The enigmatic eosinophil: investigation of the biological role of eosinophils in parasitic helminth infection

Overview of Bone Marrow Aspiration from 120 Cats in Different Hematological Conditions

Bone marrow (BM) evaluation is highly important for the diagnosis of numerous hematological alterations in animals, especially cats, given their greater propensity for hematopoietic changes associated with retrovirus infections. This study aims to describe the main aspects of the BM of cats with different hematological conditions, comparing with reference intervals established from animals without hematological alterations and also with a previously established reference interval. To do so, we evaluated full blood and BM samples from 120 cats with no abnormalities on physical examination, negative for FeLV and FIV. Hemograms were performed from automated total cell and platelet and leukocyte differential counts in blood smears. BM samples were placed in Petri dishes; medullary spicules were selected to make up to eight cytological slides stained by the May-Grunwald-Giemsa technique, which were subjected to quantitative and cellular morphology evaluations. The cats were predominantly young, 64.2% female and 35.8% male. The average number of medullary spicules in samples was 13.7%, and density was 44%. In the BM quantitative analysis, prorubricytes and rubriblasts had higher quantities than the recommended one for all cats with or without hematological alterations. In all groups, lymphocytes were decreased, and cats with lymphocytosis were closest to the reference range, showing flame cells and Mott cells. The reference interval for the bone marrow cell count obtained from the samples in this work differs from previously established data, leading to different interpretations of the patient's BM condition, according to the cell population observed and the reference interval used. This divergence strongly emphasizes the need to correlate clinical, epidemiological, hematological, and bone marrow data of each patient for a better understanding of the patient's condition. The popularization of BM assessment is essential so that more reliable reference intervals can be established according to the population served by each pathologist and clinical laboratory.

Eosinophils and helminth infection: protective or pathogenic?

Since the earliest descriptions of this enigmatic cell, eosinophils have been implicated in both protective and pathogenic immune responses to helminth infection. Nevertheless, despite substantial data from in vitro studies, human infections, and animal models, their precise role in helminth infection remains incompletely understood. This is due to a number of factors, including the heterogeneity of the many parasites included in the designation "helminth," the complexity and redundancy in the host immune response to helminths, and the pleiotropic functions of eosinophils themselves. This review examines the consequences of helminth-associated eosinophilia in the context of protective immunity, pathogenesis, and immunoregulation.

The immunomodulatory activity of Chenopodium ambrosioides reduces the parasite burden and hepatic granulomatous inflammation in Schistosoma mansoni-infection

ETHNOPHARMACOLOGICAL RELEVANCE

Folk medicine reports have described the use of Chenopodium ambrosioides as an anti-inflammatory, analgesic, and anthelmintic herb. These effects, including its activity against intestinal worms, are already scientifically observed. However, the immunological mechanisms of this species in the treatment of Schistosoma mansoni infection are unknown.

AIM OF THE STUDY

To evaluate the immunological and anti-Schistosoma mansoni effects of a crude Chenopodium ambrosioides hydro-alcoholic extract (HCE).

MATERIALS AND METHODS

For the in vitro analysis, cercariae and adult worms were exposed to different concentrations (0 to 10,000 μg/mL) of the HCE. For the in vivo evaluation, Swiss mice were infected with 50 cercariae of S. mansoni and separated into groups according to treatment as follows: a negative control (without treatment), a positive control (treated with Praziquantel®), HCE1 Group (treated with HCE during the cutaneous phase), HCE2 Group (treated with HCE during the lung phase), HCE3 Group (treated with HCE during the young worm phase), and HCE4 Group (treated with HCE during the adult worm phase). The animals treated with HCE received daily doses of 50 mg/kg, by gavage, for seven days, corresponding to the different developmental stages of S. mansoni. For comparison, a clean control group (uninfected and untreated) was also included. All animals were euthanized 60 days post-infection to allow the following assessments to be performed: a complete blood cells count, counts of eggs in the feces and liver, the quantification of cytokines and IgE levels, histopathological evaluations of the livers, and the analysis of inflammatory mediators.

RESULTS

HCE treatment increased the mortality of cercariae and adult worms in vitro. The HCE treatment in vivo reduced the eggs in feces and liver. The number and area of liver granulomas, independent of the phase of treatment, were also reduced. The treatment with HCE reduced the percentage of circulating eosinophils, IgE, IFN-γ, TNF-α, and IL-4. In contrast, the treatment with the HCE, dependent on the phase, increased IL-10 levels and the number of peritoneal and bone marrow cells, mainly of T lymphocytes, B lymphocytes, and macrophages. This effect could be due to secondary compounds presents in this extract, such as kaempferol, quercetin and derivatives.

CONCLUSIONS

This study demonstrates that Chenopodium ambrosioides has antiparasitic and immunomodulatory activity against the different phases of schistosomiasis, reducing the granulomatous inflammatory profile caused by the infection and, consequently, improving the disease prognosis.

