PAS-1, an Ascaris suum protein, modulates allergic airway inflammation via CD8+γδTCR+ and CD4+CD25+FoxP3+ T cells.

We have previously demonstrated that PAS-1, a 200 kDa protein from Ascaris suum, has a potent immunomodulatory effect on humoral and cell-mediated responses induced by APAS-3 (an allergenic protein from A. suum) or unrelated antigens. In this study, we investigated the mechanisms by which PAS-1 is able to induce this effect on an allergic airway inflammation induced by OVA in mice. C57BL/6 mice were adoptively transferred on day 0 with seven different PAS-1-primed cell populations: PAS-1-primed CD19(+) or B220(+) or CD3(+) or CD4(+) or CD8(+) or CD4(+) CD25⁻ or CD4(+) CD25(+) lymphocytes. These mice were immunized twice with OVA and alum by intraperitoneal route (days 0 and 7) and challenged twice by intranasal route (days 14 and 21). Two days after the last challenge, the airway inflammation was evaluated by antibody levels, cellular migration, eosinophil peroxidase levels, cytokine and eotaxin production, and pulmonary mechanical parameters. Among the adoptively transferred primed lymphocytes, only CD4(+) CD25(+) , CD8(+) or the combination of both T cells impaired the production of total IgE and OVA-specific IgE and IgG1 antibodies, eosinophilic airway inflammation, Th2-type cytokines (IL-4, IL-5 and IL-13), eotaxin release and airway hyperreactivity. Moreover, airway recruited cells from CD4(+) CD25(+) and CD8(+) T-cell recipient secreted more IL-10/TGF-ß and IFN-γ, respectively. Moreover, we found that PAS-1 expands significantly the number of CD4(+) CD25(+) FoxP3(+) and CD8(+) γδTCR(+) cells. In conclusion, these findings demonstrate that the immunomodulatory effect of PAS-1 is mediated by these T-cell subsets.

PAS-1, a protein from Ascaris suum, modulates allergic inflammation via IL-10 and IFN-gamma, but not IL-12.

Helminths and their products have a profound immunomodulatory effect upon the inductive and effector phases of inflammatory responses, including allergy. We have demonstrated that PAS-1, a protein isolated from Ascaris suum worms, has an inhibitory effect on lung allergic inflammation due to its ability to down-regulate eosinophilic inflammation, Th2 cytokine release and IgE antibody production. Here, we investigated the role of IL-12, IFN-gamma and IL-10 in the PAS-1-induced inhibitory mechanism using a murine model of asthma. Wild type C57BL/6, IL-12(-/-), IFN-gamma(-/-) and IL-10(-/-) mice were immunized with PAS-1 and/or OVA and challenged with the same antigens intranasally. The suppressive effect of PAS-1 was demonstrated on the cellular influx into airways, with reduction of eosinophil number and eosinophil peroxidase activity in OVA+PAS-1-immunized wild type mice. This effect well correlated with a significant reduction in the levels of IL-4, IL-5, IL-13 and eotaxin in BAL fluid. Levels of IgE and IgG1 antibodies were also impaired in serum from these mice. The inhibitory activity of PAS-1 was also observed in IL-12(-/-) mice, but not in IFN-gamma(-/-) and IL-10(-/-) animals. These data show that IFN-gamma and IL-10, but not IL-12, play an important role in the PAS-1 modulatory effect.

Suppression of antibody response to an unrelated antigen in experimental murine paracoccidioidomycosis: effect of cyclophosphamide and indomethacin.

