Differential Gene Expression of Lymphocytes Stimulated with Rhinovirus A and C in Children with Asthma.

Rationale: Individuals with asthma have heightened antibody responses to rhinoviruses (RVs), although those specific for RV-C are lower than responses specific for RV-A, suggesting poor immunity to this species.Objectives: To ascertain and compare T-cell memory responses induced by RV-A and RV-C in children with and without asthma.Methods: Peripheral blood mononuclear cells from 17 children with asthma and 19 control subjects without asthma were stimulated in vitro with peptide formulations to induce representative species-specific responses to RV-A and RV-C. Molecular profiling (RNA sequencing) was used to identify enriched pathways and upstream regulators.Measurements and Main Results: Responses to RV-A showed higher expression of IFNG and STAT1 compared with RV-C, and significant expression of CXCL9, 10, and 11 was not found for RV-C. There was no reciprocal increase of T-helper cell type 2 (Th2) cytokine genes or the Th2 chemokine genes CCL11, CCL17, and CCL22. RV-C induced higher expression of CCL24 (eotaxin-2) than RV-A in the responses of children with and without asthma. Upstream regulator analysis showed both RV-A and, although to a lesser extent, RV-C induced predominant Th1 and inflammatory cytokine expression. The responses of children with asthma compared with those without asthma were lower for both RV-A and RV-C while retaining the pattern of gene expression and upstream regulators characteristic of each species. All groups showed activation of the IL-17A pathway.Conclusions: RV-C induced memory cells with a lower IFN-γ-type response than RV-A without T-helper cell type 2 (Th2) upregulation. Children with asthma had lower recall responses than those without asthma while largely retaining the same gene activation profile for each species. RV-A and RV-C, therefore, induce qualitatively different T-cell responses.

Immunodominant T-Cell Epitopes in the VP1 Capsid Protein of Rhinovirus Species A and C.

Rhinovirus (RV) species A and C are the most frequent cause of respiratory viral illness worldwide, and RV-C has been linked to more severe exacerbations of asthma in young children. Little is known about the immune responses to the different RV species, although studies comparing IgG1 antibody titers found impaired antibody responses to RV-C. Therefore, the aim of this study was to assess whether T-cell immunity to RV-C is similarly impaired. We measured T-cell proliferation to overlapping synthetic peptides covering the entire VP1 capsid protein of an RV-A and RV-C genotype for 20 healthy adult donors. Human leukocyte antigen (HLA) was typed in all the donors in order to investigate possible associations between the HLA type and RV peptide recognition. Total and specific IgG1 antibody titers to the VP1 proteins of both RV-A and RV-C were also measured to examine associations between the antibody and T-cell responses. We identified T-cell epitopes that are specific to and representative of each RV-A and RV-C species. These epitopes stimulated CD4+-specific T-cell proliferation, with similar magnitudes of response for both RV species. All the donors, independent of their HLA-DR or -DQ type, were able to recognize the immunodominant RV-A and -C regions of VP1. Furthermore, the presence or absence of specific antibody titers was not related to changes in T-cell recognition. Our results indicate a dissociation between the antibody and T-cell responses to rhinoviruses. The species-representative T-cell epitopes identified in this study are valuable tools for future studies investigating T-cell responses to the different RV species. IMPORTANCE: Rhinoviruses (RVs) are mostly associated with the common cold and asthma exacerbations, although their contributions to most upper and lower respiratory tract diseases have increasingly been reported. Species C (RV-C) has been associated with more frequent and severe asthma exacerbations in young children and, along with RV-A, is the most clinically relevant species. Little is known about how our immune system responds to rhinoviruses, and there are limited tools to study specific adaptive immunity against each rhinovirus species. In this study, we identified immunodominant T-cell epitopes of the VP1 proteins of RV-A and RV-C, which are representative of each species. The study found that T-cell responses to RV-A and RV-C were of similar magnitudes, in contrast with previous findings showing RV-C-specific antibody responses were low. These findings will provide the basis for future studies on the immune response to rhinoviruses and can help elucidate the mechanisms of severity of rhinovirus-induced infections.