Filarial nematodes with zoonotic potential in ring-tailed coatis (Nasua nasua Linnaeus, 1766, Carnivora: Procyonidae) and domestic dogs from Iguaçu National Park, Brazil

Iguaçu National Park, which contains the largest remnant of Atlantic Forest in southern Brazil and Iguaçu Falls as one of its main visiting points, is a year-round attraction for thousands of domestic and international tourists. Ring-tailed coatis are generalist, opportunistic carnivores that benefit from human association. These animals are the most abundant carnivores in this park, where they come into close contact with tourists and the resident population around the park. Moreover, as the park is surrounded by human dwellings, free roaming domestic dogs are frequently present, favoring the exchange of pathogens with wild animals. Wild carnivores are known to be infected with several pathogens, from viruses to arthropods, some of them passed on by domestic carnivores. Among the nematodes that infect wild carnivores, those of the Onchocercidae family are of concern due to their zoonotic potential. The objective of this research was to assess the prevalence of filarial nematodes in coatis and dogs in Iguaçu National Park, as well as the potential impact of infection on host health and body condition. To this end, 75 coatis and 50 adult dogs were captured in the aforementioned area. Seven species of filarioids, Dirofilaria immitis, Dirofilaria repens, Acanthocheilonema reconditum, Brugia sp., Mansonella sp. and two undetermined species, confirmed by histochemical tests, were diagnosed in the area. Knott's concentration test in coatis and dogs showed a prevalence of 81.6% and 16.0%, respectively. Seven microfilarial morphotypes were diagnosed in the coatis and two morphotypes were found in the dogs. A specific immunoassay test for Dirofilaria immitis revealed the presence of D. immitis infection in 1.33% of the coatis and 22% of the domestic dogs. The parasitic infection had negligible effects on the body condition of both dog and coati hosts, but an increase was found in eosinophil counts in coatis with filarial infection, as well as decreases in hematocrit and hemoglobin in the infected domestic dogs. These findings represent new locality and host records for all the filarioids diagnosed in the area of this study, with some of the diagnosed parasites, given their zoonotic potential, representing a health risk for park visitors and the local population.

Immunoregulation in larval Echinococcus multilocularis infection

Alveolar echinococcosis (AE) is a clinically very severe zoonotic helminthic disease, characterized by a chronic progressive hepatic damage caused by the continuous proliferation of the larval stage (metacestode) of Echinococcus multilocularis. The proliferative potential of the parasite metacestode tissue is dependent on the nature/function of the periparasitic immune-mediated processes of the host. Immune tolerance and/or down-regulation of immunity are a marked characteristic increasingly observed when disease develops towards its chronic (late) stage of infection. In this context, explorative studies have clearly shown that T regulatory (Treg) cells play an important role in modulating and orchestrating inflammatory/immune reactions in AE, yielding a largely Th2-biased response, and finally allowing thus long-term parasite survival, proliferation and maturation. AE is fatal if not treated appropriately, but the current benzimidazole chemotherapy is far from optimal, and novel options for control are needed. Future research should focus on the elucidation of the crucial immunological events that lead to anergy in AE, and focus on providing a scientific basis for the development of novel and more effective immunotherapeutical options to support cure AE by abrogating anergy, anticipating also that a combination of immuno- and chemotherapy could provide a synergistic therapeutical effect.

Co-Infection and Wild Animal Health: Effects of Trypanosomatids and Gastrointestinal Parasites on Coatis of the Brazilian Pantanal

Wild animals are infected by diverse parasites, but how they influence host health is poorly understood. We examined the relationship of trypanosomatids and gastrointestinal parasites with health of wild brown-nosed coatis (Nasua nasua) from the Brazilian Pantanal. We used coati body condition and hematological parameters as response variables in linear models that were compared using an information theoretic approach. Predictors were high/low parasitemias by Trypanosoma cruzi and T. evansi, and indices representing the abundance of distinct groups of gastrointestinal parasites. We also analyzed how host health changed with host sex and reproductive seasonality. Hemoparasites was best related to coati body condition and hematological indices, whereas abundance of gastrointestinal parasites was relatively less associated with coati health. Additionally, some associations were best predicted by models that incorporated reproductive seasonality and host sex. Overall, we observed a lower health condition during the breeding season, when coatis are under reproductive stress and may be less able to handle infection. In addition, females seem to handle infection better than males. Body condition was lower in coatis with high parasitemias of T. evansi, especially during the reproductive season. Total red blood cell counts, packed cell volume, platelets and eosinophils were also lower in animals with high T. evansi parasitemias. Total white blood cell counts and mature neutrophils were lower in animals with high parasitemias for both Trypanosoma species, with neutrophils decreasing mainly during the reproductive season. Overall, decreases in hematological parameters of females with T. evansi high parasitemias were less evident. For T. cruzi, monocytes decreased in individuals with high parasitemias. High abundances of microfilariae in the bloodstream, and cestode eggs and coccidian oocysts in feces were also associated with coati blood parameters. This study shows the potential value of examining hematological parameters as an approach to better understand the ecological relevance of parasite-host interactions.