A suppressive effect of experimental paracoccidioidomycosis on the IgE antibody response to an unrelated antigen (ovalbumin) has been previously observed in mice. This effect was restricted to a short period, reaching maximum levels when OA was administered on the third day of Pb-infection. In order to study possible mechanisms involved in the establishment of this suppression, resistant (A/SN) and susceptible (B10.A) mice were treated with either a low dose of cyclophosphamide (CY) or indomethacin (INDO), a potent inhibitor of prostaglandin synthesis. While treatment with the first drug in A/SN mice induced only a recovery of the IgE anti-OA antibody response, in B10.A mice this effect was extended to IgG1, IgG2a and total levels of anti-OA antibodies. On the other hand, treatment with INDO reverted the anti-OA antibody suppression regarding each antibody class tested and in both strains of mice. These results suggest the participation of prostaglandins and of a cyclophosphamide-sensitive mechanism in the induction of the suppressive phenomenon in the human system.

Characterization of allergenic fractions from Drechslera monoceras.

Drechslera monoceras, a fungus of the Deuteromycota phylum, is fairly frequent in Brazil, and is spread through the atmosphere. In previous studies done in the city of Sao Paulo, it was found that in relation to 42 other fungi extracts, the crude extract of this fungi demonstrated a more intense cutaneous reaction in patients with respiratory allergies. Biochemical, antigenic and allergenic evaluations were carried out at various growth stages of this fungus. Based on these facts, the purpose of this research was the fractionation and allergenic characterization of the allergenic extract of D. monoceras to be used in diagnosis and immunotherapy in patients with positive cutaneous reaction to this fungus. In the city of Sao Paulo, 13 of 248 patients with respiratory allergy (asthma and/or rhinitis) showed positive reaction following cutaneous tests (skin prick tests). The crude extract of D. monoceras was fractionated by SDS-PAGE. The visible fractions were then separated by electroelution to be inoculated into BALB/c mice to evaluate the production of IgE antibody. The IgE content was detected by passive cutaneous anaphylaxis test in Wistar rats, and two fractions of approximate molecular weights of 14.4 and 36 KDa reacted to the test. The in vitro allergenic characterization was carried out by Western blotting, and three fractions of approximate molecular weights of 14.4, 36 and 60 KDa were positive. It was concluded that the extract of D. monoceras has at least three allergenic determinants, which can be used for diagnosis and immunotherapy in patients with respiratory allergy to this fungi.

Murine delayed type hypersensitivity is suppressed by Ascaris suum extract.

We studied the suppressive effect of an Ascaris suum extract on delayed-type hypersensitivity (DTH) reactions to ovalbumin (OVA) and to Bacillus Calmette-Guerin (BCG). The ability of mice to develop DTH reactions to both antigens was suppressed when an immunizing dose of the antigen was given subcutaneously together with the Ascaris extract. Partial or complete suppression of the response to OVA was obtained by the use of 400 or 1000 micrograms of Ascaris extract, respectively. The response to BCG, on the other hand, was totally suppressed by 400 micrograms of extract.

Suppressive effect of an Ascaris suum extract on IgE and IgG antibody responses in mice.

1. A suppressed cytotropic and agglutinating antibody response against ovalbumin was induced in mice immunized with this antigen and an Ascaris suum extract. 2. Suppression of IgE antibody production was abolished by administration of cyclophosphamide or X-irradiation before immunization. In contrast, suppression of homocytotropic IgG1 and heterocytotropic IgG2a antibody responses was considerably resistant to the same treatments. 3. The low levels of IgG agglutinating antibodies also remained unchanged after these treatments. 4. These results indicate that distinct regulatory mechanisms are the targets of suppression induced by A. suum extract in IgE and IgG responses.

Suppression of the IgE antibody response by Ascaris suum components: effect of X-irradiation.

The effect of X-irradiation on the suppression of IgE antibody responses induced by some of the Ascaris suum (ASC) components was analyzed in mice (7-week old A/Sn females). Treatment with 300 R 24 h before immunization with 50 micrograms OVA and 200 micrograms ASC suppressive components abolished the damping effect on anti-OVA IgE antibody levels. The same effect was observed on the anti-ASC IgE antibody response obtained in mice injected with 200 micrograms ASC immunogenic plus 200 micrograms ASC suppressive components. Moreover, the failure of suppressive components to induce an IgE anti-ASC antibody response on their own was also abolished by X-irradiation. These results indicate that the suppressive components are able to elicit an IgE antibody response, but simultaneously activate a regulatory mechanism which suppresses both the homologous (anti-ASC) and heterologous (anti-OVA) antibody formation.

