Characterization of a mouse model of allergy to a major occupational latex glove allergen Hev b 5

In silico approaches for the identification of potential allergens among hypothetical proteins from Alternaria alternata and its functional annotation

Direct exposure to the fungal species Alternaria alternata is a major risk factor for the development of asthma, allergic rhinitis, and inflammation. As of November 23rd 2020, the NCBI protein database showed 11,227 proteins from A. alternata genome as hypothetical proteins (HPs). Allergens are the main causative of several life-threatening diseases, especially in fungal infections. Therefore, the main aim of the study is to identify the potentially allergenic inducible proteins from the HPs in A. alternata and their associated functional assignment for the complete understanding of the complex biological systems at the molecular level. AlgPred and Structural Database of Allergenic Proteins (SDAP) were used for the prediction of potential allergens from the HPs of A. alternata. While analyzing the proteome data, 29 potential allergens were predicted by AlgPred and further screening in SDAP confirmed the allergic response of 10 proteins. Extensive bioinformatics tools including protein family classification, sequence-function relationship, protein motif discovery, pathway interactions, and intrinsic features from the amino acid sequence were used to successfully predict the probable functions of the 10 HPs. The functions of the HPs are characterized as chitin-binding, ribosomal protein P1, thaumatin, glycosyl hydrolase, and NOB1 proteins. The subcellular localization and signal peptide prediction of these 10 proteins has further provided additional information on localization and function. The allergens prediction and functional annotation of the 10 proteins may facilitate a better understanding of the allergenic mechanism of A. alternata in asthma and other diseases. The functional domain level insights and predicted structural features of the allergenic proteins help to understand the pathogenesis and host immune tolerance. The outcomes of the study would aid in the development of specific drugs to combat A. alternata infections.

High Fat Diet Inhibits Dendritic Cell and T Cell Response to Allergens but Does Not Impair Inhalational Respiratory Tolerance

The incidence of obesity has risen to epidemic proportions in recent decades, most commonly attributed to an increasingly sedentary lifestyle, and a ‘western’ diet high in fat and low in fibre. Although non-allergic asthma is a well-established co-morbidity of obesity, the influence of obesity on allergic asthma is still under debate. Allergic asthma is thought to result from impaired tolerance to airborne antigens, so-called respiratory tolerance. We sought to investigate whether a diet high in fats affects the development of respiratory tolerance. Mice fed a high fat diet (HFD) for 8 weeks showed weight gain, metabolic disease, and alteration in gut microbiota, metabolites and glucose metabolism compared to age-matched mice fed normal chow diet (ND). Respiratory tolerance was induced by repeated intranasal (i.n.) administration of ovalbumin (OVA), prior to induction of allergic airway inflammation (AAI) by sensitization with OVA in alum i.p. and subsequent i.n. OVA challenge. Surprisingly, respiratory tolerance was induced equally well in HFD and ND mice, as evidenced by decreased lung eosinophilia and serum OVA-specific IgE production. However, in a pilot study, HFD mice showed a tendency for impaired activation of airway dendritic cells and regulatory T cells compared with ND mice after induction of respiratory tolerance. Moreover, the capacity of lymph node cells to produce IL-5 and IL-13 after AAI was drastically diminished in HFD mice compared to ND mice. These results indicate that HFD does not affect the inflammatory or B cell response to an allergen, but inhibits priming of Th2 cells and possibly dendritic cell and regulatory T cell activation.

The development of a murine model for Forcipomyia taiwana (biting midge) allergy

BACKGROUND

Forcipomyia taiwana (biting midge) allergy is the most prevalent biting insect allergy in Taiwan. An animal model corresponding to the human immuno-pathologic features of midge allergy is needed for investigating the mechanisms and therapies. This study successfully developed a murine model of Forcipomyia taiwana allergy.

METHODS

BALB/c mice were sensitized intra-peritoneally with midge extract on days 0, 7, 14, 21 then intra-dermally on days 28, 31 and 35. Serum midge-specific IgE, IgG1, and IgG2a were measured every 14 days by indirect ELISA. The mice were challenged intradermally with midge extract at day 40 and then sacrificed. Proliferation and cytokine production of splenocytes after stimulation with midge extract were determined by MTT assay and ELISA, respectively. The cytokine mRNA expression in response to midge stimulation was analyzed by RT-PCR.

