Dissociation of interleukin-4 and interleukin-5 production following treatment for Schistosoma haematobium infection in humans

The Value of the Antibody Detection in the Diagnosis of Ocular Toxocariasis and the Aqueous Cytokine Profile Associated With the Condition

Introduction

To evaluate and compare the specificity of Toxocara canis-specific antibody detection in the serum and aqueous samples for the diagnosis of ocular toxocariasis (OT) and explore the cytokine profiles associated with the condition in children.

Materials and Methods

This is a prospective cohort study. The inclusion criteria were the clinical presentations of OT, which included unilateral vision reduction, typical peripheral or posterior pole granuloma with variable degrees of vitritis, and exclusion of other diagnoses. The titer of antibody against the excretory-secretory antigen of Toxocara canis [T-immunoglobulin G (IgG)] was measured in serum and aqueous samples that were taken from the affected eyes. The diagnosis of OT was made upon positive detection of T-IgG either in the serum or aqueous. The rest with typical clinical presentations as described above but a positive serum or aqueous T-IgG could not be confirmed were diagnosed as suspected OT. Cytokines were measured using multiplexed cytometric bead array system.

Results

Two hundred and eleven eyes of 211 patients had participated in the study. One hundred and twenty-eight eyes were diagnosed as OT. The median age of the cohort was 7.7 years with a male to female ratio of 2.5:1. Major initial symptoms were decreased vision (74%) and strabismus (22%). The percentages of eyes with peripheral granuloma, posterior granuloma, and endophthalmitis were 40, 18, and 41%, respectively. Vitritis (100%), vitreous strands (64%), retinal fibrotic bands (57%), and retinal detachment (42%) were the most common signs. T-IgG was positive in 66.7% of the aqueous and 57.2% of the serum samples. Forty-four patients were diagnosed T-IgG negative in both serum and aqueous of the affected eyes. Interleukin (IL)-6, monocyte chemoattractant protein (MCP)-1, IL-8, eosinophil chemotactic protein (Eotaxin), MCP-1β, and vascular endothelial growth factor (VEGF) were higher in T-IgG negative eyes when compared to controls and further increased in T-IgG positive eyes. However, only T-IgG positive eyes showed increased IL-5, IL-13, and IL-10. IL-1β, tumor necrosis factor-alpha (TNF-α), IL-12, IL-2, interferon-gamma (IFN-γ), and IL-4 were undetectable in all eyes.

Conclusions

Pediatric OT is often present with severe retinal complications. Polarized intraocular Th2 response was only found in aqueous T-IgG positive eyes. Our results supported an aqueous sample-based antibody test for the more specific diagnosis of OT.

Cytokine production in Ancylostoma duodenale infection

Cytokine response to Ancylostoma duodenale (A. duodenale) infection was measured after starting treatments with piperazine. This study aims to determine the impact of cytokine production after infection with A. duodenale before and after treatment with piperazine. Blood and stool samples of 50 patients with A. duodenale infection and 28 healthy individuals (control) were collected. In this study, IFNγ, IL-5, IL-12, and IL-13 in serum (using ELISA-based methods) were measured. Stool samples were examined using the Kato-Katz technique to detect A. duodenale parasites. Blood and stool samples were analyzed 14 days after starting piperazine treatment for A. duodenale infection. The medium concentration of IFNγ, IL-5, IL-12, and IL-13 in the serum samples with A. duodenale infection is higher than that of the control group. IFNγ, IL-5, IL-12, and IL-13 levels were significantly higher in the infected individuals (10.5±7.4 pg/ml, 14.6±5.1 pg/ml, 8.5±3.2 pg/ml and 13.6±7.5 pg/ml respectively) than the control group (4.7±2.4 pg/ml, 7.8±4.06 pg/ml, 6.3±3.4 pg/ml and 3.5±2.7 pg/ml respectively). Also, piperazine treatment can significantly reduce cytokines levels (IFN-γ: P=0.043, IL-5: P=0.02, and IL-12, p=0.001). This study shows that piperazine treatment can reduce cytokines profiles in patients with A. duodenale infection.

