Vaccination for birch pollen allergy: comparison of the affinities of specific immunoglobulins E, G1 and G4 measured by surface plasmon resonance

Easy assessment of the avidity of polyclonal allergen-specific serum antibodies

INTRODUCTION

Allergen-specific IgE-blocking IgG antibodies contribute to successful allergen immunotherapy (AIT), however, not much is known about their affinity. Since affinity measurements of polyclonal antibodies in serum are technically challenging we evaluated the applicability of acidic disruption of antibody-allergen complexes by a modified ELISA protocol with monoclonal antibodies (mAbs) specific for the relevant major allergens Betv1 and Mald1. Then, AIT-induced blocking and non-blocking Mald1-specific antibodies in sera from individuals with or without reduced apple allergy were compared.

METHODS

After testing their pH stability coated recombinant allergens were incubated with (i) mAbs diluted in PBS or human serum and (ii) sera from individuals after sublingual administration of Mald1 or Betv1 for 16 weeks. Immune complexes were exposed to buffers in the pH range of 6.4-3.4 and residual antibodies were measured. Avidity indexes (AI), defined as the pH removing 50% of antibodies, were compared to the dissociation constants (KD) of mAbs determined by surface plasmon resonance.

RESULTS

The selected pH range was applicable to disrupt allergen complexes with highly affine mAbs without compromising allergen integrity. AIs of mAbs accorded with KD values and were unaffected by epitope specificity or the presence of serum proteins. The inter-assay variability was <4% CV. Protective Mald1-specific IgG antibodies from individuals with reduced apple allergy showed a higher collective binding strength than that of the non-protective antibodies of individuals without reduced apple allergy.

CONCLUSION

Acidic disruption of allergen-antibody complexes may be used to estimate the net-binding force of polyclonal serum antibodies and eases the investigation of affinity-related research questions in AIT.

The role of IgG1 and IgG4 as dominant IgE-blocking antibodies shifts during allergen immunotherapy

BACKGROUND

The induction of allergen-specific IgE-blocking antibodies is a hallmark of allergen immunotherapy (AIT). The inhibitory bioactivity has largely been attributed to IgG₄; however, our recent studies indicated the dominance of IgG₁ early in AIT.

OBJECTIVES

Here, the IgE-blocking activity and avidity of allergen-specific IgG₁ and IgG₄ antibodies were monitored throughout 3 years of treatment.

METHODS

Serum samples from 24 patients were collected before and regularly during AIT with birch pollen. Bet v 1-specific IgG₁ and IgG₄ levels were determined by ELISA and ImmunoCAP, respectively. Unmodified and IgG₁- or IgG₄-depleted samples were compared for their inhibition of Bet v 1-induced basophil activation. The stability of Bet v 1-antibody complexes was compared by ELISA and by surface plasmon resonance.

RESULTS

Bet v 1-specific IgG₁ and IgG₄ levels peaked at 12 and 24 months of AIT, respectively. Serological IgE-blocking peaked at 6 months and remained high thereafter. In the first year of therapy, depletion of IgG₁ clearly diminished the inhibition of basophil activation while the absence of IgG₄ hardly reduced IgE-blocking. Then, IgG₄ became the main inhibitory isotype in most individuals. Both isotypes displayed high avidity to Bet v 1 ab initio of AIT, which did not increase during treatment. Bet v 1-IgG₁ complexes were enduringly more stable than Bet v 1-IgG₄ complexes were.

CONCLUSIONS

In spite of the constant avidity of AIT-induced allergen-specific IgG₁ and IgG₄ antibodies, their dominance in IgE-blocking shifted in the course of treatment. The blocking activity of allergen-specific IgG₁ should not be underestimated, particularly early in AIT.

Allergen immunotherapy, cancer, and immune disorders

PURPOSE OF REVIEW

The purpose of this review is to provide an update on the intriguing relationships between allergies, allergen immunotherapy, cancer, and immune disorders. Allergic diseases and cancer are increasing in incidence and prevalence and a potential relationship, or not, between these diseases have been suggested for many years.

RECENT FINDINGS

Recent findings suggest that there may be some causative effects between certain types of cancer and allergic diseases, as described in the text. Some types of cancer may be more linked to the presence of an allergic disease, than others. However, epigenetic factors, such as tobacco smoke alcohol and toxic substances should also be taken into consideration.

