order to modulate their host. Among these are novel products that interfere with epithelial cell alarmins, dendritic cell activation, macrophage function and T-cell responsiveness through the promotion of an immunoregulatory environment. These modulatory effects assist parasites to establish and survive, while dampening immune reactivity to allergens, autoantigens and microbiome determinants.

Inflammation during Schistosoma haematobium infection and anti-allergy in pre-school-aged children living in a rural endemic area in Zimbabwe

BACKGROUND

Allergies and autoimmune disorders are less prevalent in areas where parasitic infections are abundant. The relationship between schistosomiasis, Chitinase 3-Like 1 protein (YKL-40), an inflammatory marker, and antinuclear antibodies (ANA), an allergy marker, was investigated in pre-school-aged children (1-5 years old) living in an area endemic to Schistosoma haematobium infection.

METHODS

Cross-sectional study including 145 participants, 66 females and 79 males. S. haematobium infection was diagnosed using the urine filtration technique. Levels of YKL-40 and antinuclear antibodies concentrations were determined using enzyme-linked immunosorbent assay.

RESULTS

The prevalence of S. haematobium infection was 21.4 % (n = 31) with 114 not infected, 18 with light and 13 with moderate infections. YKL-40 levels were higher in the S. haematobium-infected group than in the uninfected group (P = 0.038). However, S. haematobium infection intensity did not correlate with YKL-40 levels. ANA levels were significantly higher in uninfected children than in infected children (P = 0.028). There was a significant inverse relationship between ANA levels and schistosome infection intensity (r = -0.225, P = 0.016). The correlation between ANA levels and YKL-40 levels was not significant.

CONCLUSION

Inflammatory marker in pre-school-aged children living in an area endemic for schistosomiasis indicate YKL-40 as a possible biomarker of S. haematobium infection in pre-school-aged children, warranting further investigations in a longitudinal study.  The study gives an insight into allergy as ANA levels were higher in schistosome-uninfected than infected participants, further studies on allergies are needed.

Placental gene expression and antibody levels of mother-neonate pairs reveal an enhanced risk for inflammation in a helminth endemic country

In utero exposure to environmental factors can modify the development of allergies later in life whereby the mechanisms of the feto-maternal crosstalk still remain largely unknown. Murine studies revealed that inflammatory maternal signals elicited by chronic helminth infection within the placenta imprint a distinct gene expression profile related to the Vitamin-D-receptor (VDR)-inflammation-axis. We thus investigated whether pro- or anti- inflammatory immune responses as well as VDR and related gene expression within the placenta differ between women from helminth-endemic and non-endemic areas. A prospective pilot study was conducted in Munich, Germany (helminth non-endemic) and Lambaréné, Gabon (helminth-endemic). At delivery, clinical information alongside placenta tissue samples and maternal and cord blood were obtained for further laboratory analysis. Schistosoma haematobium infection was detected in 13/54 (23%) Gabonese women. RT PCR revealed significantly lower gene expression of VDR, Cyp27b1, Foxp3 and IL10 in Gabonese compared to German placentae as well as significantly lower levels of plasma IgG4 in newborns resulting in a significantly higher IgE/IgG4 ratio. These findings demonstrate that exposure in utero to different environments alters placental gene expression and thus possibly plays a role in the development and modulation of the immune system of the offspring.

Cross-Domain and Viral Interactions in the Microbiome

The importance of the microbiome to human health is increasingly recognized and has become a major focus of recent research. However, much of the work has focused on a few aspects, particularly the bacterial component of the microbiome, most frequently in the gastrointestinal tract. Yet humans and other animals can be colonized by a wide array of organisms spanning all domains of life, including bacteria and archaea, unicellular eukaryotes such as fungi, multicellular eukaryotes such as helminths, and viruses. As they share the same host niches, they can compete with, synergize with, and antagonize each other, with potential impacts on their host. Here, we discuss these major groups making up the human microbiome, with a focus on how they interact with each other and their multicellular host.

