Modulation of Th2 responses by peptide analogues in a murine model of allergic asthma: amelioration or deterioration of the disease process depends on the Th1 or Th2 skewing characteristics of the therapeutic peptide

Inhalant Mammal-Derived Lipocalin Allergens and the Innate Immunity

A major part of important mammalian respiratory allergens belongs to the lipocalin family of proteins. By this time, 19 respiratory mammalian lipocalin allergens have been registered in the WHO/IUIS Allergen Nomenclature Database. Originally, lipocalins, small extracellular proteins (molecular mass ca. 20 kDa), were characterized as transport proteins but they are currently known to exert a variety of biological functions. The three-dimensional structure of lipocalins is well-preserved, and lipocalin allergens can exhibit high amino acid identities, in several cases more than 50%. Lipocalins contain an internal ligand-binding site where they can harbor small principally hydrophobic molecules. Another characteristic feature is their capacity to bind to specific cell-surface receptors. In all, the physicochemical properties of lipocalin allergens do not offer any straightforward explanations for their allergenicity. Allergic sensitization begins at epithelial barriers where diverse insults through pattern recognition receptors awaken innate immunity. This front-line response is manifested by epithelial barrier-associated cytokines which together with other components of immunity can initiate the sensitization process. In the following, the crucial factor in allergic sensitization is interleukin (IL)-4 which is needed for stabilizing and promoting the type 2 immune response. The source for IL-4 has been searched widely. Candidates for it may be non-professional antigen-presenting cells, such as basophils or mast cells, as well as CD4+ T cells. The synthesis of IL-4 by CD4+ T cells requires T cell receptor engagement, i.e., the recognition of allergen peptides, which also provides the specificity for sensitization. Lipocalin and innate immunity-associated cell-surface receptors are implicated in facilitating the access of lipocalin allergens into the immune system. However, the significance of this for allergic sensitization is unclear, as the recognition by these receptors has been found to produce conflicting results. As to potential adjuvants associated with mammalian lipocalin allergens, the hydrophobic ligands transported by lipocalins have not been reported to enhance sensitization while it is justified to suppose that lipopolysaccharide plays a role in it. Taken together, type 2 immunity to lipocalin allergens appears to be a harmful immune response resulting from a combination of signals involving both the innate and adaptive immunities.

Fundamentals and Methods for T- and B-Cell Epitope Prediction

Adaptive immunity is mediated by T- and B-cells, which are immune cells capable of developing pathogen-specific memory that confers immunological protection. Memory and effector functions of B- and T-cells are predicated on the recognition through specialized receptors of specific targets (antigens) in pathogens. More specifically, B- and T-cells recognize portions within their cognate antigens known as epitopes. There is great interest in identifying epitopes in antigens for a number of practical reasons, including understanding disease etiology, immune monitoring, developing diagnosis assays, and designing epitope-based vaccines. Epitope identification is costly and time-consuming as it requires experimental screening of large arrays of potential epitope candidates. Fortunately, researchers have developed in silico prediction methods that dramatically reduce the burden associated with epitope mapping by decreasing the list of potential epitope candidates for experimental testing. Here, we analyze aspects of antigen recognition by T- and B-cells that are relevant for epitope prediction. Subsequently, we provide a systematic and inclusive review of the most relevant B- and T-cell epitope prediction methods and tools, paying particular attention to their foundations.

A Specific Mixture of Fructo-Oligosaccharides and Bifidobacterium breve M-16V Facilitates Partial Non-Responsiveness to Whey Protein in Mice Orally Exposed to β-Lactoglobulin-Derived Peptides

Oral tolerance is a promising approach for allergy prevention in early life, but it strongly depends on allergen exposure and proper immune environment. Small tolerance-inducing peptides and dietary immunomodulatory components may comprise an attractive method for allergy prevention in at-risk infants. This study aimed to investigate whether early oral exposure to β-lactoglobulin-derived peptides (BLG-peptides) and a specific synbiotic mixture of short- and long- chain fructo-oligosaccharides (scFOS/lcFOS, FF) and Bifidobacterium breve (Bb) M-16V (FF/Bb) can prevent cow’s milk allergy (CMA). Three-week-old female C3H/HeOuJ mice were orally exposed to phosphate buffered saline (PBS), whey protein, or a mixture of four synthetic BLG-peptides combined with a FF/Bb-enriched diet prior to intragastric sensitization with whey protein and cholera toxin. To assess the acute allergic skin response and clinical signs of allergy, mice were challenged intradermally with whole whey protein. Serum immunoglobulins were analyzed after a whey protein oral challenge. Cytokine production by allergen-reactivated splenocytes was measured and changes in T cells subsets in the spleen, mesenteric lymph nodes, and intestinal lamina propria were investigated. Pre-exposing mice to a low dosage of BLG-peptides and a FF/Bb-enriched diet prior to whey protein sensitization resulted in a significant reduction of the acute allergic skin response to whey compared to PBS-pretreated mice fed a control diet. Serum immunoglobulins were not affected, but anaphylactic symptom scores remained low and splenocytes were non-responsive in whey-induced cytokine production. In addition, preservation of the T_h1/T_h2 balance in the small intestine lamina propria was a hallmark of the mechanism underlying the protective effect of the BLG-peptides–FF/Bb intervention. Prior exposure to BLG-peptides and a FF/Bb-enriched diet is a promising approach for protecting the intestinal T_h1/T_h2 balance and reducing the allergic response to whole whey protein. Therefore, it might have implications for developing successful nutritional strategies for CMA prevention.

Sesamin attenuates allergic airway inflammation through the suppression of nuclear factor-kappa B activation

The aim of the present study is to determine the role of sesamin, the most abundant lignan in sesame seed oil, on the regulation of allergic airway inflammation in a murine asthma model. A BALB/c mouse model with allergic asthma was used to evaluate the effects of sesamin on nuclear factor-kappa B (NF-κB) activation. An enzyme-linked immunosorbent assay was used to determine protein expression in bronchoalveolar lavage (BAL) fluids. Hematoxylin and eosin staining was performed to examine histological changes. Moreover, western blot analysis was used to detect the expression of proteins in tissues. Prior to administering sesamin, the mice developed the following pathophysiological features of asthma: An increase in the number of inflammatory cells, increased levels of interleukin (IL)-4, IL-5 and IL-13, decreased levels of interferon-γ in BAL fluids and lung tissues, increased immunoglobulin E (IgE) levels in the serum and an increased activation of NF-κB in lung tissues. Following treatment with sesamin, the mice had evidently reduced peribronchiolar inflammation and airway inflammatory cell recruitment, inhibited production of several cytokines in BAL fluids and lung tissues, and decreased IgE levels. Following inhalation of ovalbumin, the administration of sesamin also inhibited the activation of NF-κB. In addition, sesamin administration reduced the phosphorylation of p38 mitogen-activated protein kinases (MAPKs). The present study demonstrates that sesamin decreases the activation of NF-κB in order to attenuate allergic airway inflammation in a murine model of asthma, possibly via the regulation of phosphorylation of p38 MAPK. These observations provide an important molecular mechanism for the potential use of sesamin in preventing and/or treating asthma, as well as other airway inflammatory disorders.