RESULTS

Serum IgE, total IgG, and IgG1 antibody levels against midge extract were significantly higher in the midge-sensitized mice than in the control mice. After the two-step sensitization, all mice in the midge-sensitized group displayed immediate itch and plasma extravasation reactions in response to challenge with midge extract. Skin histology from midge-sensitized mice showed marked eosinophil and lymphocyte infiltrations similar to that observed in humans. Stimulation of murine splenocytes with midge extract elicited significant proliferation, IL-4, IL-10, IL-13 and IFN-γ protein production, and up-regulation of mRNA in a dose-dependent manner in the midge-sensitized group, but not in the control group.

CONCLUSIONS

A murine model of midge bite allergy has been successfully developed using a two-step sensitization protocol. The sensitized mice have very similar clinical and immunologic reactions to challenge with midge proteins as the reactions of human to midge bites. This murine model may be a useful platform for future research and the development of treatment strategies for insect bite allergy.

The signalling imprints of nanoparticle uptake by bone marrow derived dendritic cells

Nanoparticles (NP) possess remarkable adjuvant and carrier capacity, therefore are used in the development of various vaccine formulations. Our previous studies demonstrated that inert non-toxic 40-50 nm polystyrene NP (PS-NP) can promote strong CD8 T cell and antibody responses to the antigen, in the absence of observable inflammatory responses. Furthermore, instillation of PS-NP inhibited the development of allergic airway inflammation by induction of an immunological imprint via modulation of dendritic cell (DC) function without inducing oxidative stress in the lungs in mice. This is in contrast to many studies which show that a variety of ambient and man-made NP promote lung immunopathology, raising concerns generally about the safe use of NPs in biomedicine. Most NPs are capable of inducing inflammatory pathways in DC largely mediated by signalling via the extracellular signal-regulated kinase 1/2 (ERK). Herein, we investigate whether PS-NPs also activate ERK in DC in vitro. Our data show that PS-NP do not induce ERK activation in two different types of bone marrow derived (BM) DC cultures (expanded with GM-CSF or with GM-CSF together with IL-4). The absence of such signalling was not due to lack of PS-NP uptake by BM-DC as confirmed by confocal microscopy and flow cytometry. The process of NP uptake by DC usually initiates ERK signalling, suggesting an unusual uptake pathway may be engaged by PS-NPs. Indeed, data herein showns that uptake of PS-NP by BM-DC was substantially inhibited by phorbol myristate acetate (PMA) but not cytochalasin D (CCD), suggesting an uptake pathway utilising caveole for PS-NP. Together these data show that BM-DC take up PS-NP via a caveole-dependent pathway which does not trigger ERK signalling which may explain their efficient uptake by DC, without the concomitant activation of conventional inflammatory pathways.

Inert 50-nm polystyrene nanoparticles that modify pulmonary dendritic cell function and inhibit allergic airway inflammation

Nanoparticles are being developed for diverse biomedical applications, but there is concern about their potential to promote inflammation, particularly in the lung. Although a variety of ambient, anthropogenic and man-made nanoparticles can promote lung inflammation, little is known about the long-term immunomodulatory effects of inert noninflammatory nanoparticles. We previously showed polystyrene 50-nm nanoparticles coated with the neutral amino acid glycine (PS50G nanoparticles) are not inflammatory and are taken up preferentially by dendritic cells (DCs) in the periphery. We tested the effects of such nanoparticles on pulmonary DC function and the development of acute allergic airway inflammation. Surprisingly, exposure to PS50G nanoparticles did not exacerbate but instead inhibited key features of allergic airway inflammation including lung airway and parenchymal inflammation, airway epithelial mucus production, and serum allergen-specific IgE and allergen-specific Th2 cytokines in the lung-draining lymph node (LN) after allergen challenge 1 mo later. PS50G nanoparticles themselves did not induce lung oxidative stress or cardiac or lung inflammation. Mechanistically, PS50G nanoparticles did not impair peripheral allergen sensitization but exerted their effect at the lung allergen challenge phase by inhibiting expansion of CD11c(+)MHCII(hi) DCs in the lung and draining LN and allergen-laden CD11b(hi)MHCII(hi) DCs in the lung after allergen challenge. PS50G nanoparticles further suppressed the ability of CD11b(hi) DCs in the draining LN of allergen-challenged mice to induce proliferation of OVA-specific CD4(+) T cells. The discovery that a defined type of nanoparticle can inhibit, rather than promote, lung inflammation via modulation of DC function opens the door to the discovery of other nanoparticle types with exciting beneficial properties.