Antinuclear antibodies and interleukin responses in patients with Schistosoma japonicum infection

Schistosomiasis poses a serious threat to public health, and the infection will develop into chronic and advanced late-stage disease if not treated. Apart from the clinical signs due to immune reactions to schistosome eggs trapped in host tissues, it also increases the risk for the development of autoimmunity reflected by dysfunctional, auto-reactive antibodies. Antinuclear antibodies (ANA) have been reported in schistosomiasis due to S. mansoni and S. haematobium. We demonstrate ANA in schistosomiasis japonica and explore the relationship between this infection and autoimmune disease by measuring ANA and interleukin (IL)-10, IL-12 and IL-17 responses in the sera of 125 Chinese patients with different stages of schistosomiasis japonica. The incidence rates of ANA in the patients with acute, chronic and late stages of schistosomiasis infection were 6.7%, 23.3% and 70.0%, respectively, with statistically significant differences between each stage (P = 0.000). IL-17 concentrations were high at the acute stage of schistosomiasis compared to the other stages of the disease (P = 0.000). This pattern was also seen for IL-10 and IL-12 concentrations (P = 0.01). IL concentrations in patients in the chronic and late stages of the disease were low and showed no difference compared to the healthy adults.

Aberrant plasma MMP and TIMP dynamics in Schistosoma - Immune reconstitution inflammatory syndrome (IRIS)

Background

Among the different faces of immune reconstitution inflammatory syndrome (IRIS) developing in HIV-patients, no clinical definition has been reported for Schistosomiasis-IRIS (Schisto-IRIS). Although Schisto-IRIS remains largely uninvestigated, matrix metalloproteinases (MMP) and tissue inhibitors of metalloproteinases (TIMP) have previously been associated with S. mansoni infection and tuberculosis-IRIS. Here, we aimed to investigate the relevance of these markers in Schisto-IRIS.

Methodology

Patients were diagnosed with IRIS related to S. mansoni within a cohort of patients with Schistosomiasis-HIV co-infection, using a clinical working definition of Schisto-IRIS. We compared 9 patients who developed Schisto-IRIS to 9 Schisto⁺HIV⁺ controls who did not, and 9 Schisto^-HIV⁺ controls. Plasma levels of MMP-1, MMP-7, MMP-10, TIMP-1, TIMP-2, sCD14, intestinal fatty-acid binding protein, C-reactive protein, and 8 anti-nuclear antibodies (ANA) were analyzed prior to and during 3 months of ART.

Principal findings

Although no differences were observed for MMP-1 and -7, MMP-10 levels decreased significantly in Schisto⁺HIV⁺ controls during 3 months of ART (p = 0.005) while persisting in Schisto-IRIS patients at significantly higher levels compared to Schisto^-HIV⁺ controls (p≤0.030). In contrast TIMP-1 levels only decreased significantly in Schisto-IRIS patients (p = 0.012), while TIMP-2 levels were lower compared to Schisto⁺HIV⁺ controls at 2 weeks (p = 0.007), 1 month (p = 0.005) and 3 months (p = 0.031) of ART. Five out of 8 ANAs studied decreased significantly in Schisto-IRIS patients after 1 month of ART(p≤0.039), whereas only 1 ANA decreased for Schisto⁺HIV⁺ controls (p = 0.027).

Conclusions/Significance

In this study, we propose a working definition for the diagnosis of Schisto-IRIS in resource limited settings. We report persistent plasma levels of MMP-10, along with a more pronounced decrease in TIMP-1 and ANA-levels, and low levels of TIMP-2 during 3 months of ART. Corresponding to the clinical symptoms, these data suggest that Schisto-IRIS is marked by unbalanced MMP/TIMP dynamics which favor inflammation.