On Peptides and Altered Peptide Ligands: From Origin, Mode of Action and Design to Clinical Application (Immunotherapy)

T lymphocytes equipped with clonotypic T cell antigen receptors (TCR) recognize immunogenic peptides only when presented in the context of their own major histocompatibility complex (MHC) molecules. Peptide loading to MHC molecules occurs in intracellular compartments (ER for class I and MIIC for class II molecules) and relies on the interaction of the respective peptides and peptide binding pockets on MHC molecules. Those peptide residues not engaged in MHC binding point towards the TCR screening for possible peptide MHC complex binding partners. Natural or intentional modification of both MHC binding registers and TCR interacting residues of peptides – leading to the formation of altered peptide ligands (APLs) – might alter the way peptides interact with TCRs and hence influence subsequent T cell activation events, and consequently T cell effector functions. This review article summarizes how APLs were detected and first described, current concepts of how APLs modify T cellular signaling, which biological mechanisms might force the generation of APLs in vivo, and how peptides and APLs might be used for the benefit of patients suffering from allergic or autoimmune diseases.

Ginsenoside Rh2 attenuates allergic airway inflammation by modulating nuclear factor-κB activation in a murine model of asthma

Allergic asthma is a chronic inflammatory disease that is regulated by coordination of T-helper type 2 cell cytokines and inflammatory signaling molecules. Ginsenoside Rh2 (G-Rh2) is an active component of ginseng with anti-inflammatory and anti-tumor effects. The aim of the present study was to determine the inhibitory effects of G-Rh2 on allergic airway inflammation in a murine model of asthma, in which mice develop the following pathophysiological features of asthma: Increased abundance of inflammatory cells; increased levels of interleukin-4 (IL-4), IL-5 and IL-13; decreased abundance of interferon gamma in the bronchoalveolar lavage fluid and lung tissue; increased total and ovalbumin (OVA)-specific immunoglobulin E (IgE) levels in the serum; increased airway hyperresponsiveness (AHR); and activation of nuclear factor kappa B (NF-κB) in lung tissue. In the asthmatic mice, administration of G-Rh2 markedly reduced peribronchiolar inflammation, recruitment of airway inflammatory cells, cytokine production, total and OVA-specific IgE levels and AHR. G-Rh2 administration inhibited NF-κB activation and p38 mitogen-activated protein kinase (MAPK) phosphorylation induced by OVA inhalation. These results suggested that G-Rh2 attenuates allergic airway inflammation by regulating NF-κB activation and p38 MAPK phosphorylation. The present study identified the molecular mechanisms of action of G-Rh2, which supported the potential use of G-Rh2 to prevent and/or treat asthma and other airway inflammatory disorders.

Human CD4+ T cell responses to the dog major allergen Can f 1 and its human homologue tear lipocalin resemble each other

Lipocalin allergens form a notable group of proteins, as they contain most of the significant respiratory allergens from mammals. The basis for the allergenic capacity of allergens in the lipocalin family, that is, the development of T-helper type 2 immunity against them, is still unresolved. As immunogenicity has been proposed to be a decisive feature of allergens, the purpose of this work was to examine human CD4+ T cell responses to the major dog allergen Can f 1 and to compare them with those to its human homologue, tear lipocalin (TL). For this, specific T cell lines were induced in vitro from the peripheral blood mononuclear cells of Can f 1-allergic and healthy dog dust-exposed subjects with peptides containing the immunodominant T cell epitopes of Can f 1 and the corresponding TL peptides. We found that the frequency of Can f 1 and TL-specific T cells in both subject groups was low and close to each other, the difference being about two-fold. Importantly, we found that the proliferative responses of both Can f 1 and TL-specific T cell lines from allergic subjects were stronger than those from healthy subjects, but that the strength of the responses within the subject groups did not differ between these two antigens. Moreover, the phenotype of the Can f 1 and TL-specific T cell lines, determined by cytokine production and expression of cell surface markers, resembled each other. The HLA system appeared to have a minimal role in explaining the allergenicity of Can f 1, as the allergic and healthy subjects' HLA background did not differ, and HLA binding was very similar between Can f 1 and TL peptides. Along with existing data on lipocalin allergens, we conclude that strong antigenicity is not decisive for the allergenicity of Can f 1.

Peptide-based immunotherapy: a novel strategy for allergic disease

The T-cell component of the antigen-specific immune response is the target of various novel interventions to modify chronic immunologic disorders, such as allergic diseases. Recent clinical trials have evaluated the safety and efficacy of therapeutic vaccines consisting of short, synthetic, allergen-derived peptides, corresponding to T-cell epitopes from the eliciting antigen. The main advantage of such an approach is the reduction in systemic, immunoglobulin E-mediated adverse events compared with existing whole allergen immunotherapy, often referred to as 'allergy shots'. T-cell peptide epitopes, although capable of inducing immunologic tolerance, are short linear structures that have reduced ability to cross-link mast cell- and basophil-bound immunoglobulin E. The precise mechanism of tolerance induction remains incompletely defined. However, recent data indicate that peptide therapy induces/expands a population of antigen-specific regulatory T-cells. A novel form of treatment combining efficacy with a substantially decreased occurrence of adverse events is likely to have a major impact on the management and prevalence of allergic diseases. Furthermore, the principles of epitope-specific therapy hold promise for the development of therapeutic vaccines for the treatment of autoimmune diseases.

Combination peptide immunotherapy based on T-cell epitope mapping reduces allergen-specific IgE and eosinophilia in allergic airway inflammation

Peptide immunotherapy using soluble peptides containing allergen-derived immunodominant T-cell epitopes holds therapeutic promise for allergic asthma. Previous studies in BALB/c mice using the immunodominant peptide epitope of chicken ovalbumin (p323-339) have been unable to demonstrate therapeutic effects in ovalbumin-induced allergic airway inflammation. We have previously shown that intravenous application of p323-339 can effectively tolerise p323-339-reactive T cells in a non-allergic model in C57BL/6 mice. This study aimed to assess the effects of using p323-339 immunotherapy in a C57BL/6 model of ovalbumin-induced allergic airway inflammation, identify any additional epitopes recognized by the ovalbumin-responsive T-cell repertoire in C57BL/6 mice and assess the effects of combination peptide immunotherapy in this model. Ovalbumin-reactive T-cell lines were generated from ovalbumin-immunized C57BL/6 mice and proliferative responses to a panel of overlapping peptides covering the ovalbumin sequence were assessed. Soluble peptides (singly or combined) were administered intravenously to C57BL/6 mice before the induction of ovalbumin-induced allergic airway inflammation. Peptide immunotherapy using the 323-339 peptide alone did not reduce the severity of allergic airway inflammation. An additional immunodominant T-cell epitope in ovalbumin was identified within the 263-278 sequence. Combination peptide immunotherapy, using the 323-339 and 263-278 peptides together, reduced eosinophilia in the bronchoalveolar lavage and ovalbumin-specific IgE, with apparent reductions in interleukin-5 and interleukin-13. Characterization of the T-cell response to a model allergen has allowed the development of combination peptide immunotherapy with improved efficacy in allergic airway inflammation. This model holds important potential for future mechanistic studies using peptide immunotherapy in allergy.

Mammalian lipocalin allergens--insights into their enigmatic allergenicity

Most of the important mammal-derived respiratory allergens, as well as a milk allergen and a few insect allergens, belong to the lipocalin protein family. As mammalian lipocalin allergens are found in dander, saliva and urine, they disperse effectively and are widely present in the indoor environments. Initially, lipocalins were characterized as transport proteins for small, principally hydrophobic molecules, but now they are known to be involved in many other biological functions. Although the amino acid identity between lipocalins is generally at the level of 20-30%, it can be considerably higher. Lipocalin allergens do not exhibit any known physicochemical, functional or structural property that would account for their allergenicity, that is, the capacity to induce T-helper type 2 immunity against them. A distinctive feature of mammalian lipocalin allergens is their poor capacity to stimulate the cellular arm of the human or murine immune system. Nevertheless, they induce IgE production in a large proportion of atopic individuals exposed to the allergen source. The poor capacity of mammalian lipocalin allergens to stimulate the cellular immune system does not appear to result from the function of regulatory T cells. Instead, the T cell epitopes of mammalian lipocalin allergens are few and those examined have proved to be suboptimal. Moreover, the frequency of mammalian lipocalin allergen-specific CD4(+) T cells is very low in the peripheral blood. Importantly, recent research suggests that the lipocalin allergen-specific T cell repertoires differ considerably between allergic and healthy subjects. These observations are compatible with our hypothesis that the way CD4(+) T-helper cells recognize the epitopes of mammalian lipocalin allergens may be implicated in their allergenicity. Indeed, as several lipocalins exhibit homologies of 40-60% over species, mammalian lipocalin allergens may be immunologically at the borderline of self and non-self, which would not allow a strong anti-allergenic immune response against them.

