High prevalence of sensitization to cat allergen among Japanese children with asthma, living without cats

BACKGROUND: Cat allergy is common among children with asthma. Many cat-allergic patients in Japan and elsewhere do not keep cats, but nonetheless become sensitized through environmental exposure to cat allergen. OBJECTIVE: To assess the frequency of cat allergy and cat-specific immunoglobulin E (IgE) and immunoglobulin G (IgG) antibody responses in young Japanese patients with asthma in relation to self-reported cat exposure and Fel d 1 levels in dust samples. METHODS: Cat dander-specific IgE antibody was measured in sera from asthma patients using the CAP system. IgE and IgG antibody to Fel d 1 was measured by antigen binding radioimmunoassay and by chimeric enzyme immunoassay. Fel d 1 levels in dust samples from a subset of patients' homes were measured by monoclonal antibody-based enzyme immunoassay. RESULTS: Cat-specific IgE (CAP class>/=2) was found in sera from 70% of 44 patients who kept cats and 34% of 394 patients who had never kept cats. The prevalence of sensitization increased progressively to age 6 years (40%: positive), and then increased gradually to age 16 years (approximately 60%: positive) in patients who had never kept cats. There was an excellent correlation between cat CAP values and IgE levels to Fel d 1. The absolute amount of IgE antibody to Fel d 1 ranged from 0.01 to 15.6% of total IgE. Most patients who did not keep cats were exposed to Fel d 1 levels ranging from 0.07-8 microg/g dust. CONCLUSIONS: Sensitization to cat allergen is common among young asthmatic patients in Japan, even among patients who do not keep cats. Use of CAP and the chimeric enzyme-linked immunosorbent assay allows accurate diagnosis of cat allergy and quantification of specific IgE antibody levels.     

Higher immunoglobulin E antibody levels to recombinant Fel d 1 in cat-allergic children with asthma compared with rhinoconjunctivitis

Background Current diagnosis of allergy and asthma to cat is confirmed using cat dander extract (CDE). We have previously engineered a recombinant major cat allergen, rFel d 1, with properties identical to the natural molecule.
Objective The aim of the study was to evaluate IgE and IgG4 antibodies to rFel d 1 among sera from cat-allergic children and adults suffering from asthma and/or rhinoconjunctivitis (RC) in populations from Sweden and Austria.
Methods Cat-allergic children and adults from Sweden ( n =27 and 31, respectively) and Austria ( n =41 and 41) with RC and/or asthma were selected. Sera were tested for IgE and IgG4 antibodies to CDE and rFel d 1 by CAP, and IgE to rFel d 1 by ELISA. Healthy subjects and non-cat-allergic patients ( n =75) were included as controls.
Results There was a high correlation between IgE responses to rFel d 1 and CDE among the 140 patients ( r _s=0.85, P <0.001); however, measured levels to rFel d 1 were on average 30% higher ( P <0.0001). Ninety-eight percent of patients and none of the controls showed IgE to rFel d 1 and there was a threefold increased risk of asthma for half of the children with the highest IgE levels [odds ratio 3.23; 95% confidence interval (CI), 1.19–8.79] by ELISA. IgE responses to rFel d 1 among children with asthma were higher (median 19.4 kU/L) compared with children with RC (median 6.6 kU/L, P <0.05) and adults with asthma (median 3.0 kU/L, P <0.01). Furthermore, children with asthma displayed higher IgG4 levels than the asthmatic adults.
Conclusion A single recombinant molecule, rFel d 1, is at least as sensitive for in vitro diagnostics of cat allergy as the current extract-based test. Elevated IgE antibody levels to Fel d 1 are suggested to be a risk factor for asthma in cat-allergic children.     

