Bee venom phospholipase A2-specific T cell clones from human allergic and non-allergic individuals: cytokine patterns change in response to the antigen concentration

Molecular Characterization and In Silico Analyses of Maurolipin Structure as a Secretory Phospholipase A 2 ( sPLA 2 ) from Venom Glands of Iranian Scorpio maurus (Arachnida: Scorpionida)

The venom is a mixture of various compounds with specific biological activities, such as the phospholipase  A₂ (PLA₂) enzyme present in scorpion venom. PLA₂ plays a key role in inhibiting ryanodine receptor channels and has neurotoxic activity. This study is the first investigation of molecular characterization, cloning, and in silico analyses of PLA₂ from Iranian Scorpio maurus, named Maurolipin. After RNA extraction from S. maurus venom glands, cDNA was synthesized and amplified through RT-PCR using specific primers. Amplified Maurolipin was cloned in TA cloning vector, pTG19. For in silico analyses, the characterized gene was analyzed utilizing different software. Maurolipin coding gene with 432 base pair nucleotide length encoded a protein of 144 amino acid residues and 16.34 kilodaltons. Comparing the coding sequence of Maurolipin with other characterized PLA₂ from different species of scorpions showed that this protein was a member of the PLA₂ superfamily. According to SWISS-MODEL prediction, Maurolipin had 38.83% identity with bee venom PLA₂ with 100% confidence and 39% identity with insect phospholipase A₂ family, which Phyre2 predicted. According to the three-dimensional structure prediction, Maurolipin with five disulfide bonds has a very high similarity to the structure of PLA₂ that belonged to the group III subfamily. The in silico analyses showed that phospholipase A₂ coding gene and protein structure is different based on scorpion species and geographical condition in which they live.

New Biomarkers of Hymenoptera Venom Allergy in a Group of Inflammation Factors

Hymenoptera venom allergy significantly affects the quality of life. Due to the divergences in the results of the available test and clinical symptoms of patients, the current widely applied diagnostic methods are often insufficient to classify patients for venom immunotherapy (VIT). Therefore it is still needed to search for new, more precise, and accurate diagnostic methods. Hence, this research aimed to discover new biomarkers of Hymenoptera venom allergy in a group of inflammation factors using set of multi-marker Bioplex panel. The adoption of a novel methodology based on Luminex/xMAP enabled simultaneous determination of serum levels of 37 different inflammatory proteins in one experiment. The study involved 21 patients allergic to wasp and/or honey bee venom and 42 healthy participants. According to univariate and multivariate statistics, soluble CD30/tumor necrosis factor receptor superfamily, member 8 (sCD30/TNFRSF8), and the soluble tumor necrosis factor receptor 1 (sTNF-R1) may be considered as effective prognostic factors, their circulating levels were significantly decreased in the allergy group (p-value < 0.05; the Area Under the Curve (AUC) ~0.7; Variable Importance in Projection (VIP) scores >1.2). The obtained results shed new light on the allergic inflammatory response and may contribute to modification and improvement of the diagnostic and monitoring methods. Further, large-scale studies are still needed to explain mechanisms of action of studied compounds and to definitively prove their usefulness in clinical practice.

Venom-based peptide therapy: insights into anti-cancer mechanism

The 5-year relative survival rate of all types of cancer has increased significantly over the past three decades partly due to the targeted therapy. However, still there are many targeted therapy drugs could play a role only in a portion of cancer patients with specific molecular alternation. It is necessary to continue to develop new biological agents which could be used alone and/or in combination with current FDA approved drugs to treat complex cancer diseases. Venom-based drugs have been used for hundreds of years in human history. Nevertheless, the venom-origin of the anti-cancer drug do rarely appear in the pharmaceutical market; and this is due to the fact that the mechanism of action for a large number of the venom drug such as venom-based peptide is not clearly understood. In this review, we focus on discussing some identified venom-based peptides and their anti-cancer mechanisms including the blockade of cancer cell proliferation, invasion, angiogenesis, and metastasis (hallmarks of cancer) to fulfill the gap which is hindering their use in cancer therapy. Furthermore, it also highlights the importance of immunotherapy based on venom peptide. Overall, this review provides readers for further understanding the mechanism of venom peptide and elaborates on the need to explore peptide-based therapeutic strategies.

[Allergen specific immunotherapy for rhinitis allergica : New applications]

BACKGROUND

Allergic diseases are among the most common diseases of humans. The immune response towards allergens is regulated by T-lymphozytes and characterized by an interleukin (IL)-4, IL-5 and IL-13 dominated Th2 cytokine profile.

RESULTS

Allergen-specific immunotherapy (AIT) is the only causative treatment option and able to change the course of disease, e. g. to prevent the development of asthma and new sensitizations. The intralymphatic delivery of allergenes named intralymphatic immunotherapy (ILIT) has been evaluated in clinical trials and was demonstrated to be a highly potent application route with low effort and side effects while having equal efficacy if compared with current standard AIT forms. However, studies that verify important questions like optimal dose, new allergen forms, use of adjuvants etc. are still missing. Moreover, it has to be evaluated, whether different indications like rhinitis, or atopic dermatitis are suitable for ILIT and whether it is useful in children. Epicutaneous immunotherapy (EPIT) is a possible alternative application form. It is minimally invasive and basically consists of the affixation of allergen containing patches to the epidermis over 6 weeks. From the studies performed so far, the authors concluded, that epicutaneous immunotherapy is safe and efficacious in a dose-dependent manner after 6 patches only.

CONCLUSIONS

AIT is accepted to be the only causative treatment option for allergies. New application routes in ILIT and EPIT may become more important and allow for different delivery methods in the future, however further clinical studies are required and in preparation.

Jug r 2-reactive CD4(+) T cells have a dominant immune role in walnut allergy

Background

Allergic reactions to walnut can be life threatening. While IgE epitopes of walnut have been studied, CD4⁺ T-cell specific epitopes for walnut remain uncharacterized. Particularly, the relationship of both phenotype and frequency of walnut specific T-cells to the disease have not been examined.

Objectives

We sought to provide a thorough phenotypic analysis for walnut reactive T-cells in allergic and non-allergic subjects. Particularly, the relationship of phenotypes and frequencies of walnut specific T-cells with the disease.

Methods

CD154 up-regulation assay was used to examine CD4⁺ T-cell reactivity towards walnut allergens.Jug r 1, Jug r 2 and Jug r 3. Tetramer-Guided epitope mapping approach was utilized to identify HLA-restricted CD4⁺ T-cells epitopes in Jug r 2. Direct ex vivo staining with peptide-major histocompatibility complex class II (pMHC-II) tetramers enabled the comparison of frequency and phenotype of Jug r 2-specific CD4⁺ T-cells between allergic and non-allergic subjects. Jug r 2-specific T-cell-clones were also generated and mRNA transcription factor levels were assessed by RT qPCR. Intracellular cytokine staining (ICS) assays were performed for further phenotypical analyses.