Novel immunogenic peptides elicit systemic anaphylaxis in mice: implications for peptide vaccines

Peptide-based therapies are showing increasing potential for the development of vaccines and in the treatment of many important diseases. We previously reported two peptide conjugate vaccines that protected mice against pneumococcal disease. During this study, we observed an unexpected phenomenon; several vaccine candidates induced a rapid, fatal anaphylaxis after booster injection of the peptide conjugate. Further investigation indicated the reaction was mediated by the production of peptide-specific IgE and the release of histamine. Notably, among seven peptides tested, all of which bound the same mAb that selected them from a phage library, only four elicited this severe reaction. Sequence alignment analysis of all peptides revealed unique clusters of acidic amino acid residues in the allergenic peptides. Substitution of the acidic amino acid residues, ED, of peptide MP2 with their amine equivalents, QN, eliminated the anaphylactic effects but did not affect the production of peptide-specific IgG. These results have important implications for both the study of allergens and the development of future peptide-based therapies.

The good, the bad and the ugly: how altered peptide ligands modulate immunity

BACKGROUND

The basis of T cell immune responses is the specific recognition of an immunogenic peptide epitope by a T cell receptor. Peptide alterations of such T cell epitopes with single or few amino acid variations can have drastic effects on the outcome of this recognition. These altered peptide ligands can act as modulators of immune responses as they are capable of downregulating or upregulating responses.

OBJECTIVE/METHODS

We review how altered peptide ligands can have 'good' 'bad' and 'ugly' outcomes in treating diseases.

RESULTS/CONCLUSION

Altered peptide ligands have been used as immunotherapeutics in autoimmune (and allergic) diseases, infectious diseases and cancer. In the next five years we anticipate seeing a number of altered peptide ligands in clinical trials, progressing from contradictory classifications of good, bad or ugly, to the exciting outcome of 'useful'.

Immunotherapeutic potential of the immunodominant T-cell epitope of lipocalin allergen Bos d 2 and its analogues

Lipocalin allergens, which contain most of the important animal-derived respiratory sensitizers, induce T helper type 2 (Th2) deviation, but the reasons for this are not clear. To explore the prospects for peptide-based allergen immunotherapy and to elucidate the characteristics of the immunodominant epitope of Bos d 2, BALB/c mice were immunized with a peptide containing the epitope, peptides containing its analogues, peptides from the corresponding regions of other lipocalin proteins, and peptides with a homologous sequence. We observed that murine spleen cells recognized the immunodominant epitope of Bos d 2, p127-142, in almost the same way as human Bos d 2-specific T cells did. Enzyme-linked immunosorbent spot-forming cell assay (ELISPOT) analyses showed that p127-142 and a corresponding peptide from horse Equ c 1 induced a Th2-deviated cellular response, whereas a homologous bacterial peptide from Spiroplasma citri induced a Th0-type response. Interestingly, the spleen cell response to the bacterial peptide and p127-142 was cross-reactive, that is, able to induce reciprocally the proliferation and cytokine production of primed spleen cells in vitro. More importantly, the peptides were able to skew the phenotype of T cells primed with the other peptide. Our results suggest that modified peptides can be useful in allergen immunotherapy.

Potential of an altered peptide ligand of lipocalin allergen Bos d 2 for peptide immunotherapy

BACKGROUND

Peptide immunotherapy is a promising alternative for treating allergic diseases. One way to enhance the efficacy of peptide immunotherapy is to use altered peptide ligands (APLs) that contain amino acid substitutions compared with the natural peptide.

OBJECTIVE

To evaluate the potential of an APL of the immunodominant epitope of lipocalin allergen Bos d 2 for peptide immunotherapy.

METHODS

Peripheral blood CD4(+) T-cell responses of 8 HLA-DR4-positive subjects to the natural ligand of Bos d 2 (p127-142) or to an APL (pN135D) were analyzed by MHC class II tetramer staining after in vitro expansion with the peptides. Long-term T-cell lines (TCLs) were induced with the peptides, and the cytokine production, cross-reactivity, and T-cell receptor Vbeta subtype expression of the TCLs were analyzed.

RESULTS

CD4(+) T cells specific for both p127-142 and pN135D were readily detected in peripheral blood after a single in vitro stimulation. Whereas the TCLs induced with p127-142 were T(H)2/T(H)0-deviated, those induced with pN135D were T(H)1/T(H)0-deviated and highly cross-reactive with p127-142. Moreover, the pN135D-induced TCLs appeared to use a broader repertoire of T-cell receptor Vbeta subtypes than those induced with p127-142.

CONCLUSION

An APL of an immunodominant allergen epitope was able to induce a novel T(H)1-deviated T-cell population cross-reactive with the natural epitope in vitro. This cell population could have a therapeutic immunomodulatory function in vivo through bystander suppression.

CLINICAL IMPLICATIONS

These results support the idea that altered peptide ligands may be used to enhance the efficacy of peptide immunotherapy.

Epitope characterization of ovalbumin in BALB/c mice using different entry routes

Ovalbumin (OVA) is known as a major allergen in egg white. A number of studies have reported the partial T and B cell epitope mapping of OVA using murine models and allergic patients' sera. Recently, we have reported the IgE-binding regions of the entire OVA molecule using egg allergic patients' sera. However, the entire epitope mapping of OVA in a murine model has not been completed yet. In the present study, BALB/c mice were administered a solution of OVA using three different entry routes (oral, intraperitoneal and subcutaneous) with their respective adjuvant (cholera toxin, aluminum hydroxide and Freund's adjuvant). Two nitrocellulose membranes containing 188 overlapping synthetic peptides (with a length of 12 amino acids and an offset of two amino acids) covering the primary sequence of OVA, were probed with the three different BALB/c mice antisera. Antisera obtained from orally challenged mice identified eight IgE epitope regions, i.e. I53D60; V77R84; S103E108; G127T136; E275V280; G301F306; I323A332 and A375S384, while sera raised by intraperitoneal and subcutaneous injections exhibited two (K55D60 and K277L282) and five (K55R58; G127T136; K279L282; T303S308 and I323A332) IgE binding sequences, respectively. The residues critical for the epitope-paratope interactions were finely characterized using the oral immunization serum. Analysis of IgE binding epitopes in mice provides us with potential strategies for design of specific immunotherapy.

Prospects for peptide-based immunotherapy for dog allergy

PURPOSE OF REVIEW

Tolerance to ubiquitous environmental substances, allergens, can be accomplished with specific immunotherapy. Conducting therapy with allergen peptides helps to avoid immediate allergic reactions. Dogs are a source of important indoor allergens, which necessitates the development of effective modes of therapy against the allergy they cause.

RECENT FINDINGS

The human T-cell epitopes of the major dog allergen Can f 1 were determined recently. They were found to be distributed in seven epitope regions along the molecule. For the peptide immunotherapy of dog allergy, using a pool of seven peptides, one from each of the epitope regions of Can f 1, seems at present to be the best approach. As Can f 1 is not as immunodominant as the main allergens of some other mammals, it remains to be seen whether peptides from other dog allergens should be included in the pool.