Differences in control by UV radiation of inflammatory airways disease in naïve and allergen pre-sensitised mice

Exposure of skin to UV radiation (UVR) prior to allergen exposure can inhibit inflammatory airways disease in mice by reducing effector CD4+ T cells in both the trachea and the airway draining lymph nodes. This study analysed the immunomodulatory properties of UVR delivered to naïve versus allergen pre-sensitised mice. In a model of inflammatory airways disease, BALB/c mice were sensitised by peritoneal injection of the allergen, ovalbumin (OVA) (20 μg/mouse), in the adjuvant, alum (4 mg/mouse), on days 0 and 14. On day 21, the mice were exposed to aerosolised OVA and 24 h later, proliferative responses by the cells in the airway draining lymph nodes were examined. UVR (8 kJ m(-2)) was administered 3 days prior to first OVA sensitisation (day -3), or OVA aerosol challenge (day 18). UVR before sensitisation reduced immune responses associated with expression of allergic airways disease; seven days after first OVA sensitisation, regulation of OVA-induced proliferation in vitro but not in vivo by CD4+CD25+ cells from UV-irradiated mice was detected. UVR administered to pre-sensitised mice regulated allergen responsiveness by cells from the airway draining lymph nodes only with a sensitisation protocol involving allergen and adjuvant at 5% strength of the original dose (1 μg OVA in 0.2 mg alum/mouse). These results suggest that UVR may modulate allergic airways disease by two mechanisms. The first, and more potent, is by reducing effector cells in respiratory tissues and requires UV delivery prior to sensitisation. The second, associated with administration to pre-sensitised mice, is weaker and is detected when the mice are sensitised with lower levels of allergen and adjuvant.

Interleukin-13 regulates secretion of the tumor growth factor-{beta} superfamily cytokine activin A in allergic airway inflammation

Activin A is a member of the TGF-beta superfamily and plays a role in allergic inflammation and asthma pathogenesis. Recent evidence suggests that activin A regulates proinflammatory cytokine production and is regulated by inflammatory mediators. In a murine model of acute allergic airway inflammation, we observed previously that increased activin A concentrations in bronchoalveolar lavage (BAL) fluid coincide with Th2 cytokine production in lung-draining lymph nodes and pronounced mucus metaplasia in bronchial epithelium. We therefore hypothesized that IL-13, the key cytokine for mucus production, regulates activin A secretion into BAL fluid in experimental asthma. IL-13 increased BAL fluid activin A concentrations in naive mice and dose dependently induced activin A secretion from cultured human airway epithelium. A key role for IL-13 in the secretion of activin A into the BAL fluid during allergic airway inflammation was confirmed in IL-13-deficient mice. Eosinophils were not involved in this response because there was no difference in BAL fluid activin A concentrations between wild-type and eosinophil-deficient mice. Our data highlight an important role for IL-13 in the regulation of activin A intraepithelially and in BAL fluid in naive mice and during allergic airway inflammation. Given the immunomodulatory and fibrogenic effects of activin A, our findings suggest an important role for IL-13 regulation of activin A in asthma pathogenesis.

Changes in sputum eicosanoids and inflammatory markers after inhalation challenges with occupational agents

BACKGROUND

An increase in cysteinyl-leukotrienes (LTs) after specific inhalation challenge (SIC) with common allergens in patients with atopic asthma has been shown previously, but there are scarce data with occupational agents. We sought to determine whether there are differences in lower airway inflammatory markers and the production of cytokines and eicosanoids between patients with a positive or negative SIC response to occupational agents.