HOOKWORM AND THREADWORM INFECTIONS AND THEIR ASSOCIATION WITH HEMOGLOBIN AND EOSINOPHIL CONCENTRATIONS IN RESIDENTS OF SALVADOR-BAHIA, BRAZIL

SUMMARY Parasitic infections are responsible for substantial mortality and morbidity worldwide. In most healthy individuals, little overt pathology is observed during infection with S. stercoralis. However, the symptoms in advanced cases may include gastrointestinal bleeding. Anemia is most commonly associated with hookworm infection, especially when several hundred worms are present. Our study evaluates the relationship between the hookworm or S. stercoralis infection status and the hemoglobin concentration of individuals examined by a private network of laboratories in Salvador, Bahia, Brazil. We examined 374,120 samples from middle-class individuals living in Salvador City from January 2004 to April 2008. The stool samples were analyzed by the Lutz and Baermann-Moraes methods, and the blood samples were analyzed for hemoglobin concentration and eosinophil counting. The prevalence of hookworm and S. stercoralis were 0.27% (1,027) and 0.34% (1,286), respectively. The prevalence of hookworm and S. stercoralis infection was significantly higher in males than in females and increased with age. Eosinophilia was a common laboratorial finding in individuals infected with hookworm and S. stercoralis. The hemoglobin concentration was lower in the hookworm-infected individuals than in non-infected ones, but none of the examined patients were anemic. Lack of anemia could be a consequence of the socioeconomic status of these patients.

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.

Selenium supplementation enhances the protective response to Toxocara canis larvae in mice

The effect of oral and intraperitoneal supply of sodium selenite on the immune response to, and the course of T. canis larvae infection in mice were determined. The number of worms in the host tissue was reduced but the migratory route of larvae was not affected. Selenite (Se) supplementation influences Se retention in the liver, enhanced IL-5 and eosinophil responses and evoked IL-6 production in mice infected with T. canis. The enhanced protection in mice given Se intraperitoneally was associated with high levels of parasite-specific IgE, and enhanced concentration of Th1-related cytokines such IL-12p70, TNF-α and IFN-γ. In mice given Se orally, the predominant cytokines produced were IL-10, MCP-1 and IL-6 and these mice had lower protection. In conclusion, Se supplementation increases production of specific cytokines in mice infected with T. canis and increases protection against infection.

Enhanced protection against Heligmosomoides polygyrus in IL-2 receptor β-chain overexpressed transgenic mice with intestinal mastocytosis

IL-2 receptor β-chain overexpressed transgenic (Tg2Rβ) mice lack NK cells, but the development of other lymphocyte subsets and macrophages remained apparently intact. These mice also exhibit intestinal mastocytosis. Helminth infection induces various immune responses, such as mast cells, goblet cells, eosinophils and IgE, mediated by Th2 cytokines. IL-4 is also important in the regulation of resistance and susceptibility to Heligmosomoides polygyrus infection. However, there are contradictory results about the relation between resistance to H. polygyrus and intestinal mastocytosis. The present study showed that Tg2Rβ mice suppressed worm fecundity with mastocytosis without an increase of the levels of goblet cells, eosinophils and IgE compared with control mice. These results clearly indicated that mast cells have the ability for to protect against H. polygyrus infection. However, additional studies are required to evaluate protective effector mechanisms against H. polygyrus.

Echinococcus multilocularis and its intermediate host: a model of parasite-host interplay

Host-parasite interactions in the E. multilocularis-intermediate host model depend on a subtle balance between cellular immunity, which is responsible for host's resistance towards the metacestode, the larval stage of the parasite, and tolerance induction and maintenance. The pathological features of alveolar echinococcosis. the disease caused by E. multilocularis, are related both to parasitic growth and to host's immune response, leading to fibrosis and necrosis, The disease spectrum is clearly dependent on the genetic background of the host as well as on acquired disturbances of Th1-related immunity. The laminated layer of the metacestode, and especially its carbohydrate components, plays a major role in tolerance induction. Th2-type and anti-inflammatory cytokines, IL-10 and TGF-β, as well as nitric oxide, are involved in the maintenance of tolerance and partial inhibition of cytotoxic mechanisms. Results of studies in the experimental mouse model and in patients suggest that immune modulation with cytokines, such as interferon-α, or with specific antigens could be used in the future to treat patients with alveolar echinococcosis and/or to prevent this very severe parasitic disease.

Influence of Calicophoron microbothrium amphistomosis on the biochemical and blood cell counts of cattle

Sixteen Tuli steers aged 1 year were subdivided into four equal groups (I–IV) and infected with Calicophoron microbothrium metacercariae. Group I received a low dose (LD) of 5000 metacercariae, group II a medium dose (MD) of 15,000 metacercariae, group III a high dose (HD) of 25,000 metacercariae while group IV was the non-infected control (C) group. The experimental animals were monitored daily for clinical signs while ethylene diamine tetraacetic acid (EDTA) blood and serum samples were collected every 7 days until day 28 post-infection, when sample collection was terminated. Samples were processed for full blood count, eosinophils and blood biochemical values for calcium, magnesium, phosphorus, total protein and albumin. Moderate to severe diarrhoea developed in the MD and HD groups at day 21 post-infection. The diarrhoea coincided with a significant decrease (P < 0.05) in total plasma protein, calcium and phosphorus levels, particularly in the MD group. Similarly, a significant decrease (P < 0.05) in the packed cell volume (PCV), the haemoglobin (Hb) and red blood cell (RBC) levels occurred in the MD and HD groups from day 21 post-infection, while a significant increase (P < 0.05) in the circulating eosinophils occurred between 7 and 21 days post-infection in the LD and the HD groups.

