Heat denaturation affects the ProDer p 1 IgE reactivity and downregulates the development of the specific allergic response

Site-specific glycosylation and single amino acid substitution dramatically reduced the immunogenicity of β-lactoglobulin

To reduce the immunogenicity of β-lactoglobulin (BLG), we prepared recombinant BLG which has both site-specific glycosylation and single amino acid substitution (D28N/P126A), and expressed it in the methylotrophic yeast Pichia pastoris by fusion of the cDNA to the sequence coding for the α-factor signal peptide from Saccharomyces cerevisiae. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis indicated that the D28N/P126A was conjugated with a ∼4 kDa high-mannose chain. D28N/P126A retained ∼61% of the retinol-binding activity of BLG. Structural analyses by circular dichroism (CD) spectra, intrinsic fluorescence, and Enzyme-linked immunosorbent assay (ELISA) with monoclonal antibodies indicated that the surface structure of BLG was slightly changed by using protein engineering techniques, but D28N/P126A was covered by high-mannose chains and substituted amino acid without substantial disruption of native conformation. Antibody responses to the D28N/P126A considerably reduced in C57BL/6 mice. We conclude that inducing both site-specific glycosylation and single amino acid substitution simultaneously is an effective method to reduce the immunogenicity of BLG.

Perspectives in Allergen-Specific Immunotherapy: Molecular Evolution of Peptide- and Protein-Based Strategies

Allergen-specific Immunotherapy (AIT), through repetitive subcutaneous or sublingual administrations of allergen extracts, represents up to now the unique treatment against allergic sensitizations. However, the clinical efficacy of AIT can be largely dependent on the quality of natural allergen extracts. Moreover, the long duration and adverse side effects associated with AIT negatively impact patient adherence. Tremendous progress in the field of molecular allergology has made possible the design of safer, shorter and more effective new immunotherapeutic approaches based on purified and characterized natural or recombinant allergen derivatives and peptides. This review will summarize the characteristics of these different innovative vaccines including their effects in preclinical studies and clinical trials.

Development of a DNA-Based Detection Method for Cocos Nucifera Using TaqMan™ Real-Time PCR

So far, only a few cases of immunoglobulin E (IgE)-mediated coconut allergies have been described in the literature. Due to a growing consumption of coconut-containing foods in occidental countries, the number of coconut allergies may also increase. As there is no causative immunotherapy in clinical routine, appropriate food labelling is particularly important, also with regard to cross-contamination, to prevent serious health consequences. The purpose of this study was to develop a DNA-based detection method for coconut (Cocos nucifera). Initially, three sets of coconut-specific primers were designed and tested. A TaqMan™ probe was then developed to identify and quantify coconut by real-time PCR assay. With 27 other plant and animal species, the specificity of the primer/probe system was tested and cross reactivity was excluded. In a dilution series, a limit of detection of 1 pg/µL was determined. Thus, the developed real-time PCR assay is a suitable method to detect coconut in food.

Gamma-irradiation of Streptococcus pneumoniae for the use as an immunogenic whole cell vaccine

Streptococcus pneumoniae is a major respiratory pathogen that causes millions of deaths worldwide. Although subunit vaccines formulated with the capsular polysaccharides or their protein conjugates are currently-available, low-cost vaccines with wide serotype coverage still remain to be developed, especially for developing countries. Recently, gamma- irradiation has been considered as an effective inactivation method to prepare S. pneumoniae vaccine candidate. In this study, we investigated the immunogenicity and protective immunity of gamma-irradiated S. pneumoniae (r-SP), by comparing with heat-inactivated S. pneumoniae (h-SP) and formalin-inactivated S. pneumoniae (f-SP), both of which were made by traditional inactivation methods. Intranasal immunization of C57BL/6 mice with r-SP in combination with cholera toxin as an adjuvant enhanced S. pneumoniaespecific antibodies on the airway mucosal surface and in sera more potently than that with h-SP or f-SP under the same conditions. In addition, sera from mice immunized with r-SP potently induced opsonophagocytic killing activity more effectively than those of h-SP or f-SP, implying that r-SP could induce protective antibodies. Above all, immunization with r-SP effectively protected mice against S. pneumoniae infection. Collectively, these results suggest that gamma- irradiation is an effective method for the development of a killed whole cell pneumococcal vaccine that elicits robust mucosal and systemic immune responses.

