Low dose of orally administered antigen down-regulates the T helper type 2-response in a murine model of dust mite hypersensitivity

Oral administration of allergen extracts from mugwort pollen desensitizes specific allergen-induced allergy in mice

Clinically, sublingual immunotherapy (SLIT) using allergen extracts effectively alleviates the symptoms of allergic rhinitis and asthma. We hypothesized that oral administration of a high-dose of allergen extracts imitates SLIT, which may prevent IgE-related responses in allergic diseases. In the present study, we investigated the effects of oral administration of allergen extracts from mugwort pollen (MP) on allergen-induced inflammation and airway hyperresponsiveness (AHR) in an allergic mouse model. After administration of MPdrop containing Art v 1 and Art v 4 extracts derived from MP specifically in MP-sensitized mice, the effects of MPdrop on AHR, inflammatory cell accumulation, cytokine production in the bronchoalveolar lavage fluid and lung tissue, and serum IgE and IgG levels were investigated. The results indicated that MPdrop not only prevented the AHR in response to methacholine in a dose-dependent manner but also significantly reduced the total serum and allergen-specific IgE levels. All of the maximal effects were achieved at a dose of 100μg/(kgd) and were comparable to the effects of dexamethasone at a dose of 0.5mg/(kgd). Furthermore, oral administration of MPdrop dose-dependently elevated allergen-specific serum IgG2a levels, reduced total and allergen-specific IgE levels and normalized the imbalance between the Th1 cytokine IL-12 and Th2 cytokines IL-4 and IL-5. Finally, oral administration of MPdrop significantly reduced goblet cell hyperplasia and eosinophilia in the MP-sensitized allergic mouse model. These data suggest that MPdrop effectively improves specific allergen-induced inflammation and AHR in MP-sensitized and -challenged mice and provides the rationale for clinical use of MPdrop in the specific allergen-induced asthma.

Oral administration of allergen extracts from Dermatophagoides farinae desensitizes specific allergen-induced inflammation and airway hyperresponsiveness in rats

Clinically sublingual immunotherapy (SLIT) by using allergen extracts effectively alleviates the symptoms of allergic rhinitis and asthma. Supposed that oral administration of high-dose of allergen extracts imitates SLIT and may prevent IgE-related responses in allergic diseases, we investigated the effects of oral administration of allergen extracts from Dermatophagoides farinae (Derf) on allergen-induced inflammation and airway hyperresponsiveness (AHR) in a model of asthmatic rat. After administration to the specific Derf-sensitized rats with Derfdrop solution containing Derf1 and Derf2 extracts derived from Derf, the effects of Derfdrop on AHR, inflammatory cell accumulation, cytokine production in the bronchoalveolar lavage fluid and lung tissue, as well as serum IgE and IgG levels were investigated. Results indicated that Derfdrop not only dose-dependently prevented the AHR in response to methacholine, but also significantly reduced the serum total and allergen-specific IgE levels, all the maximal effects were achieved at dose of 5 mg/kg/d, and were as comparable as those of dexamethasone at dose of 1.0 mg/kg/d. Furthermore, oral administration of Derfdrop not only dose-dependently elevated allergen-specific serum IgG levels and reduced total and allergen-specific IgE levels, but also normalized the imbalance between the Th1 cytokine, IFN-gamma and Th2 cytokine, IL-4. Finally, oral administration of Derfdrop significantly reduced Goblet cell hyperplasia and eosinophilia in the Derf-sensitized allergic rat model. These data suggest that Derfdrop effectively improves specific allergen-induced inflammation and AHR in Derf-sensitized and -challenged rats and provide with the rationale for clinical SLIT by using Derfdrop in a specific allergen-induced asthma.