Effect of hookworm infection and anthelmintic treatment on naturally acquired antibody responses against the GMZ2 malaria vaccine candidate and constituent antigens

Background

Malaria and helminths diseases are co-endemic in most parts of sub-Saharan Africa. Immune responses from each of these pathogens interact, and these interactions may have implications on vaccines. The GMZ2 malaria vaccine candidate is a fusion protein of Plasmodium falciparum merozoite surface protein 3 (MSP3) and glutamate rich protein (GLURP R0). GMZ2 has recently showed modest efficacy in a phase IIb multicenter trial. Here, we assessed the effect of hookworm (Necator americanus) infection and anthelmintic treatment on naturally acquired antibody responses against GMZ2 and constituent antigens.

Methods

This longitudinal cross-sectional study was conducted in the Kintampo North Municipality of Ghana. Blood and stool samples were taken from 158 individuals (4–88 years old) infected with either P. falciparum alone (n = 59) or both hookworm and P. falciparum (n = 63) and uninfected endemic controls (n = 36). Stool hookworm infection was detected by the Kato-Katz method and PCR. Malaria parasitaemia was detected by RDT, light microscopy and P. falciparum-specific 18S rRNA gene PCR. Serum samples were obtained prior to hookworm treatment with a single dose of albendazole (400 mg) and 3 weeks (21 days) after treatment. Levels of IgG1, IgG3 and IgM against GMZ2, MSP3 and GLURP R0 were measured by ELISA and compared among the groups, before and after treatment.

Results

Participants with P. falciparum and hookworm co-infection had significantly higher IgG3 levels to GMZ2 than those with only P. falciparum infection and negative control (p < 0.05) at baseline. Treatment with albendazole led to a significant reduction in IgG3 levels against both GMZ2 and GLURP R0. Similarly, IgM and IgG1 levels against MSP3 also decreased following deworming treatment.

Conclusion

Individuals with co-infection had higher antibody responses to GMZ2 antigen. Treatment of hookworm/malaria co-infection resulted in a reduction in antibody responses against GMZ2 and constituent antigens after albendazole treatment. Thus, hookworm infection and treatment could have a potential implication on malaria vaccine efficacy.

Immunological Considerations for Schistosoma Vaccine Development: Transitioning to Endemic Settings

Despite mass drug administration programmes with praziquantel, the prevalence of schistosomiasis remains high. A vaccine is urgently needed to control transmission of this debilitating disease. As some promising schistosomiasis vaccine candidates are moving through pre-clinical and clinical testing, we review the immunological challenges that these vaccine candidates may encounter in transitioning through the clinical trial phases in endemic settings. Prior exposure of the target population to schistosomes and other infections may impact vaccine response and efficacy and therefore requires considerable attention. Schistosomes are known for their potential to induce T-reg/IL-10 mediated immune suppression in populations which are chronically infected. Moreover, endemicity of schistosomiasis is focal whereby target and trial populations may exhibit several degrees of prior exposure as well as in utero exposure which may increase heterogeneity of vaccine responses. The age dependent distribution of exposure and development of acquired immunity, and general differences in the baseline immunological profile, adds to the complexity of selecting suitable trial populations. Similarly, prior or concurrent infections with other parasitic helminths, viral and bacterial infections, may alter immunological responses. Consequently, treatment of co-infections may benefit the immunogenicity of vaccines and may be considered despite logistical challenges. On the other hand, viral infections leave a life-long immunological imprint on the human host. Screening for serostatus may be needed to facilitate interpretation of vaccine responses. Co-delivery of schistosome vaccines with PZQ is attractive from a perspective of implementation but may complicate the immunogenicity of schistosomiasis vaccines. Several studies have reported PZQ treatment to induce both transient and long-term immuno-modulatory effects as a result of tegument destruction, worm killing and subsequent exposure of worm antigens to the host immune system. These in turn may augment or antagonize vaccine immunogenicity. Understanding the complex immunological interactions between vaccine, co-infections or prior exposure is essential in early stages of clinical development to facilitate phase 3 clinical trial design and implementation policies. Besides well-designed studies in different target populations using schistosome candidate vaccines or other vaccines as models, controlled human infections could also help identify markers of immune protection in populations with different disease and immunological backgrounds.

Cytokine profiles of Necator americanus and Plasmodium falciparum co-infected patients in rural Ghana

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Co-infection of hookworm with P. falciparum modulates blood parasitemia levels.