SUMMARY

The use of a pool of seven peptides from the T-cell epitope regions of Can f 1 is likely to be feasible for treating dog allergy in a great majority of Caucasian populations. In the future, patient-tailored preparations of variants of the T-cell epitope-containing peptides may offer a way to enhance the efficacy of peptide-based immunotherapy.

Preliminary data on Pemphigus vulgaris treatment by a proteomics-defined peptide: a case report

Background

Although described by Hippocrates in 400 B.C., pemphigus disease still needs a safe therapeutical approach, given that the currently used therapies (i.e. corticosteroids and immunosuppressive drugs) often provoke collateral effects. Here we present preliminary data on the possible use of a proteomics derived desmoglein peptide which appears promising in halting disease progression without adverse effects.

Methods

The low-similarity Dsg3_49–60REWVKFAKPCRE peptide was topically applied for 1 wk onto a lesion in a patient with a late-stage Pemphigus vulgaris (PV) complicated by diabetes and cataract disease. The peptide was applied as an adjuvant in combination with the standard corticosteroid-based immunosuppressive treatment.

Results

After 1 wk, the treated PV eroded lesion appeared dimensionally reduced and with an increased rate of re-epithelization when compared to adjacent non-treated lesions. Short-term benefits were: decrease of anti-Dsg antibody titer and reduction of the corticosteroid dosage. Long-term benefits: after two years following the unique 1-wk topical treatment, the decrease of anti-Dsg antibody titer persists. The patient is still at the low cortisone dosage. Adverse effects: no adverse effect could be monitored.

Conclusion

With the limits inherent to any preliminary study, this case report indicates that topical treatment with Dsg3_49–60REWVKFAKPCRE peptide may represent a feasible first step in the search for a simple, effective and safe treatment of PV.

Mechanisms of allergen specific immunotherapy--T-cell tolerance and more

Specific immune suppression and induction of tolerance are essential processes in the regulation and circumvention of immune defence. The balance between allergen-specific T-regulatory (Treg) cells and T helper 2 cells appears to be decisive in the development of allergic and healthy immune response against allergens. Treg cells consistently represent the dominant subset specific for common environmental allergens in healthy individuals. In contrast, there is a high frequency of allergen-specific T helper 2 cells in allergic individuals. A decrease in interleukin (IL)-4, IL-5 and IL-13 production by allergen-specific CD4+ T cells due to the induction of peripheral T cell tolerance is the most essential step in allergen-specific immunotherapy (SIT). Suppressed proliferative and cytokine responses against the major allergens are induced by multiple suppressor factors, such as cytokines like IL-10 and transforming growth factor (TGF)-beta and cell surface molecules like cytotoxic T lymphocyte antigen-4, programmed death-1 and histamine receptor 2. There is considerable rationale for targeting T cells to increase efficacy of SIT. Such novel approaches include the use of modified allergens produced using recombinant DNA technology and adjuvants or additional drugs, which may increase the generation of allergen-specific peripheral tolerance. By the application of the recent knowledge in Treg cells and related mechanisms of peripheral tolerance, more rational and safer approaches are awaiting for the future of prevention and cure of allergic diseases.

Enzyme-linked immunosorbent assay of a linear, recombinant peptide designed for immunotherapy of Japanese cedar pollinosis

INTRODUCTION

Cry-consensus peptide, a recombinant T-cell epitope peptide for immunotherapy of Japanese cedar pollinosis, is a linear peptide that does not have disulfide bonds because no cysteine residue exists in the molecule. We examined whether a sandwich enzyme-linked immunosorbent assay (ELISA) could be performed for linear peptides such as Cry-consensus peptide.

METHODS

The 3-dimensional conformation of Cry-consensus peptide was examined by (1)H NMR analysis. Nineteen monoclonal antibodies (mAbs) that recognized various domains of Cry-consensus peptide were established to use in a sandwich ELISA. The relationship between the recognition sites of mAbs and the sensitivity of the ELISA was investigated to optimize the selection of the combination of the capture and the detection antibodies. ELISA inhibitors in serum and plasma were also studied to improve the stability and the sensitivity of determination.

RESULTS

(1)H NMR analysis of Cry-consensus peptide suggested that Cry-consensus peptide molecule had no portions with rigid conformation. The sensitivity of the ELISA showed a good correlation with the distance between the respective binding sites of the capture and the detection antibodies. Human serum albumin and alpha1-acid glycoprotein strongly inhibited the binding of the capture mAb to Cry-consensus peptide in a dose-dependent manner, and heparin also inhibited the binding in the concentration at which it is used as anticoagulant. Taken together, the findings indicated that an optimized method showed good linearity and minimal variation from 0 to 1000 ng/ml of Cry-consensus peptide.

DISCUSSION

These data indicate that this method is useful for monitoring Cry-consensus peptide concentrations in plasma or serum.

Animal models of allergen-induced tolerance in asthma: are T-regulatory-1 cells (Tr-1) the solution for T-helper-2 cells (Th-2) in asthma?

Non-specific anti-inflammatory medication is actually the treatment of choice for controlling the T-helper type 2 (Th-2) cell-driven airway inflammation in asthma. The induction of counterbalancing Th-1 cell clones, long considered a promising approach for immunotherapy, has failed to fulfil its promise because of potentially detrimental side-effects. This is therefore probably not a valid option for the treatment of asthma. With the increasing awareness that active immune mechanisms exist to control inflammatory responses, interest rises to investigate whether these can be exploited to control allergen-induced airway disease. The induction of antigen-specific T cells with suppressive characteristics (regulatory T cells) is therefore a potentially interesting approach. These regulatory T cells mediate tolerance in healthy, non-atopic individuals and have the potential of becoming an effective means of preventing allergen-induced airway inflammation and possibly of suppressing ongoing allergic immune responses. Here we review the available knowledge about allergen-induced suppressive immunity obtained from animal models taking into account the different developmental stages of allergic airway disease.

Is Genetic Vaccination against Allergy Possible?

Genetic immunization has proven a powerful method to induce antiallergic immune responses. The underlying functional principle has been described to be based on the recruitment of allergen-specific Th1 cells, CD8+ cells and the establishment of a Th1 cytokine milieu, which prevent the development of a Th2-biased response in a protective setup and can balance an ongoing Th2-type response in a therapeutic situation. Genetic immunization with plasmid DNA offers innovative solutions to the major problems associated with protein immunization, such as crosslinking of pre-existing immunoglobulin E on mast cells/basophils or induction of de novo synthesis of immunoglobulin E by the protein immunization itself. It easily enables the routine production of hypoallergenic vaccines, which do not translate native allergens, thus avoiding potential anaphylactic side effects. DNA vaccines can also be applied as mixtures of single vaccines, making them interesting candidates for treatment based on component-resolved diagnosis, followed by an individualized therapy with the relevant allergens. In addition to the description of up-to-date allergen gene vaccine approaches, this review gives an overview of animal studies dealing with the following topics: danger signals as the inherent adjuvant properties, methods to optimize the vaccine immunogenicity, modulation of the immune response, nonparenteral applications and low-dose vaccination strategies.