House Dust Mite Allergens: New Discoveries and Relevance to the Allergic Patient.

PURPOSE OF REVIEW: Recent findings on house dust allergens and their contribution to knowledge that will significantly impact on current and future allergy treatments are appraised. RECENT FINDINGS: Quantitation of IgE binding to a spectrum of allergen components in several independent studies in varying locations has largely affirmed the main components as the groups 1 and 2 and possibly 23 allergens with mid-tier contributions from the groups 4, 5, 7, and 21. Prevalent binding to Der p 23 has been recapitulated sometimes with low titers. The IgE of non-asthmatic atopic subjects binds at lower titer and to fewer components than that of asthmatics, and their IgG binding relative to IgE is higher especially for children hospitalized for exacerbation. The higher IgG ratios were associated with increased IL-10 a cytokine more readily induced from T cells of allergic subjects. Peptides representing the groups 1 and 2 allergens can be used to stimulate ex vivo T cells showing responses correlating with IgE binding and providing a valuable tool for ascertaining the contribution of IgE and T cells to disease. Also, the induction of Th2 and follicular helper T cells are shown to make different contributions in mice. Cross-reactivity of IgE binding assays with high-titer cross-reactive antibodies induced by scabies is a problem in the many areas of the world where scabies is highly prevalent and endemic and from recent increases in immigration. In the last few years, allergen research has produced results that warrant rapid translation into diagnostic tools and the formulation of allergen components for immunotherapy.

Chronic cat allergen exposure induces a TH2 cell-dependent IgG4 response related to low sensitization.

BACKGROUND: In human subjects, allergen tolerance has been observed after high-dose allergen exposure or after completed allergen immunotherapy, which is related to the accumulation of anti-inflammatory IgG4. However, the specific T-cell response that leads to IgG4 induction during chronic allergen exposure remains poorly understood. OBJECTIVE: We sought to evaluate the relationship between cat allergen-specific T-cell frequency, cat allergen-specific IgE and IgG4 titers, and clinical status in adults with cat allergy with and without cat ownership and the cellular mechanism by which IgG4 is produced. METHODS: Fel d 1-, Fel d 4-, Fel d 7-, and Fel d 8-specific T-cell responses were characterized by CD154 expression after antigen stimulation. RESULTS: In allergic subjects without cat ownership, the frequency of cat allergen (Fel d 1 and Fel d 4)-specific TH2 (sTH2) cells correlates with higher IgE levels and is linked to asthma. Paradoxically, we observed that subjects with cat allergy and chronic cat exposure maintain a high frequency of sTH2 cells, which correlates with higher IgG4 levels and low sensitization. B cells from allergic, but not nonallergic subjects, are able to produce IgG4 after cognate interactions with sTH2 clones and Fel d 1 peptide or the Fel d 1 recombinant protein. CONCLUSION: These experiments suggest that (1) allergen-experienced B cells with the capacity to produce IgG4 are present in allergic subjects and (2) cat allergen exposure induces an IgG4 response in a TH2 cell-dependent manner. Thus IgG4 accumulation could be mediated by chronic activation of the TH2 response, which in turn drives desensitization.

Identification of Der p 23, a peritrophin-like protein, as a new major Dermatophagoides pteronyssinus allergen associated with the peritrophic matrix of mite fecal pellets.

The house dust mite (HDM) Dermatophagoides pteronyssinus is one of most important allergen sources and a major elicitor of allergic asthma. We screened a D. pteronyssinus expression cDNA library with IgE Abs from HDM allergic patients. A cDNA coding for a new major allergen was isolated, which showed sequence homology to peritrophins, which contain chitin-binding domains and are part of the peritrophic matrix lining the gut of arthropods. The mature Der p 23 allergen was expressed in Escherichia coli as an 8-kDa protein without its hydrophobic leader sequence and purified to homogeneity. It reacted with IgE Abs from 74% of D. pteronyssinus allergic patients (n = 347) at levels comparable to the two major HDM allergens, Der p 1 and Der p 2. Thus, Der p 23 represents a new major D. pteronyssinus allergen. Furthermore, rDer p 23 exhibited high allergenic activity as demonstrated by upregulation of CD203c expression on basophils from D. pteronyssinus allergic patients. Immunogold electron microscopy localized the allergen in the peritrophic matrix lining the midgut of D. pteronyssinus as well as on the surface of the fecal pellets. Thus, we identified a new major D. pteronyssinus allergen as peritrophin-like protein. The high allergenic activity of Der p 23 and its frequent recognition as respiratory allergen may be explained by the fact that it becomes airborne and respirable through its association with mite feces. Der p 23 may be an essential component for diagnosis and specific immunotherapy of HDM allergy.