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Cytokine levels were higher in the parasite infected individuals.

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Serum eotaxin level correlate negatively with hookworm intensity.

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Deworming drug treatment alters cytokine profiles in hookworm infected subjects.

Background

Necator americanus (hookworm) and Plasmodium falciparum co-infections are common in endemic communities in rural Ghana. Human immune responses to P. falciparum and hookworm are complex, and the dynamics of cytokine levels and effector mediators are poorly understood. This study aimed to determine the effect of hookworm and P. falciparum co-infection on parasite intensities and cytokine profiles in individuals before and after deworming drug treatment.

Methods

In this cross-sectional study conducted in the Kintampo North Municipality of Ghana blood and stool samples were analyzed from 984 participants (aged 4–88 years). Stool samples were collected at baseline from all participants and examined for the presence of hookworm using the Kato-Katz method. Blood and stool samples were analysed again two weeks after albendazole treatment of hookworm infected individuals. Malaria parasitaemia was estimated by light microscopy and P. falciparum-specific 18S rRNA gene PCR method used for species identification. Serum levels of circulating cytokines interleukins -5, -10 (IL-5, IL-10), tumor necrosis factor [TNF]-α, and eotaxin [CCL11] were determined using ELISA based methods.

Results

Malaria parasitaemia was significantly reduced in hookworm and P. falciparum co-infected individuals (p = 0.0018) while hookworm intensity was similar between groups. IL-10 level was significantly higher in the co-infected individuals (39.9 ± 12.2 pg/ml) compared to the single infected or the uninfected group (10.7 ± 7.6 mg/ml). IL-5 level was higher in the hookworm only infected individual. TNF-α levels were higher in all infected groups compared to the uninfected controls. CCL11 levels were significantly higher in subjects infected with hookworm only or co-infected with hookworm and P. falciparum. There was a significantly negative correlation (r_s = −0.39, p = 0.021) between hookworm eggs per gram of stool and CCL11 levels in the group mono-infected with hookworm which was not affected by treatment. Treatment with albendazole led to a significant reduction of TNF-α (p = 0.041), IL-5 (p = 0.01) and IL-10 (p = 0.001) levels.

Conclusion

This study shows that in the absence of other helminths, co-infection of hookworm with P. falciparum may modulate blood parasitemia levels and cytokine responses. Data also show that deworming drug treatment alters these cytokine profiles in hookworm infected subjects. Future studies to elucidate the potential mechanisms underlying these observations should include an assessment of parasite specific cellular responses.

microRNA and Allergy

Allergy is a common hypersensitivity disorder of the immune system, which, along with other factors, is also subjected to regulation by microRNAs. The most common allergic diseases are allergic rhinitis, asthma, atopic dermatitis, and food allergy, which all are multifactorial and very heterogeneous conditions, highlighting the need for more individualized treatment techniques. More particular key questions in relation to allergic diseases are how microRNAs influence the differentiation, polarization, plasticity and functions of T helper and other immune cells, as well as the development of immune tolerance. In addition, microRNAs can affect allergic inflammation and tissue remodeling through their functions in epithelial and other tissue cells. Among immune system-related microRNAs, miR-21, miR-146a, and miR-155 are the most intensively studied and have convincingly been demonstrated to regulate immune responses and tissue inflammation in allergic diseases. Further characterization of microRNA functions is important, as similar to other conditions, the modulation of microRNA expression could potentially be used for therapeutic purposes in allergic diseases in the future. In addition, miRNAs could be implemented as biomarkers for endotyping complex allergic conditions.

Schistosomiasis vaccine candidate Sm14/GLA-SE: Phase 1 safety and immunogenicity clinical trial in healthy, male adults

DESIGN

Safety and immunogenicity of a recombinant 14kDa, fatty acid-binding protein(FABP) from Schistosoma mansoni (rSm14) were evaluated through an open, non-placebo-controlled, dose-standardized trial, performed at a single research site. The vaccine was formulated with glucopyranosyl lipid A (GLA) adjuvant in an oil-in-water emulsion (SE) and investigated in 20 male volunteers from a non-endemic area for schistosomiasis in the state of Rio de Janeiro, Brazil. Fifty microgram rSm14 with 10 μg GLA-SE (rSm14/GLA-SE)/dose were given intramuscularly three times with 30-day intervals. Participants were assessed clinically, biochemically and immunologically for up to 120 days.