A subset of HIV-patients starting antiretroviral therapy are at risk of developing immune-driven worsening symptoms of a previously treated opportunistic infection. This paradoxical immune reconstitution inflammatory syndrome (IRIS) has been abundantly described in common co-infections such as M. tuberculosis (TB-IRIS), whereas IRIS associated with Schistosoma mansoni (Schisto-IRIS) is less well studied. Nonetheless, HIV and S. mansoni are highly co-endemic in Sub-Saharan Africa and the considerable clinical burden of Schisto-IRIS in the field should not be underestimated. Moreover, no clinical definition exists to help diagnose this complication. Although little is known about the immune dysregulation in Schisto-IRIS, matrix metalloproteinases (MMPs) and tissue inhibitor of metalloproteinases (TIMPs) have been linked to schistosomiasis and TB-IRIS on account of their role in tissue-destructive inflammation. The current study is nested within a three-month case-control study in schistosomiasis/HIV co-infected fishermen starting ART in Kenya. We propose a clinical working definition for Schisto-IRIS, based on critical evaluation of symptoms developing during ART. Our study now links aberrant dynamics of MMPs and TIMPs to Schisto-IRIS as well. Given the role of MMPs and TIMPs in tissue remodeling and inflammation, our findings suggest that Schisto-IRIS is marked by unbalanced MMP/TIMP dynamics that favor inflammation.

Microbes and Viruses Are Bugging the Gut in Celiac Disease. Are They Friends or Foes?

The links between microorganisms/viruses and autoimmunity are complex and multidirectional. A huge number of studies demonstrated the triggering impact of microbes and viruses as the major environmental factors on the autoimmune and inflammatory diseases. However, growing evidences suggest that infectious agents can also play a protective role or even abrogate these processes. This protective crosstalk between microbes/viruses and us might represent a mutual beneficial equilibrium relationship between two cohabiting ecosystems. The protective pathways might involve post-translational modification of proteins, decreased intestinal permeability, Th1 to Th2 immune shift, induction of apoptosis, auto-aggressive cells relocation from the target organ, immunosuppressive extracellular vesicles and down regulation of auto-reactive cells by the microbial derived proteins. Our analysis demonstrates that the interaction of the microorganisms/viruses and celiac disease (CD) is always a set of multidirectional processes. A deeper inquiry into the CD interplay with Herpes viruses and Helicobacter pylori demonstrates that the role of these infections, suggested to be potential CD protectors, is not as controversial as for the other infectious agents. The outcome of these interactions might be due to a balance between these multidirectional processes.

Helminths in the gastrointestinal tract as modulators of immunity and pathology

Helminth parasites are highly prevalent in many low- and middle-income countries, in which inflammatory bowel disease and other immunopathologies are less frequent than in the developed world. Many of the most common helminths establish themselves in the gastrointestinal tract and can exert counter-inflammatory influences on the host immune system. For these reasons, interest has arisen as to how parasites may ameliorate intestinal inflammation and whether these organisms, or products they release, could offer future therapies for immune disorders. In this review, we discuss interactions between helminth parasites and the mucosal immune system, as well as the progress being made toward identifying mechanisms and molecular mediators through which it may be possible to attenuate pathology in the intestinal tract.

Human schistosomiasis in the post mass drug administration era

Profound changes are occurring in the epidemiology of schistosomiasis, a neglected tropical disease caused by a chronic infection with parasitic helminths of the genus Schistosoma. Schistosomiasis currently affects 240 million people worldwide, mostly in sub-Saharan Africa. The advent and proliferation of mass drug administration (MDA) programmes using the drug praziquantel is resulting in substantial increases in the number of people, mainly children aged 6-14 years, being effectively treated, approaching the point where most people in endemic areas will receive one or more treatments during their lifetimes. Praziquantel treatment not only cures infection but also frees the host from the powerful immunomodulatory action of the parasites. The treatment simultaneously enhances exposure to key parasite antigens, accelerating the development of protective acquired immunity, which would take many years to develop naturally. At a population level, these changes constitute a substantial alteration to schistosome ecology in that the parasites are more likely to be exposed not only to praziquantel directly but also to hosts with altered immune phenotypes. Here, we consider the consequences of this for schistosome biology, immunoepidemiology, and public health. We anticipate that there could be substantial effects on chronic pathology, natural immunity, vaccine development strategies, immune disorders, and drug efficacy. This makes for a complex picture that will only become apparent over decades. We recommend careful monitoring and assessment to accompany the roll-out of MDA programmes to ensure that the considerable health benefits to populations are achieved and sustained.