Th17 activation by dendritic cells stimulated with gamma-irradiated Streptococcus pneumoniae

Dendritic cells (DCs) play an important role in antigen presentation, which is an essential step for the induction of antigen-specific adaptive immunity. Inactivated bacterial whole cell vaccines have been widely used to prevent many bacterial infections because they elicit good immunogenicity due to the presence of various antigens and are relatively inexpensive and easy to manufacture. Recently, gamma-irradiated whole cells of nonencapsulated Streptococcus pneumoniae were developed as a broad-spectrum and serotype-independent multivalent vaccine. In the present study, we generated gamma-irradiated S. pneumoniae (r-SP) and investigated its capacity to stimulate mouse bone marrow-derived DCs (BM-DCs) in comparison with heat-inactivated and formalin-inactivated S. pneumoniae (h-SP and f-SP, respectively). r-SP showed an attenuated binding and internalization level to BM-DCs when compared to h-SP or f-SP. r-SP weakly induced the expression of CD80, CD83, CD86, MHC class I, and PD-L2 compared with h-SP or f-SP. Furthermore, r-SP less potently induced IL-6, TNF-α, and IL-23 expression than h-SP or f-SP but more potently induced IL-1β expression than h-SP or f-SP in BM-DCs. Since Th17-mediated immune responses are known to be important for the protection against pneumococcal infections, r-SP-primed DCs were co-cultured with splenocytes or splenic CD4⁺ T cells. Interestingly, r-SP-sensitized BM-DCs markedly induced IL-17A⁺ CD4⁺ T cells whereas h-SP- or f-SP-sensitized BM-DCs weakly induced them. Collectively, these results suggest that r-SP could be an effective pneumococcal vaccine candidate eliciting Th17-mediated immune responses by stimulation of DCs.

One mechanism of glucocorticoid action in asthma may involve the inhibition of IL-25 expression

While the mechanism of action of classic cytokines in asthma has received increased attention from researchers, certain non-classical cytokines, such as IL-25, also participate in this mechanism. The present study was performed to investigate the changes in IL-25 (IL-17E) mRNA and protein in bronchial asthma and to further characterize the mechanism underlying the action of glucocorticoids in asthma. A total of 96 specific pathogen-free BALB/c male mice were randomly divided into three normal groups (after the first allergization, after the second allergization and after excitation), three asthma groups (with the same three subgroups), a dexamethasone group and a budesonide group (n=12/group). An asthma model was established via the ovalbumin-sensitized excitation method. Mice in the dexamethasone group received intraperitoneal injections of dexamethasone 1 h prior to each excitation, the budesonide group received a budesonide suspension via inhalation 2 h before and after each provocation, and the normal group was sensitized and challenged with isotonic saline. IL-25 protein expression levels in the bronchoalveolar lavage fluid were measured by ELISA, and the relative IL-25 mRNA content in lung tissue was determined by reverse transcription-quantitative polymerase chain reaction. Compared with the normal groups, both the protein and mRNA levels of IL-25 were significantly increased (P<0.05) in the asthma groups. Dexamethasone and budesonide groups exhibited significant protein and mRNA reductions in IL-25, as compared with the asthma group after excitation (P<0.05), whereas these two groups significantly increased levels compared with the normal group after excitation (P<0.05). No significant differences in IL-25 mRNA expression levels were detected in the dexamethasone and budesonide groups when compared with the normal group after excitation. Therefore, we conclude that IL-25 is involved throughout the process of inflammation and inflammatory immune pathogenesis in asthma. One of the mechanisms of glucocorticoid action in asthma may involve inhibition of IL-25 expression.