Rush immunotherapy in an experimental model of feline allergic asthma

Specific allergen immunotherapy represents the only curative treatment of allergy. No studies have evaluated its efficacy in feline allergic asthma. We hypothesized that an abbreviated course of immunotherapy (rush immunotherapy, RIT) would blunt eosinophilic airways inflammation in experimental feline asthma induced with Bermuda grass allergen (BGA). The 6-month study included asthmatic-RIT treated cats; asthmatic-no RIT treated cats; and non-asthmatic cats. RIT involved increasing parenteral doses (20-200 microg) of BGA over 2 days. Numbers of eosinophils in bronchoalveolar lavage fluid (BALF), serum and BALF immunoglobulins, lymphocyte blastogenesis assays, and cytokines in blood and BALF were evaluated. BALF eosinophils decreased (P=0.048) only in asthmatic-RIT treated cats (baseline 1.1 x 10(6); Month 6, 2.4 x 10(5)). Serum BGA-specific IgG was higher (P<0.001) at all time points after baseline within the asthmatic-RIT group, and was higher (P<0.001) than asthmatic-no RIT cats at Months 1 and 3. No differences (P=0.133) in BGA-specific IgE levels over time were noted among asthmatic-RIT cats, but this group had lower IgE levels (P<0.001) levels than asthmatic no-RIT cats at Months 3 and 6. Differences in BGA-specific IgA levels over time and between the two groups did not reach the traditional level of significance. The mean BGA stimulation index in the asthmatic-RIT cats was biologically insignificant at 6 months, reflecting BGA-specific lymphocyte hypoproliferation. Preliminary results of cytokine profiles were not significantly different; however, BAL cytokine profiles favoring a Th2 response prior to RIT shifted to increased IFN-g and IL-10 thereafter. RIT dampens eosinophilic airways inflammation in cats with experimental asthma. The mechanism of RIT may involve changes in allergen-specific immunoglobulins, induction of hyporesponsive lymphocytes, or alteration of cytokine profiles.

Bystander Effect in Synergy to Anergy in Oral Tolerance of Blomia Tropicalis/Ovalbumin Murine Co-Immunization Model

Oral tolerance is an important approach in allergic diseases and murine model can provide useful information to improve its understanding and therapeutic measures. To address the influence of non-related allergen sensitization in immunized mice with the mite Blomia tropicalis (Bt) or ovalbumin (OVA) or with both Bt/OVA allergens. Furthermore, we sought to verify oral tolerance effect in the Bt/OVA co-immunization model. Mice sensitized with Bt and then exposed to OVA developed an enhanced IgE response to both allergens; contrariwise, this effect was not observed when OVA-sensitization was prior to Bt-sensitization. Co-injection of Bt and OVA led to a dominant IgE response towards OVA over Bt, which was not observed when co-immunization was performed with a 240-fold less amount of OVA. Induction of oral tolerance with OVA, prior to co-immunization, suppressed IgE response to both allergens, probably as a consequence of the increased levels of IFN-gamma found in these animals. The results evidenced that, depending on allergenic potential, new allergen exposure may exert an adjuvant effect to the first allergen used in the sensitization. The bystander suppression to non-related allergens through oral tolerance should be a useful mechanism to control sensitization to new allergens.

Induction of oral tolerance and the effect of interleukin-4 on murine skin allograft rejection

We studied the effect of oral and portal vein administration of alloantigens on mouse skin allograft survival. Graft receptor BALB/c mice received spleen cells (30, 90, 150 or 375 x 10(6)) from donor C57BL/6 mice intragastrically on three successive days, starting seven days before the skin graft. Allograft survival was significantly increased with the feeding of 150 x 10(6) allogeneic spleen cells by one gavage (median survival of 12 vs 14 days, P< or =0.005) or when 300 x 10(6) cells were given in six gavage (12 vs 14 days, P<0.04). A similar effect was observed when 150 x 10(6) spleen cells were injected into the portal vein (12 vs 14 days, P< or =0.03). Furthermore, prolonged allograft survival was observed with subcutaneous (12 vs 16 days, P< or =0.002) or systemic (12 vs 15 days, P< or =0.016) application of murine interleukin-4 (IL-4), alone or in combination with spleen cell injection into the portal vein (12 vs 18 days, P< or =0.0018). Taken together, these results showed that tolerance induction with spleen cells expressing fully incompatible antigens by oral administration or intraportal injection partially down-modulates skin allograft rejection. Furthermore, these findings demonstrated for the first time the effect of subcutaneous or systemic IL-4 application on allograft skin survival suggesting its use as a beneficial support therapy in combination with a tolerance induction protocol.