METHODS

Participants were screened for inclusion by physical examination, haematology and blood chemistry; then followed to assess adverse events and immunogenicity. Sera were tested for IgG (total and isotypes) and IgE. T cell induction of cytokines IL-2, IL-5, IL-10, IFNγ and TNFα was assessed by Milliplex kit and flow cytometry.

RESULTS

The investigational product showed high tolerability; some self-limited, mild adverse events were observed during and after vaccine administration. Significant increases in Sm14-specific total IgG, IgG1 and IgG3 were observed 30 days after the first vaccination with specific IgG2 and IgG4 after 60 days. An increase in IgE antibodies was not observed at any time point. The IgG response was augmented after the second dose and 88% of all vaccinated subjects had developed high anti-Sm14 IgG titres 90 days after the first injection. From day 60 and onwards, there was an increase in CD4(+) T cells producing single cytokines, particularly TNFα and IL-2, with no significant increase of multi-functional TH1 cells.

CONCLUSION

Clinical trial data on tolerability and specific immune responses after vaccination of adult, male volunteers in a non-endemic area for schistosomiasis with rSm14/GLA-SE, support this product as a safe, strongly immunogenic vaccine against schistosomiasis paving the way for follow-up Phase 2 trials. Study registration ID: NCT01154049 at http://www.clinicaltrials.gov.

Immunology of human schistosomiasis

There is a wealth of immunologic studies that have been carried out in experimental and human schistosomiasis that can be classified into three main areas: immunopathogenesis, resistance to reinfection and diagnostics. It is clear that the bulk of, if not all, morbidity due to human schistosomiasis results from immune-response-based inflammation against eggs lodged in the body, either as regulated chronic inflammation or resulting in fibrotic lesions. However, the exact nature of these responses, the antigens to which they are mounted and the mechanisms of the critical regulatory responses are still being sorted out. It is also becoming apparent that protective immunity against schistosomula as they develop into adult worms develops slowly and is hastened by the dying of adult worms, either naturally or when they are killed by praziquantel. However, as with anti-egg responses, the responsible immune mechanisms and inducing antigens are not clearly established, nor are any potential regulatory responses known. Finally, a wide variety of immune markers, both cellular and humoral, can be used to demonstrate exposure to schistosomes, and immunologic measurement of schistosome antigens can be used to detect, and thus diagnose, active infections. All three areas contribute to the public health response to human schistosome infections.

Circulating cytokine levels and antibody responses to human Schistosoma haematobium: IL-5 and IL-10 levels depend upon age and infection status

Experimental schistosome infections induce strong parasite-specific Th2 responses. This study aims to relate human systemic cytokine and antibody levels to schistosome infection levels and history. Levels of anti-Schistosoma haematobium antibodies (directed against crude cercariae, egg and adult worm antigens) and plasma cytokines (IFN-γ, IL-2, IL-4, IL-5, IL-10, IL-13, IL-17, IL-21, and IL-23) were measured by ELISA in 227 Zimbabweans (6–60 years old) in a schistosome-endemic area and related to age and infection status. Egg-positive people had significantly higher levels of specific antibodies, IL-2, IFN-γ and IL-23. In contrast, egg-negative individuals had significantly higher circulating IL-10, IL-4, IL-13 and IL-21 that were detected with high frequency in all participants. Subjects with detectable plasma IL-17 produced few or no eggs. When analyzed by age, IL-4 and IL-10 increased significantly, as did schistosome-specific antibodies. However, when age was combined with infection status, IL-5 declined over time in egg-positive people, while increased with age in the egg-negative group. Older, lifelong residents had significantly higher IL-4 and IL-5 levels than younger egg-negative people. Thus, a mixed Th1/Th2 systemic environment occurs in people with patent schistosome infection, while a stronger Th2-dominated suite of cytokines is evident in egg-negative individuals.