METHODS

Twenty-six patients with suspected occupational asthma and 13 healthy control subjects were studied. Spirometry, methacholine challenge, and sputum induction were performed at baseline and 24 h after SIC with occupational agents. Several cytokines and inflammatory mediators, including eicosanoids, were measured in sputum.

RESULTS

Twenty-six SICs were carried out with high-molecular-weight or low-molecular-weight agents, and the responses were positive in 18 patients. SIC elicited nine early asthmatic responses, two dual asthmatic responses, and seven isolated late asthmatic responses. Significant increments in sputum eosinophil counts were found only in patients with positive SIC responses compared with baseline values. Interleukin-10 levels were decreased in patients with positive and negative SIC responses compared to those in healthy control subjects. A significant increase (p < 0.05) in the LTC(4)/prostaglandin E(2) (PGE(2)) ratio was observed in patients after positive SIC responses compared to those with negative SIC responses.

CONCLUSIONS

Overexpression of LTC(4), relative underproduction of PGE(2), and greater airway eosinophilia were observed in patients with positive SIC responses.

Latex allergy: a model for therapy

Allergy to natural rubber latex products emerged as an important clinical condition following an increase in the use of latex gloves for barrier protection in the early 1980s. In addition to latex glove users, other high-risk groups with different latex exposure include spina bifida patients and others with multiple surgical procedures. Subjects with fruit and vegetable allergy are also at risk due to cross-reactive allergens. Following the significant advances in the identification and characterization of common aeroallergens, latex allergy was well placed to become an excellent model of therapy. Awareness of latex allergy and modes of sensitization enabled epidemiological studies to inform allergen avoidance initiatives, substantially reducing inadvertent exposure in major hospitals in Western countries. Spina bifida is often identified in utero or soon after birth, allowing vigorous latex allergen avoidance with enhanced efficacy of primary prevention. However, changing demographics of latex allergy and technological revolution in countries such as China and India are predicted to unleash a second wave of latex allergy reemphasizing the incentive for improved manufacturing procedures for latex products. The desirable high tensile strength and elasticity of natural rubber latex have made the commercial identification of good alternatives very difficult but this would also be attractive for primary prevention. In addition, an effective specific immunotherapy regimen would be valuable for selected high-risk atopic individuals. Current subcutaneous and sublingual immunotherapy schedules have been tested for treatment of latex allergy with evidence of efficacy but the risks of adverse events are high. For such potent allergens as latex, hypoallergenic but T cell-reactive preparations are required for clinical use. Identification of allergenic components of latex products, with generation of monoclonal antibodies and recombinant allergens, allowed sequence determination and mapping of T cell and B cell epitopes. Together, these reagents and data facilitated improved diagnostics and investigation of novel-specific therapeutics. Potential hypoallergenic latex preparations identified include modified non-IgE-reactive allergen molecules and short T cell epitope peptides. The co-administration of adjunct therapies such as anti-IgE or corticosteroids and of appropriate adjuvants for induction of regulatory T cell response offers promise for clinically effective, safe latex-specific vaccines.

Enzymatic properties of an ecto-nucleoside triphosphate diphosphohydrolase from Legionella pneumophila: substrate specificity and requirement for virulence