SUMMARY

The association between allergy and cancer is complex and depends on the specific allergy and the specific organ under consideration. Regarding pancreatic cancer, colorectal cancer (CRC), and glioma, all types of allergies were shown to be a protective factor. Conversely, asthma is a risk factor for lung cancer as is atopic dermatitis for skin cancer. Despite extensive research, no definite relationship has been determined, and no clear relationship, either positive or negative, to allergies can be observed. These results should be corroborated with large epidemiological well designed prospective studies due to some weaknesses in the previous investigations.

Novel Approaches for Inhibiting the Indoor Allergen Der f 2 Excreted from House Dust Mites by Todomatsu Oil Produced from Woodland Residues

House dust mite (HDM) is a globally ubiquitous domestic cause of allergic diseases. There is a pressing demand to discover efficient, harmless, and eco-friendly natural extracts to inhibit HDM allergens that are more likely to trigger allergies and challenging to be prevented entirely. This study, therefore, is aimed at assessing the inhibition of the allergenicity of major HDM allergen Der f 2 by todomatsu oil extracted from residues of Abies Sachalinensis. The inhibition was investigated experimentally (using enzyme-linked immunosorbent assay (ELISA), surface plasmon resonance (SPR), and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE)) and in silico using molecular docking. The results showed that todomatsu oil inhibits the allergenicity of Der f 2 by reducing its amount instead of the IgG binding capacity of a single protein. Moreover, the compounds in todomatsu oil bind to Der f 2 via alkyl hydrophobic interactions. Notably, most compounds interact with the hydrophobic amino acids of Der f 2, and seven substances interact with CYS27. Contrarily, the principal compounds fail to attach to the amino acids forming the IgG epitope in Der f 2. Interestingly, chemical components with the lowest relative percentages in todomatsu oil show high-affinity values on Der f 2, especially β-maaliene (-8.0 kcal/mol). In conclusion, todomatsu oil has been proven in vitro as a potential effective public health strategy to inhibit the allergenicity of Der f 2.

New applications of advanced instrumental techniques for the characterization of food allergenic proteins

Current approaches based on electrophoretic, chromatographic or immunochemical principles have allowed characterizing multiple allergens, mapping their epitopes, studying their mechanisms of action, developing detection and diagnostic methods and therapeutic strategies for the food and pharmaceutical industry. However, some of the common structural features related to the allergenic potential of food proteins remain unknown, or the pathological mechanism of food allergy is not yet fully understood. In addition, it is also necessary to evaluate new allergens from novel protein sources that may pose a new risk for consumers. Technological development has allowed the expansion of advanced technologies for which their whole potential has not been entirely exploited and could provide novel contributions to still unexplored molecular traits underlying both the structure of food allergens and the mechanisms through which they sensitize or elicit adverse responses in human subjects, as well as improving analytical techniques for their detection. This review presents cutting-edge instrumental techniques recently applied when studying structural and functional aspects of proteins, mechanism of action and interaction between biomolecules. We also exemplify their role in the food allergy research and discuss their new possible applications in several areas of the food allergy field.

Does clinical outcome of birch pollen immunotherapy relate to induction of blocking antibodies preventing IgE from allergen binding? A pilot study monitoring responses during first year of AIT

Background

The clinical benefit of allergen-specific immunotherapy (AIT) involves induction of blocking antibodies. It is not clear if these antibodies function via steric hindrance alone or a combination of levels, avidities, and epitope specificities, and clinical outcome cannot be predicted. We aim to in-depth characterize serum antibody profiles during birch pollen AIT, investigate therapy-induced antibodies for their capacity to block IgE binding to Bet v 1 and correlate data with clinical outcomes.

Methods

Immune responses of five birch pollen allergic patients were monitored during the first year of AIT by nasal provocation tests (NPTs), ImmunoCAP, immunoblots, direct and avidity enzyme-linked immunosorbent assays, mediator release assays, facilitated antigen binding (FAB) assays, and inhibition mediator release assays.

Results

There was no correlation between NPT results and therapy-induced changes in levels (IgE, IgG, IgA, IgM), avidities, or mediator release potency of Bet v 1-specific antibodies. In FAB assays, blocking antibodies initiated upon AIT were shown to prevent formation of Bet v 1-IgE complexes of an indicator serum pool and significantly correlated with clinical readout. Inhibition mediator release assays using patient-specific IgE for passive sensitization revealed therapy-induced blocking capacities with very good correlation to NPT results. Notably, this assay was the only one to detect a non-responder during treatment in this pilot study.

Conclusions

Clinical outcome of AIT depends on induction of blocking antibodies able to prevent the patient’s own IgE from allergen binding. Monitoring of clinical efficacy seems to be best achieved using the inhibition mediator release assay, as development of relevant blocking antibodies can be verified in a patient-tailored manner.