Results

Jug r 2 was identified as the major allergen that elicited CD4⁺ T-cell responses. Multiple Jug r 2 T-cell epitopes were identified. The majority of these T-cells in allergic subjects have a CCR4⁺ T_CM (central memory) phenotype. A subset of these T-cells express CCR4⁺CCR6⁺ irrespectively of the asthmatic status of the allergic subjects. ICS confirmed these T_H2, T_H2/T_H17 and T_H17-like heterogenic profiles. Jug r 2-specific T-cell-clones from allergic subjects mainly expressed GATA3; nonetheless, a portion of T-cell clones expressed either GATA3 and RORC, or RORC, confirming the presence of T_H2, T_H2/T_H17 and T_H17 cells.

Conclusions

Jug r 2 specific responses dominate walnut T-cell responses in subjects with walnut allergy. Jug r 2 central memory CD4⁺ cells and terminal effector T-cells were detected in peripheral blood with the central memory phenotype as the most prevalent phenotype. In addition to conventional T_H2-cells, T_H2/T_H17 and T_H17 cells were also detected in non-asthmatic and asthmatic subjects with walnut allergy. Understanding this T-cell heterogeneity may render better understanding of the disease manifestation.

Regulatory tone and mucosal immunity in asthma

The lung is constantly exposed to a variety of inhaled foreign antigens, many of which are harmless to the body. Therefore, the mucosal immune system must not only have the capacity to distinguish self from non-self, but also harmless versus dangerous non-self. To address this, mucosal immune cells establish an anti-inflammatory steady state in the lung that must be overcome by inflammatory signals in order to mount an effector immune response. In the case of inhaled allergens, the false detection of dangerous non-self results in inappropriate immune activation and eventual allergic asthma. Both basic and clinical studies suggest that the balance between tolerogenic and inflammatory immune responses is a key feature in the outcome of health or disease. This review is focused on what we term 'regulatory tone': the immunosuppressive environment in the lung that must be overcome to induce inflammatory responses. We will summarize the current literature on this topic, with a particular focus on the role of regulatory T cells in preventing allergic disease of the lung. We propose that inter-individual differences in regulatory tone have the potential to not only establish the threshold for immune activation in the lung, but also shape the quality of resulting effector responses following tolerance breakdown.

Environment and T regulatory cells in allergy

The central role of T regulatory cells in the responses against harmless environmental antigens has been confirmed by many studies. Impaired T regulatory cell function is implicated in many pathological conditions, particularly allergic diseases. The "hygiene hypothesis" suggests that infections and infestations may play a protective role for allergy, whereas environmental pollutants favor the development of allergic diseases. Developing countries suffer from a variety of infections and are also facing an increasing diffusion of environmental pollutants. In these countries allergies increase in relation to the spreading use of xenobiotics (pesticides, herbicides, pollution, etc.) with a rate similar to those of developed countries, overcoming the protective effects of infections. We review here the main mechanisms of non-self tolerance, with particular regard to relations between T regulatory cell activity, infections and infestations such as helminthiasis, and exposure to environmental xenobiotics with relevant diffusion in developing countries.

The impact of common tumor necrosis factor haplotypes on the development of asthma in children: an Egyptian model

Conflicting results have arisen among different ethnic populations with regard to the ability of tumor necrosis factor (TNF) to control the development of bronchial asthma. We examined common TNF polymorphisms (TNFA -1031C>T, TNFA -308G>A, and TNFB +252A>G) to develop a model of the associations between these genetic markers and the development of the disease in Egypt. Amplified DNA from buccal mucosa was genotyped for 240 children using polymerase chain reaction-restriction fragment length polymorphism. Skin prick test, total serum immunoglobulin E levels, and assessment of pulmonary functions were investigated. The onset age for one-third of the asthma patients in our study was between 7 and 10 years. The TNFA -1031C>T and TNFA -308G>A polymorphisms were strongly associated with the risk of asthma (p = 0.007, and p = 0.000, respectively), but the TNFB +252A>G polymorphism was not (p = 0.6). We detected a significant linkage between the +252A>G and -1031C>T, and another between the +252A>G and the -308G>A (p < 0.0001 for both). The -1031C>T and -308G>A polymorphisms were not linked (p = 0.14). The -308A/A genotype was absent, and the -308A allele was expressed only in patients with -308G/A heterozygosity (13%). All but the +252G/A genotype were also strongly associated with the severity of disease. Environmental factors, as genetic variations, clearly influence susceptibility, the onset, progression, and severity of bronchial asthma. More information is needed to develop genetic models of susceptibility for different ethnic populations.

Allergen-specific IL-10-secreting type I T regulatory cells, but not CD4(+)CD25(+)Foxp3(+) T cells, are decreased in peripheral blood of patients with persistent allergic rhinitis

We investigate the frequencies of CD4(+)CD25(+)Foxp3(+) T cells and allergen-specific IL-10(+)IL-4(-), IFN-gamma(+)IL-4(-), IL-4(+)IFN-gamma(-)CD4(+) T cells (which display characteristics of nTreg, Tr1-, Th1- and Th2- cells, respectively) in peripheral blood mononuclear cells (PBMCs) of patients with AR and of healthy individuals. In addition, we estimated the suppressive effect of CD4(+)CD25(+) Treg cells and allergen-specific, IL-10-secreting cells from both two groups. The frequency of CD4(+)CD25(+)Foxp3(+) T cells is similar in 43 AR patients compared with 38 healthy subjects. CD4(+)CD25(high) cells retain suppressive activity on allergen-stimulated cell proliferation and cytokine production of Th1 but not Th2 cells in both groups. However, the frequency of allergen-specific IL-10(+)IL-4(-)CD4(+) T cells is reduced in AR patients, and correlates inversely to clinical symptom scores. Allergen-specific, IL-10-secreting cells potently suppressed D. pteronyssinus major allergen 1-stimulated cell proliferation and cytokine production (IFN-gamma and IL-4) in healthy individuals. Altogether our data indicate that the number and function of CD4(+)CD25(+) Treg cells from allergic patients are not impaired. However, the deficiency of allergen-specific Tr1 cells may play a role in the development of AR.

A review of allergen-specific immunotherapy in human and veterinary medicine

This article reviews allergen-specific immunotherapy in human and veterinary medicine. Current hypotheses of possible mechanisms of actions are outlined. Indications, success rates, adverse effects and factors influencing outcome of therapy are discussed in humans, dogs, cats and horses.