Prolonged antigen-exposure with carbohydrate particle based vaccination prevents allergic immune responses in sensitized mice

Background:  Defined particles carrying tightly bound allergens at high density have been suggested as alternatives in allergy vaccination. Carbohydrate based particles (CBP), sized 2 μm, provide a platform for covalent coupling of allergens.
Objective:  To investigate the mechanisms of antigen presentation by CBP, as well as cellular and humoral responses after vaccination with the major cat allergen Fel d 1, covalently coupled to CBP.
Methods:  Mice ( n  = 10/group) were subcutaneously vaccinated with CBP-rFel d 1, CBP or phosphate buffer saline (PBS) before sensitization with rFel d 1 and challenged with cat dander extract. Fluorescent and ⁷⁵Se-radiolabeled tracking of allergens and particles were performed with flow cytometry and whole-body autoradiography. Humoral, cellular and regulatory immune responses were analyzed by ELISA and flow cytometry. Cytokines were measured in bronchoalveolar lavage fluid and splenocyte cultures.
Results:  CBP-rFel d 1 prevented induction of airway inflammation and induced allergen-specific T-cell anergy. CBP-rFel d 1 also induced rapid IgM and IgG1-responses compared with soluble rFel d 1. Particles were phagocytosed by antigen-presenting cells and transported to draining lymph nodes and spleen. Moreover, antigen coupled to CBP remained longer at the injection site compared with alum.
Conclusions:  Covalent coupling of rFel d 1 to CBP induces rapid antibody production, prevents induction of allergic immune responses and systemic allergen spreading. Thus, CBP comprise several attractive adjuvant features for use in allergy vaccination.
Clinical Implications:  Prolonged allergen exposure through covalent coupling to particles suitable for phagocytosis, provides an adjuvant for safer and efficient allergy vaccination.     

The cat lipocalin Fel d 7 and its cross‐reactivity with the dog lipocalin Can f 1

We investigated the prevalence of sensitization to the cat lipocalin Fel d 7 among 140 cat‐sensitized Swedish patients and elucidated its allergenic activity and cross‐reactivity with the dog lipocalin Can f 1. Sixty‐five of 140 patients had IgE to rFel d 7 whereof 60 also had IgE to rCan f 1. A moderate correlation between IgE levels to rFel d 7 and rCan f 1 was found. rFel d 7 activated basophils in vitro and inhibited IgE binding to rCan f 1 in 4 of 13 patients, whereas rCan f 1 inhibited IgE binding to rFel d 7 in 7 of 13 patients. Fel d 7 and Can f 1 showed high similarities in protein structure and epitopes in common were found using cross‐reactive antisera. Fel d 7 is a common allergen in a Swedish cat‐sensitized population that cross‐reacts with Can f 1, and may contribute to symptoms in cat‐ but also in dog‐allergic patients.     

Allergic potency of recombinant Fel d 1 is reduced by low concentrations of chlorine bleach

BACKGROUND: Sodium hypochlorite (NaOCl), the primary component of household bleach, has been shown to alter the purified mouse allergen Mus m 1, such that antibody recognition, or immunogenicity, is lost. Results of initial experiments suggest that antibody recognition is lost at lower concentrations of NaOCl than those required to fragment Mus m 1. OBJECTIVE: We sought to determine whether NaOCl had similar effects on recombinant (r)Fel d 1 and whether the loss of antibody recognition correlated with the loss of biologic activity, as measured with a basophil histamine release assay. METHODS: Recombinant Fel d 1 was treated with increasing amounts of NaOCl, and the product of the reaction was analyzed by using SDS-PAGE, Western blotting, and ELISA. The biologic activity of NaOCl-treated rFel d 1 was analyzed with a basophil histamine release assay. RESULTS: The protein fragmented at an NaOCl/rFel d 1 molar ratio of 7000, whereas cat-specific IgG recognition was lost at a lower molar ratio of 560. Basophil histamine release assays were performed to determine the effect of NaOCl on the biologic activity of rFel d 1. An NaOCl/protein molar ratio of 70 caused a significant reduction in histamine release from basophils of subjects with cat allergy. A molar ratio of 140 further inhibited histamine release by rFel d 1, suggesting a dose-response relationship between NaOCl and loss of biologic activity. CONCLUSIONS: NaOCl modifies rFel d 1, resulting in loss of immunogenicity and attenuation of biologic activity, as measured by its ability to stimulate basophil histamine release.     