Triggering and modulation of the host-parasite interplay byEchinococcus multilocularis: a review

As more facts emerge regarding the ways in whichE. multilocularis-derived molecules trigger the host immune response and modulate the host-parasite interplay, it becomes possible to envisage how the parasite can survive and proliferate in its intermediate host, while in other hosts it dies out. Through effects on cells of both the innate and adaptive arms of the immune response,E. multiloculariscan orchestrate a range of outcomes that are beneficial not only to the parasite, in terms of facilitating its intrahepatic proliferation and maturation, and thus life cycle over all, but also to its intermediate host, in limiting pathology. The present review deals with the role of metacestode surface molecules as well as excretory/secretory (E/S) metabolic products of the parasite in the modulation of the host responses such as to optimize its own survival.

Echinococcus multilocularis metacestode metabolites contain a cysteine protease that digests eotaxin, a CC pro-inflammatory chemokine

In many helminthic infections, eotaxin, a CC-chemokine, triggers the mobilization of eosinophils, thus, contributing to an elevated blood and periparasitic eosinophil level. Following an experimental intraperitoneal infection of C57BL6 mice with Echinococcus multilocularis metacestodes, however, we observed the absence of eosinophils in the peritoneal cavity and a low number of such cells in the blood of infected animals. Therefore, we carried out an explorative study to address the question why eosinophilia did not occur especially in the peritoneal cavity of such secondarily AE-infected mice. In an in vitro assay, we showed that metacestode antigens (in vitro generated vesicle fluid and E/S products) were able to proteolytically digest eotaxin. This effect was confirmed with semiquantitative Western blotting, which demonstrated a decreasing intensity of remaining eotaxin signals. Proteolysis of eotaxin was, thus, dose-dependent and proportional to the time of incubation with the metacestode antigens. Using appropriate inhibitors, the respective protease was identified as a cysteine protease, which required the presence of Ca(++) as co-enzyme. A chromatographic fractionation procedure by successive separation of VF molecules using a superpose column and subsequently a MonoQ column mounted on an FPLC system allowed to yield a fraction, referred to us as fraction 6; containing the enriched cysteine protease, this fraction will be used for further molecular studies. Eotaxin inactivation by VF and E/S products may contribute to explain the absence of eosinophils within the peritoneal cavity of AE-secondary infected mice. Absent eosinophils, thus, may be a part of a series of events that maintain a low level of inflammation displayed within the peritoneal cavity of experimentally infected mice.

Necator americanus infection: a possible cause of altered dendritic cell differentiation and eosinophil profile in chronically infected individuals

BACKGROUND

Hookworms survive for several years (5 to 7 years) in the host lumen, inducing a robust but largely ineffective immune response. Among the most striking aspects of the immune response to hookworm (as with many other helminths) is the ablation of parasite-specific T cell proliferative response (hyporesponsiveness). While the role of the adaptive immune response in human helminth infection has been well investigated, the role of the innate immune responses (e.g., dendritic cells and eosinophils) has received less attention and remains to be clearly elucidated.

METHODOLOGY/PRINCIPAL FINDINGS

We report on the differentiation/maturation of host dendritic cells in vitro and the eosinophil activation/function associated with human hookworm infection. Mature DCs (mDCs) from Necator americanus (Necator)-infected individuals showed an impaired differentiation process compared to the mDCs of non-infected individuals, as evidenced by the differential expression of CD11c and CD14. These same hookworm-infected individuals also presented significantly down-regulated expression of CD86, CD1a, HLA-ABC, and HLA-DR. The lower expression of co-stimulatory and antigen presentation molecules by hookworm-infected-derived mDCs was further evidenced by their reduced ability to induce cell proliferation. We also showed that this alternative DC differentiation is partially induced by excreted-secreted hookworm products. Conversely, eosinophils from the same individuals showed a highly activated status, with an upregulation of major cell surface markers. Antigen-pulsed eosinophils from N. americanus-infected individuals induced significant cell proliferation of autologous PBMCs, when compared to non-infected individuals.

CONCLUSION

Chronic N. americanus infection alters the host's innate immune response, resulting in a possible modulation of the maturation process of DCs, a functional change that may diminish their ability for antigen presentation and thus contribute to the ablation of the parasite-specific T cell proliferative response. Interestingly, a concomitant upregulation of the major cell surface markers of eosinophils was observed in hookworm-infected individuals, indicative of antigen-specific immune responses, especially antigen presentation. We showed that in addition to the postulated role of the eosinophils as effector cells against helminth infection, activated cells may also be recruited to sites of inflammation and contribute to the immune response acting as antigen presenting cells.