Genetics of asthma: a molecular biologist perspective

Asthma belongs to the category of classical allergic diseases which generally arise due to IgE mediated hypersensitivity to environmental triggers. Since its prevalence is very high in developed or urbanized societies it is also referred to as "disease of civilizations". Due to its increased prevalence among related individuals, it was understood quite long back that it is a genetic disorder. Well designed epidemiological studies reinforced these views. The advent of modern biological technology saw further refinements in our understanding of genetics of asthma and led to the realization that asthma is not a disorder with simple Mendelian mode of inheritance but a multifactorial disorder of the airways brought about by complex interaction between genetic and environmental factors. Current asthma research has witnessed evidences that are compelling researchers to redefine asthma altogether. Although no consensus exists among workers regarding its definition, it seems obvious that several pathologies, all affecting the airways, have been clubbed into one common category called asthma. Needless to say, genetic studies have led from the front in bringing about these transformations. Genomics, molecular biology, immunology and other interrelated disciplines have unearthed data that has changed the way we think about asthma now. In this review, we center our discussions on genetic basis of asthma; the molecular mechanisms involved in its pathogenesis. Taking cue from the existing data we would briefly ponder over the future directions that should improve our understanding of asthma pathogenesis.

Antagonism of airway tolerance by endotoxin/lipopolysaccharide through promoting OX40L and suppressing antigen-specific Foxp3+ T regulatory cells

Respiratory exposure to allergens can lead to airway tolerance. Factors that antagonize tolerance mechanisms in the lung might result in susceptibility to diseases such as asthma. We show that inhalation of endotoxin/LPS with Ag prevented airway tolerance and abolished protection from T cell-driven asthmatic lung inflammation. Under conditions leading to tolerance, adaptive Ag-specific CD4(+)Foxp3(+) T regulatory cells (Treg) were generated following exposure to intranasal Ag and outnumbered IL-4- and IFN-gamma-producing CD4 T cells by 100:1 or greater. Inhaled LPS altered the ratio of Treg to IL-4(+) or IFN-gamma(+) T cells by concomitantly suppressing Treg generation and promoting effector T cell generation. LPS induced OX40L expression on dendritic cells and B cells that resulted in a synergistic activity between TLR4 and OX40 signals, leading to production of IL-4, IFN-gamma, and IL-6, which blocked Treg development. Furthermore, inhibiting OX40/OX40L interactions prevented LPS from suppressing tolerance, and resulted in the generation of greater numbers of adaptive Treg. Thus, cooperation between TLR4 and OX40 controls susceptibility to developing airway disease via modulating the balance between adaptive Treg and IL-4(+) or IFN-gamma(+) T cells. Targeting OX40L then has the potential to improve the efficacy of Ag immunotherapy to promote tolerance.

Immunological mechanisms of allergen-specific immunotherapy

Allergen-specific immunotherapy has been carried out for almost a century and remains one of the few antigen-specific treatments for inflammatory diseases. The mechanisms by which allergen-specific immunotherapy exerts its effects include the modulation of both T-cell and B-cell responses to allergen. There is a strong rationale for improving the efficacy of allergen-specific immunotherapy by reducing the incidence and severity of adverse reactions mediated by IgE. Approaches to address this problem include the use of modified allergens, novel adjuvants and alternative routes of administration. This article reviews the development of allergen-specific immunotherapy, our current understanding of its mechanisms of action and its future prospects.

Hymenoptera venom allergens

Hymenoptera venoms each contain a variety of protein allergens. The major components have all been characterized, and most of the amino acid sequences are known. This article concentrates on the use of contemporary techniques including cloning, mass spectrometry and genomics in the characterization of venom allergens, and newer separation techniques for protein isolation. Examples of the use of these techniques with venom proteins are presented.

T regulatory cells in allergy: novel concepts in the pathogenesis, prevention, and treatment of allergic diseases

The identification of T regulatory (T(Reg)) cells as key regulators of immunologic processes in peripheral tolerance to allergens has opened an important era in the prevention and treatment of allergic diseases. Both naturally occurring CD4(+)CD25(+) T(Reg) cells and inducible populations of allergen-specific IL-10-secreting T(R)1 cells inhibit allergen-specific effector cells in experimental models. Allergen-specific T(Reg) cell responses contribute to the control of allergic inflammation in several ways. Skewing of allergen-specific effector T cells to a T(Reg) phenotype appears to be a crucial event in the development of a healthy immune response to allergens and successful outcome in allergen-specific immunotherapy. The increased levels of IL-10 and TGF-beta produced by T(Reg) cells can potently suppress IgE production while simultaneously increasing the production of the noninflammatory antibody isotypes IgG4 and IgA, respectively. T(Reg) cells directly or indirectly suppress effector cells of allergic inflammation, such as mast cells, basophils, and eosinophils, and contribute to remodeling in asthma and atopic dermatitis. In addition, mediators of allergic inflammation that trigger cyclic AMP-associated G protein-coupled receptors, such as histamine receptor 2, might play a role in peripheral tolerance mechanisms against allergens. Current strategies for drug development and allergen-specific immunotherapy exploit these observations with the potential to provide cure for allergic diseases.

Immunomodulatory potential of heteroclitic analogs of the dominant T-cell epitope of lipocalin allergen Bos d 2 on specific T cells

Peptide-based allergen immunotherapy is a novel alternative for conventional allergen immunotherapy. Here, we have characterized the immunomodulatory potential of heteroclitic peptide analogs of the immunodominant epitope of lipocalin allergen Bos d 2 on specific human T-cell clones. The TCR affinity of Bos d 2-specific T-cell clones for the natural peptide ligand and its heteroclitic analogs was assessed with fluorescent-labeled MHC class II tetramers. The activation and cytokine production of the clones were analyzed upon stimulation with the different ligands. Moreover, the capacity of the heteroclitic analogs to induce hyporesponsiveness and cell death was examined. The T-cell clones F1-9 and K3-2 bound MHC class II tetramers loaded with the heteroclitic peptide analogs of the immunodominant epitope of Bos d 2 with increased affinity. At similar peptide concentrations, stimulation of the clones with the heteroclitic analogs favored increased IFN-gamma/IL-4 and IFN-gamma/IL-5 ratios in comparison with stimulation with the natural peptide ligand. Moreover, the T-cell clones stimulated with the heteroclitic analogs exhibited an increased susceptibility to cell death or hyporesponsiveness upon re-stimulation. Our results suggest that heteroclitic analogs of a T-cell epitope of an allergen may enhance the efficacy of peptide-based allergen immunotherapy.

Characterization of the human T cell response to antigen 5 from Vespula vulgaris (Ves v 5)

BACKGROUND

The T cell reactivity to the major allergen of bee venom, phospholipase A2, has been thoroughly characterized. In contrast, only little is known about the human cellular response to major allergens from wasp venom.

