Modified antigenic reactivity of anti-phospholipase A2 IgG antibodies in patients allergic to bee venom: conversion with immunotherapy and relation to subclass expression

Allergen Immunotherapy-Induced Immunoglobulin G4 Reduces Basophil Activation in House Dust Mite-Allergic Asthma Patients

It is unclear if allergen immunotherapy (AIT) can reduce allergy effector cell activation. We evaluated the basophil response during Dermatophagoides pteronyssinus (Der p) subcutaneous immunotherapy (SCIT) and its relationship to allergen-specific immunoglobulin G4 (sIgG4) in allergic rhinitis and/or asthma patients. The study included 55 subjects, of which 35 cases received Der p SCIT and 20 controls received standard medications. Symptom and medication scores (SMSs), sIgG4 levels, specific immunoglobulin E (sIgE) levels, allergen-induced basophil activation tests (BATs) in whole blood, and BAT inhibition assays in serum were determined at weeks 0, 4, 12, 16, 52, and 104 of SCIT. Levels of Der p sIgG4 in SCIT patients significantly increased after 12 weeks of treatment compared to week 0. Serum obtained from SCIT patients significantly inhibited basophil activation after 12 weeks of treatment. Removal of immunoglobulin G4 (IgG4) antibodies at week 104 reduced the ability of serum to block basophil activation. An increase of Der p sIgG4 rather than reduction of Der p sIgE correlated with the reduction of basophil activation during SCIT. The sIgG4 antibodies may compete with sIgE binding to allergens to form an immunoglobulin E (IgE)-allergen complex. SCIT reduced the sensitivity of allergen-triggered basophil activation in Der p allergic rhinitis and/or asthma patients through induction of sIgG4.

Efficacy of a therapeutic treatment using gas-filled microbubble-associated phospholipase A2 in a mouse model of honeybee venom allergy

BACKGROUND

Venom immunotherapy is efficient to desensitize people suffering from insect sting allergies. However, the numerous injections required over several years and important risks of severe side reactions complicate the widespread use of immunotherapy. In the search for novel approaches to blunt the overwhelming pro-allergic Th2 response, we evaluated the therapeutic efficacy of a treatment based on a denatured form of the major allergen, phospholipase A2, associated with microbubbles (PLA2denat -MB) in a mouse model of honeybee venom allergy.

METHODS

Antibodies measured by ELISA, T-cell responses assessed by CFSE-based proliferation assays and ELISA, and basophil degranulation were examined after PLA2denat -MB-based therapeutic treatment of sensitized mice. Mice were challenged with a lethal dose of PLA2 to evaluate protection against anaphylaxis.

RESULTS

Therapeutic subcutaneous administration of two different PLA2denat -MB formulations, in contrast to PLA2denat alone, reduced allergic symptoms and protected all mice from anaphylaxis-mediated death after allergen challenge. At the functional level, the use of PLA2denat decreased IgE-mediated basophil degranulation as compared to the native form of the allergen. In comparison with PLA2denat alone, both PLA2denat -MB formulations decreased allergen-specific Th2 CD4 T-cell reactivity. At the mechanistic level, PLA2denat -MB containing 20% palmitic acid and PEG induced PLA2-specific IgA and increased Foxp3(+) Treg frequencies and TGF-β production, whereas the formulation bearing 80% palmitic acid triggered the production of IFN-γ, IgG2a, and IgG3.

CONCLUSIONS

In contrast to conventional PLA2 subcutaneous immunotherapy, the therapeutic administration of PLA2-MB treatment to mice that already had established allergy to PLA2 protects all subsequently challenged animals.

Allergen immunotherapy for birch pollen-allergic patients: recent advances

As of today, allergen immunotherapy is performed with aqueous natural allergen extracts. Recombinant allergen vaccines are not yet commercially available, although they could provide patients with well-defined and highly consistent drug substances. As Bet v 1 is the major allergen involved in birch pollen allergy, with more than 95% of patients sensitized to this allergen, pharmaceutical-grade recombinant Bet v 1-based vaccines were produced and clinically tested. Herein, we compare the clinical results and modes of action of treatments based on either a birch pollen extract or recombinant Bet v 1 expressed as hypoallergenic or natural-like molecules. We also discuss the future of allergen immunotherapy with improved drugs intended for birch pollen-allergic patients suffering from rhinoconjunctivitis.

Novel routes for allergen immunotherapy: safety, efficacy and mode of action

Allergen immunotherapy is the only curative treatment of IgE-mediated type I respiratory allergies. Subcutaneous immunotherapy (SCIT) is used as a reference therapy and has transformed allergic treatments; it improves symptoms (asthma and rhinitis) as well as the quality of life of patients. SCIT requires repetitive administration and carries the risk of severe systemic adverse effects, including anaphylaxis. Sublingual immunotherapy is now a valid noninvasive alternative to SCIT, as a safe and efficacious treatment for respiratory allergies. In this article, we compare various routes of allergen immunotherapy, including SCIT and sublingual immunotherapy, as well as more exploratory routes currently under investigation (i.e., intralymphatic, epicutaneous, intranasal and oral). We discuss their respective advantages, as well as their foreseen modes of action.