Regulatory and activated T cells in human Schistosoma haematobium infections

Acquired immunity against helminths is characterised by a complex interplay between the effector Th1 and Th2 immune responses and it slowly manifests with age as a result of cumulative exposure to parasite antigens. Data from experimental models suggest that immunity is also influenced by regulatory T cells (Treg), but as yet studies on Treg in human schistosome infections are limited. This study investigated the relationship between schistosome infection intensity and the two cell populations regulatory T cells (TREG: CD4(+(dim))CD25(+(high))FOXP3(+)CD127(low)), and activated (Tact: CD4(+)CD25(+)FOXP3(-)) T cells in Zimbabweans exposed to Schistosoma haematobium parasites. Participants were partitioned into two age groups, young children (8-13 years) in whom schistosome infection levels were rising to peak and older people (14+ years) with declining infection levels. The relationship between Tact proportions and schistosome infection intensity remained unchanged with age. However Treg proportions rose significantly with increasing infection in the younger age group. In contrast Treg were negatively correlated to infection intensity in the older age group. The relative proportions of regulatory T cells differ significantly between young individuals in whom high infection is associated with an enhanced regulatory phenotype and older infected patients in whom the regulatory response is attenuated. This may influence or reflect different stages of the development of protective schistosome acquired immunity and immunopathogenesis.

Acquired immune heterogeneity and its sources in human helminth infection

Similarities in the immunobiology of different parasitic worm infections indicate that co-evolution of humans and helminths has shaped a common anti-helminth immune response. However, recent in vitro and immuno-epidemiological studies highlight fundamental differences and plasticity within host-helminth interactions. The 'trade-off' between immunity and immunopathology inherent in host immune responses occurs on a background of genetic polymorphism, variable exposure patterns and infection history. For the parasite, variation in life-cycle and antigen expression can influence the effector responses directed against them. This is particularly apparent when comparing gastrointestinal and tissue-dwelling helminths. Furthermore, insights into the impact of anti-helminthic treatment and co-infection on acquired immunity suggest that immune heterogeneity arises not from hosts and parasites in isolation, but also from the environment in which immune responses develop. Large-scale differences observed in the epidemiology of human helminthiases are a product of complex host-parasite-environment interactions which, given potential for exposure to parasite antigens in utero, can arise even before a parasite interacts with its human host. This review summarizes key differences identified in human acquired immune responses to nematode and trematode infections of public health importance and explores the factors contributing to these variations.

Mechanisms and treatment of allergic disease in the big picture of regulatory T cells

Various populations of regulatory T (Treg) cells have been shown to play a central role in the maintenance of peripheral homeostasis and the establishment of controlled immune responses. Their identification as key regulators of immunologic processes in peripheral tolerance to allergens has opened an important era in the prevention and treatment of allergic diseases. Both naturally occurring CD4+CD25+ Treg cells and inducible populations of allergen-specific, IL-10-secreting Treg type 1 (T(R)1) cells inhibit allergen-specific effector cells in experimental models. Skewing of allergen-specific effector T cells to a regulatory phenotype appears to be a key event in the development of healthy immune response to allergens and successful outcome in allergen-specific immunotherapy. Forkhead box protein 3-positive CD4+CD25+ Treg cells and T(R)1 cells contribute to the control of allergen-specific immune responses in several major ways, which can be summarized as suppression of dendritic cells that support the generation of effector T cells; suppression of effector T(H)1, T(H)2, and T(H)17 cells; suppression of allergen-specific IgE and induction of IgG4; suppression of mast cells, basophils, and eosinophils; interaction with resident tissue cells and remodeling; and suppression of effector T-cell migration to tissues. Current strategies for drug development and allergen-specific immunotherapy exploit these observations, with the potential for preventive therapies and cure for allergic diseases.

Effect of treating Schistosoma haematobium infection on Plasmodium falciparum-specific antibody responses

BACKGROUND

The overlapping geographical and socio-economic distribution of malaria and helminth infection has led to several studies investigating the immunological and pathological interactions of these parasites. This study focuses on the effect of treating schistosome infections on natural human immune responses directed against plasmodia merozoite surface proteins MSP-1 (DPKMWR, MSP1(19)), and MSP-2 (CH150 and Dd2) which are potential vaccine candidates as well as crude malaria (schizont) and schistosome (whole worm homogenate) proteins.