Recombinant house dust mite allergens.

House dust mites (HDM) are a globally important source of allergen responsible for the sensitization of more than 50% of allergic patients. Specific immunotherapy with HDM extracts is effective but allergen extracts cannot be fully standardized and severe side-effects can occur during the protracted course of treatment. The introduction of molecular biological techniques into allergy research allowed the indentification of more than 20 groups of HDM allergens. Recombinant HDM allergens can be produced in defined concentrations and consistent quality and allow the development of vaccines for HDM allergy with reduced allergenic activity and retained immunogenicity. The immunotherapy trials in pollen allergic patients with recombinant pollen allergens/hypoallergenic allergen derivatives have shown that this treatment is effective and indicated that recombinant HDM vaccines might improve immunotherapy of HDM allergic patients. Here we report the steps for the development of vaccines for HDM allergy. After selection of the most prevalent HDM species, the panel of allergens to be included into a therapeutic vaccine for HDM allergy needs to be determined. HDM allergens with high IgE-binding frequency and clinical relevance will be modified into hypoallergenic variants and evaluated for their allergenic activity and immunogenicity. Derivatives with reduced allergenic activity but with retained immunogenicity would be good candidates for a HDM vaccine for safe and efficient immunotherapy.

Comparison of rhinovirus antibody titers in children with asthma exacerbations and species-specific rhinovirus infection.

BACKGROUND: Asthma exacerbations are associated with human rhinovirus (HRV) infections, and more severe exacerbations are associated with HRV-C. We have previously shown that the HRV-C-specific antibody response is low in healthy adult sera and that most of the antibody to HRV-C is cross-reactive with HRV-A. OBJECTIVES: To compare the antibody response to each HRV species in asthmatic and nonasthmatic children in whom the type of HRV infection was known. METHODS: Total and specific IgG1 binding to HRV viral capsid protein antigens of HRV-A, -B, and -C were tested in the plasma from nonasthmatic children (n = 47) and children presenting to the emergency department with asthma exacerbations (n = 96). HRV, found in most of the children at the time of their exacerbation (72%), was analyzed using molecular typing. RESULTS: Asthmatic children had higher antibody responses to HRV. The titers specific to HRV-A, and to a lesser extent HRV-B, were higher than in nonasthmatic controls. The species-specific responses to HRV-C were markedly lower than titers to HRV-A and HRV-B in both asthmatic and nonasthmatic children (P < .001). The titers both at presentation and after convalescence were not associated with the HRV genotype detected during the exacerbation. CONCLUSIONS: The higher total anti-HRV antibody titers of asthmatic children and their higher anti-HRV-A and -B titers show their development of a heightened antiviral immune response. The low species-specific HRV-C titers found in all groups, even when the virus was found, point to a different and possibly less efficacious immune response to this species.

Hierarchy and molecular properties of house dust mite allergens.

