Edward Mitre

Inhibition of type 1 diabetes in filaria-infected non-obese diabetic mice is associated with a T helper type 2 shift and induction of FoxP3+ regulatory T cells

We sought to determine whether Litomosoides sigmodontis, a filarial infection of rodents, protects against type 1 diabetes in non‐obese diabetic (NOD) mice. Six‐week‐old NOD mice were sham‐infected or infected with either L3 larvae, adult male worms, or adult female worms. Whereas 82% of uninfected NOD mice developed diabetes by 25 weeks of age, no L. sigmodontis‐infected mice developed disease. Although all mice had evidence of ongoing islet cell inflammation by histology, L. sigmodontis‐infected mice had greater numbers of total islets and non‐infiltrated islets than control mice. Protection against diabetes was associated with a T helper type 2 (Th2) shift, as interleukin‐4 (IL‐4) and IL‐5 release from α‐CD3/α‐CD28‐stimulated splenocytes was greater in L. sigmodontis‐infected mice than in uninfected mice. Increased circulating levels of insulin‐specific immunoglobulin G1, showed that this Th2 shift occurs in response to one of the main autoantigens in diabetes. Multicolour flow cytometry studies demonstrated that protection against diabetes in L. sigmodontis‐infected NOD mice was associated with significantly increased numbers of splenic CD4+ CD25+ FoxP3+ regulatory T cells. Interestingly, injection of crude worm antigen into NOD mice also resulted in protection against type 1 diabetes, though to a lesser degree than infection with live L. sigmodontis worms. In conclusion, these studies demonstrate that filarial worms can protect against the onset of type 1 diabetes in NOD mice. This protection is associated with a Th2 shift, as demonstrated by cytokine and antibody production, and with an increase in CD4+ CD25+ FoxP3+ regulatory T cells.

Helminth Protection against Autoimmune Diabetes in Nonobese Diabetic Mice Is Independent of a Type 2 Immune Shift and Requires TGF-β

Leading hypotheses to explain helminth-mediated protection against autoimmunity postulate that type 2 or regulatory immune responses induced by helminth infections in the host limit pathogenic Th1-driven autoimmune responses. We tested these hypotheses by investigating whether infection with the filarial nematode Litomosoides sigmodontis prevents diabetes onset in IL-4–deficient NOD mice and whether depletion or absence of regulatory T cells, IL-10, or TGF-β alters helminth-mediated protection. In contrast to IL-4–competent NOD mice, IL-4–deficient NOD mice failed to develop a type 2 shift in either cytokine or Ab production during L. sigmodontis infection. Despite the absence of a type 2 immune shift, infection of IL-4–deficient NOD mice with L. sigmodontis prevented diabetes onset in all mice studied. Infections in immunocompetent and IL-4–deficient NOD mice were accompanied by increases in CD4+CD25+Foxp3+ regulatory T cell frequencies and numbers, respectively, and helminth infection increased the proliferation of CD4+Foxp3+ cells. However, depletion of CD25+ cells in NOD mice or Foxp3+ T cells from splenocytes transferred into NOD.scid mice did not decrease helminth-mediated protection against diabetes onset. Continuous depletion of the anti-inflammatory cytokine TGF-β, but not blockade of IL-10 signaling, prevented the beneficial effect of helminth infection on diabetes. Changes in Th17 responses did not seem to play an important role in helminth-mediated protection against autoimmunity, because helminth infection was not associated with a decreased Th17 immune response. This study demonstrates that L. sigmodontis-mediated protection against diabetes in NOD mice is not dependent on the induction of a type 2 immune shift but does require TGF-β.

Saturation of Immunoglobulin E (IgE) Binding Sites by Polyclonal IgE Does Not Explain the Protective Effect of Helminth Infections against Atopy

ABSTRACT One hypothesis for the decreased rates of atopy observed among helminth-infected individuals is that parasite-induced polyclonal immunoglobulin E (IgE) outcompetes allergen-specific IgE for FcεRI binding on basophils and mast cells. In experiments with fresh blood drawn from filaria-infected patients, we found no association between ratios of polyclonal to Brugia malayi antigen (BmAg)-specific IgE (range, 14:1 to 388:1) and basophil responses to BmAg as measured by histamine release. Using serum samples from a filaria-infected patient who also had dust mite (Dermatophagoides pteronyssinus)-specific IgE antibodies from time points with various ratios of polyclonal to D. pteronyssinus-specific IgE (16:1 to 86:1), we demonstrated that increased ratios of polyclonal to D. pteronyssinus-specific IgE did not attenuate basophil sensitization as measured by D. pteronyssinus-specific histamine release. Suppression of histamine release was likely not observed in either of these sets of experiments because polyclonal to antigen-specific IgE ratios were not sufficiently high, as concurrent passive sensitization of basophil experiments required ratios of polyclonal to antigen-specific IgE of greater than 500:1 to suppress basophil histamine release. Further, the intensity of IgE staining in basophil populations from 20 patients with active filaria infections correlated strongly with total serum IgE levels (rho = 0.698; P = 0.0024) with no plateau in intensity of IgE staining, even though some patients had total IgE levels of greater than 10,000 ng/ml. Our data therefore suggest that in helminth infections (and in filarial infections in particular), the ratios of polyclonal to allergen-specific IgE rarely reach those levels necessary to inhibit allergen-specific IgE-FcεRI binding and to suppress allergen-induced degranulation of mast cells and basophils.