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.

Parasitic helminth infections and the control of human allergic and autoimmune disorders

The profile of global health today presents a striking reciprocal distribution between parasitic diseases in many of the world's lower-income countries, and ever-increasing levels of inflammatory disorders such as allergy, autoimmunity and inflammatory bowel diseases in the more affluent societies. Attention is particularly focused on helminth worm parasites, which are associated with protection from allergy and inflammation in both epidemiologic and laboratory settings. One mechanistic explanation of this is that helminths drive the regulatory arm of the immune system, abrogating the ability of the host to expel the parasites, while also dampening reactivity to many bystander specificities. Interest has therefore heightened into whether helminth parasites, or their products, hold therapeutic potential for immunologic disorders of the developed world. In this narrative review, progress across a range of trials is discussed, together with prospects for isolating individual molecular mediators from helminths that may offer defined new therapies for inflammatory conditions.

Schistosoma mansoni Larvae Do Not Expand or Activate Foxp3+ Regulatory T Cells during Their Migratory Phase

Foxp3⁺ regulatory T (Treg) cells play a key role in suppression of immune responses during parasitic helminth infection, both by controlling damaging immunopathology and by inhibiting protective immunity. During the patent phase of Schistosoma mansoni infection, Foxp3⁺ Treg cells are activated and suppress egg-elicited Th2 responses, but little is known of their induction and role during the early prepatent larval stage of infection. We quantified Foxp3⁺ Treg cell responses during the first 3 weeks of murine S. mansoni infection in C57BL/6 mice, a time when larval parasites migrate from the skin and transit the lungs en route to the hepatic and mesenteric vasculature. In contrast to other helminth infections, S. mansoni did not elicit a Foxp3⁺ Treg cell response during this early phase of infection. We found that the numbers and proportions of Foxp3⁺ Treg cells remained unchanged in the lungs, draining lymph nodes, and spleens of infected mice. There was no increase in the activation status of Foxp3⁺ Treg cells upon infection as assessed by their expression of CD25, Foxp3, and Helios. Furthermore, infection failed to induce Foxp3⁺ Treg cells to produce the suppressive cytokine interleukin 10 (IL-10). Instead, only CD4⁺ Foxp3⁻ IL-4⁺ Th2 cells showed increased IL-10 production upon infection. These data indicate that Foxp3⁺ Treg cells do not play a prominent role in regulating immunity to S. mansoni larvae and that the character of the initial immune response invoked by S. mansoni parasites contrasts with the responses to other parasitic helminth infections that promote rapid Foxp3⁺ Treg cell responses.

Differences in the Faecal Microbiome in Schistosoma haematobium Infected Children vs. Uninfected Children

Background

Several infectious diseases and therapeutic interventions cause gut microbe dysbiosis and associated pathology. We characterised the gut microbiome of children exposed to the helminth Schistosoma haematobium pre- and post-treatment with the drug praziquantel (PZQ), with the aim to compare the gut microbiome structure (abundance and diversity) in schistosome infected vs. uninfected children.

Methods

Stool DNA from 139 children aged six months to 13 years old; with S. haematobium infection prevalence of 27.34% was extracted at baseline. 12 weeks following antihelminthic treatment with praziqunatel, stool DNA was collected from 62 of the 139 children. The 16S rRNA genes were sequenced from the baseline and post-treatment samples and the sequence data, clustered into operational taxonomic units (OTUs). The OTU data were analysed using multivariate analyses and paired T- test.