T cell epitope-containing peptides of the major dog allergen Can f 1 as candidates for allergen immunotherapy

One prerequisite for developing peptide-based allergen immunotherapy is knowing the T cell epitopes of an allergen. In this study, human T cell reactivity against the major dog allergen Can f 1 was investigated to determine peptides suitable for immunotherapy. Seven T cell epitope regions (A-G) were found in Can f 1 with specific T cell lines and clones. The localization of the epitope regions shows similarities with those of the epitopes found in Bos d 2 and Rat n 1. On average, individuals recognized three epitopes in Can f 1. Our results suggest that seven 16-mer peptides (p15-30, p33-48, p49-64, p73-88, p107-122, p123-138, and p141-156), each from one of the epitope regions, show widespread T cell reactivity in the population studied, and they bind efficiently to seven HLA-DRB1 molecules (DRB1*0101, DRB1*0301, DRB1*0401, DRB1*0701, DRB1*1101, DRB1*1301, and DRB1*1501) predominant in Caucasian populations. Therefore, these peptides are potential candidates for immunotherapy of dog allergy.

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.

Oral administration of a T cell epitope inhibits symptoms and reactions of allergic rhinitis in Japanese cedar pollen allergen-sensitized mice

Although the concept of a T cell epitope in specific immunoprophylaxis was proposed more than a decade ago, it had not been well demonstrated since then that a T cell epitope inhibits symptoms and reactions of allergic disease in animal models. In this study, we have established a system to evaluate symptoms and reactions of allergic rhinitis in mice, and investigated whether oral administration of a T cell epitope relieves sensitized mice of allergic rhinitis. P2-246-259 (RAEVSYVHVNGAKF) is a BALB/c mouse T-cell epitope of Cry j 2, which is a major Japanese cedar (Cryptomeria japonica) pollen allergen. Mice were administered orally with 200 microg/animal of P2-246-259 four times within 2 weeks before sensitization, and sensitized intranasally with Cry j 2 twice. Of the cardinal symptoms of allergic rhinitis, we assessed sneezing and airway obstruction, but could not estimate rhinorrhea or pruritus. Sneezing frequency was significantly increased by challenge with Cry j 2. Concerning allergic reactions, vascular permeability of the nasal mucosa in the early phase and hyperreactivity to histamine in the late phase were also exacerbated by the challenge. These symptoms and reactions of allergic rhinitis were significantly inhibited by oral administration of P2-246-259. These results indicate utility of mice as models for allergic rhinitis; furthermore, the effects of P2-246-259 on allergic rhinitis imply that oral administration of a T cell epitope is a promising approach for specific immunoprophylaxis.

Treatment with Flt3 ligand plasmid reverses allergic airway inflammation in ovalbumin-sensitized and -challenged mice

We have previously reported that fms-like tyrosine kinase 3 ligand (Flt3-L) prevents and reverses established allergic airway inflammation in an ovalbumin (OVA) induced mouse model of asthma. In this study, we investigated the effect of pUMVC3-hFLex, a plasmid, mammalian expression vector for the secretion of Flt3-L on the same mouse model as well as the duration of the effect of the treatment. Allergic airway inflammation to OVA was established in BALB/c mice. OVA-sensitized mice received three intramuscular (i.m.) injections of 200 mug pUMVC3-hFLex over 10 days. The response to pUMVC3-hFLex therapy was assessed based on airway hyperresponsiveness (AHR) to methacholine and inflammation, measured as serum cytokine and immunoglobulins (Ig) levels, and the total and differential cells in bronchoalveolar lavage fluid (BALF). pUMVC3-hFLex treatment completely reversed established AHR (P<0.01) and this effect lasted for at least 24 days after the last treatment injection (P<0.001). pUMVC3-hFLex treatment significantly increased BALF interferon-gamma (IFN-gamma) (P<0.01), serum interleukin (IL)-10 (P<0.01) and anti-OVA IgG2a levels (P<0.01). In contrast, serum IL-4 and IgE levels were significantly reduced (P<0.05). Total BALF cellularity, eosinophiles counts and BALF IL-5 levels were also reduced (P<0.01). pUMVC3-hFLex treatment can reverse established experimental asthma and might provide a novel approach for treating asthma.

Novel immunomodulatory oligonucleotides prevent development of allergic airway inflammation and airway hyperresponsiveness in asthma

Oligodeoxynucleotides containing unmethylated CpG motifs (CpG oligos) have been shown to prevent development of allergic airway inflammation and airway hyperresponsiveness (AHR) in mouse models of asthma. Recently, we reported immunomodulatory oligonucleotides (IMOs) containing novel structures (immunomers) and synthetic immunostimulatory CpR (R=2'-deoxy-7-deazguanosine) motifs show potent stimulatory activity with distinct cytokine secretion profiles. Since type 2 T cells predominate in asthma and increase in type 1 cells can prevent the differentiation of naïve T lymphocytes to a type 2 phenotype, we hypothesized that IMOs can prevent the development of allergic airway inflammation and AHR in the ovalbumin (OVA)-sensitized and challenged mouse model. We found that co-administration of novel IMOs during OVA-sensitization abrogated both early and late allergic responses (LARs). AHR to methacholine was also blocked with IMO treatment. Analysis of bronchoalveolar lavage (BAL) fluid of mice treated with IMOs demonstrated complete reduction in eosinophils, with concomitant decreases in both serum and BAL fluid IL-4, IL-5, and IL-6 levels. In addition, there was a significant reduction in serum IL-10 levels. IMOs, in general, significantly attenuated the rise in serum IgE levels. In comparison, IMOs showed a significantly more potent effect on early and late allergic response than a conventional CpG oligo in this model. These data suggest that the treatment with these novel IMOs prevents OVA-induced allergic airway inflammation and AHR in asthma in the mouse and may provide a useful agent in the treatment of human asthma.

Genes of tolerance

Activation-induced cell death, anergy and/or immune response modulation by T-regulatory cells (T(Reg)) are essential mechanisms of peripheral T-cell tolerance. There is growing evidence that anergy, tolerance and active suppression are not entirely distinct, but rather, represent linked mechanisms possibly involving the same cells and multiple suppressor mechanisms. Skewing of allergen-specific effector T cells to T(Reg) cells appears as a crucial event in the control of healthy immune response to allergens and successful allergen-specific immunotherapy. The T(Reg) cell response is characterized by abolished allergen-induced specific T-cell proliferation and suppressed T helper 1 (Th1)- and Th2-type cytokine secretion. In addition, mediators of allergic inflammation that trigger cAMP-associated G-protein coupled receptors, such as histamine receptor 2 may contribute to peripheral tolerance mechanisms. The increased levels of interleukin-10 (IL-10) and transforming growth factor-beta (TGF-beta) that are produced by T(Reg) cells potently suppress immunoglobulin E (IgE) production, while simultaneously increasing production of noninflammatory isotypes IgG4 and IgA, respectively. In addition, T(Reg) cells directly or indirectly suppress effector cells of allergic inflammation such as mast cells, basophils and eosinophils. In conclusion, peripheral tolerance to allergens is controlled by multiple active suppression mechanisms. It is associated with regulation of antibody isotypes and effector cells to the direction of a healthy immune response and opens a window for novel therapies of allergic diseases.

Antigen stimulation of TH2 cells augments acute bacterial sinusitis in mice

BACKGROUND

Previously, we showed that an ongoing nasal allergic response augmented bacterial sinusitis in mice. In those experiments mice were sensitized to ovalbumin (OVA) by means of intraperitoneal injections of OVA-alum and then exposed to OVA intranasally before being infected with Streptococcus pneumoniae.

OBJECTIVE

We sought to study the importance of TH2 cells and to eliminate potential alum effects.

METHODS

In this study we sensitized mice by adoptively transferring OVA-specific TH2- or TH1-skewed cells.