Basophils Amplify Type 2 Immune Responses, but Do Not Serve a Protective Role, during Chronic Infection of Mice with the Filarial Nematode Litomosoides sigmodontis

Chronic helminth infections induce a type 2 immune response characterized by eosinophilia, high levels of IgE, and increased T cell production of type 2 cytokines. Because basophils have been shown to be substantial contributors of IL-4 in helminth infections, and because basophils are capable of inducing Th2 differentiation of CD4+ T cells and IgE isotype switching in B cells, we hypothesized that basophils function to amplify type 2 immune responses in chronic helminth infection. To test this, we evaluated basophil function using the Litomosoides sigmodontis filaria model of chronic helminth infection in BALB/c mice. Time-course studies showed that eosinophilia, parasite Ag-specific CD4+ T cell production of IL-4 and IL-5 and basophil activation and IL-4 production in response to parasite Ag all peak late (6–8 wk) in the course of L. sigmodontis infection, after parasite-specific IgE has become detectable. Mixed-gender and single-sex worm implantation experiments demonstrated that the relatively late peak of these responses was not dependent on the appearance of circulating microfilariae, but may be due to initial low levels of parasite Ag load and/or habitation of the developing worms in the pleural space. Depletion of basophils throughout the course of L. sigmodontis infection caused significant decreases in total and parasite-specific IgE, eosinophilia, and parasite Ag-driven CD4+ T cell proliferation and IL-4 production, but did not alter total worm numbers. These results demonstrate that basophils amplify type 2 immune responses, but do not serve a protective role, in chronic infection of mice with the filarial nematode L. sigmodontis.

CD200R surface expression as a marker of murine basophil activation

Background Basophils are increasingly recognized as playing important roles in the immune responses of allergic diseases and helminth infections. One of the main obstacles to studying basophils has been the lack of a simple and rapid assay to measure basophil activation in mice.

Molecular mimicry between cockroach and helminth glutathione S-transferases promotes cross-reactivity and cross-sensitization

BACKGROUND The extensive similarities between helminth proteins and allergens are thought to contribute to helminth-driven allergic sensitization. OBJECTIVE The objective of this study was to investigate the cross-reactivity between a major glutathione-S transferase allergen of cockroach (Bla g 5) and the glutathione-S transferase of Wuchereria bancrofti (WbGST), a major lymphatic filarial pathogen of humans. METHODS We compared the molecular and structural similarities between Bla g 5 and WbGST by in silico analysis and by linear epitope mapping. The levels of IgE, IgG, and IgG(4) antibodies were measured in filarial-infected and filarial-uninfected patients. Mice were infected with Heligmosomoides bakeri, and their skin was tested for cross-reactive allergic responses. RESULTS These 2 proteins are 30% identical at the amino acid level with remarkable similarity in the N-terminal region and overall structural conservation based on predicted 3-dimensional models. Filarial infection was associated with IgE, IgG, and IgG(4) anti-Bla g 5 antibody production, with a significant correlation between antibodies (irrespective of isotype) to Bla g 5 and WbGST (P< .0003). Preincubation of sera from cockroach-allergic subjects with WbGST partially depleted (by 50%-70%) anti-Bla g 5 IgE, IgG, and IgG(4) antibodies. IgE epitope mapping of Bla g 5 revealed that 2 linear N-terminal epitopes are highly conserved in WbGST corresponding to Bla g 5 peptides partially involved in the inhibition of WbGST binding. Finally, mice infected with H bakeri developed anti-HbGST IgE and showed immediate-type skin test reactivity to Bla g 5. CONCLUSION These data demonstrate that helminth glutathione-S transferase and the aeroallergen Bla g 5 share epitopes that can induce allergic cross-sensitization.

Chronic Helminth Infection Reduces Basophil Responsiveness in an IL-10–Dependent Manner

Basophils play a key role in the development and effector phases of type 2 immune responses in both allergic diseases and helminth infections. This study shows that basophils become less responsive to IgE-mediated stimulation when mice are chronically infected with Litomosoides sigmodontis, a filarial nematode, and Schistosoma mansoni, a blood fluke. Although excretory/secretory products from microfilariae of L. sigmodontis suppressed basophils in vitro, transfer of microfilariae into mice did not result in basophil suppression. Rather, reduced basophil responsiveness, which required the presence of live helminths, was found to be dependent on host IL-10 and was accompanied by decreases in key IgE signaling molecules known to be downregulated by IL-10. Given the importance of basophils in the development of type 2 immune responses, these findings help explain the mechanism by which helminths protect against allergy and may have broad implications for understanding how helminth infections alter other disease states in people.