Predictors and markers of resistance to neurotropic nematode infection in rodent host

Parasite-mediated selection is currently believed to play an important role in life-history evolution. To assess how simple hematoserological and biochemical condition indices reflect host immunocompetence and infection resistance controlled laboratory experiments are required. We addressed these issues by infecting laboratory rats with the standard dose of embryonated eggs of a neurotropic nematode Toxocara canis. Urine baseline corticosterone concentrations, measured 1 week before infection, predicted the number of nematode larvae later recovered from host brains. Thus, this noninvasive clinical marker appeared useful for assessment of potential infection resistance. Rats who had accumulated high number of larvae in their brains and muscle had large spleens and high peripheral eosinophil counts 17 days postinfection. This finding is consistent with the concept that induction of eosinophilic Th2 type humoral immune response benefits the parasite rather than host. Hence, excessive peripheral eosinophilia and spleen enlargement are not markers of efficient antiparasite response in larval toxocariasis.

Influence of murine Toxocara canis infection on plasma and bronchoalveolar lavage fluid eosinophil numbers and its correlation with cytokine levels

Toxocara canis is a nematode of the Ascaridae family that normally parasites the small intestine of canid species. Humans are accidentally infected upon ingestion of embryonated eggs, and can manifest several clinical alterations such as fever, hepatomegaly, splenomegaly, respiratory symptoms, muscle pain and anorexia. In the present work, we investigated the kinetics of tissue distribution of L2 larva in lungs, liver, kidney, brain, skeletal muscle and myocardium. Also, we analyzed the blood and bronchoalveolar lavage fluid (BAL) for levels of IL-6, IFN-gamma, eotaxin and Regulated on Activation Normal T Cell Expressed and Secreted (RANTES) in experimental murine T. canis infection. We observed liver, lung and kidney lesions correlated to larva migration as early as the first day of infection. After the seventh post-infection day, larva could also be detected in brain, skeletal muscle and heart, as an indicator of biphasic migration pattern. Increased inflammatory activity was detected in BAL and plasma of infected animals, as was an intense eosinophil migration associated with an increase in the levels of all the cytokines studied. In conclusion, our results establish a tight correlation between tissue lesions caused by larva migration and increased plasma levels of pro-inflammatory and eosinophil chemotactic cytokines. Thus, murine T. canis infection may prove to be useful in understanding the role of cytokines in infection.

IL-4 dependent resistance to the tapeworm Mesocestoides corti (Cestoda) in mice

Three-week Mesocestoides corti infections of C57BL/6 mice showed significantly raised parasite counts in animals with a targeted knockout of the IL-4 gene. By contrast, antibody neutralization of IL-5 and inhibition of eosinophilia had no effect on parasite numbers. In SV/129 mice, knockout of the interferon gamma receptor and inducible nitric oxide synthase genes had no significant effect on parasite counts. In IL-4(-/-)mice the dominant IgG1 antibody response was dramatically reduced, with a concomitant increase in IgG2a/b responses and a partial twofold reduction in IgM and IgE responses. We conclude that murine resistance to M. corti is dependent on IL-4, but occurs independently of IL-5 and eosinophils. This provides the first direct evidence for IL-4 mediated immunity of mice to infection with a tissue-dwelling platyhelminth.

Immunity, antigenic heterogeneity, and aggregation of helminth parasites

Empirical studies of helminth parasites reveal that the distribution of parasite burdens in their host populations is highly aggregated. This aggregation is fundamental to the ecology and epidemiology of helminth parasites. Results from a stochastic model predict that aggregation of helminth parasites is inversely related to the intensity of host immunity. Aggregation also decreases with antigenic heterogeneity and increases with heterogeneity in transmissibility among parasite strains. It is also found that the degree of aggregation is greater when immunity affects parasite fecundity than when immunity acts on host susceptibility. Potential relevance of this result for assessing the influence of vaccines that target either host susceptibility or parasite fecundity on the level of aggregation and consequent effects on drug resistance and disease prevalence are discussed.

The CCR3 receptor is involved in eosinophil differentiation and is up-regulated by Th2 cytokines in CD34+ progenitor cells

The involvement of chemokines in eosinophil recruitment during inflammation and allergic reactions is well established. However, a functional role for chemokines in eosinophil differentiation has not been investigated. Using in situ RT-PCR, immunostaining, and flow cytometric analysis, we report that human CD34+ cord blood progenitor cells contain CCR3 mRNA and protein. Activation of CD34+ progenitor cells under conditions that promote Th2 type differentiation up-regulated surface expression of the CCR3. In contrast, activation with IL-12 and IFN-gamma resulted in a significant decrease in the expression of CCR3. Eotaxin induced Ca2+ mobilization in CD34+ progenitor cells, which could explain the in vitro and in vivo chemotactic responsiveness to eotaxin. We also found that eotaxin induced the differentiation of eosinophils from cord blood CD34+ progenitor cells. The largest number of mature eosinophils was found in cultures containing eotaxin and IL-5. The addition of neutralizing anti-IL-3, anti-IL-5, and anti-GM-CSF Abs to culture medium demonstrated that the differentiation of eosinophils in the presence of eotaxin was IL-3-, IL-5-, and GM-CSF-independent. These results could explain how CD34+ progenitor cells accumulate and persist in the airways and peripheral blood of patients with asthma and highlight an alternative mechanism by which blood and tissue eosinophilia might occur in the absence of IL-5.