OBJECTIVE

To characterize the human T cell response to antigen 5 from Vespula vulgaris, Ves v 5.

METHODS

Recombinant Ves v 5 was used to establish allergen-specific T cell lines (TCL) and T cell clones (TCC) from the peripheral blood of vespid-allergic and non-allergic individuals. Ves v 5-specific TCL were mapped for T cell epitopes using overlapping synthetic peptides representing the complete amino acid sequence of Ves v 5. Ves v 5-specific TCC were analysed for antigen-induced secretion of IL-4, IFN-gamma and IL-10.

RESULTS

Seventeen distinct T cell epitopes were recognized by allergic individuals among which Ves v 5(181-192) was identified as a dominant T cell epitope. Partially different epitopes were observed in TCL from non-allergic subjects and the dominant epitope Ves v 5(181-192) was not prevalent in these cultures. Ves v 5-specific TCC isolated from allergic individuals did not show the typical T helper type 2 (Th2)-like cytokine profile in response to specific stimulation, i.e. high amounts of IL-4 and low IFN-gamma. TCC from non-allergic individuals showed a Th1-like cytokine pattern.

CONCLUSIONS

Our findings provide evidence that the allergic T cell response to Ves v 5 is not Th2-dominated and that different immunogenic sites on this major wasp venom allergen are recognized by allergic and non-allergic individuals.

Recombinant allergens for analysing T-cell responses

T-cell responses constitute a central element of allergic disease and a model for studying Th1 and Th2 cytokine pathways. Most studies to date have used extracts of allergens which contain variable quantities of different allergens and non-allergenic antigens. Recombinant allergens provide the tools for studying the responses to allergens in a reproducible and dose-dependent manner and the different T-cell responses of allergic and non-allergic subjects provide a method for verifying the responses and their relationship to allergic sensitisation. Most allergies show dominant responses to one or a few major allergens. These allergens have been described for the common allergies and have been produced as recombinant allergens. A particular problem for allergens is that many are mixtures of proteins from multi-gene families or are highly polymorphic. Information now exists so the sequence variation can be represented. Purified recombinant allergens produced by standard expression systems stimulate the expected T-cell responses from the peripheral blood of allergic and non-allergics to allergen extracts. Although stimulation with recombinant allergens which are not produced with a natural IgE binding activity can provide a measure of allergenicity, the altered tertiary structure can reduce Th2 responses. The sequence information now available provides the means to use PCR to produce cDNA for the production of recombinant allergens from readily available sources. The production of the highly reactive recombinant Der p 2 allergen of house dust mite from natural sources is described.

TH1 and TH2 lymphocyte development and regulation of TH cell-mediated immune responses of the skin

Since the first description of the subpopulations of TH1 and TH2 cells, insights into the development and control of these cells as two polarized and physiologically balanced subsets have been generated. In particular, implications of the TH1-TH2 concept for TH cell-mediated skin disorders have been discovered. This article will review the basic factors that control the development of TH1 and TH2 cells, such as the cytokines IL-12 and IL-4 and transcription factors, the possible role of costimulatory molecules, and specialized dendritic cell populations. These regulatory mechanisms will be discussed in the context of polarized TH1 or TH2 skin disorders such as psoriasis and atopic dermatitis. Also presented are the principles that govern how chemokines and chemokine receptors recruit TH1 and TH2 cells to inflammatory sites and how they amplify these polarized TH cell responses. All of these concepts, including a novel role for IL-4-inducing TH1 responses, can contribute to the design of better therapeutic strategies to modulate TH cell-mediated immune responses.

Immune responses in healthy and allergic individuals are characterized by a fine balance between allergen-specific T regulatory 1 and T helper 2 cells

The mechanisms by which immune responses to nonpathogenic environmental antigens lead to either allergy or nonharmful immunity are unknown. Single allergen-specific T cells constitute a very small fraction of the whole CD4⁺ T cell repertoire and can be isolated from the peripheral blood of humans according to their cytokine profile. Freshly purified interferon-γ–, interleukin (IL)-4–, and IL-10–producing allergen-specific CD4⁺ T cells display characteristics of T helper cell (Th)1-, Th2-, and T regulatory (Tr)1–like cells, respectively. Tr1 cells consistently represent the dominant subset specific for common environmental allergens in healthy individuals; in contrast, there is a high frequency of allergen-specific IL-4–secreting T cells in allergic individuals. Tr1 cells use multiple suppressive mechanisms, IL-10 and TGF-β as secreted cytokines, and cytotoxic T lymphocyte antigen 4 and programmed death 1 as surface molecules. Healthy and allergic individuals exhibit all three allergen-specific subsets in different proportions, indicating that a change in the dominant subset may lead to allergy development or recovery. Accordingly, blocking the suppressor activity of Tr1 cells or increasing Th2 cell frequency enhances allergen-specific Th2 cell activation ex vivo. These results indicate that the balance between allergen-specific Tr1 cells and Th2 cells may be decisive in the development of allergy.

TSST-1 induces Th1 or Th2 differentiation in naïve CD4+ T cells in a dose- and APC-dependent manner

Superantigens are potent activators of the immune system, causing a variety of diseases, ranging from food poisoning to septic shock. Here, we examined the effects of different toxic shock syndrome toxin 1 (TSST-1) concentrations on the activation, proliferation and synthesis of interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) in purified naïve human CD4+ T cells in a serum-free in vitro system. TSST-1 given in low doses (1-10 pg/ml) generates a pronounced T helper 2 (Th2)-like cytokine profile, characterized by elevated IL-4-expressing T-cell populations and reduced IFN-gamma-producing populations, whereas higher doses (100 pg/ml) induce a Th1-like profile, with increased expression of IFN-gamma and reduced expression of IL-4. These patterns were even more pronounced by adding exogenous cytokines like IL-12 and IL-4 and by the type of antigen-presenting cells (APCs). Thus, B cells induced Th2 shifts, whereas monocytes favoured Th1 induction. Moreover, IL-12 in conditions with B cells counteracted their Th2 bias. Interestingly, in purified naïve T-cell cultures, containing a small population of HLA-DR+ T cells, Th1/Th2 differentiation can be induced by TSST-1 too. There, Th-cell polarization is strongly dependent on TSST-1 concentration, indicating that this is a key parameter in regulating the differentiation of T cells. In conclusion, our data show that Th1/Th2 differentiation of TSST-1-stimulated naïve T cells is controlled by the type of APCs, and in APC-depleted cultures, it depends on the presence of HLA-DR+ cells and TSST-1 concentration.