Legionella pneumophila is the predominant cause of Legionnaires disease, a severe and potentially fatal form of pneumonia. Recently, we identified an ecto-nucleoside triphosphate diphosphohydrolase (NTPDase) from L. pneumophila, termed Lpg1905, which enhances intracellular replication of L. pneumophila in eukaryotic cells. Lpg1905 is the first prokaryotic member of the CD39/NTPDase1 family of enzymes, which are characterized by the presence of five apyrase conserved regions and the ability to hydrolyze nucleoside tri- and diphosphates. Here we examined the substrate specificity of Lpg1905 and showed that apart from ATP and ADP, the enzyme catalyzed the hydrolysis of GTP and GDP but had limited activity against CTP, CDP, UTP, and UDP. Based on amino acid residues conserved in the apyrase conserved regions of eukaryotic NTPDases, we generated five site-directed mutants, Lpg1905E159A, R122A, N168A, Q193A, and W384A. Although the mutations E159A, R122A, Q193A, and W384A abrogated activity completely, N168A resulted in decreased activity caused by reduced affinity for nucleotides. When introduced into the lpg1905 mutant strain of L. pneumophila, only N168A partially restored the ability of L. pneumophila to replicate in THP-1 macrophages. Following intratracheal inoculation of A/J mice, none of the Lpg1905 mutants was able to restore virulence to an lpg1905 mutant during lung infection, thereby demonstrating the importance of NTPDase activity to L. pneumophila infection. Overall, the kinetic studies undertaken here demonstrated important differences to mammalian NTPDases and different sensitivities to NTPDase inhibitors that may reflect underlying structural variations.

Follistatin is a candidate endogenous negative regulator of activin A in experimental allergic asthma

BACKGROUND

Activin A is a member of the transforming growth factor-beta superfamily which is directly implicated in airway structural change and inflammation in asthma. In vitro, the biological effects of activin A are neutralized by the soluble binding protein follistatin.

OBJECTIVE

To determine the potential of endogenous follistatin to suppress activin A in vivo by analysing their relative tissue and kinetic compartmentalization during the effector phase of subchronic Th2-driven mucosal inflammation in a murine model of allergic asthma.

METHODS

Eosinophilic mucosal inflammation was elicited by triggering Th2 recall responses by antigen challenge in ovalbumin-sensitized BALB/c mice. The kinetics and distribution of activin A and follistatin protein were assessed in lung tissue and bronchoalveolar lavage fluid and measured in relation to airway eosinophilia, goblet cell metaplasia and Th2 cytokine production in mediastinal lymph nodes.

RESULTS

Follistatin was released concurrently with activin A suggesting it acts as an endogenous regulator: peak BAL concentrations coincided with maximal airway eosinophilia, and frequency of IL-4, IL-5 and IL-13 producing cells in mediastinal lymph nodes but induction lagged behind the onset of inflammation. Follistatin and activin A immunoreactivity were lost in airway epithelial cells in parallel with goblet cell metaplasia. Exogenous follistatin inhibited the allergen-specific Th2 immune response in mediastinal lymph nodes and mucus production in the lung.

CONCLUSION

Follistatin is preformed in the normal lung and released in concert with activin A suggesting it serves as an endogenous regulator. Disturbance of the fine balance between activin A and its endogenous inhibitor follistatin may be a determinant of the severity of allergic inflammation or tissue phenotypic shift in asthma.

A latex-induced allergic airway inflammation model in mice

Latex allergy is important due to serious health impacts and widespread use of its products. Latex allergic reactions can be induced in skin and mucosal surfaces including the respiratory tract. The development of murine models of allergic airway inflammation has provided a framework to dissect out the cellular and molecular mechanisms of allergic respiratory inflammation. In this study we have developed a new mouse model of latex allergic airway inflammation using aerosol inhalation. The allergic inflammatory responses were characterized in this model. Mice were injected intraperitoneally with 0, 10, 50, or 200 microg of latex extract and their serum anti-latex IgE titers were determined. In the second stage, a standard protocol of inhalation was designed and three doses of latex extract solutions including 1%, 0.1%, and 0.01% were used to induce allergic airway inflammation. Bronchoalveolar lavage cytokines (IL-5 and IL-13) and serum anti-latex IgE and IgG(1) titers were determined by ELISA. Eosinophil levels in lung, peripheral blood, bronchoalveolar lavage and bone marrow were also evaluated. Histological analysis of lung tissue was also performed after latex inhalation. The aerosol inhalation of 1% latex allergens solution and presensitization with 50 mug of latex in this study resulted in the development of allergic airway inflammation characterized by elevated allergen specific IgE and IgG(1), peripheral blood, bronchoalveolar lavage and bone marrow eosinophilia. Histological analysis of the lung revealed an inflammatory response characterized by eosinophil accumulation. Elevated levels of Th2 cytokines IL-5 and IL-13 also were shown in bronchoalveolar lavage samples. These studies demonstrate that sensitization and subsequent aerosol inhalational challenge of latex allergen extract promotes allergic airway inflammation characterized by elevated IL-5 and IL-13 and eosinophils.