Colorimetric assay for the measurement of thymocyte/thymic stromal cell adhesion.

1. We describe a simple and accurate colorimetric adhesion assay (CAA) and illustrate the assay by measuring the adhesion of mouse thymocytes to mouse 2BH4 cells. 2. The assay is based on the crystal violet staining of thymocytes adhered to a subconfluent layer of 2BH4 cells (plated at 2 x 10(4) cells/well for 24 h). The optimal incubation time was shown to be 1 h and washing in PBS of non-bound and non-specifically bound thymocytes is the critical step for the precision and accuracy of the assay. 3. Saturation curves were obtained for thymocytes adhered to plated 2BH4 cells. The blank (only 2BH4 cells) was near 0.200 +/- 0.010 (mean +/- SD) and was quite reproducible. As expected, the extent of adhesion was also dependent on the number of plated 2BH4 cells. Standard curves need to be run with each assay for quantitative measurements. The intra-assay and interassay coefficients of variation were 5% and 20%, respectively. 4. The specificity of the reaction was demonstrated by the reduction of adherence by trypsin pretreatment of thymocytes, and the dose-dependent inhibition of adherence by rabbit anti-mouse thymocyte antisera but not rabbit anti-mouse immunoglobulin antisera. 5. The proposed method is simple and requires less effort than the counting of adhered cells with the light microscope and does not require the use of radioactive material as when labelling with Na2(51)CrO4 is utilized.

Suppression of IgE antibody production by Ascaris suum extract: characterization of suppressive component(s).

Partial characterization of the suppressive component(s) of A. suum extract that is (are) responsible for damping production of IgE antibody to ovalbumin was performed by physical and chemical methods. Digestion of the whole extract with trypsin and chymotrypsin completely abolished the suppressive activity. Oxidation with sodium metaperiodate or heating at 56 degrees C, however, had no effect. These results indicate that the integrity of heat-stable protein(s) present in the crude extract is essential for its suppressive effect. In addition, the carbohydrate moiety does not seem to play an important role in this effect.

PAF antagonists do not modify IgE antibody production in mice.

The effect of selective PAF antagonists on the in vivo production of IgE antibodies was investigated. The anti-ovalbumin IgE antibody content was estimated by passive cutaneous anaphylactic reaction (PCA) in the plasma of Balb/c mice 10 days after immunization with ovalbumin and alum. The PAF antagonists, BN 52021 (5 mg/kg, ip), BN 50730 (20 mg/kg, po), WEB 2086 (2 mg/kg, ip) and WEB 2170 (5 mg/kg, ip) were administered 1 h before immunization and twice a day for 8 days thereafter. The effect of the antagonists on the PAF-induced vasopermeability was also assayed. In the immunized mice the level of antiovalbumin IgE antibody, estimated by PCA titer, was 1/640. The treatment with the PAF antagonists did not change this level. At the concentrations employed, the antagonists BN 50730, WEB 2086 and WEB 2170 significantly reduced the PAF-induced vascular permeability. These results suggest that PAF does not seem to have a relevant effect on the production of IgE antibodies in vivo in the system used in the present study.

Further characterization of Ascaris suum component(s) with suppressive activity on the IgE antibody response.

In order to characterize the component(s) of Ascaris suum responsible for damping of the IgE antibody production we demonstrated that the extract incubated in sodium acetate buffer, pH 4.5, maintained its suppressive effect and the same protein banding pattern by SDS-PAGE. Elimination of the lipoprotein components of the extract also left its damping properties unchanged. SDS-PAGE of the lipoprotein-free extract revealed practically the same pattern as shown by the whole extract, except for the high molecular weight polypeptides. These results indicate that the suppressive component(s) of A. suum did not precipitate and retained their activity at low pH. In addition, they appear not to be lipoproteins.