Electronic supplementary material

The online version of this article (10.1186/s13601-018-0226-7) contains supplementary material, which is available to authorized users.

Allergen-specific immunotherapy: is it vaccination against toxins after all?

IgE-mediated allergies, in particular allergic rhinoconjunctivitis and asthma, have reached epidemic proportions, affecting about one-third of the population in developed countries. The most effective treatment for allergies is specific immunotherapy (SIT), which involves the injection of increasing doses of an allergen extract to allergic individuals. The current form of SIT was first introduced in 1911 and recently celebrated its 100th birthday for the treatment of hay fever. The concept of this therapy at the time was straightforward, as it was believed that pollen contained toxins against which the patient could be vaccinated. However, the understanding became blurred with the discovery that IgE antibodies were the effector molecules of the allergic response. Subsequent research focused on the idea that SIT should induce tolerance keeping the IgE antibodies at bay. In this review, we will discuss the various hypotheses for the mechanism of SIT and we will put forward the concept that allergens may be viewed as 'protoxins' which need to be activated by IgE antibodies. Within this framework, protoxin-neutralizing antibodies are the key effector molecules while a shift to Th1 or Treg cells mainly contributes to the efficacy of SIT by helping B cells to produce neutralizing IgG antibodies.

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.

Changes in markers associated with dendritic cells driving the differentiation of either TH2 cells or regulatory T cells correlate with clinical benefit during allergen immunotherapy

BACKGROUND

Regulatory dendritic cell (DC) markers, such as C1Q, are upregulated in PBMCs of patients with grass pollen allergy exhibiting clinical benefit during allergen immunotherapy (AIT).

OBJECTIVES

We sought to define markers differentially expressed in human monocyte-derived DCs differentiated toward a proallergic (DCs driving the differentiation of TH2 cells [DC2s]) phenotype and investigate whether changes in such markers in the blood correlate with AIT efficacy.

METHODS

Transcriptomes and proteomes of monocyte-derived DCs polarized toward DCs driving the differentiation of TH1 cells (DC1s), DC2s, or DCs driving the differentiation of regulatory T cells (DCreg cells) profiles were compared by using genome-wide cDNA microarrays and label-free quantitative proteomics, respectively. Markers differentially regulated in DC2s and DCreg cells were assessed by means of quantitative PCR in PBMCs from 80 patients with grass pollen allergy before and after 2 or 4 months of sublingual AIT in parallel with rhinoconjunctivitis symptom scores.

RESULTS

We identified 20 and 26 new genes/proteins overexpressed in DC2s and DCreg cells, respectively. At an individual patient level, DC2-associated markers, such as CD141, GATA3, OX40 ligand, and receptor-interacting serine/threonine-protein kinase 4 (RIPK4), were downregulated after a 4-month sublingual AIT course concomitantly with an upregulation of DCreg cell-associated markers, including complement C1q subcomponent subunit A (C1QA), FcγRIIIA, ferritin light chain (FTL), and solute carrier organic anion transporter family member 2B1 (SLCO2B1), in the blood of clinical responders as opposed to nonresponders. Changes in such markers were better correlated with clinical benefit than alterations of allergen-specific CD4(+) T-cell or IgG responses.

CONCLUSIONS

A combination of 5 markers predominantly expressed by blood DCs (ie, C1Q and CD141) or shared with lymphoid cells (ie, FcγRIIIA, GATA3, and RIPK4) reflecting changes in the balance of regulatory/proallergic responses in peripheral blood can be used as early as after 2 months to monitor the early onset of AIT efficacy.

Heterogeneity of antibody responses among clinical responders during grass pollen sublingual immunotherapy

BACKGROUND

During allergen-specific sublingual immunotherapy (SLIT), the relevance of changes in specific IgE and IgG antibody titres to treatment efficacy remains to be evaluated at an individual patient level.

OBJECTIVE

To investigate whether antibody responses can be used as biomarkers for SLIT efficacy.

METHODS

Comprehensive quantitative, qualitative and functional analyses of allergen-specific IgA, IgE, IgG1-4 and IgM responses were performed using purified Phl p 1 to 12 allergens in sera, saliva and nasal secretions from 82 grass pollen allergic patients. These patients were enrolled in a randomized, double-blind placebo-controlled study and assessed in an allergen challenge chamber (ClinicalTrials.gov NCT00619827). Antibody responses were monitored in parallel to clinical responses before and after daily sublingual treatment for 4 months with either a grass pollen or a placebo tablet.