Pathogenesis of murine experimental allergic rhinitis: a study of local and systemic consequences of IL-5 deficiency

Recent studies have demonstrated an important role for IL-5-dependent bone marrow eosinophil progenitors in allergic inflammation. However, studies using anti-IL-5 mAbs in human asthmatics have failed to suppress lower airway hyperresponsiveness despite suppression of eosinophilia; therefore, it is critical to examine the role of IL-5 and bone marrow responses in the pathogenesis of allergic airway disease. To do this, we studied the effects of IL-5 deficiency (IL-5(-/-)) on bone marrow function as well as clinical and local events, using an established experimental murine model of allergic rhinitis. Age-matched IL-5(+/+) and IL-5(-/-) BALB/c mice were sensitized to OVA followed by 2 wk of daily OVA intranasal challenge. IL-5(-/-) OVA-sensitized mice had significantly higher nasal mucosal CD4(+) cells and basophilic cell counts as well as nasal symptoms and histamine hyperresponsiveness than the nonsensitized group; however, there was no eosinophilia in either nasal mucosa or bone marrow; significantly lower numbers of eosinophil/basophil CFU and maturing CFU eosinophils in the presence of recombinant mouse IL-5 in vitro; and significantly lower expression of IL-5Ralpha on bone marrow CD34(+)CD45(+) progenitor cells in IL-5(-/-) mice. These findings suggest that IL-5 is required for normal bone marrow eosinophilopoiesis, in response to specific Ag sensitization, during the development of experimental allergic rhinitis. However, the results also suggest that suppression of the IL-5-eosinophil pathway in this model of allergic rhinitis may not completely suppress clinical symptoms or nasal histamine hyperresponsiveness, because of the existence of other cytokine-progenitor pathways that may induce and maintain the presence of other inflammatory cell populations.

Socio-economic health inequalities in Brazil: gender and age effects

This paper analyses Brazilian socio-economic inequalities in health by measuring the concentration indices for the following variables: health expectancy, self-assessed health status and chronic health problems. Data used were taken from the 1996/1997 Living Standard Measurement Study (LSMS). In summary, as far as gender distinction is concerned, the results showed that up to 5 years of age the mortality rates, reported appearance of chronic health problems as well as the self-assessed health indicated that the boys were in worse health condition than the girls. After this age group there was a tendency for differences to disappear until adulthood, when the situation changed and the women consistently considered themselves less healthy. With reference to the socio-economic inequalities, one generally finds larger differences within the women's groups. The analysis for the different age groups indicated that the pro-rich inequalities increased with age. Both results were clearly proved, especially for the health expectancy variable, by adopting an adjustment of the dominance concept derived from literature on economic inequalities, consisting of comparing concentration curves.

Ileal mucosal mast cell, eosinophil, and goblet cell populations during Hymenolepis diminuta infection of the rat

The population dynamics in the enteric connective tissues of eosinophils, mucosal mast cells (MMC), and in the mucosal epithelium of goblet cells were examined morphometrically in fixed ileal tissue of outbred Sprague Dawley rats during the first 32 days of infection with the tapeworm Hymenolepis diminuta. MMC and eosinophils were present in the lamina propria and submucosa; however, only eosinophils were also present in the muscularis externa. Eosinophilic infiltrate was first observed in the lamina propria at 15 days postinfection (dpi) and the numbers of eosinophils remained elevated through 32 dpi. Initial mucosal mastocytosis was detected on 6 dpi and MMC numbers continued to rise over the study period without reaching a plateau. Goblet cell hyperplasia occurred only at 32 dpi. In contrast to some intestinal nematode infections where these same 3 cell types are associated with the host's expulsion responses, H. diminuta is not lost by a rapid host response in the outbred Sprague Dawley rat strain used in these experiments. We suggest that either the induction of hyperplasia of these host effector cells in ileum tissue during H. diminuta infection is not capable of triggering parasite rejection mechanisms, or the function of the induced hyperplasia is necessary for some as yet unassociated physiological or tissue architecture change in the host's intestine.

Integrative neuroimmunomodulation of gastrointestinal function during enteric parasitism

Enteric helminths have a significant impact on the structure, function, and neural control of the gastrointestinal (GI) tract of the host. Interactions between the host's nervous and immune systems redirect activity in neuronal circuits intrinsic to the gut into an alternative repertoire of defensive and adaptive motor programs. Gut inflammation and activation of the enteric neuroimmune axis play integral roles in the dynamic interaction between host and parasite that occurs at the mucosal surface. Three inter-related themes are stressed in this review to underscore the pivotal role that neural control mechanisms play in the host's GI tract functional responses to enteric parasitism. First, we address the discovery that signaling molecules of both parasite and host origin can reorient the dynamic ecology of enteric host-parasite interactions. Second, we explore what has been learned from investigations of altered gut propulsive and secretomotor reflex activities that occur during enteric parasitic infections and the emerging picture derived from these studies that elucidates how nerves help facilitate and orchestrate functional reorganization of the parasitized gut. Third, we provide an overview of the direct impact that enteric parasitism has on nerve cell function and neurotransmission pathways in both the enteric and central nervous systems of the host. In summary, this review highlights and clarifies the complex mechanisms underlying integrative neuroimmunophysiological responses to the presence of both invasive and noninvasive enteric helminths and identifies directions for future research investigations in this highly important but understudied area.