Results

Pre-treatment, the most abundant phyla were Bacteroidetes, followed by Firmicutes and Proteobacteria respectively. The relative abundance of taxa among bacterial classes showed limited variation by age group or sex and the bacterial communities had similar overall compositions. Although there were no overall differences in the microbiome structure across the whole age range, the abundance of 21 OTUs varied significantly with age (FDR<0.05). Some OTUs including Veillonella, Streptococcus, Bacteroides and Helicobacter were more abundant in children ≤ 1 year old compared to older children. Furthermore, the gut microbiome differed in schistosome infected vs. uninfected children with 27 OTU occurring in infected but not uninfected children, for 5 of these all Prevotella, the difference was statistically significant (p <0.05) with FDR <0.05. PZQ treatment did not alter the microbiome structure in infected or uninfected children from that observed at baseline.

Conclusions

There are significant differences in the gut microbiome structure of infected vs. uninfected children and the differences were refractory to PZQ treatment.

The role of the gut microbiome in host health is becoming clearer with better characterisation of the nutritional, biochemical and immunological function of the microbes. However, to date, there is a paucity of studies describing/ investigating the role of the gut microbiome in infection, pathology and acquired immunity in children exposed to helminths, in sub-Saharan Africa. We determined how the diversity and abundance of different gut bacteria taxonomic groups differ with age, sex and infection with the helminths parasites causing bilharzia/schistosomiasis in children aged 6 months -13 years. The parasites are controlled by treatment with the antihelminthic praziquantel (PZQ), which is associated with diarrhoea within the first 24 hours of treatment in some children. We therefore also investigated the effects of PZQ treatment on the gut microbiome of the children 12 weeks post-PZQ treatment. The composition of the gut microbiome changed with age within the 0–3 year age range and also differed significantly in abundance of the different taxonomic groups between infected and uninfected children prior to treatment with PZQ. However, the pre-treatment microbiome structure was not altered by antihelminthic treatment of infected or uninfected children. Further studies are required to investigate causality and mechanisms of interaction.

Down Regulation of the TCR Complex CD3ζ-Chain on CD3+ T Cells: A Potential Mechanism for Helminth-Mediated Immune Modulation

The CD3ζ forms part of the T cell receptor (TCR) where it plays an important role in coupling antigen recognition to several intracellular signal-transduction pathways leading to T cell effector functions. Down regulation of CD3ζ leads to impairment of immune responses including reduced cell proliferation and cytokine production. In experimental models, helminth parasites have been shown to modulate immune responses directed against them and unrelated antigens, so called bystander antigens, but there is a lack of studies validating these observations in humans. This study investigated the relationship between expression levels of the TCR CD3ζ chain with lymphocyte cell proliferation during human infection with the helminth parasite, Schistosoma haematobium, which causes uro-genital schistosomiasis. Using flow cytometry, peripheral blood mononuclear cells (PBMCs) from individuals naturally exposed to S. haematobium in rural Zimbabwe were phenotyped, and expression levels of CD3ζ on T cells were related to intensity of infection. In this population, parasite infection intensity was inversely related to CD3ζ expression levels (p < 0.05), consistent with downregulation of CD3ζ expression during helminth infection. Furthermore, PBMC proliferation was positively related to expression levels of CD3ζ (p < 0.05) after allowing for confounding variables (host age, sex, and infection level). CD3ζ expression levels had a differing relationship between immune correlates of susceptibility and immunity, measured by antibody responses, indicating a complex relationship between immune activation status and immunity. The relationships between the CD3ζ chain of the TCR and schistosome infection, PBMC proliferation and schistosome-specific antibody responses have not previously been reported, and these results may indicate a mechanism for the impaired T cell proliferative responses observed during human schistosome infection.

Induction of regulatory cells by helminth parasites: exploitation for the treatment of inflammatory diseases