RESULTS

A significant mean improvement (i.e. 33-40.6%) in rhinoconjunctivitis total symptom scores was observed in SLIT recipients, irrespective of their baseline patterns of IgE sensitization (i.e. narrow, intermediate, broad) to grass pollen allergens. SLIT did not induce any de novo IgE sensitization. Clinical responders encompassed both immunoreactive patients who exhibited strong increases in titres, affinity and/or blocking activity of grass-pollen-specific IgGs (representing 17% of treated patients), as well as patients with no detectable antibody responses distinguishing them from the placebo group. No significant changes were detected in antibody titres in saliva and nasal washes, even in clinical responders.

CONCLUSIONS AND CLINICAL RELEVANCE

Sublingual immunotherapy with a grass pollen tablet is efficacious irrespective of the patients' baseline sensitization to either single or multiple grass pollen allergens. Seric IgG responses may contribute to SLIT-induced clinical tolerance in a fraction (i.e. 17%) of patients, but additional immune mechanisms are involved in most patients. Consequently, antibody responses cannot be used as a marker of SLIT efficacy at an individual patient level.

Changes in cat specific IgE and IgG antibodies with decreased cat exposure

BACKGROUND

Current understanding of the effects of reducing exposure to cat allergens is limited. It has also become clear that there are different forms of immune response to cat allergens.

OBJECTIVE

To investigate changes in skin tests and cat specific IgG and IgE antibodies when students from a home with a cat move to a college dormitory.

METHODS

Ninety-seven college students participated in a prospective study that consisted of allergy skin prick testing and serum measurement of IgE and IgG antibodies to cat at the beginning and end of one academic year in college. A subgroup returned for follow-up at the end of 2 years.

RESULTS

Among 97 students, 33% had IgG antibodies to Fel d 1 but no evidence of sensitization, 25% had positive skin test results and/or serum IgE antibodies, and 42% had negative skin test results and no detectable serum antibodies. Among the non-cat sensitized students with IgG antibodies, the titers decreased during 8 months (P = .002). Titers of IgG4 to Fel d 1 also decreased (P < .001). Among the sensitized students, no change in IgE antibodies to cat occurred in 8 months (P = .20), whereas Fel d 1 specific IgG antibodies decreased (P < .001). Thus, ratios of IgG to IgE decreased highly significantly (P = .007). Among the students with negative skin test results who returned for follow-up (n = 56), none developed positive skin test results or serum IgE antibodies.

CONCLUSION

Under conditions of marked decrease in exposure, no participants developed new-onset sensitization. Among the individuals sensitized at study entry, there were major decreases in the ratio of IgG to IgE.

Surface Plasmon Resonance imaging: a method to measure the affinity of the antibodies in allergy diagnosis

AIM

The biological diagnosis of type I hypersensitivity reactions is based on the quantification of specific IgEs. However, the IgE titer is not always strongly related to the clinical symptoms or predictive of the evolution of the disease. The specificity and affinity of antibodies of other isotypes may contribute to the allergic status of the patients. The aim of the present work was to develop a method that simultaneously detects the complex antibody response to various allergens and measures the avidity of the antibodies directed to each allergen.

METHODS

A chip based on a covalent binding of 3 major milk allergens on a gold-activated surface was developed. The binding of specific antibodies to α-lactalbumin, β-lactoglobulin or caseins was monitored using Surface Plasmon Resonance imaging (SPRi). The sensitivity and specificity of the method were compared to those obtained by ELISA, the reference method.

RESULTS

The specificity of the antibodies characterized by SPRi was identical to the one obtained by ELISA. The intensity of the signal was proportional to the quantity of antibodies bound to each allergen. The sensitivity of the SPRi detection was about 8-10 times lower than for ELISA but the SPRi is faster and the analysis of association/dissociation kinetics allowed the determination of the avidity of the antibody response.

CONCLUSION

The present study shows that SPRi allows a multiplex monitoring of the complex antibody response to the major allergens of an allergenic source. This label-free method constitutes a new tool that may be added to IgE detection to improve allergy diagnosis.

Role of skin prick test in allergic disorders: a prospective study in kashmiri population in light of review

Background:

Skin prick test (SPT) is the most effective diagnostic test to detect IgE mediated type I allergic reactions like allergic rhinitis, atopic asthma, acute urticaria, food allergy etc. SPTs are done to know allergic sensitivity and applied for devising immunotherapy as the therapeutic modality.

Materials and Methods:

This prospective study was conducted in the department of Immunology and Molecular medicine at SKIMS. A total of 400 patients suffering from allergic rhinitis, asthma and urticaria were recruited in this study. SPT was performed with panel of allergens including house dust mite, pollens, fungi, dusts, cockroach, sheep wool and dog epithelia. Allergen immunotherapy was given to allergic rhinitis and asthmatic patients as therapeutic modality.