RESULTS

TH2 passive sensitization followed by intranasal OVA showed a robust local eosinophilic response (5-fold increase) compared with that seen in mice with only TH2 passive sensitization alone (P <.001). Mice with TH2 passive sensitization and intranasal OVA exposure followed by infection showed an increase in the number of recovered S pneumoniae (P <.05) and an increase in sinus inflammation compared with that seen in those with infection alone (P <.01). In contrast, mice passively sensitized with TH1 followed by intranasal OVA exposure and infection showed no significant increase in the recovery of S pneumoniae and sinus inflammation compared with those with infection alone.

CONCLUSIONS

These data support the importance of antigen-stimulated TH2 cells in the augmented response to infection in allergic mice. Whether the increased infection is related to the direct effect of TH2 cells and their cytokines or subsequent recruitment of other cells, such as eosinophils, will be determined in further studies.

Flt-3 ligand reverses late allergic response and airway hyper-responsiveness in a mouse model of allergic inflammation

Flt3 ligand (Flt3-L) is a growth factor for dendritic cells and induces type 1 T cell responses. We recently reported that Flt3-L prevented OVA-induced allergic airway inflammation and suppressed late allergic response and airway hyper-responsiveness (AHR). In the present study we examined whether Flt3-L reversed allergic airway inflammation in an established model of asthma. BALB/c mice were sensitized and challenged with OVA, and AHR to methacholine was established. Then mice with AHR were randomized and treated with PBS or 6 microg of Flt3-L i.p. for 10 days. Pulmonary functions and AHR to methacholine were examined after rechallenge with OVA. Treatment with Flt3-L of presensitized mice significantly suppressed (p < 0.001) the late allergic response, AHR, bronchoalveolar lavage fluid total cellularity, absolute eosinophil counts, and inflammation in the lung tissue. There was a significant decrease in proinflammatory cytokines (TNF-alpha, IL-4, and IL-5) in bronchoalveolar lavage fluid, with a significant increase in serum IL-12 and a decrease in serum IL-5 levels. There was no significant effect of Flt3-L treatment on serum IL-4 and serum total IgE levels. Sensitization with OVA significantly increased CD11b(+)CD11c(+) cells in the lung, and this phenomenon was not significantly affected by Flt3-L treatment. These data suggest that Flt3-L can reverse allergic airway inflammation and associated changes in pulmonary functions in murine asthma model.

Selection of similar naive T cell repertoires but induction of distinct T cell responses by native and modified antigen

To study the T cell responses induced by native and modified Ag, we have followed in vivo TCR selection and cytokine profile of T cells, as well as the isotype of induced Abs, in response to the model Ag hen egg-white lysozyme (HEL) and its reduced and carboxymethylated form (RCM-HEL). RCM-HEL induces in vivo a T cell response focused on the same immunodominant determinant characterizing the response to native HEL, but further skewed to the Th1 pathway. No difference between HEL and RCM-HEL could be observed in the efficiency of processing, nor in the type of APCs involved. In vivo experiments show that coimmunization with HEL and RCM-HEL generates distinct Th2 or Th1 responses in naive mice, but the two forms of Ag expand the same HEL-specific public clonotype, characterized by the Vbeta8.2-Jbeta1.5 rearrangement, indicating that the populations of naive T cells activated by the two Ag forms overlap. T cells primed by RCM-HEL are restimulated by soluble HEL in vivo, but divert the phenotype of the HEL-specific response to Th1, implying that priming of naive T cells by a structurally modified Ag can induce Th1-type memory/effector T cells more efficiently than native Ag.

Antigen selection based on expression levels during infection facilitates vaccine development for an intracellular pathogen

Vaccines effective against intracellular pathogens could save the lives of millions of people every year, but vaccine development has been hampered by the slow largely empirical search for protective antigens. In vivo highly expressed antigens might represent a small attractive antigen subset that could be rapidly evaluated, but experimental evidence supporting this rationale, as well as practical strategies for its application, is largely lacking because of technical difficulties. Here, we used Salmonella strains expressing differential amounts of a fluorescent model antigen during infection to show that, in a mouse typhoid fever model, CD4 T cells preferentially recognize abundant Salmonella antigens. To identify a large number of natural Salmonella antigens with high expression levels during infection, we used a quantitative in vivo screening strategy. Immunization studies with five particularly attractive candidates revealed two highly protective antigens that might permit the development of an improved typhoid fever vaccine. In conclusion, we have established a rationale and an experimental strategy that will substantially facilitate vaccine development for Salmonella and possibly other intracellular pathogens.

Intranasal treatment with ovalbumin but not the major T cell epitope ovalbumin 323-339 generates interleukin-10 secreting T cells and results in the induction of allergen systemic tolerance

BACKGROUND

Nasal administration of major peptide T cell epitopes gives contradictory data on the induction of peripheral tolerance.

OBJECTIVE

To compare the prophylactic effect of intranasal treatment (INT) on the development of an allergic response, using either ovalbumin (OVA) or its major T cell epitope OVA 323-339 (OVAp).

METHODS

BALB/c mice were treated intranasally with OVA or OVAp and subsequently immunized s.c. with OVA. Anti-OVA-specific antibody, T cell proliferation and cytokine responses were analysed. In an adoptive transfer model using OVAp specific TCR transgenic (Tg) T cells from D011.10 mice, in vivo tracking and characterization of transferred T cells in the cervical, inguinal and bronchial lymph nodes (BLN) and in the spleen were determined by FACS analysis.

RESULTS

Prophylactic INT with OVA induced T cell tolerance towards subsequent OVA s.c. immunizations, inhibiting OVA specific T cell proliferation, IgE and IgG1 production, in contrast to INT with OVAp, which was unable to induce tolerance. In vivo analysis of transferred OVA-specific TCR Tg T cells showed that INT with OVA induced a preferential activation of T cells in BLN, as opposed to a broad, systemic activation with OVAp. In vivo, OVAp INT led to faster and more sustained cell division cycles than OVA INT. Ex vivo, tolerance to OVA was associated with the generation of IL-10 secreting CD4(+) T cells in BLN of OVA-treated mice only.

CONCLUSION

INT with OVA but not with OVAp led to regional (as opposed to systemic) T cell activation and the induction of IL-10 secreting CD4(+) T cells in BLN, potentially critical steps in the induction of T cell-specific tolerance via the nasal route.

Emerging principles for the design of promiscuous HLA-DR-restricted peptides: an example from the major bee venom allergen

Mechanisms underlying successful immunotherapy of allergic patients operate at the level of CD4+ helper T cells. T cell epitopes from allergens may thus constitute interesting molecules for immunotherapy, provided they are efficient for all patients and are not recognized by IgE. In an attempt to define such peptides for allergy to bee venom, we have investigated the capacity of peptides encompassing the sequence of the major bee venom allergen to stimulate PBMC from allergic patients and to react specifically with their IgE. The region 77-110 emerged as the most frequently T cell stimulating. We then analyzed the binding modes of the sequence 81-97 for ten different HLA-DR molecules and introduced punctual mutations to enhance the peptide affinity for these molecules. Six different modes have been identified on the sequence 81-97, one mode being common to eight HLA-DR molecules. Four HLA-DR molecules can bind the P85-97 peptide by two different modes with an equivalent affinity. The peptide N89L has a higher affinity for DRB1*0301 and DRB3*0101 and remains as active as the native peptide towards the other HLA-DR molecules.