Helminth parasites are highly successful pathogens, chronically infecting a quarter of the world's population, causing significant morbidity but rarely causing death. Protective immunity and expulsion of helminths is mediated by T-helper 2 (Th2) cells, type 2 (M2) macrophages, type 2 innate lymphoid cells, and eosinophils. Failure to mount these type 2 immune responses can result in immunopathology mediated by Th1 or Th17 cells. Helminths have evolved a wide variety of approaches for immune suppression, especially the generation of regulatory T cells and anti-inflammatory cytokines interleukin-10 and transforming growth factor-β. This is a very effective strategy for subverting protective immune responses to prolong their survival in the host but has the bystander effect of modulating immune responses to unrelated antigens. Epidemiological studies in humans have shown that infection with helminth parasites is associated with a low incidence of allergy/asthma and autoimmunity in developing countries. Experimental studies in mice have demonstrated that regulatory immune responses induced by helminth can suppress Th2 and Th1/Th17 responses that mediate allergy and autoimmunity, respectively. This has provided a rational explanation of the 'hygiene hypothesis' and has also led to the exploitation of helminths or their immunomodulatory products in the development of new immunosuppressive therapies for inflammatory diseases in humans.

Reciprocal effects of Schistosoma mansoni infection on spontaneous autoimmune arthritis in IL-1 receptor antagonist-deficient mice

Schistosome infections have been shown to prevent inflammation in induced-type arthritis models. However, its effects on spontaneous arthritis remain unknown. We here investigated the effects of Schistosoma mansoni (Sm) infection on spontaneous autoimmune arthritis in IL-1 receptor antagonist (IL-1Ra)-deficient mice. Sm infection partially reduced the severity of arthritis in male IL-1Ra-deficient mice. The splenic responses of IL-17 and TNF-α were reduced, while those of IL-4 and IL-10 were enhanced by the infection. However, Sm infection increased IgG rheumatoid factor and anti-dsDNA IgG serum levels. These results suggest that Sm infection has both ameliorating and exacerbating effects on autoimmunity in IL-1Ra-deficient mice.

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?

Cytokine responses to the anti-schistosome vaccine candidate antigen glutathione-S-transferase vary with host age and are boosted by praziquantel treatment

Background

Improved helminth control is required to alleviate the global burden of schistosomiasis and schistosome-associated pathologies. Current control efforts rely on the anti-helminthic drug praziquantel (PZQ), which enhances immune responses to crude schistosome antigens but does not prevent re-infection. An anti-schistosome vaccine based on Schistosoma haematobium glutathione-S-transferase (GST) is currently in Phase III clinical trials, but little is known about the immune responses directed against this antigen in humans naturally exposed to schistosomes or how these responses change following PZQ treatment.

Methodology

Blood samples from inhabitants of a Schistosoma haematobium-endemic area were incubated for 48 hours with or without GST before (n = 195) and six weeks after PZQ treatment (n = 107). Concentrations of cytokines associated with innate inflammatory (TNFα, IL-6, IL-8), type 1 (Th1; IFNγ, IL-2, IL-12p70), type 2 (IL-4, IL-5, IL-13), type 17 (IL-17A, IL-21, IL-23p19) and regulatory (IL-10) responses were quantified in culture supernatants via enzyme-linked immunosorbent assay (ELISA). Factor analysis and multidimensional scaling were used to analyse multiple cytokines simultaneously.

Principal Findings

A combination of GST-specific type 2 (IL-5 and IL-13) and regulatory (IL-10) cytokines was significantly lower in 10–12 year olds, the age group at which S. haematobium infection intensity and prevalence peak, than in 4–9 or 13+ year olds. Following PZQ treatment there was an increase in the number of participants producing detectable levels of GST-specific cytokines (TNFα, IL-6, IL-8, IFNγ, IL-12p70, IL-13 and IL-23p19) and also a shift in the GST-specific cytokine response towards a more pro-inflammatory phenotype than that observed before treatment. Participant age and pre-treatment infection status significantly influenced post-treatment cytokine profiles.

Conclusions/Significance

In areas where schistosomiasis is endemic host age, schistosome infection status and PZQ treatment affect the cellular cytokine response to GST. Thus the efficacy of a GST-based vaccine may also be shaped by the demographic and epidemiological characteristics of targeted populations.