METHODS

IgG1 and IgG3 antibody responses directed against Schistosoma haematobium crude adult worm antigen (WWH) and Plasmodium falciparum antigens (merozoite surface proteins 1/2 and schizont extract), were measured by enzyme linked immunosorbent assay (ELISA) in 117 Zimbabweans (6-18 years old) exposed to S. haematobium and P. falciparum infection. These responses were measured before and after anti-helminth treatment with praziquantel to determine the effects of treatment on anti-plasmodial/schistosome responses.

RESULTS

There were no significant associations between antibody responses (IgG1/IgG3) directed against P. falciparum and schistosomes before treatment. Six weeks after schistosome treatment there were significant changes in levels of IgG1 directed against schistosome crude antigens, plasmodia crude antigens, MSP-1(19), MSP-2 (Dd2), and in IgG3 directed against MSP-1(19). However, only changes in anti-schistosome IgG1 were attributable to the anti-helminth treatment.

CONCLUSION

There was no association between anti-P. falciparum and S. haematobium antibody responses in this population and anti-helminth treatment affected only anti-schistosome responses and not responses against plasmodia crude antigens or MSP-1 and -2 vaccine candidates.

Cytokine responses to Schistosoma haematobium in a Zimbabwean population: contrasting profiles for IFN-gamma, IL-4, IL-5 and IL-10 with age

BACKGROUND

The rate of development of parasite-specific immune responses can be studied by following their age profiles in exposed and infected hosts. This study determined the cytokine-age profiles of Zimbabweans resident in a Schistosoma haematobium endemic area and further investigated the relationship between the cytokine responses and infection intensity.

METHODS

Schistosome adult worm antigen-specific IFN-gamma, IL-4, IL-5 and IL-10 cytokine responses elicited from whole blood cultures were studied in 190 Zimbabweans exposed to S. haematobium infection (aged 6 to 40 years old). The cytokines were measured using capture ELISAs and the data thus obtained together with S. haematobium egg count data from urine assays were analysed using a combination of parametric and nonparametric statistical approaches.

RESULTS

Age profiles of schistosome infection in the study population showed that infection rose to peak in childhood (11-12 years) followed by a sharp decline in infection intensity while prevalence fell more gradually. Mean infection intensity was 37 eggs/10 ml urine (SE 6.19 eggs/10 ml urine) while infection prevalence was 54.7%. Measurements of parasite-specific cytokine responses showed that IL-4, IL-5 and IL-10 but not IFN-gamma followed distinct age-profiles. Parasite-specific IL-10 production developed early, peaking in the youngest age group and declining thereafter; while IL-4 and IL-5 responses were slower to develop with a later peak. High IL-10 producers were likely to be egg positive with IL-10 production increasing with increasing infection intensity. Furthermore people producing high levels of IL-10 produced little or no IL-5, suggesting that IL-10 may be involved in the regulation of IL-5 levels. IL-4 and IFN-gamma did not show a significant relationship with infection status or intensity and were positively associated with each other.

CONCLUSION

Taken together, these results show that the IL-10 responses develop early compared to the IL-5 response and may be down-modulating immunopathological responses that occur during the early phase of infection. The results further support current suggestions that the Th1/Th2 dichotomy does not sufficiently explain susceptibility or resistance to schistosome infection.

TH17 cells in the big picture of immunology

The pathogenesis of chronic inflammatory diseases is assumed to depend on activated T cells interacting with resident tissue cells or migratory inflammatory cells. The discovery of new T-cell subsets such as the IL-17-producing T(H)17 and T-regulatory cells innovated our understanding of T-cell biology. Studies on new subsets confirm the important role of T cells in the instruction of tissue cells and also demonstrate the important role of feedback regulation for the polarization toward distinct T-cell subsets. The understanding of IL-17 and T(H)17 differentiation pathways has also changed the perspective of immunologists regarding the basis of chronic tissue inflammation, particularly where T(H)1 cells were considered as driving force of the pathology. This review summarizes the recent developments on T(H) cell subsets and integrates these findings into existing concepts of immunopathologic mechanisms.