Fel d 4, a cat lipocalin allergen

BACKGROUND: Cat allergy is unique among allergy to mammals in that the major allergen Fel d 1 is a uteroglobin-like protein and not a lipocalin. The biochemical spectrum of the cat allergens is thus uncertain, particularly with regard to the role that a cat lipocalin protein may play in sensitization to cats in allergic individuals. OBJECTIVE: To analyse cDNA encoding a lipocalin allergen and the corresponding recombinant allergen at both the molecular and immunological levels. METHODS: A submandibular salivary gland cDNA expression library was constructed and screened for clones producing IgE-binding polypeptides. cDNA encoding a lipocalin allergen and its corresponding recombinant allergen were analysed. RESULTS: An IgE binding molecule with high sequence identity to the boar salivary lipocalin and the horse lipocalin Equ c 1 allergen was isolated and designated, Fel d 4. Serum from 62.96% of cat-allergic subjects examined had measurable IgE antibody to Fel d 4 but typically at low levels. Despite this in 47% of sera the anti-Fel d 4 IgE titres were higher than the anti-Fel d 1 titres. IgE binding to the lipocalin allergen could be blocked by an allergen extract from cow and to a lesser degree by extracts from horse and dog. CONCLUSION: Fel d 4 is a lipocalin allergen produced by the cat, which binds IgE at relatively high frequency in cat-sensitive individuals. The allergen provides not only a means for investigating differences in the immune response to lipocalin allergens from that found for other mammalian species but also an important reagent for the diagnosis of cat allergy.     

Detection of an allergen in dog dander that cross-reacts with the major cat allergen, Fel d 1

BACKGROUND: A considerable proportion of animal-allergic patients are sensitized to both cat and dog allergens but knowledge about cross-reactive allergens in cat and dog dander is limited. OBJECTIVE: To investigate whether dog dander contains an allergen that cross-reacts with the major cat allergen, Fel d 1. METHODS: Recombinant Fel d 1 with the same immunological properties as natural Fel d 1 was used for quantitative (CAP) IgE competition experiments performed with sera obtained from cat-allergic patients (n=36). A Fel d 1 cross-reactive dog allergen was characterized by one- and two-dimensional immunoblotting using rFel d 1 for IgE inhibition experiments and with monospecific, polyclonal rabbit anti-recombinant Fel d 1 antibodies. RESULTS: In 25% of Fel d 1-reactive cat-allergic patients, more than 50% inhibition of IgE reactivity to dog allergens was achieved with recombinant Fel d 1. An Fel d 1 cross-reactive 20 kDa allergen with a pI of approximately 3.4 was detected in dander extracts of several different dog breeds. CONCLUSION: This is the first report demonstrating the presence of an Fel d 1-like allergen in dog dander extracts, which may be responsible for double positivity to cat and dog in serology. However, the clinical relevance of this cross-sensitization needs to be confirmed. These results are important for the diagnostic and therapeutic use of dog dander allergen extracts.     

The relevance of maternal immune responses to inhalant allergens to maternal symptoms,passive transfer to the infant,and development of antibodies in the first 2 years of life

BACKGROUND: Asthma and other atopic diseases are strongly hereditary. Although the mother might play a special role, the mechanisms for such an effect are not clear. OBJECTIVE: We sought to investigate the influence of maternal immune responses to cat and mite allergens on (1) maternal symptoms, (2) the development of immune responses in the infant, and (3) the development of allergic disease during the first 3 years of life. METHODS: In sera from 465 mothers and 424 infants (cord blood), as well as in sera from 230 of the children at age 2 to 3 years, total IgE and IgE antibodies were measured by using CAP testing; IgG and IgG4 antibodies for the cat allergen Fel d 1 were measured by means of radioimmunoprecipitation. RESULTS: In both mothers and children, approximately 15% of sera contained IgG antibodies to Fel d 1 without IgE antibodies to cat. The strongest predictor of the maternal IgG antibody response was exposure to greater than 8 microg of Fel d 1/g of dust. Thus approximately 70% of children living in a house with a cat had received IgG antibodies from their mothers. In many cases the infant received IgG and IgG4 antibodies to Fel d 1 from a nonallergic mother. Maternal IgE antibodies were consistently associated with asthma; by contrast, the IgG antibody was not independently related to asthma but was related to rhinitis in the mothers (odds ratio, 2.6; 95% CI, 1.1-6.2) and to eczema in children. At age 3 years, 13 of 230 sera contained IgE antibodies to mite, but only 5 had IgE antibodies to cat. CONCLUSIONS: A significant proportion (approximately 15%) of mothers and children exposed to high concentrations of cat (but not mite) allergens have serum IgG antibodies without IgE antibodies. This IgG antibody is freely transferred to the infant and might influence IgG antibody production in the child. The results indicate the importance of understanding the mechanisms of tolerance to cats and raise questions about the independent role of the mother in the inheritance of allergy.     