Production of a chimeric allergen derived from the major allergen group 1 of house dust mite species in Nicotiana benthamiana

Plants are widely accepted as a general platform for the large-scale production of recombinant proteins, which has been demonstrated by the successful expression of various exogenous proteins. Using plants as a bioreactor for mass production of target proteins for vaccines is thought to show the most potential. This study explores whether a chimeric allergen R8, derived from the major allergen group 1 of house dust mites species (Dermatophagoides farinae and Dermatophagoides pteronyssinus), is expressed in tobacco. The highly efficient and useful Tobacco mosaic virus RNA-based overexpression (TRBO) vector was used to investigate expression of the R8 molecule in tobacco by agroinfection. Presence of R8 was detected using SDS-PAGE and Western blotting. Purified allergens were characterized using IgE-binding activity assay and allergen-specific immunotherapy (ASIT) in murine asthmatic models. The recombinant R8 was successfully expressed in tobacco leaves. The pro-peptide was observed in the herbaceous leaf extracts. This protein exhibits properties similar to the parental allergen ProDer f 1 expressed in Escherichia coli or tobacco with respect to IgE immunoreactivity. R8 also rectifies imbalance of TH1/TH2 cells. An herbaceous plant expression system model allows mass production of R8, which might be used in the future for diagnosis of asthma or production of a candidate vaccine for allergen-specific immunotherapy of asthma.

Highly aggregated antibody therapeutics can enhance the in vitro innate and late-stage T-cell immune responses

Aggregation of biotherapeutics has the potential to induce an immunogenic response. Here, we show that aggregated therapeutic antibodies, previously generated and determined to contain a variety of attributes (Joubert, M. K., Luo, Q., Nashed-Samuel, Y., Wypych, J., and Narhi, L. O. (2011) J. Biol. Chem. 286, 25118–25133), can enhance the in vitro innate immune response of a population of naive human peripheral blood mononuclear cells. This response depended on the aggregate type, inherent immunogenicity of the monomer, and donor responsiveness, and required a high number of particles, well above that detected in marketed drug products, at least in this in vitro system. We propose a cytokine signature as a potential biomarker of the in vitro peripheral blood mononuclear cell response to aggregates. The cytokines include IL-1β, IL-6, IL-10, MCP-1, MIP-1α, MIP-1β, MMP-2, and TNF-α. IL-6 and IL-10 might have an immunosuppressive effect on the long term immune response. Aggregates made by stirring induced the highest response compared with aggregates made by other methods. Particle size in the 2–10 μm range and the retention of some folded structure were associated with an increased response. The mechanism of aggregate activation at the innate phase was found to occur through specific cell surface receptors (the toll-like receptors TLR-2 and TLR-4, FcγRs, and the complement system). The innate signal was shown to progress to an adaptive T-cell response characterized by T-cell proliferation and secretion of T-cell cytokines. Investigating the ability of aggregates to induce cytokine signatures as biomarkers of immune responses is essential for determining their risk of immunogenicity.

Production of native and modified recombinant Der p 1 molecules in tobacco plants

BACKGROUND

As a complex molecule requiring post-translational processing, it has been difficult to produce the Der p 1 major allergen from the Dermatophagoides pteronyssinus house dust mite in a recombinant form.

OBJECTIVE

Here, we tested whether transgenic tobacco plants are suitable to express Der p 1, either as a wild-type molecule or as variants lacking N-glycosylation sites (Gly(-)) and/or cysteine protease activity (Enz(-)). Methods Using Agrobacterium tumefaciens-based transformation, pro Der p 1 molecules bearing mutations within either the N-glycosylation sites (N34Q, N150Q) and/or the cysteine protease-active site (C132V) were expressed in tobacco plants. After purification by ion exchange chromatography, allergens were characterized using immunoblotting, circular dichroism (CD), as well as basophil and T lymphocyte stimulation assays.

RESULTS

Four forms of recombinant Der p 1 (i.e. wild-type Gly(+)/Enz(+), as well as Gly(-)/Enz(+), Gly(+)/Enz(-) or Gly(-)/Enz(-) variants) were successfully expressed in tobacco leaves as pro Der p 1 molecules. Spontaneous cleavage of the pro-peptide was observed in tobacco leaf extracts for all forms of recombinant Der p 1 (r Der p 1). CD confirmed that all r Der p 1 molecules, with the exception of the Gly(-)/Enz(-) variant, exhibited secondary structures comparable to the natural protein. A cysteine protease activity was associated only with the Gly(+)/Enz(+) form. All these molecules exhibit a profile similar to natural Der p 1 with respect to IgE immunoreactivity, basophil activation and T cell recognition.