Schistosomiasis is caused by infection with Schistosoma spp. parasites, for which the main treatment is the drug praziquantel (PZQ). Since PZQ does not prevent reinfection, an anti-schistosome vaccine based on the Schistosoma haematobium enzyme glutathione-S-transferase (GST) is being developed. In this study we investigated the GST-specific immune responses of people naturally exposed to schistosomes and the affect that PZQ has on these responses. We cultured blood samples from a schistosome-exposed community with GST before and six weeks after PZQ treatment and measured a range of soluble proteins (cytokines) in culture supernatants as indicators of blood cell activation and phenotype. Before treatment, GST-specific cytokine responses varied with host age, particularly in children with high intensity schistosome infections. Following treatment, GST activated blood samples from more individuals to produce a broader range of cytokines and the combination of GST-specific cytokine responses reflected a more pro-inflammatory immune phenotype than that observed pre-treatment. Post-treatment responses varied according to host age and pre-treatment infection status. Taken together, our study suggests that current and future GST-based vaccine trials should take host age, schistosome infection status and PZQ treatment history into account since these factors influence GST-specific immune activation.

Sources of heterogeneity in human monocyte subsets

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Variation in monocyte phenotype is explored using the markers CD14, CD16, HLA-DR, CX3CR1 and CCR2.

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The CD14++CD16+ monocytes exhibit a spectrum of markers dependent on location within the gate.

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Monocyte phenotype varies dependent on genetic background and history of exposure to infection.

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Processing technique for PBMC purification does not lead to changes in monocyte subsets.

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Processing technique for purification can alter intensity but not pattern of marker expression.

Human monocytes are commonly defined and discriminated by the extent of their cell surface expression of CD14 and CD16, with associated differences in function and phenotype related to the intensity of expression of these markers. With increasing interest into the function and behaviour of monocytes, it is important to have a clear understanding of how differing strategies of analysis can affect results and how different protocols and population backgrounds can affect this highly morphogenic cell type.

Using PBMCs from populations with differing ethnicities and histories of parasite exposure we have characterized monocyte phenotype based on intensity of CD14 and CD16 expression. Using the surface markers HLA-DR, CCR2 and CX3CR1, we compared monocyte phenotype between populations and further assessed changes in monocytes with freezing and thawing of PBMCs.

Our results reveal that there is a progression of surface marker expression based on intensity of CD14 or CD16 expression, stressing the importance of careful gating of monocyte subtypes. Freezing and thawing of the PBMCs has no effect generally on the monocytes, although it does lead to a decrease in CD16 and CX3CR1 expression. We show that there are differences in the monocyte populations based on ethnicity and history of exposure to the common parasites Plasmodium falciparum and Schistosoma haematobium.

This study highlights that blood monocytes consist of a continuous population of cells, within which the dominant phenotype may vary dependent on the background of the study population. Comparing results from monocyte studies therefore needs to be done with great care, as ethnic background of donor population, gating strategy and processing of PBMCs may all have an effect on outcome of monocyte phenotype.

Chitinase 3-like 1 protein levels are elevated in Schistosoma haematobium infected children

BACKGROUND

Currently there are few studies characterising the nature and aetiology of human schistosome-related inflammatory processes. The aim of this study was to determine the relationship between Chitinase 3-like 1 (CHI3L1), also known as YKL-40, a molecule associated with inflammatory processes, and schistosome infection, morbidity and systemic cytokine levels.

METHODS

Serological levels of CHI3L1 and a panel of cytokines (IFN-y, IL-4/5/6/9/10/13 and 17) were measured in two Zimbabwean populations resident in a high and low schistosome infection area. CHI3L1 levels were related to schistosome infection, haematuria status and cytokine levels after allowing for confounding variables. The effect of antihelminthic treatment with praziquantel on CHI3L1 levels was determined in 246 participants 6 weeks post-treatment.

RESULTS

CHI3L1 levels increased with age in both areas but were significantly higher in the high infection areas compared to the low infection area. CHI3L1 levels were also higher in infected compared to uninfected individuals with this difference being significant in the youngest age group. Curative antihelminthic treatment resulted in a significant decrease in CHI3L1 levels. Of the cytokines, only IL-10 and IL-17 had a significant association with CHI3L1 levels, and this association was negative.