Preconception maternal immunization to dust mite inhibits the type I hypersensitivity response of offspring

BACKGROUND

The maternal immunologic experience associated with early life exposure to allergens might contribute to the development of allergy during infancy.

OBJECTIVES

We sought to analyze the effect of the mother's immunization before conception with the dust mite Dermatophagoides pteronyssinus on the allergen priming and hypersensitivity response in early immunized offspring. The kinetics of D pteronyssinus immunization were observed from newborn to adult age, and the secondary response to D pteronyssinus was followed in offspring immunized in early life.

METHODS

Female A/Sn mice were immunized or not with D pteronyssinus and mated with male C57BL/6 mice. The hybrid offspring were immunized to investigate allotypes and subclasses of anti-D pteronyssinus antibody, as well as total IgE levels, by using ELISA and anti-D pteronyssinus IgE antibody by using the passive cutaneous anaphylaxis reaction. Ovalbumin was used for heterologous immunization. Cytokines were measured in the cell-culture supernatant by means of ELISA, and CD4(+)CD25(+) cells were analyzed by means of flow cytometry.

RESULTS

Offspring from immune mothers have not shown evidence of prenatal or postnatal allergen priming with respect to humoral level. Immunization with D pteronyssinus of offspring at very early life and in the postweaning period inhibited anti-D pteronyssinus IgE and IgG1 antibody production, along with the expected presence of maternal antibody. Furthermore, offspring antibody responsiveness from immune mothers has remained quiescent on secondary allergenic challenge. This maternal influence on the offspring antibody response was specific to D pteronyssinus because the immunization with a heterologous antigen did not alter IgE response. Maternal D pteronyssinus immunization induced a significant decrease of the IFN-gamma level in the offspring, avoided an exacerbation of T(H)2 cytokine secretion, and, concomitantly, upregulated the number of CD4(+)CD25(+) T cells.

CONCLUSION

Maternal immunization to D pteronyssinus seems to protect offspring from the development of allergy.

Oral tolerance induction to Dermatophagoides pteronyssinus and Blomia tropicalis in sensitized mice: occurrence of natural autoantibodies to immunoglobulin E

BACKGROUND

The dust mites Dermatophagoides pteronyssinus (Dp) and Blomia tropicalis (Bt) are important sources of indoor allergens in tropical and subtropical countries. Murine models allow the analysis of the immune response and regulation of IgE production to Dp and Bt allergens. Oral tolerance induces unresponsiveness in naive animals, but its application in sensitized animals can provide useful information to improve allergy therapy.

OBJECTIVE

To study the profile of IgE and IgG subclasses antibody upon oral administration with Bt and Dp extract in previously sensitized mice. Further, the occurrence of autoantibodies IgG anti-IgE in the immunization and in the oral tolerance was investigated.

METHODS

A/Sn mice were immunized with Bt or Dp extract in alum, orally administrated with 0.25 mg of Bt or Dp extract or PBS at the 6th, 7th and 8th days after immunization and boosted twice with their respective allergens. To analyse the mice groups, specific IgE antibodies were measured by passive anaphylaxis reaction and specific IgG subclasses and anti-IgE IgG autoantibody by ELISA assay.

RESULTS

IgE levels were markedly increased in Bt-immunized mice compared with Dp-immunized mice. A distinct profile of the specific isotypes was verified in Bt-immunized mice with a preferential production of IgG3 and IgA antibodies, whereas Dp-immunized mice developed high titres of anti-Dp IgG1, IgG2a and IgG2b antibodies. The antigen feeding inhibited IgE response in both fed-mice groups but only Dp-fed mice presented decreased levels of IgG antibodies. Free anti-IgE IgG autoantibodies were detected mainly in the Dp-immunization and they correlated with the antibody isotypes found against the allergen.