Novel ways for immune intervention in immunotherapy: mucosal allergy vaccines

Allergen-specific immunotherapy is currently the only curative treatment for allergy. Subcutaneous immunotherapy (SCIT) has been successfully used to treat patients who are allergic to insect venom, house dust mites, or tree or grass pollens. In the context of potentially severe, albeit infrequent, side effects associated with SCIT, mucosal routes of administration are being investigated to conduct allergenic desensitization. This article reviews recent developments in the field of nasal, oral, and sublingual immunotherapy as they relate to safety, clinical efficacy, and immune mechanisms of action. Implications for the design and development of improved allergy vaccines that could be used through such nonparenteral routes are discussed. Specifically, allergen presentation platforms and adjuvants facilitating the targeting of immune cells at mucosal surfaces to promote tolerance induction are reviewed.

Immune mechanisms of allergen-specific sublingual immunotherapy

Sublingual immunotherapy has been shown in some clinical studies to modulate allergen-specific antibody responses [with a decrease in the immunoglobulin E/immunoglobulin G4 (IgE/IgG4) ratio] and to reduce the recruitment and activation of proinflammatory cells in target mucosa. Whereas a central paradigm for successful immunotherapy has been to reorient the pattern of allergen-specific T-cell responses in atopic patients from a T helper (Th)2 to Th1 profile, there is currently a growing interest in eliciting regulatory T cells, capable of downregulating both Th1 and Th2 responses through the production of interleukin (IL)-10 and/or transforming growth factor (TGF)-beta. We discuss herein immune mechanisms involved during allergen-specific sublingual immunotherapy (SLIT), in comparison with subcutaneous immunotherapy. During SLIT, the allergen is captured within the oral mucosa by Langerhans-like dendritic cells expressing high-affinity IgE receptors, producing IL-10 and TGF-beta, and upregulating indoleamine dioxygenase (IDO), suggesting that such cells are prone to induce tolerance. The oral mucosa contains limited number of proinflammatory cells, such as mast cells, thereby explaining the well-established safety profile of SLIT. In this context, second-generation vaccines based on recombinant allergens in a native conformation formulated with adjuvants are designed to target Langerhans-like cells in the sublingual mucosa, with the aim to induce allergen-specific regulatory T cells. Importantly, such recombinant vaccines should facilitate the identification of biological markers of SLIT efficacy in humans.

Mechanisms of immunotherapy: IgG revisited

PURPOSE OF REVIEW

This paper will review historical and recent evidence for the induction of 'blocking' IgG antibodies during successful specific immunotherapy.

RECENT FINDINGS

Specific immunotherapy is frequently associated with a rise in allergen-specific IgG4 antibodies and a modest reduction in specific IgE titres, although this does not always correlate with clinical efficacy. There is accumulating evidence that specific immunotherapy also influences the blocking activity on IgE-mediated responses by IgG4, and cellular assays are commonly used to investigate these changes. Recently, a novel assay, which detects allergen-IgE binding using flow cytometry, has been used to detect 'functional' specific immunotherapy-induced changes in IgG antibody activity. Results suggest that successful specific immunotherapy is associated with an increase in IgG blocking activity that is not solely dependent on the quantity of IgG antibodies.

SUMMARY

Successful immunotherapy is associated with quantitative and qualitative changes in the allergen-specific IgG antibody response. The induction of IgG antibodies with blocking activity may have a protective role not only through the inhibition of allergen-induced, IgE-mediated release of inflammatory mediators from mast cells and basophils, but also through the inhibition of IgE-facilitated antigen presentation to T cells. Qualitative changes in the allergen-specific IgG antibody response may possibly be an important mechanism underlying the clinical efficacy of specific immunotherapy. Monitoring changes in blocking activity using cellular assays may give an early indication of the potential success of treatment.

Evaluation of recombinant and native timothy pollen (rPhl p 1, 2, 5, 6, 7, 11, 12 and nPhl p 4)- specific IgG4 antibodies induced by subcutaneous immunotherapy with timothy pollen extract in allergic patients

BACKGROUND

Allergen immunotherapy is a widely accepted treatment for IgE-mediated allergies. The evaluation of immunotherapy-induced IgG4 antibodies based on allergen extract is questionable because the amount of allergen-extract-specific IgG4 to individual disease-eliciting allergens cannot be determined using crude allergen extracts. In this study, we examined the specific IgE and IgG4 serum binding profiles to individual Phleum pratense allergens in grass-pollen-sensitive patients who had received grass-pollen-specific immunotherapy (SIT).