The other side of the coin: the protective role of the TH2 cytokines

Although T(H)2 cytokine involvement in allergy makes these cytokines attractive therapeutic targets, they protect against ectoparasites and gastrointestinal worms and suppress inflammation induced by T(H)1 cytokines. T(H)2 cytokines induce mastocytosis, eosinophilia, IgE synthesis, and mucus production. Each element of this response protects against some worms; however, different worms are protected against by different elements of the total response. The induction of the entire response by most parasitic worms suggests that it is safer for the immune system to make a stereotyped worm-protective response than to attempt to match a more specific response to a particular worm. In contrast, the reciprocal antagonism between T(H)1 and T(H)2 cytokines suggests that it is safer for the immune system to limit immunopathology by suppressing inflammatory effector mechanisms not required for host protection against a particular pathogen class than to make an all-purpose inflammatory response. This, in turn, implies that innate immunity can distinguish different classes of parasites (eg, worms vs protozoa) but has limited ability to distinguish individual parasites within a class (eg, different worms). Although these considerations suggest that T(H)2 cytokine antagonists may increase the risk and severity of worm infections and T(H)1 cytokine-mediated inflammatory disorders, such therapy should be relatively safe if it is restricted to areas in which worm infections are rare and commonsense precautions are taken to minimize the risk of inducing T(H)1 cytokine-related inflammatory disease.

Mucosal immunity against parasitic gastrointestinal nematodes

The last two decades witnessed significant advances in the efforts of immunoparasitologists to elucidate the nature and role of the host mucosal defence mechanisms against intestinal nematode parasites. Aided by recent advances in basic immunology and biotechnology with the concomitant development of well defined laboratory models of infection, immunoparasitologists have more precisely analyzed and defined the different immune effector mechanisms during the infection; resulting in great improvement in our current knowledge and understanding of protective immunity against gastrointestinal (GI) nematode parasites. Much of this current understanding comes from experimental studies in laboratory rodents, which have been used as models of livestock and human GI nematode infections. These rodent studies, which have concentrated on Heligmosomoides polygyrus, Nippostrongylus brasiliensis, Strongyloides ratti/S. venezuelensis, Trichinella spiralis and Trichuris muris infections in mice and rats, have helped in defining the types of T cell responses that regulate effector mechanisms and the effector mechanisms responsible for worm expulsion. In addition, these studies bear indications that traditionally accepted mechanisms of resistance such as eosinophilia and IgE responses may not play as important roles in protection as were previously conceived. In this review, we shall, from these rodent studies, attempt an overview of the mucosal and other effector responses against intestinal nematode parasites beginning with the indices of immune protection as a model of the protective immune responses that may occur in animals and man.

Cytokines in airway inflammation

With over 50 potential asthma mediators, cytokines are the latest group of substances which have been investigated for their potential role in this disease. The use of murine models of allergic inflammation has facilitated the investigation of the role of individual cytokines in this response. The use of targeted gene disruption, overexpression of genes and monoclonal antibodies directed against cytokines have allowed a detailed examination of the role cytokines play in IgE production, eosinophil recruitment and bronchial hyperresponsiveness, which are the characteristic features of the asthma phenotype. Despite the introduction of this new methodology, conflicting reports relating to the role of cytokines in allergic inflammation, highlight the complexity of allergic inflammation and challenge the notion that a single cytokine can explain the asthma phenotype.

Drastic reduction of a filarial infection in eosinophilic interleukin-5 transgenic mice

In order to establish the role of eosinophils in destroying parasites, transgenic mice have been used in experimental helminthiases but not in filariasis. Litomosoides sigmodontis offers a good opportunity for this study because it is the only filarial species that completes its life cycle in mice. Its development was compared in transgenic CBA/Ca mice overexpressing interleukin-5 (IL-5) and in wild-type mice following subcutaneous inoculation of 40 infective larvae. An acceleration of larval growth was observed in the IL-5 transgenic mice. However, the recovery rate of adult worms was considerably reduced in these mice, as evidenced 2 months postinoculation (p.i.). The reduction occurs between days 10 and 30 p.i. in the coelomic cavities. As early as day 10, spherical aggregates of eosinophils and macrophages are seen attached on live developing larvae (always similarly localized on the worm) in both wild-type and transgenic mice. However, on day 60 p.i., granulomas were found in the transgenic mice only, probably because of the higher density of eosinophils. Furthermore, on day 30 p.i., young filariae are seen trapped in granulomas, some of them surrounded by Splendore-Hoeppli deposits, which illustrates the release of the major basic protein by eosinophils. The high protection rate obtained (65%) is similar to that observed previously in BALB/c mice following vaccination with irradiated larvae. Both protocols have a common factor, the high production of IL-5 and eosinophilia. However, protection occurs later in primary infected transgenic mice because specific antibodies are not yet present at the time of challenge.