The allergenic load of house dust mite allergy is largely constituted by a few proteins with a hierarchical pattern of allergenicity. The serodominant specificities are the group 1&2 and the group 23 faecal allergens. The collective IgE binding to the group 1&2 allergens can measure unequivocal HDM sensitisation better than HDM extracts although discrepancies have been found in regions with complex acarofauna suggesting a need to investigate the specificity with allergen components. The group 4, 5, 7&21 allergens that each induce responses in about 40% of subjects are mid-tier allergens accounting for most of the remaining IgE binding. Their titres are proportional to the concomitant responses to Der p1&2. Group 2 allergen variants have different antibody binding. Body proteins only occasionally induce sensitisation although a higher prevalence of binding by atopic dermatitis patients provides a new avenue of research. A broad spectrum of IgE binding has been associated with diverse symptoms but not with the severity of asthma which is associated with low IgG antibody. Some allergens such as the group 14 large lipid binding proteins and the recently described proteins Der f 24-33, need further investigation but with the cognoscence that other denominated allergens have been found to be minor sensitisers by comparative quantitative analyses. Scabies is a confounder for diagnosis with extracts, inducing cross-reactive antibodies with Der p 4&20 as is seafood allergy with cross reactivity to Der p 10 a minor HDM allergen. The HDM genome sequence can now be used to verify allelic and paralogous variations.

Allergen ligands in the initiation of allergic sensitization.

As investigations into the innate immune responses that lead to allergic sensitization become better defined, there is a need to determine how allergens could interact with pattern recognition receptors that bind non-proteinaceous moieties. Many important allergens are not covalently bound to lipid or carbohydrate, but have structures belonging to lipid, glycan and glycolipid-binding families. These include ML-domain proteins, lipopolysaccharide-binding/cell permeability-increasing proteins, von Ebner gland lipocalins, salivary lipocalins/major urinary proteins, plant pathogenesis-related proteins PR-5 and -10, uteroglobins, non-specific lipid transfer proteins, large lipid transfer proteins and proteins with chitin and other carbohydrate-binding modules. The binding expected is overviewed with regard to importance of the allergens and their ability to elicit responses proposed from experimental models. The evidence compiled showing that allergens from the same source sensitize for different types of adaptive immune responses supports the concept that individual allergens within these sources have their own distinctive interactions with innate immunity.

Quantitation of IgE binding to the chitinase and chitinase-like house dust mite allergens Der p 15 and Der p 18 compared to the major and mid-range allergens.

BACKGROUND: The prevalence of IgE binding to the group 15 and 18 house dust mite (HDM) allergens of the Dermatophagoides species is reported to be >50% and they are the major allergens of HDM-sensitised dogs. The objective was to quantitate the IgE titres to Der p 15 and Der p 18 and evaluate their importance in human HDM sensitisation compared to the known major and mid-tier allergens. METHODS: Der p 15 and Der p 18 were produced in Pichia pastoris, and their structure validated by circular dichroism. IgE binding was measured in 37 Australian HDM-allergic adults using a quantitative DELFIA™ assay. RESULTS: The prevalence of IgE titres to Der p 15 and Der p 18 >0.1 ng/ml was low (38%) and only one subject had a titre >10 ng/ml to either allergen. The mean anti-Der p 15 and Der p 18 titres were 1.2 and 2.6 ng/ml, respectively, i.e. approximately 10- to 20-fold lower than the response to the major Der p 1 and Der p 2 allergens (p < 0.001). The IgE responses to Der p 15 and Der p 18 were lower than the mid-tier allergens Der p 5 and Der p 7 and although they correlated with each other, they did not correlate with titres to either the major or mid-tier allergens. CONCLUSIONS: Sensitisation to Der p 15 and Der p 18 makes a minor contribution to anti-HDM IgE titres, and the titres do not correlate with the size of the response to the major allergens.

Hypoallergenic Der p 1/Der p 2 combination vaccines for immunotherapy of house dust mite allergy.