CONCLUSION

A tobacco plant expression system allows the production of various forms of mature Der p 1, which could be used for diagnostic or immunotherapeutic purposes.

A hypoallergenic variant of Der p 1 as a candidate for mite allergy vaccines

BACKGROUND

Recombinant hypoallergens that display reduced allergenicity but retain T-cell reactivity represent promising candidates to improve the safety and efficacy of allergen-specific vaccines or immunotherapy.

OBJECTIVE

The current study reports the immunologic characterization of a hypoallergenic variant of the major mite allergen Der p 1.

METHODS

The recombinant proform of Der p 1 (ProDer p 1) was expressed in Escherichia coli (ProDer p 1 coli), purified and characterized at the level of its secondary structure, and IgE and T-cell reactivities. Moreover, the prophylactic potential of ProDer p 1 coli vaccinations was evaluated in a murine Der p 1 sensitization model.

RESULTS

After purification and refolding, ProDer p 1 coli remained aggregated with a higher beta-sheet content and altered Der p 1 conformational epitopes compared with the correctly folded monomeric ProDer p 1 produced in Chinese hamster ovary cells. Both ProDer p 1 forms were able to retain the Der p 1-specific T-cell reactivity but direct ELISA, competitive inhibition, and rat basophil leukemia assays clearly showed that ProDer p 1 coli displays a very weak IgE reactivity. Mice vaccinations with aggregated ProDer p 1 adjuvanted with alum induced a T(H)1-biased immune response that prevented the subsequent allergic response after Der p 1 sensitization and airway challenge with aerosolized mite extracts. Furthermore, ProDer p 1 coli treatment inhibited the development of airway eosinophilia and airway hyperresponsiveness to inhaled methacholine.

CONCLUSION

Aggregated forms of Der p 1 could represent hypoallergens suitable for the prevention of mite allergy.

In vivo and in vitro immunomodulation of Der p 1 allergen-specific response by Lactobacillus plantarum bacteria

BACKGROUND

Lactic acid bacteria (LAB) were reported to reduce some allergic manifestations in mice and humans but their impact on the aeroallergen-dependent immune mechanisms is still debated.

OBJECTIVE

The potential capacities of Lactobacillus plantarum NCIMB8826 to reduce the allergic response induced by Der p 1, the major house dust mite allergen of Dermatophagoides pteronyssinus, were evaluated in vivo and in vitro. Methods First, the effect of the intranasal co-administration of LAB and purified Der p 1 allergen before a sensitization protocol was evaluated. The allergen-specific antibody and cellular responses as well as airway inflammation were measured. Second, the impact of LAB on the cytokine profile of spleens cells from Der p 1-sensitized mice was assessed. Third, upon stimulation with LAB, the levels of cytokine produced by dendritic cells derived from the bone marrow (BMDCs) of wild-type, Toll-like receptor 2 (TLR2)-, TLR4- and MyD88-KO mice were compared. Results The co-application of L. plantarum and Der p 1 induced a T-helper type 1 (Th1)-biased allergen-specific IgG response, the absence of specific IgE response and favoured the production of INF-gamma upon allergen re-stimulation. Moreover, the previous LAB administration reduced the development of bronchoalveolar lavage eosinophilia usually induced by aerosol exposure. Additionally, the studied LAB strain was shown to modify in vitro the cytokine level produced by Der p 1-sensitized spleen cells mainly towards a Th1 profile. Finally, L. plantarum stimulated high IL-12 and moderate IL-10 production in mouse BMDCs notably through the TLR2-, MyD88-dependent and TLR4-independent pathway.

CONCLUSION

In vivo co-administration of probiotic LAB with Der p 1 might prevent the development of the mite allergic response. The probiotic L. plantarum was shown to display in vitro therapeutic potentials for the treatment of allergy and to trigger the immune system by a TLR2- and MyD88-dependent signalling pathway.