T-cell activation in occupational asthma and rhinitis

BACKGROUND

Allergic asthma and rhinitis are described as associated with a Th2 activation. However, recent works indicate that a Th1 activation can also be associated with these diseases, concomitantly to a defect in regulatory T (Treg) cell activation. Occupational asthma (OA) and occupational rhinitis (OR) are peculiar cases of these diseases in which the T-cell activation profile is largely unknown.

OBJECTIVE

To characterize T-cell activation induced after a specific inhalation test (SIT) in OA and OR.

MATERIAL AND METHODS

A total of 21 subjects with OA, 10 subjects with OR, 10 exposed nonallergic (ENA) subjects, and 14 healthy volunteers were included. The SIT with the incriminated substance was performed in patients and ENA subjects. Blood and induced sputum were obtained before and after SIT. T cells were analysed for CD69, CD25, IL-13, and IFN-gamma expression by flow cytometry. IL-4 and IFN-gamma were assayed by enzyme-linked immunosorbent assay (ELISA) in cell culture supernatants. Treg cells were identified as CD4(+)CD25(+high)CD45RO(+)CD69(-) T cells in peripheral blood.

RESULTS

Baseline IFN-gamma production was decreased in OA and OR compared with controls. The SIT induced an increase in both Th1 and Th2 cells in blood and sputum from OA. In this group, the proportion of peripheral Treg cells decreased after SIT. Similar results were found in the CD8(+) population. ELISA assays were concordant with flow cytometry. In OR, an attenuated activation profile was found, with an increase in the proportion of IL-13-producing T cells after SIT. By contrast, in ENA subjects, SIT induced Th2 activation, with an increase in Treg cells and a decrease in Th1 cells.

CONCLUSIONS

Our results demonstrate a gradient of T-cell activation from a tolerating profile in ENA subjects to an inflammatory profile in OA, with an intermediate stage in OR.

A rodent model for allergic dermatitis induced by flea antigens

There have been very few reports of experimentally induced animal models of allergic dermatitis, an immunologic disorder. This report describes the induction of histopathology confirmed allergic dermatitis in C57BL/6 mice along with the consistent clinical sign of alopecia following the administration of flea antigens emulsified in complete Freund's adjuvant (CFA). By comparing different strains of mice, routes of injection, types of adjuvants and different dosages of flea antigens, C57BL/6 mice were found to be most susceptible to flea antigens administered intramuscularly (i.m.) and subsequently developed dermatologic excoriations and local alopecia. The level of specific IgE reactive to flea antigens in C57BL/6 mice after the onset of clinical signs was significantly higher than such levels in mice without clinical signs, suggesting that flea antigen-specific IgE level can be correlated to the severity of allergic hyper-reaction. CD4(+) T lymphocytes and IL-4 rather than IL-10, or IFN-gamma were found to be the predominant cytokines associated with the clinical onset of allergic symptoms in C57BL/6 mice. Further, histopathologic analysis indicated that not only mast cells had infiltrated into the area of the skin lesion, but the damage was found to be at a stage where mast cells were degranulating causing considerable exacerbation of the local injury. In conclusion, this murine allergic dermatitis model induced by flea antigens may provide a useful means to evaluate vaccines or immunodulatory drugs; thus providing researchers with a tool to study allergy-related disorders and other parameters needed in the area of allergic investigations.

Advances in development of hypoallergenic latex immunotherapy

PURPOSE OF REVIEW

The characterization of clinically relevant latex allergens and the production of recombinant allergens is now well advanced, but this knowledge needs to be translated into new strategies for the safe and effective specific treatment of latex allergic diseases including asthma and anaphylaxis.