Extracts of Ascaris suum egg and adult worm share similar immunosuppressive properties.

Adult Ascaris suum body extract (Asc) prepared from male and female worms (with stored eggs) down-regulates the specific immune response of DBA/2 mice to ovalbumin (OA) and preferentially stimulates a Th2 response to its own components, which is responsible for the suppression of the OA-specific Th1 response. Here, we investigated the participation of soluble extracts prepared from male or female worms or from eggs (E-Asc) in these immunological events. Extracts from either sex (1 mg/animal) or E-Asc (0.35 or 1 mg protein/animal) suppressed the delayed-type hypersensitivity (DTH) reaction (60-85%), proliferative response (50-70%), IL-2 and IFN-gamma secretion (below detection threshold) and IgG1 antibody production (70-90%) of DBA/2 mice to OA. A dose of 0.1 mg E-Asc/animal did not change DTH or proliferation, but was as effective as 0.35 mg in suppressing IL-2 and IFN-gamma, and OA-specific IgG1 antibodies. Lymph node cells from DBA/2 mice injected with Asc (1 mg/animal) or a high dose of E-Asc (1 mg protein/animal) secreted IL-4 upon in vitro stimulation with concanavalin A. As previously demonstrated for Asc, the cytokine profile obtained with the E-Asc was dose dependent and changed towards Th1 when a low dose (0.1 mg protein/animal) was used. Taken together, these results suggest that adult worms of either sex and eggs induce the same type of T cell response and share similar immunosuppressive properties.

Interference of methysergide, a specific 5-hydroxytryptamine receptor antagonist, with airway chronic allergic inflammation and remodelling in a murine model of asthma.

BACKGROUND: Airway remodelling encompasses the structural changes observed in asthmatic airways. Mast cells, through the release of histamine and 5-hydroxytryptamine (serotonin), are implicated in early asthmatic reactions, bronchoconstriction and mucosal oedema, and in the development of bronchial hyperresponsiveness. However, the association between serotonin and remodelling processes in murine model of airways inflammation remains to be elucidated. OBJECTIVE: As serotonin is released by murine mast cells upon antigen challenge, we tested the hypothesis of its involvement in the development of inflammatory and remodelling processes in a murine model of chronic airway inflammation following prolonged allergen challenge. Methods BALB/c mice were exposed to aerosolized ovalbumin for 20 min 2 days a week, for 4 consecutive weeks. Two hours before each challenge, they were treated with methysergide (intranasally, 40 microg/kg). Forty-eight hours after the last aerosol challenge, bronchoalveolar lavage (BAL) and lung tissue were collected for analysis. RESULTS: Methysergide inhibited the allergen-induced increase in airway eosinophilia, reduced T helper type 2 (Th2) cytokines in lung, spleen or thoracic lymph nodes, and specific IgE levels. The extravasation of plasma and fibronectin production in the lung, and collagen deposition in the lung were also inhibited after methysergide treatment. Although methysergide treatment induced an increase in IFN-gamma levels, experiments with neutralizing antibody suggest that this is not responsible for inhibition. In addition, instillation of serotonin to immunized mice induced eosinophil recruitment to BAL, Th2 cytokine production and fibronectin release in lung as well as collagen deposition. CONCLUSION: Serotonin may contribute to the development and maintenance of remodelling through the release of cytokines and of fibrogenic mediators. Serotonin should therefore be considered as relevant for the development and maintenance of airway remodelling.

Early stages of Ascaris suum induce airway inflammation and hyperreactivity in a mouse model.