A novel adjuvant-allergen complex, CBP-rFel d 1, induces up-regulation of CD86 expression and enhances cytokine release by human dendritic cells in vitro

Allergen-specific immunotherapy is commonly performed with allergen extracts adsorbed to aluminium hydroxide (alum). The undesirable effects associated with the use of alum, including granuloma formation at the site of injection and stimulation of T helper 2 (Th2) cytokine production, has generated interest in alternative allergen carriers, one being carbohydrate-based particles (CBPs). Here, we have investigated the in vitro effects of the recombinant major cat allergen Fel d 1 (rFel d 1) coupled to CBPs (CBP-rFel d 1) on human monocyte-derived dendritic cells (MDDCs) obtained from healthy blood donors. A majority of the CD1a(+) MDDCs internalized fluorescein isothiocyanate-labelled CBP-rFel d 1, as demonstrated by flow cytometry and confocal laser-scanning microscopy. Furthermore, an up-regulation of the expression of the costimulatory molecule, CD86, on the MDDCs was induced by CBP-rFel d 1, but not by rFel d 1 or CBPs alone. Finally, three- and fourfold increases in the release of interleukin-8 and tumour necrosis factor-alpha, respectively, were observed when MDDCs were cultured in the presence of CBP-rFel d 1. Altogether, our results indicate that the use of CBPs as an allergen carrier and adjuvant is a promising candidate for the improvement of allergen-specific immunotherapy.     

Carbohydrate-based particles reduce allergic inflammation in a mouse model for cat allergy

Background:  Allergen-specific immunotherapy (ASIT) is the only treatment of allergic disease that gives long-lasting relief of symptoms. However, concerns for safety and efficiency have highlighted the need for improvement of the therapy. We have previously suggested carbohydrate-based particles (CBPs) as a novel adjuvant and allergen carrier for ASIT. Our aim of this study was to evaluate the therapeutic potential of CBPs in ASIT, employing a mouse model for cat allergy.
Methods:  BALB/c mice were subcutaneously immunized with the recombinant (r) cat allergen Fel d 1 followed by intranasal challenge with cat dander extract (CDE). The sensitized mice were therapeutically treated with rFel d 1 covalently coupled to CBPs (CBP-rFel d 1). Airway hyper-reactivity (AHR), infiltration of leucocytes in bronchoalveolar lavage (BAL) fluid, allergen-specific serum immunoglobulin levels and in vitro splenocyte responses were evaluated.
Results:  Mice treated with CBP-rFel d 1 showed reduced features of allergic inflammation. They responded with (i) significantly decreased AHR and infiltration of eosinophils in BAL fluid after CDE challenge, (ii) the serum level of rFel d 1-specific IgE was reduced and the level of IgG₂a was more pronounced after CBP-rFel d 1 treatment, and (iii) there was also a tendency of decreased allergen-specific cellular response.
Conclusions:  Carbohydrate-based particles are effective tools as adjuvant and allergen carriers for use in ASIT and constitutes a promising strategy to improve allergy treatment.     