CONCLUSIONS

Serum CHI3L1 levels differ between infected and uninfected people before and after antihelminthic treatment. The greatest difference occurs in the youngest age group, in keeping with the period when schistosome-related pathological processes are initiated. Following from previous studies in non-infectious diseases showing that CHI3L1 is a biomarker for the inflammatory process, this study suggests that the potential for CHI3L1 as a biomarker for schistosome-related pathology should be explored further.

Integrated analysis of innate, Th1, Th2, Th17, and regulatory cytokines identifies changes in immune polarisation following treatment of human schistosomiasis

Background. Schistosomiasis elicits cross-regulatory immune responses, but it is unclear how antihelminthic treatment affects this balance. This study integrates data on 13 cytokines elicited by 3 schistosome to examine how praziquantel treatment alters immune polarization and whether post-treatment cytokine profiles influence reinfection status.

Methods. Venous blood from 72 Schistosoma haematobium–exposed participants was cultured with schistosome egg, adult worm, and cercaria antigens pre– and 6 weeks post–praziquantel treatment. Innate inflammatory (tumor necrosis factor α [TNF-α], interleukin(IL-)-6, IL-8), Th1 (interferon γ [IFN-γ], IL-2, IL-12p70), Th2 (IL-4, IL-5, IL-13), Th17 (IL-17A, IL-21, IL-23p19), and regulatory (IL-10) cytokines were quantified via enzyme-linked immunosorbent assay. Cytokine data was integrated using nonmetric multidimensional scaling and factor analysis.

Results. Egg-specific cytokine phenotypes became more proinflammatory post-treatment due to increased TNF-α, IL-6, IL-8, IFN-γ, IL-12p70, and IL-23 levels. Post-treatment cercariae-specific responses were also more proinflammatory reflecting elevated IL-8. In contrast, post-treatment adult worm-specific responses were less inflammatory, reflecting lower post-treatment IL-6. A combination of egg-induced IL-6, IL-12p70, IL-21, and IL-23 and adult worm-induced IL-5 and IL-21 post-treatment was associated with reduced reinfection risk 18 months later.

Conclusions. Praziquantel treatment markedly alters polarization of schistosome-specific cytokine responses, and these changes, particularly in response to egg-stage parasites, may promote resistance to reinfection.

Helminth infections and host immune regulation

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.

Schistosoma haematobium infection levels determine the effect of praziquantel treatment on anti-schistosome and anti-mite antibodies

Field studies show an association between schistosome infection and atopy, but the effects of anti-helminthic treatment on this association have not yet been investigated in human populations with different schistosome endemicity levels. This study aimed to compare the effects of anti-helminthic treatment on responses directed against the house dust mite Dermatophagoides pteronyssinus (Derp1) and Schistosoma haematobium in Zimbabwean populations living in high and low schistosome infection areas. Derp1- and schistosome-specific IgE and IgG4 antibodies were quantified by ELISA before and 6 weeks after anti-helminthic treatment. Following treatment, there were changes in the immune responses, which varied with place of residence. After allowing for the effects of sex, age and baseline infection intensity, there was no significant treatment effect on the change in anti-schistosome IgE and IgG4 in the high infection area. However, the anti-schistosome IgE/IgG4 ratio increased significantly, while anti-Derp1 IgE responses decreased as a result of treatment. In the low infection area, treatment resulted in a significant increase in anti-worm IgE levels, but there was no significant treatment effect on anti-schistosome or anti-Derp1 IgE/IgG4 ratios. Thus, the study shows that the level of schistosome endemicity affects the host responses to schistosome and mite antigens following anti-helminthic treatment.

Schistosome: its benefit and harm in patients suffering from concomitant diseases

Schistosomiasis is an important tropical disease affecting approximately 200 million people worldwide. Because of its chronicity and robust immunomodulatory activity, the effects of schistosomes on other diseases, such as allergies, autoimmunity, and infectious diseases, have been studied extensively in both epidemiological and experimental settings. In this paper, we summarize the beneficial and harmful effects of schistosomes. The importance of controlling schistosomiasis is also discussed.