Mite immunotherapy

Dermatophagoides pteronyssinus and D. farinae are the most common house dust mites and are among the most common sources of indoor allergens worldwide. These species are very common in humid regions, where most allergic individuals are sensitized to house dust mites. Specific immunotherapy with mite extracts has demonstrated clinical benefits in several double-blind, placebo-controlled trials that are included in recent reviews of subcutaneous immunotherapy, including pediatric and adult patients with rhinoconjunctivitis and or asthma. Most successful studies of mite immunotherapy have used native allergen extracts adsorbed onto aluminum hydroxide, or chemically modified mite-allergen extracts. Several studies have also shown efficacy using sublingual immunotherapy in pediatric and adult patients with asthma and/or rhinitis. Additionally, the efficacy of subcutaneous immunotherapy has been demonstrated in patients with atopic dermatitis, although more double-blind, placebo-controlled studies are needed. Based on several studies, it cannot be concluded that mite immunotherapy is more dangerous or safer than immunotherapy with grasses, epithelia, or animal epithelia. Because the delivery of high doses of allergen carries with it the risk for immunoglobulin E (IgE)-mediated events, several methods have been developed to reduce specific IgE binding to mite-allergen extracts. An important challenge for future mite immunotherapy modalities is the delivery of relatively high doses without a significant risk for severe reactions.

Hypoallergenic fragment of Par j 2 increases functional expression of Toll-like receptors in atopic children

BACKGROUND

Parietaria judaica (Par j) is one of the main causes of allergy in the Mediterranean countries. The activation of Toll-like receptor 4 (TLR4) by lipopolysaccharide (LPS) inhibits nasal inflammation of atopic children.

OBJECTIVE

To examine, in vivo and in vitro, the effect of recombinant Par j 2 (rPar j 2) and of its fragments (1-55 and 52-102) on atopic children.

METHODS

We used skin prick test for in vivo evaluations. We assessed, in vitro, in peripheral blood mononuclear cells (PBMC), the effect of rPar j 2 and of the two fragments on neutrophil chemotaxis, on CD45RO, on TLR2 and TLR4 expression, on LPS binding and on interferon (IFN)-gamma release, by a microchemotaxis chamber, by flow cytometry and by enzyme-linked immunosorbent assay, respectively.

RESULTS

In vivo while rPar j 2 induced a positive skin reaction, 1-55 and 52-102 fragments did not. In vitro, while rPar j 2 increased both CD45RO expression and neutrophils chemotaxis in PBMC, both Par j 2 fragments did not. 1-55 fragment of Par j 2 upregulated both TLR2 and TLR4 expression and LPS binding, while the rPar j 2 and 52-102 fragment did not. Finally, 1-55 fragment of Par j 2 induced IFNgamma release, while the rPar j 2 and 52-102 fragment did not.

CONCLUSIONS

Hypoallergenic 1-55 fragment, upregulating innate immunity receptors and increasing IFNgamma, might re-orientate, in atopics, the immune system toward a physiologic balance between Th1 and Th2 responses.

Heat denaturation, a simple method to improve the immunotherapeutic potential of allergens

Allergen-specific immunotherapy (SIT) leads to a long-term amelioration of IgE- and Th2-mediated allergic diseases. However, SIT efficiency is low, with years of treatment along with frequent allergic side effects. The goal of this study was to reduce the side effects by destroying IgE-binding epitopes, i.e. by heat-denaturation, while preserving the therapeutic effect. Mice were immunised with bee venom, birch pollen, grass pollen or cat hair allergens, or with ovalbumin. Heat-denatured allergens bound less IgE but enhanced Th1-dependent IgG2a production as measured by ELISA. The strong IgG2a antibody responses also prevented allergic anaphylaxis in mice, as measured by body temperature drop after a challenge with a high allergen dose. We found that optimal heat-denaturation of allergens left a small proportion in the native conformation to sufficiently stimulate B cells, while non-B cell-mediated effects were probably amplified. The enhanced immunogenicity of heat-denatured allergens is likely explained by enhanced antigen presentation to T cells due to the particulate nature of heat-denatured proteins. This enables Th1 skewing of the immune response with strong production of IgG2a in mice. Therefore, heat-denaturation represents probably the simplest way to enhance the efficiency of SIT while reducing its side effects.