RECENT FINDINGS

The current status of latex allergy is discussed indicating a changing demographic paradigm. A new wave of latex allergy is emerging outside the healthcare setting with the widespread use of latex products. An increased prevalence in developing countries is also reported. Limited studies on current specific immunotherapy for latex allergy are reviewed, confirming the feasibility but demonstrating an unacceptable risk of adverse events. The characterization of latex allergens and the identification of B and T-cell epitopes point to rational strategies for the generation of hypoallergenic preparations for specific immunotherapy. Results to date for latex allergens are reviewed, including recombinant, chemical modification and synthetic peptide approaches. Candidate hypoallergenic preparations for targeting sensitization to the major allergens Hev b 1, Hev b 3, Hev b 5 and Hev b 6.01 have been identified. Further investigations of optimal regimens for the delivery of specific immunotherapy to induce regulatory T-cell function are warranted.

SUMMARY

The findings point to the selection of suitable hypoallergenic preparations for clinical trials of effective and safe latex allergy immunotherapy.

Cutaneous, but not airway, latex exposure induces allergic lung inflammation and airway hyperreactivity in mice

As respiratory symptoms are common in addition to skin reactions in natural rubber latex allergy, we investigated the significance of different allergen exposure routes in the development of lung inflammation and airway hyperreactivity (AHR). Both intracutaneous (IC) and intraperitoneal (IP) exposure followed by airway challenge with latex proteins induced an influx of mononuclear cells and eosinophils to the lungs. AHR and lung mucus production increased significantly after IC and IP but not after intranasal (IN) exposure. Infiltration of inflammatory cells was associated with the induction of T-helper type 2 (Th2) cytokines and several CC chemokines. Only a marginal induction of these mediators was found after IN exposure. On the contrary, increased levels of transforming growth factor-beta1 and forkhead box 3 mRNA, markers of regulatory activities, were found in the lungs after IN but not after IC exposure. Finally, IC and IP, but not IN, latex exposure induced a striking increase in specific immunoglobulin E (IgE) levels. Cutaneous latex exposure in the absence of adjuvant followed by airway challenge induces a local Th2-dominated lung inflammation and a systemic IgE response. Cutaneous exposure to proteins eluting from latex products may therefore profoundly contribute to the development of asthma in latex allergy.

The hevein domain of the major latex-glove allergen Hev b 6.01 contains dominant T cell reactive sites

BACKGROUND

Sensitization to natural rubber latex (Hevea brasiliensis) is a major cause of occupational asthma and rhinitis affecting frequent latex-glove users. Hev b 6.01, a known major latex allergen, is cleaved naturally into hevein (4.7 kDa) and a C-terminal fragment (14 kDa). Hevein is an abundant protein in latex-glove extracts. As the immune response to allergens is initiated by activation of allergen-specific CD4(+) T cells, identification of dominant T cell epitopes is crucial for the development of specific immunotherapy.

OBJECTIVE

To identify dominant T cell epitopes of Hev b 6.01 in latex-allergic glove users.

METHODS

Ten latex-allergic frequent glove users and six non-latex-allergic atopic control subjects were selected, based on clinical symptoms and positive latex-specific serum IgE. Serum IgE reactivity to glove extract and recombinant Hev b 6.01 (rHev b 6.01) were analysed by ELISA. Latex-specific short-term oligoclonal T cell lines were generated from peripheral blood of latex-allergic subjects. These lines were tested for proliferative responses to overlapping 20-mer peptides of the Hev b 6.01 molecule. CD4(+) T cell intracellular cytokines, IL-4 and IFN-gamma were assessed following stimulation with immobilized anti-CD3 in the presence of IL-2.

RESULTS

All ten of the latex-allergic patients showed serum IgE binding to glove extract while eight of these also showed IgE binding to rHev b 6.01 by ELISA. Western blotting confirmed reactivity with rHev b 6.01 at around 20 kDa. T cell proliferation assays showed that latex-specific T cell lines from all subjects responded to one or more peptides, with greatest frequency of reactivity to peptides Hev b 6.01 p(10-29) and Hev b 6.01 p(19-38) in the hevein domain. An allergic-type cytokine profile with considerable IL-4 in addition to IFN-gamma was evident from intracellular cytokine staining.

CONCLUSION

Hevein is an important T cell as well as B cell immunogen and contains dominant T cell reactive sites.