Immune system development during early childhood in tropical Latin America: Evidence for the age-dependent down regulation of the innate immune response

The immune response that develops in early childhood underlies the development of inflammatory diseases such as asthma and there are few data from tropical Latin America (LA). This study investigated the effects of age on the development of immunity during the first 5 years of life by comparing innate and adaptive immune responses in Ecuadorian children aged 6–9 months, 22–26 months, and 48–60 months. Percentages of naïve CD4+ T cells declined with age while those of memory CD4+ and CD8+ T cells increased indicating active development of the immune system throughout the first five years. Young infants had greater innate immune responses to TLR agonists compared to older children while regulatory responses including SEB-induced IL-10 and percentages of FoxP3+ T-regulatory cells decreased with age. Enhanced innate immunity in early life may be important for host defense against pathogens but may increase the risk of immunopathology.

Impact of early life exposures to geohelminth infections on the development of vaccine immunity, allergic sensitization, and allergic inflammatory diseases in children living in tropical Ecuador: the ECUAVIDA birth cohort study

BackgroundGeohelminth infections are highly prevalent infectious diseases of childhood in many regions of the Tropics, and are associated with significant morbidity especially among pre-school and school-age children. There is growing concern that geohelminth infections, particularly exposures occurring during early life in utero through maternal infections or during infancy, may affect vaccine immunogenicity in populations among whom these infections are endemic. Further, the low prevalence of allergic disease in the rural Tropics has been attributed to the immune modulatory effects of these infections and there is concern that widespread use of anthelmintic treatment in high-risk groups may be associated with an increase in the prevalence of allergic diseases. Because the most widely used vaccines are administered during the first year of life and the antecedents of allergic disease are considered to occur in early childhood, the present study has been designed to investigate the impact of early exposures to geohelminths on the development of protective immunity to vaccines, allergic sensitization, and allergic disease.Methods/DesignA cohort of 2,403 neonates followed up to 8 years of age. Primary exposures are infections with geohelminth parasites during the last trimester of pregnancy and the first 2 years of life. Primary study outcomes are the development of protective immunity to common childhood vaccines (i.e. rotavirus, Haemophilus influenzae type B, Hepatitis B, tetanus toxoid, and oral poliovirus type 3) during the first 5 years of life, the development of eczema by 3 years of age, the development of allergen skin test reactivity at 5 years of age, and the development of asthma at 5 and 8 years of age. Potential immunological mechanisms by which geohelminth infections may affect the study outcomes will be investigated also.DiscussionThe study will provide information on the potential effects of early exposures to geohelminths (during pregnancy and the first 2 years of life) on the development of vaccine immunity and allergy. The data will inform an ongoing debate of potential effects of geohelminths on child health and will contribute to policy decisions on new interventions designed to improve vaccine immunogenicity and protect against the development of allergic diseases.Trial registrationCurrent Controlled Trials ISRCTN41239086.

Methotrexate as a Corticosteroid-Sparing Agent in Complicated Neurocysticercosis

BACKGROUND A subset of patients with neurocysticercosis developed chronic or recurrent perilesional inflammation and required long-term and high-dose corticosteroid therapy. Such therapy frequently results in severe adverse effects. The purpose of this study was to determine whether methotrexate can be used as an effective corticosteroid-sparing or replacement agent in patients with complicated neurocysticercosis. METHODS This study was a nonblinded, prospective, observational trial. Patients with neurocysticercosis who required prednisone (15 mg/day) or its equivalent for > or =2 months, were likely to require long-term corticosteroid therapy by nature of their disease, developed serious complications due to corticosteroid use, or presented with a long-term history of corticosteroid use and had continued evidence of ongoing inflammation were eligible for methotrexate treatment. RESULTS Four patients are described in this study: 2 with subarachnoid neurocysticercosis, 1 with severe intraventricular and parenchymal disease, and 1 with recurrent perilesional edema around calcified lesions. Chronic inflammation due to neurocysticercosis resulted in lacunar infarcts, visual impairment, hydrocephalus, and seizures in these patients and necessitated long-term treatment with corticosteroids, which resulted in multiple adverse effects. The addition of methotrexate, prescribed at < or =20 mg/week, allowed for the successful reduction of corticosteroid use in all 4 patients and resulted in the improvement of many corticosteroid-associated adverse effects. CONCLUSIONS Methotrexate is a beneficial corticosteroid-sparing or replacement agent for patients with neurocysticercosis who develop chronic or recurrent perilesional inflammation.