Results:

In our study, age of patients ranged from 6 to 65 years. Majority of patients were in the age group of 20-30 years (72%) with Male to female ratio of 1:1.5. Of the 400 patients, 248 (62%) had urticaria, 108 (27%) patients had allergic rhinitis and 44 (11%) patients had asthma. SPT reaction was positive in 38 (86.4%) with allergic asthma, 74 (68.5%) patients with allergic rhinitis and 4 (1.6%) patient with urticaria, respectively. Allergen immunotherapy was effective in 58% patients with allergic rhinitis and 42% allergic asthma.

Conclusion:

Identifiable aeroallergen could be detected in 86.4% allergic asthma and 68.5% allergic rhinitis patients by SPT alone. Pollens were the most prevalent causative allergen. There was significant relief in the severity of symptoms, medication intake with the help of allergen immunotherapy.

Can Serum-Specific IgE/Total IgE Ratio Predict Clinical Response to Allergen-Specific Immunotherapy in Children Monosensitized to House Dust Mite?

Background. Allergen-specific immunotherapy (SIT) is one of the important regimens for the treatment of allergic diseases. Predictive tests for the clinical response to SIT are limited. In this study we aimed to evaluate whether specific IgE/total IgE levels can predict clinical improvement in monosensitized patients to house dust mite treated with immunotherapy. Patients and Methods. We analyzed 32 patients who had undergone 2 years of SIT. Serum t-IgE and s-IgE levels, and serum s-IgE/t-IgE ratios were calculated and tested for correlation with clinical response to SIT. Asthma symptom score (ASS), rhinitis symptom score (RSS), pulmonary functions and visual analogue scales (VAS) were evaluated at the beginning and after 2 years. Results. There were 17 boys and 15 girls with the mean age of 10.78 ± 3.03 years. The mean serum house dust mite s-IgE level was 128.62 ± 142.61 kU/L, t-IgE 608.90 ± 529.98 IU/mL, and s-IgE/t-IgE ratio 33.83 ± 53.18. Before immunotherapy, ASS was 6.23 ± 1.63, RSS; 8.20 ± 1.88, VAS; 7.38 ± 2.01, FEV1 (%); 89.14 ± 8.48, PEF (%); 88.93 ± 13.57, and after 2 years, these values were determined as 1.90 ± 1.10, 3.05 ± 1.39, 1.35 ± 1.24, 97.6 ± 11.26, and 97.0 ± 11.55, respectively. s-IgE/t-IgE ratio was correlated with change in RSS (r = −0.392, P = 0.08) and VAS (r = −0.367, P = 0.05). Conclusion. Although SIT is very effective treatment, all patients do not benefit from treatment. We assumed that s-IgE/t-IgE ratio would be useful to predict the clinical response to SIT.

Immunological mechanisms of allergen-specific immunotherapy

The studies on the mechanisms of specific immunotherapy (SIT) point out its targets that decide on the efficacy of SIT and hence might be used for its further improvement. Several mechanisms have been proposed to explain the beneficial effects of immunotherapy. The knowledge of the mechanisms underlying allergic diseases and curative treatment possibilities has experienced exciting advances over the last three decades. Studies in several clinical trials in allergen-SIT have demonstrated that the induction of a tolerant state against allergens in many ways represents a key step in the development of a healthy immune response against allergens. Several cellular and molecular mechanisms have been demonstrated: allergen-specific suppressive capacities of both inducible subsets of CD4(+) CD25(+) forkhead box P3(+) T-regulatory and IL-10-secreting type 1 T-regulatory cells increase in peripheral blood; suppression of eosinophils, mast cells, and basophils; Ab isotype change from IgE to IgG4. This review aims at the better understanding of the observed immunological changes associated with allergen SIT.