BACKGROUND: More than 50% of allergic patients have house dust mite (HDM) allergy. Group 1 and 2 allergens are the major HDM allergens. OBJECTIVE: We sought to produce and perform preclinical characterization of a recombinant hypoallergenic combination vaccine for specific immunotherapy of HDM allergy. METHODS: Synthetic genes coding for 2 hybrid proteins consisting of reassembled Der p 1 and Der p 2 fragments with (recombinant Der p 2 [rDer p 2]/1C) and without (rDer p 2/1S) cysteines were expressed in Escherichia coli and purified to homogeneity by means of affinity chromatography. Protein fold was determined by using circular dichroism analysis, allergenic activity was determined by testing IgE reactivity and using basophil activation assays, and the presence of T-cell epitopes was determined based on lymphoproliferation in allergic patients. Mice and rabbits were immunized to study the molecules' ability to induce an allergic response and whether they induce allergen-specific IgG capable of inhibiting allergic patients' IgE binding to the allergens, respectively. RESULTS: rDer p 2/1C and rDer p 2/1S were expressed in large amounts in E coli as soluble and folded proteins. Because of the lack of disulfide bonds, rDer p 2/1S did not form aggregates and was obtained as a monomeric protein, whereas rDer p 2/1C did form aggregates. Both hypoallergens lacked relevant IgE reactivity and had reduced ability to induce allergic inflammation and allergic responses but induced similar T-cell proliferation as the wild-type allergens. Immunization with the hypoallergens (rDer p 2/1S > rDer p 2/1C) induced IgG antibodies in rabbits that inhibited the IgE reactivity of patients with HDM allergy to Der p 1 and Der p 2. CONCLUSION: The preclinical characterization indicates that particularly rDer p 2/1S can be used as a safe hypoallergenic molecule for both tolerance and vaccination approaches to treat HDM allergy.

Antibacterial antibody responses associated with the development of asthma in house dust mite-sensitised and non-sensitised children.

BACKGROUND: Infants who develop house dust mite (HDM) allergy and HDM-sensitised children with severe persistent asthma have low antibody responses to the P6 antigen of Haemophilus influenzae. OBJECTIVE: To measure the development of antibody to two ubiquitous bacteria of the respiratory mucosa in a prospective birth cohort at high risk of allergic disease and to assess which responses are associated with asthma and atopy. METHODS: IgG1 and IgG4 antibody to H influenzae (P4 and P6) and Streptoccocus pneumoniae (PspA and PspC) surface antigens was measured in yearly blood samples of children aged 1-5 years. IgE to the P6 antigen was examined for the 5-year group. The children were stratified based on HDM sensitisation and asthma at 5 years of age. RESULTS: HDM-sensitised children had lower IgG1 antibody titres to the bacterial antigens, and early responses (<3 years and before the development of HDM sensitisation and asthma) corrected for multiple antigens were significantly reduced for P4, P6 and PspC (p=0.008, p=0.004 and p=0.028, respectively). Similar associations with asthma were also found (p=0.008, p=0.004 and p=0.032 for P4, P6 and PspC, respectively). The IgG4 antibody titre and prevalence were similar in both HDM-sensitised and non-sensitised groups, but sensitised children had a slower downregulation of the IgG4 response. Children with asthma (27/145 at 5 years) had lower anti-P6 IgE responses (p<0.05). CONCLUSIONS: HDM-sensitised children have early defective antibody responses to bacteria that are associated with asthma. Surprisingly, antibacterial IgE was associated with a reduced risk for asthma.

Sensitizing and Th2 adjuvant activity of cysteine protease allergens.

BACKGROUND: Innate properties that enhance immune responses might increase the propensity of certain allergens to induce allergic sensitization. Either a direct adjuvant effect or the increased immune response to the allergen could then increase allergic responses to bystander antigens. Here, we report on a model that does not use Th2-skewing adjuvants and yet achieves sensitization solely via the nasal mucosa. METHODS: Animals were sensitized with either enzymatically active, inactive or non-activated cysteine proteases via the nasal mucosa. Following two sensitization phases, mice were challenged with a higher dose of allergen. For bystander sensitization, mice received recombinant Der p 2 at sensitization in conjunction with the cysteine protease and were challenged with rDer p 2 alone. Sensitization was determined by measuring allergen-specific antibody responses and cytokine and cellular infiltrates into the lungs following challenge. RESULTS: Sensitization for Th2-type lung hypersensitivity for both the cysteine protease and bystander antigens was readily achieved and both were dependent on the proteolytic activity of the allergen. Bystander adjuvant activity was demonstrated for mice that were low IgE responders to the cysteine protease, showing a response independent from the immune response to the enhancing cysteine protease. Airway hyperreactivity was induced in the susceptible NOD strain of mouse, and mice subjected to prolonged administration of papain maintained the ability to produce lung hypersensitivity and Th2-type responses. CONCLUSIONS: These experiments demonstrate that cysteine protease activity at low doses can be an adjuvant for respiratory Th2 responses for themselves and bystander antigens in the absence of another adjuvant.