Crucial Commitment of Proteolytic Activity of a Purified Recombinant Major House Dust Mite Allergen Der p1 to Sensitization toward IgE and IgG Responses

The major proteolytic allergen derived from the house dust mite Dermatophagoides pteronyssinus, Der p1, is one of the most clinically relevant allergens worldwide. In the present study, we evaluate the contribution of the proteolytic activity and structure of a highly purified rDer p 1 to immune responses. Mice were i.p. immunized with three forms of rDer p 1 adsorbed to Alum: one enzymatically active, one treated with an irreversible cysteine protease-specific inhibitor, E-64, and one heat denatured. Immunization with E-64-treated or heat-denatured rDer p 1 elicited much less production of serum total IgE and not only rDer p 1-specific IgE but also IgGs compared with immunization with active rDer p 1. Assays for Ab-binding and its inhibition and structural analyses indicated that E-64-treated rDer p 1 retained its global structure and conformational B cell epitopes. A proliferative response and production of IL-5 by spleen cells restimulated with rDer p 1 were observed on immunization with the active rDer p 1 but not E-64-treated rDer p 1. The cells from mice immunized with heat-denatured rDer p 1 exhibited the highest levels of proliferation and production of IL-5 and IFN-gamma. The results indicate that the proteolytic activity of the highly purified rDer p 1 crucially commits to the sensitization process, including both IgE and IgG responses. Additionally, we demonstrated immunogenic differences by functional or structural manipulations of the rDer p 1. The findings have implications for sensitization to this relevant allergen in humans and for the design of modified allergen-vaccines for future allergen-specific immunotherapy.

Influence of aggregation on immunogenicity of recombinant human Factor VIII in hemophilia A mice

Recombinant human factor VIII (rFVIII), a multidomain glycoprotein is used in replacement therapy for treatment of hemophilia A. Unfortunately, 15%-30% of the treated patients develop inhibitory antibodies. The pathogenesis of antibody development is not completely understood. The presence of aggregated protein in formulations is generally believed to enhance the immune response. rFVIII has a tendency to aggregate but the effect of such aggregation on the immunogenicity of rFVIII is not known. We have, therefore, characterized aggregated rFVIII produced by thermal stress and evaluated its effect on the immunogenicity of rFVIII in hemophilia A mice. Aggregated rFVIII alone and mixtures of rFVIII with aggregated rFVIII were less immunogenic than native rFVIII. In vitro Th-cell proliferation studies and cytokine analyses conducted on splenocytes obtained from immunized animals suggest that aggregated rFVIII behaves as a unique antigen compared to native monomeric rFVIII. The antigenic properties of the aggregated and native rFVIII were compared using ELISAs (epitope availability) and cathepsin-B (an antigen processing enzyme) digestion. The data suggest significant differences in the antigenic properties of rFVIII and aggregated rFVIII. Overall it appears that aggregated rFVIII does not enhance the immunogenicity (inhibitor development) of rFVIII in hemophilia A mice but rather acts as a distinct antigen.

Three-dimensional structure and IgE-binding properties of mature fully active Der p 1, a clinically relevant major allergen

BACKGROUND

Der p 1 is a 25-kd allergen with cysteine protease activity. Sensitization to Der p 1 affects a large proportion of individuals with allergy, resulting in rhinitis, asthma, and/or atopic dermatitis.

OBJECTIVE

We determined the Der p 1 crystallographic structure to understand the relationships among structure, function, and allergenicity.

METHODS

Recombinant pro-Der p 1 was produced in Pichia pastoris and allowed to mature spontaneously before purification by a 2-step procedure. Protease activity was checked by using a fluorogenic peptide substrate. Allergenicity was analysed by IgE binding assays and basophil activation test. The determination of the 3-dimensional structure was obtained by X-ray crystallography at 1.9 A resolution.

RESULTS

The recombinant protein is fully active and expresses an allergenicity equivalent to its natural counterpart. Der p 1 exhibits a cysteine protease fold typical of the papain family, has a magnesium binding site, and forms dimers with a large interface. The crystal lattice shows that the dimers are tightly packed in a compact double layer of proteins. Such an assembly likely exists in dry fecal pellets, the natural form of allergen exposure, and appears ideal to interact with cell surface and trigger allergic inflammation.

CONCLUSION

We present here the 3-dimensional structural features of mature fully active Der p 1, one of the main allergens involved in human allergic diseases. This opens the possibility to evaluate the importance of enzymatic activity in pathology and possible new therapeutic interventions.