Generation and epitope analysis of human monoclonal antibody isotypes with specificity for the Timothy grass major allergen Phl p 5a

The scarcity of monoclonal human IgE antibodies with specificity for defined allergens is a bottleneck for the molecular characterisation of allergens and their epitopes. Insights into the characteristics of such antibodies may allow for analyses of the molecular basis underlying allergenicity and cross-reactivity, standardisation of allergens as well as improvement of allergy diagnostics and therapeutics. Here we report the generation and application of the first set of authentic human IgG, IgE and IgA antibodies. On the basis of a Phl p 5a specific antibody fragment, a lambda light chain and the IgG1, IgG4, IgE, IgA1, and IgA2 heavy chains, the corresponding human immunoglobulins were constructed and produced in mammalian cells. In parallel, a murine hybridoma line with specificity for Phl p 5a was established, recloned and produced as human chimeric IgE. After purification, immunoreactivity of the antibodies with the allergen was assessed. Applicability in allergy diagnostics was confirmed by establishment of artificial human sera. Functionality of both antibodies was further demonstrated in receptor binding studies and mediator release assays using humanised rat basophil leukaemia cells (RBL-SX38) suggesting the presence of spatially separate epitopes. By using Phl p 5 fusion proteins and recombinant IgE in immunoblotting and mediator release assays we assigned the epitope of the authentic IgE to a looped stretch exclusively present in Phl p 5a. In summary, the Phl p 5-specific antibodies are the first full set of allergy-related antibody isotypes of their kind and represent valuable tools for studies of fundamental mechanisms and structure/function relationships in allergy.

Passive immunization with allergen-specific antibodies

The induction of allergen-specific IgG antibodies has been identified as a major mechanism responsible for the reduction of allergic inflammation in allergic patients treated by allergen-specific immunotherapy. Several studies suggest that allergen-specific IgG antibodies induced by vaccination with allergens block mast cell and basophil degranulation, IgE-facilitated allergen presentation to T cells and IgE production. The availability of recombinant allergens and technologies for the production of recombinant human antibodies allows engineering of allergen-specific antibodies which can be used for passive immunization (i.e., therapy) and eventually for the prevention of allergy (i.e., prophylaxis). This chapter summarizes data supporting the possible use of allergen-specific antibodies for treatment and prophylaxis. Finally, concrete approaches for the treatment and prevention of allergy based on blocking antibodies are envisioned.

Allergen-specific subcutaneous immunotherapy in allergic asthma: immunologic mechanisms and improvement

Allergic asthma is a disease characterized by persistent allergen-driven airway inflammation, remodeling, and airway hyperresponsiveness. CD4(+) T-cells, especially T-helper type 2 cells, play a critical role in orchestrating the disease process through the release of the cytokines IL-4, IL-5, and IL-13. Allergen-specific immunotherapy (SIT) is currently the only treatment with a long-term effect via modifying the natural course of allergy by interfering with the underlying immunological mechanisms. However, although SIT is effective in allergic rhinitis and insect venom allergy, in allergic asthma it seldom results in complete alleviation of the symptoms. Improvement of SIT is needed to enhance its efficacy in asthmatic patients. Herein, the immunoregulatory mechanisms underlying the beneficial effects of SIT are discussed with the ultimate aim to improve its treatment efficacy.

Therapeutic manipulation of immune tolerance in allergic disease

Immune tolerance - the adaptation of the immune system to external antigens or allergens - might be therapeutically manipulated to restore normal immunity in conditions such as allergy, asthma and autoimmune diseases. The field of allergen-specific immunotherapy is experiencing exciting and novel developments for the treatment of allergic and autoimmune diseases, and recent insights into the reciprocal regulation and counter-balance between different T-cell subsets is foreseen to facilitate new strategies for immunointervention. This Review highlights current knowledge of immunomodulatory therapies for the manipulation of immune tolerance and highlights recent approaches to improve allergen-specific immunotherapy for the treatment of allergic diseases.

Gender-medicine aspects in allergology

Despite the identical immunological mechanisms activating the release of mediators and consecutive symptoms in immediate-type allergy, there is still a clear clinical difference between female and male allergic patients. Even though the risk of being allergic is greater for boys in childhood, almost from adolescence onwards it seems to be a clear disadvantage to be a woman as far as atopic disorders are concerned. Asthma, food allergies and anaphylaxis are more frequently diagnosed in females. In turn, asthma and hay fever are associated with irregular menstruation. Pointing towards a role of sex hormones, an association of asthma and intake of contraceptives, and a risk for asthma exacerbations during pregnancy have been observed. Moreover, peri- and postmenopausal women were reported to increasingly suffer from asthma, wheeze and hay fever, being even enhanced by hormone replacement therapy. This may be on account of the recently identified oestradiol-receptor-dependent mast-cell activation. As a paradox of nature, women may even become hypersensitive against their own sex hormones, resulting in positive reactivity upon intradermal injection of oestrogen or progesterone. More importantly, this specific hypersensitivity is associated with recurrent miscarriages. Even though there is a striking gender-specific bias in IgE-mediated allergic diseases, public awareness of this fact still remains minimal today.