Human T and B cell immune responses to Fel d 1 in cat-allergic and non-cat-allergic subjects

Background In allergic individuals exposure to allergen leads to the induction of allergen-specific IgE which, upon binding to its high affinity receptors on mast cells and basophils. primes these cells for degranulation. This degranulation. a result of specific IgE allergen-interaction, initiates the debilitating symptoms of allergy and the potentially life-threatening symptoms of anaphylaxis. The lack of symptoms following antigen encounter by non-allergic individuals is probably due to the undetectable levels of allergen-specific IgE in the plasma of non-allergic individuals. Objective To compare the immune responses of allergic and non-allergic individuals. Method We compared the immune responses of 42 cat-allergic subjects with 16 nem-cat-allergic subjects to the major cat allergen. Fel d I. We have measured plasma immunoglobulin levels and the proliferative responses of fel d 1 primed T cell lines to Fel d 1 peptides. Results While these two groups have similar levels of Fel d 1 specific IgG. only subjects in the cat-allergic group have detectable Fel d 1 specific IgE. Affinity purified Fel d 1 was used to generate T cell lines from peripheral blood mononuclear cells of these same subjects. The proliferative responses of these T cell lines to intact Fel d 1 and a set of overlapping peptides covering the entire sequence of the molecule demonstrated that the pattern of epitope recognition was similar in both groups. Conclusion Our data suggest that factors other than T cell recognition of specific epitopes are responsible for the nature of allergic immune responses generated when allergen is encountered.     

Vaccination for birch pollen allergy. Induction of affinity-matured or blocking IgG antibodies does not account for the reduced binding of IgE to Bet v 1

Specific allergy vaccination (SAV) is associated with increased levels of allergen specific IgG in serum. It is not clear, however, to what extent qualitative changes in allergen binding to IgG may be induced as well. We therefore analyzed the binding of the major allergen in pollen of birch (Betula verrucosa) (Bet v 1), the major allergen in birch pollen, to serum IgG and IgE, separately and in competition. Sera from six birch pollen-allergic patients were obtained before and after 5 years of SAV, and binding was assessed with 125I-Bet v 1. Before SAV, IgG bound more than eight times the amount of Bet v 1 compared with IgE, and together they accounted for more than 85% of the serum binding capacity. While SAV induced minimal changes in IgE binding, the IgG binding capacities increased 6-32 times. In contrast, the binding avidities (K(d) 28-40pM) changed less than 20%, pre- and post-SAV IgG provided similar inhibition of Bet v 1 binding to IgE at equimolar levels, and cross inhibition studies between IgG and IgE showed low inter-individual differences. Following SAV, all sera reduced Bet v 1 binding to CD23(+) cells, correlating with reduced binding of Bet v 1 to IgE (P<0.001). These results show that high avidity IgG of low inter-individual difference in Bet v 1 binding quality is the dominant binding factor of Bet v 1 in sera of birch pollen-allergic patients, and that SAV-induced inhibition of binding of Bet v 1 to IgE can be explained mainly or solely by increased amounts of IgG.     

Evidence for a Fel d I-like molecule in the "big cats" (Felidae species).

In this study, we investigated the cross-reactivity pattern of IgE and IgG4 antibodies to the major feline allergen, Fel d I. We studied the IgE and IgG4 response of 11 cat-allergic patients against Fel d I-like structures in eight members of the Felidae family: ocelot, puma, serval, siberian tiger, lion, jaguar, snow leopard, and caracal. Hair from these "big cats" was collected, extracted, and used in a RAST system and histamine-release test. By means of a RAST-inhibition assay with affinity-purified Fel d I from cat dander, it was established that, in the Felidae species, a Fel d I equivalent is present that reacts with IgE and IgG4 antibodies. We found that all patients had cross-reacting IgE antibodies to seven of the Felidae tested; no IgE antibodies reactive with the caracal were found. Eight of 10 patients with IgG4 antibodies directed to cat dander also had IgG4 antibodies directed to several Felidae species, including the caracal. However, the correlation between the IgE and the IgG4 antibody specificity was low, indicating that, in the case of Fel d I IgE and IgG4, antibodies do not necessarily have the same specificity.     