Mycobacterium bovis BCG producing interleukin-18 increases antigen-specific gamma interferon production in mice

Interleukin-18 (IL-18) and IL-12 play a critical role in the expression of cell-mediated immunity involved in host defense against intracellular pathogens. Both cytokines are produced by macrophages and act in synergy to induce gamma interferon (IFN-gamma) production by T, B, and natural killer cells. In the present study, we analyzed both cellular and humoral responses upon infection with IL-18-secreting BCG of BALB/c and C3H/HeJ mice, two strains known to differ in their ability to support the growth of BCG. The cDNA encoding mature IL-18 was fused in frame with the alpha-antigen signal peptide-coding sequence, cloned downstream of the mycobacterial hsp60 promoter and expressed in BCG. IL-18 produced by the recombinant BCG strain was functional, as judged by NF-kappaB-mediated luciferase induction in a tissue culture assay. When susceptible mice were infected with IL-18-producing BCG, their splenocytes were found to produce higher amounts of Th1 cytokines after stimulation with mycobacterial antigens than the splenocytes of mice infected with the nonrecombinant BCG. This was most prominent for IFN-gamma, although the mycobacterial antigen-specific secretion of granulocyte-macrophage colony-stimulating factor and IL-10 was also augmented after infection with the recombinant BCG compared to infection with nonrecombinant BCG. In contrast, the immunoglobulin G levels in serum against mycobacterial antigens were lower when the mice were infected with IL-18-producing BCG compared to infection with nonrecombinant BCG. The IL-18 effect was delayed in BALB/c compared to C3H/HeJ mice. These results indicate that the production of IL-18 by recombinant BCG may enhance the immunomodulatory properties of BCG further toward a Th1 profile. This may be particularly useful for immunotherapeutic or prophylactic interventions in which a Th1 response is most desirable.

In vivo kinetics of the immunoglobulin E response to allergen: bystander effect of coimmunization and relationship with anaphylaxis

BACKGROUND

Murine models of hypersensitivity to allergens are useful tools for the evaluation of preclinical strategies to down-regulate the IgE response.

OBJECTIVE

To monitor the long-term kinetics of T and B cell responses to allergen as a function of allergen dosage and to investigate the effect of parallel immunization with a second antigen; to correlate B cell response with anaphylaxis.

METHODS

CBA/J mice were sensitized every other week by subcutaneous injections of phospholipase A2 (PLA2) and/or ovalbumin (OVA) adsorbed to alum. Specific antibody isotype responses, T cell proliferation, T cell cytokine production and anaphylaxis were assessed throughout the sensitization phase.

RESULTS

Low-dose immunization with PLA2 (0.1 microg) favoured a long-term, specific T helper (Th)2 response with high IgE and IL-4 production in contrast to high-dose PLA2 (10 microg) immunization, which biased the immune response towards a Th1 response with high IgG2a and low IL-4 production. Parallel immunization with an unrelated antigen (ovalbumin) had a significant bystander effect on the immunization with PLA2, which was also dose-dependent. Finally, although anaphylaxis as measured by rectal temperature drop was allergen-specific, it could be induced in the high- and low-dose immunization groups, and was not solely dependent on IgE levels.

CONCLUSION

Though low-dose allergen immunization appears to induce an efficient IgE response, the intensity and quality of this response may be modulated by bystander effects of parallel immunization and does not correlate strictly with anaphylaxis. This observation has relevance to the design of clinical immunotherapy protocols using murine model-based data.

Role of IL-10 in allergen-specific immunotherapy and normal response to allergens

Induction of specific unresponsiveness (tolerance/anergy) in peripheral T cells by interleukin-10 (IL-10) and recovery by cytokines from the tissue microenvironment represent two key steps in specific immunotherapy of allergy and in natural exposure to allergens in healthy individuals. IL-10 elicits anergy in T cells by selective inhibition of the CD28 costimulatory pathway and controls suppression and development of antigen-specific immunity.

Wasp venom immunotherapy induces a shift from IL-4-producing towards interferon-gamma-producing CD4+ and CD8+ T lymphocytes

BACKGROUND

Venom immunotherapy (VIT) has proven to be very effective in hymenoptera venom anaphylaxis. However, the underlying immunoregulatory mechanisms of venom immunotherapy remain poorly understood. Recent studies measured the total amount of cytokine in culture supernatans, suggesting a shift in cytokine production from Th2 to a Th1 cytokine profile during VIT. We wanted to examine the contribution of specific T lymphocyte subpopulations, which is impossible using an extracellular method to determine cytokines in supernatants.

OBJECTIVE

The present study was designed to evaluate the effect of VIT on the percentages of type 1 (IL-2, interferon-gamma (IFN-gamma)) and type 2 (IL-4) CD4+ and CD8+ T lymphocytes of patients with wasp venom anaphylaxis during immunotherapy.

METHODS

Peripheral blood mononuclear cells of 20 individuals with a history of wasp sting anaphylaxis and a positive serum wasp venom specific IgE were isolated and in vitro stimulated with phorbol-12-myristate-13-acetate and ionomycin before VIT, at the end of a 5-day semirush VIT and at 6 months during VIT. Three-colour flow cytometric analysis was used for intracellular cytokine (IL-2, IFN-gamma, IL-4) detection in CD4+ (CD3+CD8-) T lymphocytes and CD8+ (CD3+CD8+) T lymphocytes.

RESULTS

At the end of a 5-day semirush VIT, there was a significant decrease in percentage of IL-4-producing CD4+ and CD8+ T cells, compared with cytokine-producing cells before VIT (P = 0.0002 and 0.004). After 6 months of VIT, patients showed an increased number of IL-2-producing stimulated CD4+ and CD8+ lymphocytes compared with values before VIT (P = 0.002 and P = 0.0003). A higher amount of IFN-gamma-producing stimulated CD4+ and CD8+ cells was found after 6 months of VIT (P = 0.001 and P = 0.0006). There was no correlation between cytokine-producing cells and specific IgE for wasp.

CONCLUSION

Venom immunotherapy induced a shift from IL-4-producing towards IFN-gamma-producing CD4+ as well as CD8+ T lymphocytes.

The low efficiency of dendritic cells and macrophages from mice susceptible to Paracoccidioides brasiliensis in inducing a Th1 response

In the present study we evaluated T cell proliferation and Th lymphokine patterns in response to gp43 from Paracoccidioides brasiliensis presented by isolated dendritic cells from susceptible and resistant mice. T cell proliferation assays showed that dendritic cells from susceptible mice were less efficient than those from resistant mice. The pattern of T cell lymphokines stimulated by dendritic cells was always Th1, although the levels of IL-2 and IFN-gamma were lower in T cell cultures from susceptible mice. To determine whether different antigen-presenting cells such as macrophages and dendritic cells stimulated different concentrations of Th1 lymphokines, the production of IFN-gamma and IL-2 was measured. It was observed that dendritic cells were more efficient than macrophages in stimulating lymphoproliferation in resistant mice. However, no significant difference was observed for IFN-gamma or IL-2 production. When cells from susceptible mice were used, macrophages were more efficient in stimulating lymphoproliferation than dendritic cells, but no difference was observed in the production of Th1 cytokine. Taken together, these results suggest the lower efficiency of dendritic cells and macrophages from B10.A mice in stimulating T cells that secrete Th1 lymphokines in vitro, an effect that may be involved in the progression of the disease in vivo.