The inflammatory and functional changes that occur in murine lung after infection with 2500 infective Ascaris suum eggs were studied in this work. A sequential influx of neutrophils, mononuclear cells and eosinophils occurred into airways concomitantly with migration of larvae from liver to the lungs. Histological analysis of the lung showed a severe intra-alveolar haemorrhage at the peak of larval migration (day 8) and the most intense inflammatory cell infiltrate on day 14. Ascaris L3 were found in alveolar spaces and inside bronchioles on day 8. The number of eosinophils was elevated in the blood on days 8 and 14. The peak of eosinophil influx into the lung was at day 14, as indicated by the high levels of eosinophil peroxidase activity, followed by their migration into the airways. The antibody response against egg and larval antigens consisted mainly of IgG1 and IgM, and also of IgE and anaphylactic IgG1, that cross-reacted with adult worm antigens. Total IgE levels were substantially elevated during the infection. Measurement of lung mechanical parameters showed airway hyperreactivity in infected mice. In conclusion, the murine model of A. suum infection mimics the Th2-induced parameters observed in pigs and humans and can be used to analyse the immunoregulatory properties of this helminth.

Anti-inflammatory activity of PAS-1, a protein component of Ascaris suum.

BACKGROUND: Recently, we identified a 200 kDa protein (PAS-1) from Ascaris suum worms, that suppresses the humoral immune response. Here, the effect of PAS-1 on inflammatory leukocyte migration induced by bacterial lipopolysaccharide (LPS) was investigated. METHODS: Cellular migration and cytokine release, stimulated by LPS or LPS+PAS-1, were analyzed in air pouches induced in the shaved back of BALB/c mice. Cytokines were determined by ELISA and RT-PCR on air pouch exudates and in vitro stimulated peritoneal macrophages. RESULTS: The significant cellular influx induced by LPS, consisting predominantly of neutrophils, was highly suppressed in the presence of PAS-1, but not a non-related protein. PAS-1 led also to a marked reduction of TNF-alpha, IL-1 beta and IL-6 levels in both LPS-stimulated air pouches and peritoneal macrophage cultures. In contrast, PAS-1 induced a significant increase of IL-10 and TGF-beta production. CONCLUSIONS: These results demonstrate that PAS-1 has a potent anti-inflammatory activity, probably due to the stimulation of regulatory cytokines in macrophages, thus leading to the inhibition of pro-inflammatory cytokine production.

Modulation of murine experimental asthma by Ascaris suum components.

BACKGROUND: We have recently isolated two distinct components from Ascaris suum adult worms with different effects on the immune system: the allergenic protein of A. suum (APAS-3), which induces IgE antibody production, and suppressive protein of A. suum (PAS-1), which inhibits humoral and cellular immune responses induced by unrelated antigens. In this study, we investigated the immunomodulatory effect of PAS-1 on a murine model of asthma induced by APAS-3. METHODS: BALB/c mice were immunized twice with APAS-3 or APAS-3 plus PAS-1 by the intraperitoneal and subcutaneous route (on days 0 and 7) and challenged twice with the same antigens intranasally (days 14 and 21). Two days after the last challenge, the allergic airway inflammation was evaluated by cellular migration, eosinophil peroxidase (EPO) activity, cytokine and chemokine production and pulmonary mechanical parameters. RESULTS: The allergenic properties of APAS-3 were confirmed by the stimulation of anaphylactic IgE and IgG1 antibody production and eosinophilic airway inflammation and hyper-responsiveness. On the other hand, PAS-1-treated mice showed a marked suppression of cellular migration and EPO activity that correlated well with a significant reduction in the levels of IL-4, IL-5, eotaxin and RANTES in the bronchoalveolar lavage (BAL) fluid. In contrast, considerable amounts of IL-10 were observed in the BAL fluid of PAS-1-treated mice. Airway hyper-responsiveness was obtained in APAS-3-immunized mice, but the conductance of the respiratory system was restored to normal values in the presence of PAS-1. CONCLUSION: These results indicate that A. suum allergenic protein APAS-3 induces a T helper 2-type immune response and, consequently, eosinophilic airway inflammation and hyper-responsiveness. Moreover, the modulatory protein PAS-1 has a marked suppressive effect on this response, and the inhibition of cytokine (IL-4, IL-5) and chemokine (eotaxin and RANTES) release, probably because of the presence of IL-10, may contribute to this effect.