Distal regulatory elements play an important role in regulation of the human IL-5 gene

Eosinophil infiltration of the lung is a feature of both allergic and nonallergic asthma, and IL-5 is the key cytokine regulating the production and activation of these cells. Despite many studies focusing on the IL-5 promoter in both humans and mice there is as yet no clear picture of how the IL-5 gene is regulated. The aim of this study was to determine if distal regulatory elements contribute to appropriate regulation of the human IL-5 (hIL-5) gene. Activity of the -507/+44 hIL-5 promoter was compared to expression of the endogenous IL-5 gene in PER-117 T cells. The IL-5 promoter was not sufficient to reproduce a physiological pattern of IL-5 expression. Further, functional analysis of the 5' and 3' intergenic regions revealed a number of novel regulatory elements. We have identified a conserved enhancer located approximately 6.2 kb upstream of the hIL-5 gene. This region contains two potential GATA-3-binding sites and increases expression from the hIL-5 promoter by up to ninefold.

Cluster analysis of schistosome-specific antibody responses partitions the population into distinct epidemiological groups

Immuno-epidemiological studies in schistosomiasis continue to generate large amounts of immunology data, whose analysis requires sophisticated statistical approaches. Here cluster analysis, is used to explore the relationship between immune responses and observed epidemiological patterns of schistosome infection in two Zimbabwean communities. Analysis of cross-sectional antibody data (IgA, IgE, IgG1, IgG2, IgG3, IgG4 and IgM directed against Schistosoma haematobium soluble egg antigen (SEA)) showed that cluster analysis partitioned the data into distinct epidemiological groups based on all seven antibody isotypes (defined by age, infection intensity, treatment status and history of infection) confirming an already known partitioning based on IgA/IgG1 production. All treated participants (children) changed cluster membership following treatment from clusters where IgA was the predominant antibody to clusters where IgG1 predominated. There was a differential distribution of IgE and IgG4 between clusters consistent with the recently proposed balance between T-helper cells (Th) 1, Th2 and regulatory T cells. The analysis suggested that naturally acquired anti-schistosome responses associated with resistance to infection were different from drug-induced responses associated with resistance to re-infection. Furthermore, the analysis suggested that parasite-specific immune responses were dynamic. The analysis conducted on data from participants resident in the S. mansoni endemic area who were all children partitioned the data into two clusters, one with predominately pre-treatment data (cluster 1) and the other with post-treatment data (cluster 2). The antibody profiles of both clusters were most similar to the profile of people with a modified Th2 response. Following treatment 43% of the children in cluster 1 moved to cluster 2, which generally had higher levels of antibodies. A detailed study of factors determining which children moved between the clusters showed that it was mostly the older, infected children who moved to cluster 2. The results of the analysis are discussed in terms of current theories of the development of acquired immunity to schistosomiasis. The relative merits of cluster analysis as a statistical tool for analysing these data are also discussed.

Immunoregulation and World Health Assembly resolution 54.19: why does treatment control morbidity?

World Health Assembly resolution 54.19, passed in May, 2001, declares the intent of the World Health Organization member States to implement a combined strategy for the control of morbidity caused by schistosomiasis and soil-transmitted helminths. Among other things, the resolution urges ministries to treat all clinical cases and groups at high risk of morbidity such as children, women and those exposed occupationally. The policy is predicated on the evidence that morbidity due to these infections can be controlled by periodic treatment with appropriate chemotherapeutic, anti-helminthic drugs. While it is true that annual or biannual praziquantel treatment for schistosomiasis decreases morbidity, we now question how treatment leads to this beneficial effect. It is clear that treatment kills worms, but we propose that this is only a part of how it leads to reduced morbidity in areas of ongoing transmission and reinfection. By killing worms, we postulate that treatment also effects immunologic changes to the normal host/parasite relationship, and the resulting immune responses lead to both increased resistance (protection against reinfection), and increased immunoregulatory mechanisms that control morbidity upon subsequent reinfections. If the effects of treatment contribute to morbidity control in these ways, a better understanding of how this occurs may allow optimization of these effects of treatment through appropriate periodic treatment regimens, resulting in less reinfection and better morbidity control when reinfection does occur.