IL-4 fails to regulate in vitro beryllium-induced cytokines in berylliosis

Bronchoalveolar lavage (BAL) cells from patients with chronic beryllium disease (CBD) have been used to evaluate the beryllium-specific immune response and potential immunotherapeutics. Beryllium induces interferon-gamma (IFN-gamma), interleukin-2 (IL-2), tumour necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6) and interleukin-10 (IL-10) from BAL cells. An antibody to IL-2 and recombinant human (rHu) IL-10 is able to partially suppress the beryllium-stimulated immune response. To obtain BAL cells, bronchoscopy is required, providing risk to the patient and a limited number of cells to study the immune response. As a result, the objectives of the study were to determine 1) whether CBD peripheral blood mononuclear cells (PBMNs) stimulated with beryllium would produce a similar cytokine pattern as BAL cells, and 2) whether this response could be modulated by interleukin-4 (IL-4), an immunomodulatory cytokine. CBD and normal individuals' PBMN and BAL cells were stimulated with and without beryllium sulfate. To modulate this antigen-stimulated response, we added rHu IL-4 to the unstimulated and beryllium-stimulated cells. IFN-gamma, IL-2, TNF-alpha, IL-6 and IL-10 cytokine concentrations were determined from cell supernatants by enzyme-linked immunosorbent assays (ELISA), while IL-4 messenger ribonucleic acid (mRNA) was assessed using polymerase chain reaction (PCR). Beryllium did not stimulate any of these cytokines from normal PBMNs. Increasing levels of IL-6 and TNF-alpha were produced constituitively by CBD PBMNs over time. Compared to the unstimulated CBD PBMNs, beryllium stimulated significant IFN-gamma, TNF-alpha, IL-2, IL-6 and IL-10 production. This response was similar to that stimulated from CBD BAL cells, although of a much lower magnitude. Low levels of IL-4 mRNA were found in CBD and control PBMNs, which were not increased with beryllium stimulation. The beryllium-stimulated cytokine levels were not decreased by the addition of IL-4. IL-4 was unable to downregulate any of these beryllium-stimulated cytokines from CBD BAL cells or increase IL-4 mRNA from either CBD PBMN or BAL cells, and thus is an unlikely immunomodulatory agent in CBD. From the data, it was concluded that chronic beryllium disease peripheral blood mononuclear cells provide a model to study the beryllium-stimulated immune response. Interleukin-4's inability to downregulate any of the beryllium-stimulated cytokines makes it an unlikely therapeutic candidate in chronic beryllium disease.

HLA-DR restricted peptide candidates for bee venom immunotherapy

T cell epitopes containing peptides have been recently proposed as an alternative to conventional immunotherapy of allergic diseases because they are expected to be better tolerated than allergen extracts. A principal limitation to their clinical use is that they present an important diversity, which primarily results from the polymorphism of HLA class II molecules. In Caucasian populations, however, seven alleles of the most expressed molecules (namely DRB1*0101, DRB1*0301, DRB1*0401, DRB1*0701, DRB1*1101, DRB1*1301, and DRB1*1501) predominate. Peptides from allergens that would efficiently bind to them should be potential candidates for specific immunotherapy. In this paper, we have determined the peptides present in the major bee venom allergen by investigating the capacity of synthetic peptides that encompass its whole sequence to bind to each allele. Several efficient binders have been identified and are either allele-specific or common to several HLA-DR molecules. Interestingly enough, the 81-97 sequence is universal in the sense that it binds to all studied molecules. This sequence is surrounded by several active regions, which make the 76-106 sequence particularly rich of binding determinants and a good candidate for specific immunotherapy. Statistical analyses of the binding data also provide an overview of the preponderant HLA-DR alleles specificity.

Immunohistochemical investigation of the cellular infiltrates at the sites of allergoid-induced late-phase cutaneous reactions associated with pollen allergen-specific immunotherapy

BACKGROUND

Reduction in the size of the allergen-induced late-phase reaction (LPR) is seen as a consequence of successful allergen specific immunotherapy.

OBJECTIVE

It was the aim of this study to characterize the cellular infiltrate at the sites of cutaneous LPR that may occur following injection of a depot pollen allergoid (Allergovit(R)) during immunotherapy and thereby determine the immunological nature of the response.

METHODS

Punch biopsies were taken 24 h after subcutaneous injection of a depot pollen allergoid from eight patients that showed LPR and a further five patients that did not. Additional biopsies taken 24 h after injection of allergoid-free depot in the same patients served as controls. Immunoenzymatic labelling of the cryostat sections with different antibodies was performed with the APAAP technique. Results were expressed as cells/field (400 x magnification).

RESULTS

Similar dermal cellular infiltrations were seen following depot allergoid injections in patients both with and without LPR. Patients with LPR showed statistically significant increases in total cells, CD4+ cells, CD11c+ cells, CD45RO+ cells, CD45RB+ cells and activated eosinophils at the reactions sites as compared with control sites. In patients without LPR CD11c+ cells, HLA-DR+ cells and CD45RA+ T cells increased significantly. CD8+, CD1a+, NP57+, CD23+ and CD25+ cells did not differ significantly in either group.

CONCLUSION

These results indicate that activation of T cells, monocytes/macrophages and eosinophils at the sites of LPR following injection of depot allergoid are comparable with those following injection of allergen. Even in the absence of a cutaneous LPR, subsets of T cells and monocytes/macrophages increased. These cell activations may reflect events associated with the mechanisms of allergoid-based specific immunotherapy, and suggest that at least part of the late-phase reaction may be independent of IgE.