The role of eosinophils in parasitic helminth infections: insights from genetically modified mice

Eosinophilia - an increase in the number of eosinophils in the blood or tissues - has historically been recognized as a distinctive feature of helminth infections in mammals. Yet the precise functions of these cells are still poorly understood. Many scientists consider that their primary function is protection against parasites, although there is little unequivocal in vivo evidence to prove this. Eosinophils are also responsible for considerable pathology in mammals because they are inevitably present in large numbers in inflammatory lesions associated with helminth infections or allergic conditions. In this review, Carolyn Behm and Karen Ovington outline some of the cellular and biological properties of eosinophils and evaluate the evidence for their role(s) in parasitic infections.

Cyclooxygenase-2-derived prostaglandin E2 and lipoxin A4 accelerate resolution of allergic edema in Angiostrongylus costaricensis-infected rats: relationship with concurrent eosinophilia

In noninfected rats, challenge with allergen following local IgE sensitization induced a pleurisy marked by intense protein exudation that plateaued from 30 min to 4 h after challenge, reducing thereafter. Infection of rats with Angiostrongylus costaricensis induced a 5-fold increase in blood eosinophil numbers by 25 days postinfection, whereas the numbers of eosinophils in the pleural cavity ranged from normal to a weak increase. In infected rats, identically sensitized, challenge with Ag induced a much shorter duration of pleural edema with complete resolution by 4 h, but no change in the early edema response. In parallel, infection increased the number of eosinophils recovered from the pleural cavity at 4 h, but not at 30 min, following allergen challenge. Pretreatment with IL-5 (100 IU/kg, i.v.) also increased eosinophil numbers in blood and, after allergen challenge, shortened the duration of the pleural edema and increased pleural eosinophil numbers. There were increases in the levels of both PGE2 and lipoxin A4 (LXA4) in pleural exudate. Selective cyclooxygenase (COX)-2 inhibitors, NS-398, meloxicam, and SC-236, did not alter pleural eosinophilia, but reversed the curtailment of the edema in either infected or IL-5-pretreated rats. Pretreatment of noninfected animals with the PGE analogue, misoprostol, or two stable LXA4 analogues did not alter the magnitude of pleural exudation response, but clearly shortened its duration. These results indicate that the early resolution of allergic pleural edema observed during A. costaricensis infection coincided with a selective local eosinophilia and seemed to be mediated by COX-2-derived PGE2 and LXA4.

Vaccination against helminth parasites--the ultimate challenge for vaccinologists?

Helminths are multicellular pathogens which infect vast numbers of human and animal hosts, causing widespread chronic disease and morbidity. Vaccination against these parasites requires more than identification of effective target antigens, because without understanding the immunology of the host-parasite relationship, ineffective immune mechanisms may be invoked, and there is a danger of amplifying immunopathogenic responses. The fundamental features of the immune response to helminths are therefore summarised in the context of vaccines to helminth parasites. The contention between type-1 and type-2 responses is a central issue in helminth infections, which bias the immune system strongly to the type-2 pathway. Evidence from both human and experimental animal infections indicates that both lineages contribute to immunity in differing circumstances, and that a balanced response leads to the most favourable outcome. A diversity of immune mechanisms can be brought to bear on various helminth species, ranging from antibody-independent macrophages, antibody-dependent granulocyte killing, and nonlymphoid actions, particularly in the gut. This diversity is highlighted by analysis of rodent infections, particularly in comparisons of cytokine-depleted and gene-targeted animals. This knowledge of protective mechanisms needs to be combined with a careful choice of parasite antigens for vaccines. Many existing candidates have been selected with host antibodies, rather than T-cell responses, and include a preponderance of highly conserved proteins with similarities to mammalian or invertebrate antigens. Advantage has yet to be taken of parasite genome projects, or of directed searches for novel, parasite-specific antigens and targets expressed only by infective stages and not mature forms which may generate immunopathology. With advances under way in parasite genomics and new vaccine delivery systems offering more rapid assessment and development, there are now excellent opportunities for new antihelminth vaccines.

Regulation of primary Strongyloides ratti infections in mice: a role for interleukin-5

C57BL/6 mice genetically deficient in interleukin-5 (IL-5-/-) and normal C57BL/6 (IL-5+/+) mice were infected with larvae of a homogonic strain of the nematode Strongyloides ratti. In primary infections both male and female IL-5-/- mice released two to four times more eggs and larvae than IL-5+/+ mice. IL-5-/- mice harboured about 60% more intestinal worms, which were more fecund, than IL-5+/+ mice. The duration of the infection was similar in normal and IL-5-deficient mice. Both IL-5-/- and IL-5+/+ mice resisted a secondary infection. IL5-/- mice lost more weight during the infection than normal mice and took longer to regain their initial weight after expelling the worms. The number of eosinophils increased in the bone marrow, peritoneal cavity and small intestine of IL-5+/+ mice, but not IL-5-/- mice, following infection. No significant differences between infected IL-5+/+ and IL-5-/- mice in mast cells or other leucocytes were observed in the peritoneal cavity. Thus, IL-5 functions to protect the host in a primary infection of S. ratti by limiting the number and fecundity of worms establishing in the small intestine. This protection is correlated with elevated blood and tissue eosinophilia which occurs in normal mice but not in IL-5-/- mice.