Affinity of IgE and IgG against cross-reactive carbohydrate determinants on plant and insect glycoproteins

BACKGROUND

Cross-reactive carbohydrate determinants (CCDs) are probably the most widely occurring IgE epitopes. Approximately one fifth of patients with allergy develop IgE antibodies against such glycans. However, they appear to be of low clinical significance.

OBJECTIVE

We wanted to elucidate the reasons for this lack of clinical symptoms on contact with CCD allergens by determination of the binding affinities of patients' IgE and IgG antibodies.

METHODS

IgE and IgG against CCDs were affinity-purified from sera of selected patients. The binding affinity to defined glyco-epitopes was measured by surface plasmon resonance.

RESULTS

From a pool of CCD-positive sera, we isolated 0.1 and 25 microg CCD-specific IgE and IgG, respectively. The binding affinity of purified IgE antibodies to core alpha1,3-fucosylated glycans was in the 10(-10) mol/L range. The affinity was highest when both fucose and xylose were present, whereas xylosylation alone did not cause IgE binding. CCD-specific IgG exhibited a dissociation constant of approximately 10(-8) mol/L. IgG(4) amounted to only 20% of the CCD-specific IgG (as well as total IgG).

CONCLUSION

Low binding affinity of anti-CCD IgE cannot be the reason for the observed clinical insignificance of IgE against plant/insect glycan epitopes. Notably, the affinity of IgG to CCDs is higher than that to protein allergens, and it may therefore function as blocking antibody.

Maintenance of tolerance to cow's milk in atopic individuals is characterized by high levels of specific immunoglobulin G4

BACKGROUND

The central role of specific IgE in cow's milk allergy (CMA) is well documented. However, less is known about the function of other immunoglobulin isotypes in allergy and tolerance to cow's milk proteins (CMPs).

OBJECTIVE

To determine differences in the antibody responses that are associated with allergy and tolerance to cow's milk in allergic, atopic and non-atopic individuals of different age groups.

METHODS

Nineteen infants (<1 year), 18 children (6-14 years) and 41 adults (21-68 years) were included. Each age group was comprised of subjects with CMA, atopic individuals without a history of CMA and non-atopic subjects. Levels of specific IgE, IgG4, IgG1 and IgA to whole cow's milk and the six most abundant individual CMPs were determined in plasma by ELISA. For comparison, specific IgE and IgG4 were measured to ovomucoid and house dust mite (HDM) in individuals allergic for the respective allergens, and in atopic and non-atopic subjects without allergy.

RESULTS

In infants and children with CMA, alphas1-casein and beta-lactoglobulin induced the highest specific IgE response, whereas alphas1-casein was the most allergenic CMP in adult patients. Specific IgG4 and IgG1 responses were the highest to alphas1-casein and beta-lactoglobulin in all age groups, while kappa-casein and alpha-lactalbumin induced the highest levels of IgA. CMP-specific IgG4 was higher in atopic children and adults without CMA, as compared with non-atopic individuals. A similar difference between tolerant atopic and non-atopic subjects was observed for IgG4 specific to ovomucoid, whereas HDM-specific IgG4 was not detectable in these subjects.

CONCLUSION

Maintenance of tolerance to cow's milk in atopic children and adults without CMA is associated with elevated levels of specific IgG4, in combination with low specific IgE. The up-regulation of specific IgG4 in tolerant atopic individuals may be related to the type of allergen and its regular dose of exposure.

Generation of Human Monoclonal Allergen-Specific IgE and IgG Antibodies from Synthetic Antibody Libraries

Background: Allergen-specific IgE and IgG antibodies play pivotal roles in the induction and progression of allergic hypersensitivity reactions. Consequently, monoclonal human IgE and IgG4 antibodies with defined specificity for allergens should be useful in allergy research and diagnostic tests. We used combinatorial antibody libraries and subsequent recombinant production to make and assess IgE, IgG1, and IgG4 allergen-specific antibodies.

Methods: We used phage display to select a synthetic single-chain antibody fragment (scFv) library against 3 different allergens, from bee venom, bovine milk, and apple. The scFv obtained were converted into IgG1, IgG4, and IgE antibody formats and assessed for their biochemical properties by ELISA, immunoblotting, and fluorescence-activated cell sorting.

Results: Two different antibody formats for each IgG1, IgG4, and IgE antibody were produced in mammalian cells as disulfide-linked and glycosylated Ig, which were usable in allergen-specific ELISA assays and immunoblots. In addition, the recombinant IgE antibodies mediated the binding of allergens to HEK-293 cells transfected with the high-affinity IgE receptor, and this binding was blocked by corresponding IgG antibodies.