METHODS

The study included 33 patients from North-West Italy. All suffered from seasonal rhinoconjunctivitis and/or asthma. A modified "cluster" regimen of injections of a standardized aluminium-adsorbed P.pratense extract, with once-weekly visits and 10 injections for 5 weeks followed by 3 weeks of maintenance injections was instituted. Patients' sera were analyzed for specific IgE and IgG4 reactivity to individual P. pratense allergens (recombinant Phl p 1, Phl p 2, Phl p 5, Phl p 6, Phl p 7, Phl p 11, Phl p12 and native Phl p 4) and natural P. pratense extract using the Pharmacia CAP system.

RESULTS

IgE reactivities to new allergen components were not detected by CAP in treated patients after 15 weeks and a cumulative dose of approximately 65 microg of the major allergen Phl p 5. Patients lacking specific IgE reactivity towards individual allergens at the start of SIT did not produce significant levels of specific serum IgG4 to serum IgE-negative allergens. On the other hand, an increase in specific IgG4 only to allergens to which patients were previously sensitized was observed. Significant increases in specific IgG4 levels to rPhl p 1 (p < 0.05), 2 (p < (0.01), 5 (p < 0.0001), 6 (p < 0.0001), 7 (p < 0.05), 11 (p < 0.05) and nPhl p 4 (p < 0.01) were observed after P. pratense extract immunotherapy. No significant rPhl p 12-specific IgG4 antibody increase was documented after treatment.

CONCLUSION

These findings suggest that Phl p 12 was underrepresented in the extract used, as indicated by the low specific IgG4 response induced by this grass-pollen-specific vaccine. Thus, the simple detection of specific serum IgG4 antibodies a few weeks after the start of SIT could represent a valuable tool to estimate the presence of relevant allergens in a given immunotherapeutic allergen extract.

Specific immunotherapy in honeybee venom allergy: a comparative study using aqueous and aluminium hydroxide adsorbed preparations

BACKGROUND

For the immunotherapy of Hymenoptera venom allergy various preparations and treatment protocols are in use. However, controlled studies making direct comparisons of the efficacy and safety of different regimens are rare.

OBJECTIVE

To assess prospectively different venom immunotherapy (VIT) protocols using an aqueous or an aluminium hydroxide adsorbed allergen preparation for the treatment of honeybee venom (HBV) allergy.

METHODS

Sixty-five HBV allergic patients (42 males, 23 females; aged 17-75 years) with a history of systemic anaphylactic reactions (SARs) to honeybee stings were treated according to three different regimens. During the incremental phase, patients in group A (n = 21) or B (n = 21) received an aqueous preparation according to a rush protocol. Patients in group C (n = 23) were treated with conventional ("slow") VIT using an aluminium hydroxide adsorbed depot preparation. The maintenance dose was 100 microg venom in all groups. Maintenance treatment in group A was performed with the aqueous preparation administered every 4 weeks, whereas in groups B and C the depot preparation was administered every 8 weeks (group B) or every 4 weeks (group C). A sting challenge test with a living honeybee was performed in 49 patients, 6-12 months after reaching the maintenance dose. Another seven patients were stung accidentally by a honeybee ("field sting").

RESULTS

Treatment with the aqueous preparation evoked large local reactions more frequently than the depot preparation in the dose increase phase [53/693 (7.6%) vs 8/206 (3.9%); P = 0.059] and also in the course of maintenance therapy [85/172 (49.4%) vs 58/478 (12.1%); P < 0.001]. During the dose increase phase, systemic side-effects seemed to occur more frequently in patients on rush VIT with the aqueous preparation compared to patients initially treated with the conventional schedule using the depot preparation [13/42 (31.0%) vs 3/23 (13.0%); not significant). When re-stung by the culprit insect, SARs were observed in 3/20 patients (15.0%) in group A, 2/18 (11.1%) in group B and 3/18 (16.7%) in group C (not significant).

CONCLUSIONS

The aluminium hydroxide adsorbed HBV preparation caused fewer large local reactions than the aqueous preparation. The therapeutic efficacy of the three treatment protocols did not differ.

Inhibition of allergen-IgE binding to B cells by IgG antibodies after grass pollen immunotherapy

BACKGROUND

Among atopic individuals, levels of allergen-specific IgG antibodies have been inversely associated with the degree of allergen sensitization. Additionally, allergen-specific IgG antibodies are markedly increased by allergen injection immunotherapy. These observations have led to proposals that allergen-specific IgG antibodies might have protective properties in atopic individuals.

OBJECTIVE

We hypothesized that after grass pollen immunotherapy, these antibodies disrupt IgE-dependent allergen processing by antigen-presenting cells.