Revisiting the "hygiene hypothesis" in gastrointestinal allergy

The "hygiene hypothesis" in its original form hypothesized that infection in early childhood acquired through unhygienic contact with siblings or the mother may prevent the development of allergic disease. Several recent epidemiologic surveys showing an inverse relationship between the frequency of infectious disease and the incidence of allergic diseases lend support to this hypothesis. Allergen sensitization of the immune system can occur early in utero against a background of neonatal commitment to a Th2 immune response involving the production of Th2 cytokines (eg, interleukin (IL)-4, IL-5, IL-13) that are the principal mediators of allergic inflammation. Continued allergen exposure is associated with predominantly CD4+ Th2 cell proliferation but does not exclude a minor Th1 allergen-specific subpopulation that can be further expanded nonspecifically and polyclonally by microbial superantigens or as bystanders, by interferon-gamma (IFN-gamma) and IL-2 released from Th1 effectors responding to antigens associated with infectious pathogens. Th1 cytokines can also subvert allergen-specific Th2 lymphocytes to become allergen-specific Th1 cells-a process reminiscent of the increased tendency of the maturing immune system of growing adults to mount a Th1 response to some environmental and dietary antigens. Unlike Th2 cytokines, IFN-gamma and IL-2 inhibit B-cell production of IgE and, hence, delimit the capacity of mast cells to degranulate and release allergenic mediators. The ability of infectious agents through their danger signals to initiate a Th1 response that deviates the Th2 allergenic bias is the basis of the hygiene hypothesis.

Novel vaccines protecting against the development of allergic disorders: a double-edged sword?

The severity and incidence of allergic disorders is steadily increasing despite the widespread use of steroids and other drugs. Recent results obtained in animals suggest that it may be possible to develop novel anti-allergy vaccines for human use, thereby stopping this alarming worldwide increase in allergic diseases. The most promising approaches are the induction of allergen-specific T helper 1 or allergen-specific T regulatory responses. However, both approaches potentially harbour negative side effects that need to be ruled out before vaccinating young children -- the best candidates for the primary prevention of allergic disorders.

Allergy immunotherapy and inhibition of Th2 immune responses: a sufficient strategy?

Th2 immune responses mediated by the secretion of IL-4, IL-5 and IL-13 are key in the pathogenesis of atopic disorders, including allergen-induced asthma, rhinoconjunctivitis and anaphylaxis. Although such responses are downregulated to some degree by conventional specific immunotherapy, this approach is only partially effective and has a substantial risk of adverse effects. Many strategies for immunotherapeutic prophylaxis and for treatment of atopic diseases have been devised on the basis of mouse allergy and autoimmune models, including the downregulation of Th2 responses by the induction of regulatory T cell activity, Th2 to Th1 immune deviation, Th1 crossregulation of Th2 immune responses, anergy and immunosuppressive cytokines. The blockade of events that are not allergen-specific, such as T cell costimulation and downstream events dependent on IgE, cytokines and chemokines, has also been pursued. With the exception of monoclonal antibody therapy for the blockade of IgE effector function, the application of most of these strategies to humans is at an early stage. Whether the inhibition of Th2 responses without concurrent downregulation of Th1 responses will be sufficient for allergic immunotherapy, particularly for atopic dermatitis and asthma, is an important but unresolved issue.

Effect of minocycline and doxycycline on IgE responses

BACKGROUND

We have recently found that the tetracycline minocycline suppresses inflammatory responses in serum immunoglobulin (Ig)E-positive asthmatic patients, and that IgE levels can decrease in these patients. The mechanism by which minocycline suppresses these responses is unknown.

OBJECTIVE

We have now investigated the ability of the tetracyclines, minocycline and doxycycline, to regulate IgE responses of peripheral blood mononuclear cells (PBMC) obtained from serum IgE-positive asthmatic patients.

METHODS

The distributions of CD3+, CD4+, CD8+, and CD19+ lymphocytes in peripheral blood of serum IgE-positive asthmatic patients and IgE-negative nonasthmatic controls, and cytokine-specific mRNA expression by their PBMC were determined by flow cytometry (reverse transcriptase-polymerase chain reaction). Serum Ig levels also were determined (nephelometry, fluoroenzymeimmunoassay, enzyme-linked immunoadsorbent assay; n = 7/group). PBMC (1.5 x 10(6)/mL) were cultured with anti-CD40 monoclonal antibody and recombinant human interleukin-4 in the presence/absence of minocycline or doxycycline (0.1 to 10 microg/mL), and IgE levels in supernatants determined on days 0, 3, and 10 (enzyme-linked immunoadsorbent assay).

RESULTS

Asthmatic and nonasthmatic subjects had similar numbers of blood CD4+ T cells (779/mm3 +/- 73 and 766 +/- 115, respectively) and CD19+ B-cells (239/mm3 +/- 35 and 379 +/- 95, respectively); however, CD8+ T cell numbers were decreased in asthmatic compared with nonasthmatic subjects (378/mm3 +/- 66 and 568 +/- 53, respectively; P = 0.045). High IgE levels were detected in supernatants of asthmatic PBMC on day 10 (28 ng/mL +/- 12), whereas control IgE levels did not change (<2.5 ng/mL). When either minocycline or doxycycline was included in culture, IgE production by asthmatic PBMC was strongly suppressed in dose-dependent fashion on day 10 (>80% with 10 microg/mL); control IgE did not change (<2.5 ng/mL).

CONCLUSIONS

The results are consistent with the idea that the therapeutic benefits obtained by asthmatic patients from minocycline may, in part, result from IgE suppression.

Immunomodulatory effects of antigen-pulsed macrophages in a murine model of allergic asthma

Macrophages (Mphi) play an unique role in the activation and regulation of T cells through their ability to modulate specific costimulatory and cytokine signals. Here we investigated the immunomodulatory effects of allergen presentation by Mphi in a murine model of allergic asthma. Purified peritoneal Mphi were pulsed with ovalbumin (OVA) (OVA-Mphi), or the immunodominant epitope OVA(323-339) (OVA(323-339)-Mphi), and characterized for cell surface markers, cytokine production, and antigen-presenting capacity toward OVA(323-339)-specific DO11.10 T cells. Antigen-pulsed Mphi were injected (intravenously) in OVA-sensitized Balb/c mice that were repeatedly challenged with OVA or saline aerosol. Administration of OVA-Mphi inhibited airway eosinophilia and hyperresponsiveness to methacholine concomitant with a reduced interleukin (IL)-4 and IL-5 production by T cells upon OVA stimulation in vitro. Interestingly, OVA-induced IL-10 levels remained unchanged, whereas interferon-gamma could not be detected. In contrast to OVA-Mphi, OVA(323-339)-Mphi administration had no effects on these asthma manifestations. Additional in vitro studies demonstrated that OVA-Mphi, but not OVA(323-339)-Mphi, produced high levels of IL-10 upon interaction with the DO11.10 T cells. This IL-10 production by the OVA-Mphi was dependent on MHC-TCR and CD86-CD28, but not CD80-CD28 or CD40-CD154 interactions. Our data suggest that IL-10 production by allergen presenting Mphi plays a crucial role in successful immunotherapy.

Cryptic determinants and promiscuous sequences on human acetylcholine receptor: HLA-dependent dichotomy in T-cell function

Experimental autoimmune myasthenia gravis can be induced in some strains of mice and rats by immunizing with acetylcholine receptor. Also, epidemiologic studies demonstrate an MHC linkage of myasthenia gravis in the man. In order to obtain direct experimental evidence for the influence of the genes of the MHC complex in the development of myasthenia gravis, we used mice transgenic to individual HLA molecules. We observed an increased susceptibility to the disease in HLA DQ8 transgenic mice compared to HLA DQ6 transgenic mice ( J. Immunol. 160:4169; 1998). These mice lacked endogenous mouse class II molecules. In the present study we mapped the cryptic and dominant sequences on the extra cellular region of human acetylcholine receptor. Although some epitopes (e.g., alpha11-30, alpha141-160, alpha171-190) were common between DQ8 and DQ6 transgenic mice, several others were disparately recognized. We also found a functional dichotomy in T cells from mice differing by one MHC molecule (HLA DQ8 or DQ6) when primed by sequences immunodominant in DQ8 and DQ6 tg mice. Differential disease manifestation in the two different HLA transgenic mice could be explained not only by differential recognition of peptides by these antigen presenting molecules, but also by the difference in the functional profile of T cells generated when primed by promiscuous sequence regions.