Conclusions: The use of synthetic libraries for the generation of allergen-specific recombinant IgE and IgG antibodies should have broad applications in allergological research and diagnosis.

Pollen immunotherapy: selection,prevention, and future directions

Pollens are an important cause of allergic rhinitis and asthma. Pollen immunotherapy is effective and potentially curative. It has been shown to prevent new sensitizations, to prevent the development of asthma in children, and to induce long-term benefit. Standardization of allergen extracts is necessary to improve immunotherapy safety and efficacy. Knowledge of the local plant taxonomy and allergen cross-reactivity is important in selecting clinically relevant vaccines. In general, allergenic cross-reactivities correspond to taxonomic relations. Tree and weed species demonstrate variable degrees of cross-reactivity. Most grasses have extensive allergenic cross-reactivity. Mechanism of action continues to be an area of investigation, including the induction of immunoglobulin G blocking antibodies. Sublingual immunotherapy, concurrent anti-immunoglobulin E use, hypoallergic peptides, and DNA vaccines are other promising technologies.

Sublingual immunotherapy of allergic diseases

The only disease-modifying treatment that is available for allergic patients is allergen-specific immunotherapy. Two competing application forms are used: subcutaneous immunotherapy, which has been used for > 90 years, and a relatively new immunotherapy where the allergen is applied sublingually. Numerous studies have shown efficacy for subcutaneous immunotherapy and have identified possible mechanisms that are responsible for the observed reduction in allergic responses. In contrast, the efficacy of sublingual immunotherapy has not been documented to the same degree and the responsible immunological mechanisms have not yet been clearly defined. This review focuses on the published clinical and experimental data on sublingual immunotherapy and points at possible mechanisms of how sublingual immunotherapy may differ from subcutaneous immunotherapy in its mode of action, and also discusses the potential advantages and pit falls of both therapies.

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.

IgE-Facilitated Antigen Presentation: Role in Allergy and the Influence of Allergen Immunotherapy

IgE-facilitated allergen presentation (FAP) is an important pathogenic mechanism in allergic disease and represents a potential therapeutic target. Allergen immunotherapy is a highly effective therapy, particularly in patients with seasonal pollinosis who fail to respond to usual pharmacotherapy. Allergen immunotherapy induces "blocking" IgG antibodies that are detectable in serum and have been shown to inhibit IgE-FAP in vitro. This review summarizes the main components involved in IgE-FAP and the potential value of a validated functional assay of serum inhibitory antibodies for IgE-FAP for monitoring the clinical response to immunotherapy.

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.

Survey of the year 2005 commercial optical biosensor literature

We identified 1113 articles (103 reviews, 1010 primary research articles) published in 2005 that describe experiments performed using commercially available optical biosensors. While this number of publications is impressive, we find that the quality of the biosensor work in these articles is often pretty poor. It is a little disappointing that there appears to be only a small set of researchers who know how to properly perform, analyze, and present biosensor data. To help focus the field, we spotlight work published by 10 research groups that exemplify the quality of data one should expect to see from a biosensor experiment. Also, in an effort to raise awareness of the common problems in the biosensor field, we provide side-by-side examples of good and bad data sets from the 2005 literature.

Peptide-based vaccination: where do we stand?

PURPOSE OF REVIEW

Allergen-specific immunotherapy represents the only causative approach towards allergy treatment. Specific immunotherapy can, however, include allergic reactions and occasionally life-threatening anaphylaxis. Peptides have been evaluated as a potential therapeutic approach in atopic allergic disease because they have the potential to inhibit T-cell function but not induce anaphylaxis.

RECENT FINDINGS

Data from early clinical trials of peptide vaccination revealed that therapy was associated with a modest improvement in allergic disease, and was accompanied by a high frequency of adverse reactions. More recent studies have demonstrated improved clinical outcomes, improved safety, and have defined the mechanisms of adverse events observed in earlier studies. Mechanisms of peptide vaccination include the hyporesponsiveness of allergen-specific responses and the induction of regulatory T cells and cytokines. Novel peptide design has allowed the generation of fragments that contain T-cell stimulatory epitopes, lack B cell epitopes, and can induce protective IgG responses in both mice and humans. Other approaches have focused on hypoallergenic B-cell epitopes that induce inhibitory IgG antibodies. Peptides that specifically induce regulatory cytokine production would also enhance peptide vaccines. Several recent studies have described immunodominant epitopes from major allergens that may form candidate peptides for use in peptide vaccination.

SUMMARY

The manipulation of peptide epitopes may provide a strategy for the rational design of peptide allergy vaccines further improving safety and efficacy.