Distinctive immunoglobulin E anti-house dust allergen-binding specificities in a tropical Australian Aboriginal community

BACKGROUND: There is evidence that the specificity of the IgE binding in allergy tests can vary for different populations. OBJECTIVE: We aimed to examine the allergenic specificity of IgE binding in sera from house dust mite (HDM)-atopic subjects in a tropical Australian Aboriginal community. METHODS: Sera shown to contain IgE antibodies to an HDM extract of Dermatophagoides pteronyssinus were examined for IgE binding to a panel of nine purified HDM allergens from this mite species by quantitative microtitre assays. IgG antibody binding (IgG1 and IgG4) was also measured. RESULTS: The IgE-binding activity in the sera from the Aboriginal community was not directed to the expected major groups 1 and 2 HDM allergens but instead to the group 4 amylase allergen. There was also little IgE binding to the potentially cross-reactive tropomyosin (Der p 10) or arginine kinase (Der p 20) allergens. The IgG4 antibody was rarely detected and limited to the Der p 4 allergen. IgG1 antibody binding was frequently measured to all the allergens regardless of an individual's atopic status, whereas in urban communities it is restricted to the major allergens and to atopic subjects. CONCLUSION: The high IgE anti-HDM response of Australian Aboriginals predominantly bound Der p 4 and not the Der p 1 and 2 allergens, showing a distinctive allergy that could affect the disease outcome and diagnosis.     

An essential role for dendritic cells in human and experimental allergic rhinitis

BACKGROUND: In allergic rhinitis (AR) CD4(+) T(H)2 lymphocytes control inflammation by secreting T(H)2 cytokines, but little is known about how these cells are activated to cause disease. OBJECTIVE: We sought to study the contribution of antigen-presenting dendritic cells (DCs) in activating T(H)2 cells and controlling allergic inflammation. METHODS: Nasal mucosal biopsy specimens were taken from patients with house dust mite allergy and perennial AR and healthy control subjects. DC numbers were evaluated by using immunohistochemistry. The functional role of DCs was studied in a novel mouse model for AR using BALB/c mice and CD11c-diphtheria toxin (DT) receptor transgenic mice. RESULTS: In symptomatic patients with perennial AR, the number of CD1a(+) and CD11c(+) MHCII(+) DCs was higher in the epithelium and lamina propria of the nasal mucosa compared with that seen in healthy control subjects. In patients with AR, DCs had a more mature (CD86(+)) phenotype and were found in close approximation with T lymphocytes. Similarly, in a mouse model of ovalbumin (OVA)-induced AR, CD11c(+) DCs accumulated in areas of nasal eosinophilic inflammation and clustered with CD4(+) T lymphocytes. CD11c(+) DCs were conditionally depleted during allergen challenge by means of systemic administration of DT to CD11c-diphtheria toxin receptor transgenic mice to address the functional role of DCs in maintaining inflammation. In the absence of CD11c(+) DCs, nasal OVA challenge in OVA-sensitized mice did not induce nasal eosinophilia and did not boost OVA-specific IgE levels or T(H)2 cytokine production in the cervical lymph nodes. Conversely, when OVA-pulsed DCs were administered intranasally to sensitized mice, they strongly enhanced OVA-induced nasal eosinophilia and T(H)2 cytokine production. CONCLUSIONS: These data in human subjects and mice suggest an essential role for nasal DCs in activation of effector T(H)2 function leading to AR. CLINICAL IMPLICATIONS: Nasal DCs play an essential role in AR and therefore constitute a novel target for therapeutic intervention.     

Longitudinal study on the relationship between cat allergen and endotoxin exposure, sensitization, cat-specific IgG and development of asthma in childhood--report of the German Multicentre Allergy Study (MAS 90)