METHODS

We have developed a novel flow cytometric assay based on detection of allergen-IgE binding to the low-affinity IgE receptor on B cells to examine the blocking effects of sera collected from 18 patients who participated in a double-blind, controlled trial of grass pollen immunotherapy for 1 year.

RESULTS

In all 10 patients who received active therapy, there was induction of activity that inhibited allergen-IgE binding to B cells (P =.02, vs placebo subjects), as well as subsequent allergen presentation to T cells. This activity copurified with IgG and was allergen specific, because sera taken from patients treated with grass pollen immunotherapy but who were also birch pollen sensitive did not inhibit IgE-birch pollen allergen binding to B cells.

CONCLUSION

We conclude that allergen-specific IgG antibodies induced by immunotherapy can disrupt formation of allergen-IgE complexes that bind to antigen-presenting cells and facilitate allergen presentation.

Early effect of ultrarush venom immunotherapy on the IgG antibody response

BACKGROUND

We have previously shown in several allergy models that allergic and tolerance status with respect to allergens is associated with a somewhat different dominant specificity of IgG antibodies. The objective was to test this hypothesis in the compelling model of ultrarush venom immunotherapy (VIT), which induces clinical tolerance after only a few hours of treatment.

METHODS

Antibody titers and specificity were evaluated through solid-phase ELISA using streptavidin-biotin technology in 12 patients allergic to wasp venom before and during the ultrarush procedure (at 12 h, 24 h, and 15 days). The results were compared with those from another group of 20 patients treated with venom injections for at least 2 years.

RESULTS

No significant change was observed in IgG titers during the early phase of VIT. The capacity of individual sera to prevent the antigen binding of pooled IgG from allergic patients changed rapidly, with mean percentage inhibitions falling from 80+/-15%, before starting VIT, to 26+/-14%, 35+/-15%, and 34+/-5% after 12 h, 24 h, and 15 days of treatment, respectively (P<0.001 by one-way ANOVA). The capacity of individual sera to prevent the antigen binding of pooled IgG from patients receiving prolonged VIT changed, with mean percent inhibitions increasing from 47+/-8%, before starting VIT, to 76+/-7%, 83+/-6%, and 87+/-6% after 12 h, 24 h, and 15 days of treatment, respectively (P<0.001 by one-way ANOVA).

CONCLUSIONS

During the initial phase of ultrarush VIT, a change in IgG specificity, i.e., a change in the set of epitopes dominantly recognized by IgG on wasp-venom antigens, occurred concomitantly with early clinical tolerance and was already detectable a few hours after the onset of treatment. Although it may be an epiphenomenon, this change represents the earliest humoral modification described so far during this procedure. The mechanism is unknown, but it appears to be a selective depletion of the highest avidity antibody fraction by the venom injected in large doses at this stage of therapy. Finally, our data now show the previously documented association between a particular IgG specificity and the clinical status (allergy vs tolerance) to be true also with ultrarush VIT, a model in which the clinical ability to display allergic symptoms is rapidly reversed.

Relationship between allergic status and specificity of IgG antibody to inhaled allergens: the grass pollen model

BACKGROUND

We have previously reported that IgG antibodies from healthy individuals and patients suffering from non-seasonal mite allergy bind to different sets of epitopes on Der p 1, allowing almost complete discrimination of the populations.

OBJECTIVES

To confirm this observation in a seasonal allergy model where a clear relationship between allergic symptoms and exposure to the offending agent is established. To investigate whether the pattern of modified specificity is related to the differences in IgG subclass hierarchy usually exhibited by nonallergic and allergic populations.

METHODS

The capacity of individual sera from patients allergic to grass pollen and healthy individuals, including grass pollen-sensitized subjects, to prevent the binding of pooled IgG, IgG1, and IgG4 fractions from grass pollen-allergic patients and healthy individuals to solid-phase bound grass pollen antigen was evaluated in enzyme-linked immunosorbent assay (ELISA) using streptavidin-biotin technology. Specificity controls were performed using sera from patients allergic to cat dander and house dust mite.

RESULTS

The capacity of sera to prevent the antigen binding of allergic IgG averaged 84 +/- 5% for allergic sera and 53 +/- 6% for healthy sera (P < 0.001 by one-way anova). Conversely, using the antigen-binding capacity of healthy control IgG as reference, percentage inhibitions averaged 46 +/- 9% in grass pollen-allergic subjects compared with 80 +/- 4%, 82 +/- 2% in healthy individuals, and mite- and cat-allergic patients, respectively, resulting in two well-separated populations (P < 0.0001 by one-way anova). Similar results were found regardless of whether pooled IgG1 or IgG4 were used.

CONCLUSION

Together with previous data, our results define a new type of humoral signature in the immune response to inhaled allergens. Allergic and healthy status differ not only in the presence or absence of specific IgE antibody but also in the preferential expression of distinct IgG specificities that are better correlated with clinical manifestations and are unrelated to subclass distribution.