A recombinant BCG vaccine generates a Th1-like response and inhibits IgE synthesis in BALB/c mice

The tubercle vaccine, bacille Calmette-Guérin (BCG), is a strong inducer of T-helper type 1 (Th1) responsiveness, and it has been suggested that recombinant BCG (rBCG), which produces and secretes antigens, may be used to prevent allergic diseases. The effects of rBCG vaccination on allergic responses in a murine model were examined in this study. A BCG-Escherichia coli shuttle vector was developed with the promoter and signal sequence of the alpha-antigen of Mycobacterium bovis, and the vector was tested using E. coli beta-galactosidase as the model antigen and allergen. This vector enabled the expression of the E. coli beta-galactosidase gene in BCG, which was detected in its protein extract by immunoblotting analysis. Vaccination of mice with a single dose of 106 recombinant BCG generated a beta-galactosidase-specific antibody response. The splenocytes of vaccinated mice compared with controls produced significantly higher amounts of interferon-gamma (IFN-gamma) (P<0. 01) and interleukin-2 (IL-2) (P<0.05) and lower amounts of IL-5 (P<0. 01). Mice vaccinated with rBCG had significantly less (P<0.01) serum IgE compared with controls. These results together demonstrate that rBCG secreting antigens or allergens may be utilized for the induction of a Th1-like response and the down-regulation of IgE antibody response.

An Altered Peptide Ligand Specifically Inhibits Th2 Cytokine Synthesis by Abrogating TCR Signaling

Altered peptide ligands (APL) can modify T cell effector function by their diversity in binding to the TCR or MHC class II-presenting molecules. The capacity to inhibit Th2 cytokine production by allergen-specific T cells would contribute to combating allergic inflammation. The presence of APL generated by Ala-substitutions in a synthetic dodeca-peptide spanning an immunodominant epitope of bee venom phospholipase A2 (PLA) was investigated in human T cells. Four of five substituted peptides reduced proliferation, IL-4, and IFN-γ production by cloned PLA-specific Th0 cells proportionately. However, one APL, PLA-F82A, inhibited IL-4 but had no effect on IFN-γ production. This uncoupling of IL-4 from IFN-γ production was also observed on immunogenic restimulation of the cloned T cells pre-exposed to the APL/APCs. It appeared to result from lower affinity of binding to MHC class II by the APL compared with the native peptide. The APL also inhibited IL-4 production by polyclonal T cells. In consequence of the change in cytokine secretion, the production of IgG4 in vitro increased by PLA-F82A stimulation, compared with the native peptide. Exposure of the cloned T cells to either the APL or the native peptide, in the absence of professional APC, induced anergy such that proliferation and production of IL-4, IL-5, and IL-13 was abrogated on immunogenic rechallenge. Defective T cell activation appeared to result from alterations in transmembrane signaling through the TCR, specifically to lack of tyrosine phosphorylation of the tyrosine kinase, ZAP-70.

Infective dose modulates the balance between Th1- and Th2-regulated immune responses during blood-stage malaria infection

Plasmodium chabaudi infection of mice provides an excellent model for examining acquired immunity to the blood-borne stage of malaria infection. CD4+ T-cell receptor (TCR) alphabeta-bearing T lymphocytes play a critical role in mediating protection, ascribed to both T helper (Th) 1 and Th2 subsets. One factor that may influence the Th1/Th2 cell balance is infective dose. In this study, we found that the size of the infective dose of P. chabaudi, and thus the level of antigen presented to the immune system, correlated with the balance of responder CD4+ T-cell phenotypes. Increasing the infective dose in a resistant mouse strain enhanced the Th1 cytokine (interferon-gamma; IFN-gamma) response and reduced the Th2 cytokine (interleukin-4; IL-4) response. In contrast, increasing the infective dose in a susceptible mouse strain led to a prominent and accelerated up-regulation of IL-4 production. These data show that the dose of antigen can significantly affect the balance between Th1- and Th2-mediated immune functions during infection of the mammalian host with blood-stage malaria parasites. This demonstration that parasite numbers may modulate CD4+ T-cell regulation has novel implications for the successful implementation of antimalarial vaccination and chemotherapeutic strategies.

High Antigen Density and IL-2 Are Required for Generation of CD4 Effectors Secreting Th1 Rather Than Th0 Cytokines

We reevaluated the effects of Ag dose on the polarization of CD4 effectors generated in vitro from naive pigeon cytochrome c-specific TCR transgenic T cells under conditions in which we could eliminate contaminating non-naive CD4 cells and the effects of heterogeneous Ag-presenting populations. When the possibility of contaminating non-naive T cells was reduced by using T cells from transgenic mice on a RAG-2−/− background, Ag dose did not have a significant effect in Th1 and Th2 polarization unless exogenous IL-2 was initially added to cultures. Effectors generated were uniformly Th0 but produced only IL-2 in substantial amounts. When exogenous IL-2 was added to priming cultures, T cells secreting a Th0 phenotype (large quantities of IL-2, IL-4, IL-5, and IFN-γ) developed, except at very high doses of Ag, where there was a striking reduction in IL-4 and IL-5 secretion. Our results imply that Ag dose does not have a direct effect on Th1/Th2 polarization, except under conditions that include a high level of TCR ligation and in the presence of high levels of IL-2, where production of Th2 cytokines may be down-regulated by a mechanism that is not yet clear.

Decrease of allergen-specific T-cell response induced by local nasal immunotherapy

BACKGROUND

The clinical efficacy and safety of local nasal immunotherapy (LNIT) with lyophilized 'macronized' powder has been demonstrated. However, the immunological changes possibly induced by LNIT which may account for the clinical improvement are still unclear.

OBJECTIVE

To investigate the effects of a successful LNIT-treatment on the allergen-driven T cell response, cytokine secretion and IgE and IgG antibody production.

METHODS

Three groups (untreated, subcutaneous immunotherapy- SIT- and LNIT-treated) of grass-sensitive patients suffering from seasonal rhinitic symptoms were ramdomized for the 2-year study. The proliferative response of PBMC to purified Rye-1 allergen and serum levels of grass-specific IgE and IgG were evaluated before treatment and during the 2-year subsequent pollination periods. The proliferative response of allergen-specific short-term T-cell lines, as well as production of allergen-driven cytokine by PBMC, were also assessed.

RESULTS

Both SIT and LNIT induced a significant reduction of symptom scores during the pollination season. SIT, but not LNIT, induced a significant change in serum levels of allergen-specific IgE and IgG antibody. By contrast, both SIT and LNIT reduced the increase of the proliferative response of allergen-specific T cells driven by natural allergen exposure and significantly decreased T cell proliferation to low doses of allergen, as shown also by the mitogenic index of allergen-specific T-cell lines. A reduced IL-4 and IFNgamma production by PBMC of LNIT- and SIT-treated patients was also observed in the absence of a clearcut TH2-TH1 switch.

CONCLUSIONS

These data suggest that a common mechanism of both LNIT and SIT is the induction of T-cell tolerance, thus providing a rational basis to explain why LNIT may be clinically successful in allergic patients with rhinits.