CONCLUSIONS

This is the first time that the murine-type I hypersensitivity is employed to study Bt-immunization, showing a marked IgE production, associated with IgG response, which is at least in part driven by T-independent antigens. The oral tolerance protocol in previously sensitized animals was able to down-modulate IgE response and points out this route as a strategy for allergy therapy.

Oral tolerance induction in dermatophagoides pteronyssinus-sensitized mice induces inhibition of IgE response and upregulation of TGF-beta secretion

Oral antigen administration induces peripheral tolerance in naive animals. Studies of oral tolerance induction in sensitized mice have clinical relevance as a strategy to modulate allergy. In this study, the A/Sn mice sensitized with extract of Dermatophagoides pteronyssinus (Dp) and submitted to oral Dp administration showed a marked decrease in IgE anti-Dp antibody production compared with sensitized phosphate-buffered saline (PBS)-fed mice. T cells from Dp-fed mice cocultured with spleen cells from PBS-fed mice were able to inhibit IgE anti-Dp antibody production and did not interfere in IgG1 antibody levels. The analysis of cytokine profile after Dp feeding showed a significant decrease in interleukin-4 (IL-4), IL-5, and IL-13 antigen-induced secretion levels by spleen cells, without shifting to IL-2 and interferon-gamma (IFN-gamma) production. Both transforming growth factor-beta (TGF-beta) baseline and TGF-beta antigen-stimulated levels were increased in Dp-fed mice. The effects of regulatory cytokines on anti-Dp IgE antibody production were investigated in vitro. The addition of recombinant TGF-beta (rTGF-beta) to spleen cell cultures stimulated by Dp inhibited IgE antibody secretion in both mouse groups. Neutralizing antibodies to IL-4, but not anti-TGF-beta, induced a marked inhibition of IgE production. Therefore, a negative modulatory effect on IgE response by inhibition of the axis Th2 was observed in sensitized Dp-fed mice, possibly mediated by induction of regulatory cytokines.

Modulation of IgE response and cytokine production in Peyer's patches and draining lymph nodes in sensitized mice made tolerant by oral dust mite administration

Such allergic diseases as rhinitis and asthma are IgE-mediated type I reactions and are controlled primarily by Th2 cells. One of the major dust mites, Dermatophagoides pteronyssinus (Dp), is considered to cause allergic reactions. Oral tolerance, largely used to modulate immune response, opens the possibility of modulating Th2 allergic responses. We observed downmodulation of total and specific IgE antibody levels as well as the number of specific IgE-secreting cells with Dp feeding in previously sensitized mice. Analysis of the cytokine profile in mucosal lymphoid tissues in the protocol revealed altered patterns of interferon-gamma (IFN-gamma), interleukin-5 (IL-5), and transforming growth factor-beta (TGF-beta) secretion in Dp-fed animals. The results suggest that both the Th and B cell populations are modulated in mice made tolerant by oral Dp feeding. Understanding the mechanisms at the mucosal level that underlie oral tolerance can improve its use in allergy immunotherapy.

Immunotherapy of asthma and allergic diseases

The goals of therapy for allergic disease and asthma, which have increased dramatically during the past 2 decades, are to relieve and prevent symptoms. Currently, allergen immunotherapy is the only available treatment that can reduce symptoms, alter the natural course of disease, and induce long-term clinical remission effectively and safely in patients with allergic rhinitis, asthma, and insect venom anaphylaxis. Allergen immunotherapy may even prevent the evolution towards polysensitization and prevent the development of asthma in allergic children. In the long run, it is more cost-effective than pharmacotherapy and environmental control measures alone. Future developments, such as using alternate routes of administration, peptide fragments of allergen, adjuvants, and DNA vaccines, may improve its efficiency in inducing long-term clinical relief of symptoms.