Antigenic competition in IgE antibody production. I. Establishment of parameters involved in primary and secondary responses.

Antigenic competition was demonstrated in IgE antibody response in mice immunized with ovalbumin or DNP-ovalbumin associated with several non-related proteins: DNP-Ascaris, DNP-keyhole limpet haemocyanin or Ascaris. Simultaneous injection of two antigens caused a suppression of IgE antibody production to the test antigen, IgG1 antibody formation being only diminished under certain conditions. Competition was dose-dependent and effective only in the primary response. However, the secondary response could be also partially suppressed if the competitor antigen was given in both first and second antigenic stimulation. Competition was abolished by irradiation prior to immunization.

Antigenic competition in IgE antibody production. II. Effect of cyclophosphamide.

The effects of cyclophosphamide (CY) on antigenic competition in IgE antibody production were studied in mice treated with the drug on different days and immunized with a mixture of two non-related antigens. Injection of 100 mg of CY/kg of body weight 3 days before or 6 days after immunization resulted in a partial or total recovery of the IgE, but not of the IgGl antibody response to the test antigen. In contrast, when the same dose was given together or 3 days after immunization both responses were much more suppressed than in untreated animals. This same effect was obtained when a higher concentration (200 mg/kg) of cyclophosphamide was injected on day--3. When a different antigenic system was tested, the suppressive effects of competition in IgGl antibody production were also abolished after CY treatment. These results seem to provide further evidence for an important role of suppressor T cells in the mechanism of antigenic competition.

Effect of X irradiation on homocytotropic and agglutinating antibody production in mice.

The effect of X irradiation on homocytotropic and agglutinating antibody production was studied in mice exposed to 400 rad either before or after immunization with dinitrophenylated Ascaris plus aluminium hydroxide as adjuvant. The adjuvant effect of irradiation was also determined in animals receiving antigen alone. Irradiation 1 day before immunization with adjuvant enhanced IgE and slightly enhanced IgM-antibody formation, although the onset was delayed, but partially suppressed IgG-antibody formation. When the same treatment followed antigen priming, there was a similar enhancement of IgE production which varied with the time between the two procedures. IgG AND IgM production, however, were fairly resistant under the same conditions. Irradiation preceding immunization with soluble antigen had no significant adjuvant effect on IgE-, IgG- or IgM-antibody production. On the contrary, it suppressed production of the latter two classes. The results may indicate that production of IgE and IgG and IgM antibodies in the mouse is regulated by separate mechanisms.

Induction of IL-4-dependent, anaphylactic-type and IL-4-independent, non-anaphylactic-type IgG1 antibodies is modulated by adjuvants.

Adjuvants can modulate the levels of anaphylactic- and non-anaphylactic-type IgG1 antibodies produced in response to a particular antigen. Mice immunized with ovalbumin (OVA) in Al(OH)(3) gel (alum) produced mostly the anaphylactic type, irrespective of the s.c. or i.p. route used, and this antibody was not detectable in IL-4(-/-) mice. In contrast, when OVA was injected in complete Freund's adjuvant (CFA), it induced substantial amounts of non-anaphylactic-type IgG1 in both IL-4(+/+) and IL-4(-/-) mice, and some anaphylactic IgG1 antibody in IL-4(+/+) mice only. When IFN-gamma was neutralized by specific mAb in wild-type mice immunized with OVA in CFA, the anaphylactic-type IgG1 antibody increased reaching the same levels as in alum-injected mice. This result indicates that the induction of IFN-gamma by the immunization with CFA down-regulates the production of IL-4-dependent, anaphylactic-type IgG1. Despite their different effects on IgG1 antibody production, both adjuvants dramatically increased the production of IgG2a in IL-4-deprived mice and did not induce any detectable IgE in these mice.