Chronic soluble antigen sensitization primes a unique memory/effector T cell repertoire associated with th2 phenotype acquisition in vivo

Although much progress has been made in characterization of the signaling pathways that control Th cell commitment, little is known about the early events that govern differentiation of IL-4-producing T lymphocytes in vivo. We have previously shown that chronic administration of low dose, soluble hen egg white lysozyme (HEL) induced the selective development of Ag-specific Th2 in genetically predisposed BALB/c mice. Here, we show that these memory/effector Th2 cells express a unique TCR Vbeta repertoire, different from the TCR Vbeta profile of primary effector cells from HEL-adjuvant-primed mice. This Th2-associated repertoire contains a highly frequent public clonotype characterized by preferred TCR AV and BV gene segment usage along with conserved sequences in the third hypervariable regions of both TCR chains. This Th2 clonotype, which is not recruited in primary effector T cells from HEL-adjuvant-immunized mice, recognized an IA(d)-restricted HEL determinant, preferentially processed by dendritic cells, but not by B cells. Thus, IL-4-producing CD4 T cells that expand following chronic Ag sensitization emerge from a distinct pool of precursors, supporting the hypothesis that ligand-TCR interactions play a crucial role in the regulation of Ag-specific Th2 cell development in vivo.

Atopic disorders: a vaccine around the corner?

The incidence and severity of atopic disorders, in particular asthma, is steadily increasing at an alarming rate. Furthermore, no primary prevention measure exists to date. However, recent results obtained from numerous animal studies suggest that primary prevention in humans might be possible in the near future. The most promising approaches include the induction of systemic or local allergen-dependent or -independent T helper 1 (Th1) immune responses, through the use of killed bacteria (or components derived from them), CpG oligodeoxynucleotides or plasmid DNA, and the induction of allergen-specific T-cell tolerance. Here, we review the data showing that animals can be protected from developing allergic Th2 responses by vaccination. Possible future use in humans and potential side-effects of the described vaccination strategies are discussed also.

Flt3 ligand: a novel cytokine prevents allergic asthma in a mouse model

Flt-3 ligand (FL), a recently described growth factor affecting early hematopoietic progenitor cells, can also support the expansion of dendritic cells secreting IL-12. Since type 2 T cells predominate in asthma and IL-12 prevents the differentiation of naive T lymphocytes to a type 2 phenotype, we hypothesized that FL could prevent the development of asthma-like conditions in the ovalbumin mouse model. We found that co-administration of FL during ovalbumin sensitization abrogated late allergic responses, but had no effect on early allergic responses. Airway hyperresponsiveness to methacholine was also blocked by FL treatment. Analysis of bronchoalveolar lavage (BAL) fluid demonstrated a significant reduction in eosinophils, with concomitant decreases in IL-5 and increases in IFN-gamma levels. However, there was no change in BAL fluid IL-4 and serum IgE levels. These data suggest that FL treatment prevents ovalbumin-induced asthma in the mouse and may provide a useful adjuvant in the treatment of human asthma.

Elongation factor 1 beta/delta of Echinococcus granulosus and allergic manifestations in human cystic echinococcosis

Allergic reactions, such as urticaria, itching and anaphylactic shock, often complicate the course of cystic echinococcosis (CE). To investigate the role of the IgE-immunoreactive recombinant Echinococcus granulosus elongation factor-1 beta/delta (EgEF-1 beta/delta) in the allergic disorders during CE we determined humoral and cell-mediated responses to this antigen in patients with CE grouped according to the clinical presence or absence of allergic reactions. Immunoblotting analysis showed that serum IgE-binding reactivity to EgEF-1 beta/delta differed significantly in patients with and without allergic reactions (38 of 42, 90% vs. 31 of 56, 56%; P < 10(-4)). EgEF-1 beta/delta induced a proliferative response in 14 of 19 (74%) patients' peripheral blood mononuclear cells (PBMC) irrespective of the allergic manifestations and skewed Th1/Th2 cytokine activation towards a preferentially Th2 polarization. Epitope mapping identified an immunodominant epitope of 18 residues with 78% identity and 89% similarity with an IgE-immunoreactive Strongyloides stercoralis antigen. Overall these findings suggest that EgEF-1 beta/delta is an allergenic molecule that may be a general marker of the intensity of CE immune response and that could lead to a deeper understanding of the specific antigen-induced mechanisms underlying allergic reactions in the human host.

New trends in immunotherapy to prevent atopic diseases

Advances in the understanding of the molecular and cellular immunological mechanism of atopy have led to the development of new therapies for allergic diseases. However, only a few new drugs have reached the clinic and none provides long-term immunomodulatory effects. Immunotherapy, through its capacity to produce a long-term, antigen-specific, protective immune response, is the only aetiologic treatment that offers the possibility of preventing or even curing atopic diseases. However, the potential severe side-effects associated with conventional immunotherapy using whole allergen extract limits its widespread use. Thus, novel strategies to minimize the side-effects and improve the efficacy of immunotherapy are of considerable interest in the treatment of atopic diseases. Promising animal and human studies, using approaches such as peptide immunotherapy, DNA vaccination, CpG oligonucleotides and mycobacterial vaccines, suggest that it might be possible to prevent or cure atopic diseases in the future.

The efficacy of immunotherapy in an experimental murine model of allergic asthma is related to the strength and site of T cell activation during immunotherapy

In the present study, the relation between the efficacy of immunotherapy, and the strength and site of T cell activation during immunotherapy was evaluated. We used a model of allergic asthma in which OVA-sensitized and OVA-challenged mice display increased airway hyperresponsiveness, airway inflammation, and Th2 cytokine production by OVA-specific T cells. In this model, different immunotherapy strategies, including different routes of administration, or treatment with entire OVA or the immunodominant T cell epitope OVA(323-339), or treatment with a peptide analogue of OVA(323-339) with altered T cell activation capacity were studied. To gain more insight in how immunotherapy affects allergen-specific T cells, the site of Ag-specific T cell activation and the magnitude of the T cell response induced during different immunotherapy strategies were determined using an adoptive transfer model. Our data suggest that amelioration of airway hyperresponsiveness and inflammation is associated with the induction of a strong, synchronized, and systemic T cell response, resulting in a decreased OVA-specific Th2 response. In contrast, deterioration of the disease after immunotherapy is associated with the induction of a weak nonsynchronized T cell response, resulting in the enhancement of the OVA-specific Th2 response after challenge.

Artificial antigen-presenting cells as a tool to exploit the immune 'synapse'

Recent progress in molecular medicine has provided important tools to identify antigen-specific T cells. In most cases, the approach is based on oligomeric combinations of recombinant major histocompatibility complex-peptide complexes fixed to various rigid supports available for binding by the T-cell receptor. These tools have greatly increased our insight into mechanisms of immune responses mediated by CD8+ T cells. Examples of the diverse fields of application for this technology include immunization, viral infections and oral tolerance induction.

Mechanisms of food allergy

The prevalence of food allergy continues to rise, particularly in 'westernized' societies; it has been linked to the 'hygiene hypothesis' and the increased diversity of food consumption worldwide. The pathogenic mechanisms and Th1/Th2 paradigm are being closely examined with respect to the occurrence of inflammatory and injury/repair responses at different mucosal sites. Genetically modified plants as potential food sources and allergenicity are current topics of controversy.