BACKGROUND: Controversial data have emerged regarding the question whether cat exposure in childhood favours or decreases the risk of sensitization and allergic airway disease. In a prospective birth-cohort study, we assessed the association between longitudinal cat allergen exposure, sensitization (immunoglobulin E, IgE), IgG antibody (ab) levels to cat and the development of asthma in children up to the age of 10 years. METHODS: Of 1314 newborn infants enrolled in five German cities in 1990, follow-up data at age 10 years were available for 750 children. Assessments included yearly measurements of specific serum IgE to cat and at age 6 and 18 months, 3, 4 and 10 years measurement of cat allergen Fel d 1 in house dust samples. Additionally, Fel d 1-specific IgG ab were determined in 378 serum samples of 207 children. Endotoxin exposure in mattress dust was measured in a subgroup of 153 children at age 10 years. From age 4 years on, International Study of Asthma and Allergy in Childhood (ISAAC) questionnaires were completed yearly in order to assess the prevalence of wheeze and asthma. RESULTS: Serum IgG-levels to cat showed a large variation, however, intraindividually values showed rather constant concentration over a longer time period. The IgG levels at school-age correlated with cat allergen exposure during the first 2 years of life. Specific IgE to cat was clearly associated with wheeze ever, current wheeze and bronchial hyperresponsiveness (BHR), this was also observed for children with specific IgE ab to cat (>0.35 kU/l) plus IgG levels above 125 U/ml. A large percentage of very highly exposed children showed high IgG but no IgE responses to cat, however, not all highly exposed children were found to be protected from sensitization. Children with IgG but without IgE ab to cat showed the lowest prevalence of wheeze ever and current wheeze despite high cat allergen exposure, however, this trend did not achieve significance. While homes of cat owners showed higher Fel d 1 concentrations than homes without cats, homes of cat owners were not found to have higher endotoxin levels in carpet dust samples than homes without cats. CONCLUSIONS: We could confirm that high cat allergen exposure in a cohort with lower community prevalence of cats is associated with higher serum IgG and IgE levels to cat in schoolchildren. Sensitization to cat allergen (IgE) is a risk factor for childhood asthma. While exposure to cat allergen during infancy is associated with sensitization (IgE), only in the very highly exposed children the likelihood of sensitization (IgE) is decreased and high IgG levels to cat without IgE were associated with low risk of wheeze. However, cat-specific IgG ab levels did not protect children with IgE-mediated sensitization from wheeze.     

Comparison of allergen-stimulated dendritic cells from atopic and nonatopic donors dissecting their effect on autologous naive and memory T helper cells of such donors

BACKGROUND: Because of their production of IL-12, mature dendritic cells (DC) are potent inducers of T(H)1 responses. However, recent reports have demonstrated that DCs can also induce T(H)2 differentiation. OBJECTIVE: In the current study we investigated which immune response is induced by DCs in naive CD45RA(+) or memory CD45R0(+) CD4(+) T cells from atopic individuals (patients with grass pollen, birch pollen, or house dust mite allergy) compared with nonatopic control subjects. METHODS: Immature DCs, generated from peripheral blood monocytes from atopic and nonatopic donors, were pulsed with the respective allergen and fully matured. Then the mature DCs were cocultured in vitro with autologous naive (CD45RA(+)) and memory (CD45R0(+)) CD4(+) T cells and cytokine and IgE production were measured by ELISA. RESULTS: After the second restimulation with allergen-pulsed DCs, naive as well as memory autologous CD4(+) T cells from atopic but not from nonatopic donors showed an enhanced production of the T(H)2-type cytokines IL-4, IL-5, and IL-10, resulting in an increased IgE production, whereas IFN-gamma production and proliferation were not different. IL-12 production and surface marker expression of DCs derived from atopic and nonatopic donors did not differ and addition of neutralizing anti-IL-12 mAbs did not increase IL-4 but diminished IFN-gamma production. CONCLUSION: These data indicate that mature DCs are able to induce naive and activate allergen-specific T helper cells to produce T(H)2 cytokines if the T cells are derived from atopic donors. This phenomenon is not due to diminished IL-12 production by DCs of atopic donors.     

Asian ladybugs (Harmonia axyridis): a new seasonal indoor allergen

BACKGROUND: Harmonia axyridis, the Asian ladybug (ALB), was repeatedly introduced between 1916 and 1990. These beetles are intolerant to cold and move indoors during the winter. OBJECTIVE: To investigate sensitization to ALB. METHODS: Proteins in ALB extracts were purified by gel filtration and ion exchange chromatography. Purified fractions were screened for IgE antibody using the streptavidin CAP technique in sera from 20 patients with allergy living in ALB-infested houses. Two proteins were fully purified. Serum antibodies were also assessed in sera from 68 adult patients with asthma. RESULTS: Fifteen of the 20 sera had measurable IgE antibody, 7 with high titers, > 10 IU/mL, to ALB extract. The 2 proteins, Har a 1, 10 kd, and Har a 2, 55 kd, bound IgE antibody in 65% and 75% of the sera, respectively. Sequencing revealed a novel N-terminal sequence for Har a 1. Sequencing of Har a 2 demonstrated homology to a dehydrogenase from the red flour beetle. Although sera from 18 of the patients with asthma were positive for IgE antibody to ALB, they were also positive to Blatella germanica. These subjects did not report exposure to H axyridis, and inhibition studies with B germanica blocked > or = 95% of ALB IgE antibody binding. CONCLUSION: Two proteins of ALB have been purified and used to demonstrate that patients exposed to this beetle can develop high-titer IgE antibody. Cross-reactivity with B germanica was found but was significant only among patients primarily exposed to cockroaches. CLINICAL IMPLICATIONS: Asian ladybug has become an important seasonal indoor allergen in the United States.     