Activation of STAT Proteins and Cytokine Genes in Human Th1 and Th2 Cells Generated in the Absence of IL-12 and IL-4

We have shown previously that human CD4+45RO− T cells could be primed for a Th2 phenotype independent of IL-4 if they were activated by anti-CD28 mAb plus IL-2. If additional TCR signals were provided, the cells differentiated toward Th1 independent of IL-12. Here we show that anti-CD28/IL-2-primed Th2 cells expressed high levels of activated STAT6, but no cytokine mRNA. Moreover, both Th1 and Th2 cells expressed active STAT1 and -3, but not STAT2, -4, and -5. Restimulation of Th1 or Th2 cells via CD3 plus CD28 induced production of IFN-γ or IL-4, respectively, but did not alter the activation status/DNA binding activity of STATs. Addition of IL-4 (or anti-IL-4 mAb) to restimulated Th2 cells did not modulate STAT6 activation or IL-4 expression, confirming the full commitment. However, Th2 cells remained responsive to IL-12, which repressed STAT6 DNA binding but activated STAT4, and this coincided with a suppression of IL-4/IL-5 and an induction of IFN-γ. In Th1 cells, IL-12 activated both STAT6 and STAT4, and IL-4 activated STAT6, but in both cases the Th1 phenotype remained. Together the data show that CD28/IL-2-dependent Th2 priming activated STAT6 without inducing IL-4 expression. The primed Th cells resembled memory cells and produced IL-4 upon the first CD3/CD28 costimulus without detectable modulation of STATs. Th2 cells remained responsive to IL-12, which repressed STAT6 DNA binding and activated STAT4, and switched the cells to Th1. The effects of IL-12 may depend on the commitment of the cells, since IL-12 phosphorylated STAT6 in Th1 and dephosphorylated STAT6 in Th2 cells.

Infection of mice with Mycobacterium bovis-Bacillus Calmette-Guérin (BCG) suppresses allergen-induced airway eosinophilia

It has been proposed that the increase in prevalence and severity of atopic disorders inversely correlates with exposure to infectious diseases such as tuberculosis. We have investigated this issue by combining an intranasal Mycobacterium bovis-Bacillus Calmette-Guérin (BCG) infection with a murine model of allergen, (ovalbumin [OVA]) induced airway eosinophilia. BCG infection either 4 or 12 wk before allergen airway challenge resulted in a 90-95 and 60-70% reduction in eosinophilia within the lungs, respectively, compared to uninfected controls. The inhibition of airway eosinophilia correlated with a reduced level of IL-5 production by T cells from the lymph node draining the site of OVA challenge. Interestingly, BCG infection of the lung had no effect on IgG1 and IgE OVA-specific serum immunoglobulin or blood eosinophil levels. Furthermore, BCG-induced inhibition of airway eosinophilia was strongly reduced in interferon (IFN)-gamma receptor-deficient mice and could be partially reversed by intranasal IL-5 application. Intranasal BCG infections could also reduce the degree of lung eosinophilia and IL-5 produced by T cells after Nippostrongylus brasiliensis infection. Taken together, our data suggest that IFN-gamma produced during the T helper cell (Th)1 immune response against BCG suppresses the development of local inflammatory Th2 responses in the lung. Most importantly, this inhibition did not extend to the systemic immunoglobulin response against OVA. Our data support the view that mycobacterial infections have the potential to suppress the development of atopic disorders in humans.

Modulation of IgE reactivity of allergens by site-directed mutagenesis: potential use of hypoallergenic variants for immunotherapy

Specific immunotherapy is an efficient treatment for patients suffering from type I allergy. The mechanisms underlying successful immunotherapy are assumed to operate at the level of T helper cells, leading to a modulation of the immune response to allergens. During immunotherapy, increasing doses of allergens are given on a regular basis, and the beneficial effects for the patient depend on the concentration of allergen used. On the other hand, the risk of IgE-mediated anaphylactic side effects also increase with the amount of allergen applied per injection. Therefore, we have proposed the use of hypoallergenic (low IgE binding activity) forms of allergens for immunotherapy. We evaluated by site-directed mutagenesis the contributions of individual amino acid residues/positions for IgE binding to Bet v 1, the major allergen of birch pollen. We found that IgE binding to Bet v 1 depended on at least six amino acid residues/positions. Immunoblot analyses and inhibition experiments showed that the multiple-point Bet v 1 mutant exhibited extremely low reactivity with serum IgE from birch pollen-allergic patients. In vivo (skin prick) tests showed that the potency of the multiple-point mutant to induce typical urticarial type I reactions in pollen-allergic patients was significantly lower than for wild-type Bet v 1. Proliferation assays of allergen-specific T cell clones demonstrated that these six amino acid exchanges in the Bet v 1 sequence did not influence T cell recognition. Thus, the Bet v 1 six-point mutant displayed significantly reduced IgE binding activity, but conserved T cell activating capacity, which is necessary for immunomodulation. The approach described here may be generally applied to produce allergen variants to be used in a safe therapy form of immediate-type allergies.

Immunohistochemical analysis of late local skin reactions during rush venom immunotherapy

During rush venom immunotherapy (VIT), about 65% of patients develop large local reactions (LLR) at the application site that last for at least 24 h. However, LLR subside during long-term treatment. To learn more about the provenance of infiltrating cells in late, local skin reactions during VIT, we analyzed the skin infiltrates of 23 Hymenoptera venom (HV)-allergic patients. Punch biopsies were obtained 24 h after s.c. injection of HV allergens from 23 HV-allergic patients and five nonallergic controls. Seven patients did not show LLR at the beginning of VIT. Ten patients had LLR when the dose of HV allergens was increased. Six patients showed reduced LLR after long-term treatment. Immunoenzymatic labeling of the cryostal sections with a panel of monoclonal antibodies was performed by the APAAP method. S.c. application of HV allergens induced a perivascular and periadnexial cutaneous mononuclear cell infiltrate consisting mainly of CD4+, CD45RO+; and HLA-DR+ cells in patients without clinically apparent LLR. In contrast, LLR were associated with a significant increase in total cells, CD4+ cells, CD8+ cells, CD11c+ cells, EG2+ cells, NP57+ cells, HLA-DR+ cells, CD45RO+ cells, CD45RA+ cells, CD23+ cells and CD25+ cells (P < 0.001). Decreased LLR after long-term VIT was correlated with a significantly reduced recruitment of CD4+ cells, EG2+ cells, and CD23+ cells as compared to LLR in the course of dose increases (P < 0.05), whereas the number of CD8+ cells, CD11c+ cells, NP57+ cells, and CD25+ cells remained high. Our data suggest that s.c. injections of HV allergens attract CD4+ helper T cells, of both the naive (CD45RA+) and memory (CD45RO+) phenotypes, to the allergen application site. LLR represent delayed allergic rather than toxic reactions to HV components and might be relevant to the development of clinical protection during VIT.