Contrasting cellular responses in Schistosoma haematobium infected and exposed individuals from areas of high and low transmission in Zimbabwe

The study compared cytokine profiles of individuals from two areas with different transmission patterns for Schistosoma haematobium. One area was a high transmission (HT) while the other was a low transmission (LT) area for S. haematobium. Observations on cellular immune responses were made on stimulated peripheral blood mononuclear cells (PBMC), which were collected pre-treatment, then at 12 and 18 months post treatment. Stimulation was with schistosome worm and egg antigens and a mitogen, phaetohaemaglutinin (PHA). Observations were made on PBMC proliferation and the profiles of cytokine produced over a 5-day incubation period. The two distinct areas showed significant differences on both levels of proliferation and cytokine production for all the measured classes (IL-4, IL-5, IL-10 and IFN-gamma). PBMC from individuals from the LT area had high levels of proliferation but low cytokine production to both antigen stimulants while PBMC from individuals from the HT area showed low levels of proliferation but high cytokine production levels. Prior to treatment, individuals not excreting schistosome ova in the HT area had higher levels of proliferation to the stimulants, than the infected individuals. However, after treatment re-infected individuals showed high levels of proliferation. Before treatment, both infected and uninfected groups showed low and similar ratios, respectively, of IL-4:IFN-gamma, IL-5:IFN-gamma and IL-10:IFN-gamma, while IFN-gamma was high in the infected individuals. After treatment the non re-infected had higher levels of IL-4, IL-5 and IL-10, with the infected having high levels of IFN-gamma. Th1-like response dominated during infection with the Th2-like responses dominating post treatment and in uninfected individuals. The results indicated that the cytokine balance determines, in part, susceptibility or resistance to S. haematobium infection.

A comparison of cellular and humoral immune responses to trichuroid derived antigens in human trichuriasis

Individuals, residing in a region highly endemic for Trichuris trichiura, were examined for cytokine and proliferative responses to T. trichiura worm homogenate (TtAg), T. trichiura excretory/secretory products (TtES) and the equivalent antigenic preparations from the murine whipworm, Trichuris muris. Serum antibody levels against TtAg, T. muris worm homogenate and T. muris ES products were also studied. Measurable levels of immunoglobulin (Ig)G1, IgG4, IgA and IgE against T. muris antigens were detected, indicating a degree of conservation of epitopes between antigens derived from both species. Although levels of interleukin (IL)-4, IL-10, IL-13, tumour necrosis factor (TNF)-alpha and proliferative responses produced were comparable between homogenate antigens of either species and ES antigens of either species, a markedly different cellular response was observed in cultures stimulated with homogenate antigens compared to ES antigens. ES antigens preferentially induced IL-10 (P > 0.001) and TNF-alpha (P > 0.001) production, whereas levels of IL-4 (P > 0.001), IL-13 (P > 0.001) and proliferative responses (P > 0.001) were greater in cultures stimulated with whole worm extracts. Our findings suggest that T. muris preparations could be used as an alternative to T. trichiura proteins as a source of antigens in ex vivo cultures and that ES products stimulate a distinct immune response compared to somatic antigens.

Cytokine responses to mitogen and Schistosoma haematobium antigens are different in children with distinct infection histories

Prevalence of Schistosoma haematobium infection in children from two neighbouring villages in Zimbabwe was 77.1% and 40.3%, respectively. The age-intensity data indicated peak intensities of infection at a lower age in the high prevalence village. This study investigated whether the difference in infection histories was reflected in a difference in cytokine profiles between children resident in these two villages. Blood samples were taken to assay for cytokine secretion 1 year after treatment for schistosomiasis. They were cultured with phytohaemagglutinin (PHA), schistosome egg antigens (SEA) or cultured without stimulant and tested for the presence of interleukin (IL)-4, IL-5, IL-10, granulocyte-macrophage colony-stimulating factor (GM-CSF) and IFN-gamma. Blood samples from children from the low prevalence village were more likely to produce IL-4 (P < 0.0001) and produced higher levels of IFN-gamma (P < 0.02) and GM-CSF (P < 0.03) when cultured with PHA for 24 h. Residence in the high prevalence village was associated with production of IL-10 (P < 0.006) and GM-CSF (P < 0.04) in response to culture with SEA and IL-5 (P < 0.02) with PHA for 48 h. The interaction between age and village was not significant for these results; however, there was a significant interaction between age and village for IL-5 detected in blood samples cultured with PHA for 24 h (P < 0.01). These results concur with previous observations that major patterns of cytokine production can be related to immunosuppression, but also indicate an underlying pattern which reflects the importance of history of infection to the immune response.