The role of allergen-specific IgE,IgG and IgA in allergic disease

Immunoglobulin E (IgE)-mediated allergy is the most common hypersensitivity disease affecting more than 30% of the population. Exposure to even minute quantities of allergens can lead to the production of IgE antibodies in atopic individuals. This is termed allergic sensitization, which occurs mainly in early childhood. Allergen-specific IgE then binds to the high (FcεRI) and low-affinity receptors (FcεRII, also called CD23) for IgE on effector cells and antigen-presenting cells. Subsequent and repeated allergen exposure increases allergen-specific IgE levels and, by receptor cross-linking, triggers immediate release of inflammatory mediators from mast cells and basophils whereas IgE-facilitated allergen presentation perpetuates T cell–mediated allergic inflammation. Due to engagement of receptors which are highly selective for IgE, even tiny amounts of allergens can induce massive inflammation. Naturally occurring allergen-specific IgG and IgA antibodies usually recognize different epitopes on allergens compared with IgE and do not efficiently interfere with allergen-induced inflammation. However, IgG and IgA antibodies to these important IgE epitopes can be induced by allergen-specific immunotherapy or by passive immunization. These will lead to competition with IgE for binding with the allergen and prevent allergic responses. Similarly, anti-IgE treatment does the same by preventing IgE from binding to its receptor on mast cells and basophils. Here, we review the complex interplay of allergen-specific IgE, IgG and IgA and the corresponding cell receptors in allergic diseases and its relevance for diagnosis, treatment and prevention of allergy.     

Isolation and characterization of relevant allergens from boiled lentils

BACKGROUND: Lentils seem to be the most common legume implicated in pediatric allergic patients in the Mediterranean area. However, no lentil allergen has been isolated and characterized. OBJECTIVE: We sought to purify and characterize relevant IgE-binding proteins from boiled lentil extracts. METHODS: IgE-binding proteins from crude and boiled lentil extracts were detected with a pool of sera from patients with lentil allergy. Allergens were isolated by gel-filtration chromatography followed by cation- and anion-exchange chromatography or by reverse-phase HPLC. Their characterization included N-terminal amino acid sequencing, complex asparagine-linked glycan detection, specific IgE immunodetection with 22 individual sera from allergic patients, and immunoblot and CAP inhibition assays. RESULTS: Heat treatment of lentils produced substantial changes in the SDS-PAGE patterns of whole extracts, mainly a strong increase of 12- to 16-kd bands and a decrease of 25- to 45-kd components. Major IgE-binding proteins from the boiled lentil extract were located in the 12- to 16-kd and 45- to 70-kd ranges. Two allergens of 16 kd, proteins L1 and L2, and another one of 12 kd, protein L3, were purified. N-terminal sequencing indicated that all 3 were related and allowed their identification as gamma-vicilin subunits. Protein L1 was recognized by 68% of the individual sera tested and inhibited 64% of the IgE binding by commercial lentil CAPs. A second type of allergen of 66 kd, named protein H, was also isolated and identified as a seed-specific biotinylated protein. Protein H reacted with 41% of the individual sera and produced 45% inhibition in CAP inhibition assays. CONCLUSIONS: Two different types of allergens have been identified in boiled lentils. Those of 12 to 16 kd, called Len c 1, correspond to gamma-vicilin subunits, and those of 66 kd, designated Len c 2, correspond to seed-specific biotinylated protein. Homology with proteins from other legume species can explain potential cross-reactions among these foods.