Varying allergen composition and content affects the in vivo allergenic activity of commercial Dermatophagoides pteronyssinus extracts.

BACKGROUND: Diagnosis and immunotherapy of house-dust mite (HDM) allergy is still based on natural allergen extracts. The aim of this study was to analyze commercially available Dermatophagoides pteronyssinus extracts from different manufacturers regarding allergen composition and content and whether variations may affect their allergenic activity. METHODS: Antibodies specific for several D. pteronyssinus allergens (Der p 1, 2, 5, 7, 10 and 21) were used to analyze extracts from 10 different manufacturers by immunoblotting. Sandwich ELISAs were used to quantify Der p 1 and Der p 2 in the extracts. Mite-allergic patients (n = 45) were skin-tested with the extracts and tested for immunoglobulin E (IgE) reactivity to a panel of 10 mite allergens (Der p 1, 2, 4, 5, 7, 8, 10, 14, 20 and 21) by dot blot. RESULTS: Only Der p 1 and Der p 2 were detected in all extracts but their concentrations and ratios showed high variability (Der p 1: 6.0-40.8 µg ml(-1); Der p 2: 1.7-45.0 µg ml(-1)). At least 1 out of 4 allergens (i.e. Der p 5, 7, 10 and 21) was not detected in 8 of the studied extracts. Mite-allergic subjects showed different IgE reactivity profiles to the individual mite allergens, the extracts showed different allergenic activity in skin-prick tests and false-negative results. CONCLUSIONS: Commercially available D. pteronyssinus extracts lack important allergens, show great variability regarding allergen composition and content and some gave false-negative diagnostic test results in certain patients.

Reduced rhinovirus-specific antibodies are associated with acute exacerbations of chronic obstructive pulmonary disease requiring hospitalisation.

BACKGROUND: Acute exacerbations of chronic obstructive pulmonary disease (AECOPD) are often linked to respiratory infections. However, it is unknown if COPD patients who experience frequent exacerbations have impaired humoral immunity. The aim of this study was to determine if antibodies specific for common respiratory pathogens are associated with AECOPD. METHODS: Plasma was obtained from COPD patients when clinically stable. AECOPD requiring hospitalisation were recorded. IgG1 antibodies to H. Influenzae outer membrane protein 6 (P6), pneumococcal surface protein C (PspC) and the VP1 viral capsid protein of rhinovirus were measured. RESULTS: COPD patients who had an AECOPD (n = 32) had significantly lower anti-VP1 IgG1 antibody levels when stable compared to COPD patients who did not have an AECOPD (n = 28, p = 0.024). Furthermore, the number of hospitalisations was inversely proportional to anti-VP1 antibody levels (r = -0.331, p = 0.011). In contrast, antibodies specific for P6 and PspC were present at similar concentrations between groups. Plasma IL-21, a cytokine important for B-cell development and antibody synthesis, was also lower in COPD patients who had an AECOPD, than in stable COPD patients (p = 0.046). CONCLUSION: Deficient humoral immunity specific for rhinoviruses is associated with AECOPD requiring hospitalisation, and may partly explain why some COPD patients have an increased exacerbation risk following respiratory viral infections.

The advent of recombinant allergens and allergen cloning.

When the allergen nomenclature system was adopted in 1986, allergens were identified by their behavior on electrophoresis and chromatography and by reactivity to shared antisera. Not only was this unsatisfactory for standardization, but the processes of allergic sensitization and immunotherapy could not be studied in the framework of antigen processing and B- and T-cell epitopes. Recombinant technologies developed in the 1980s for cloning cDNA from low-abundance mRNA permitted the cloning of allergens, beginning with the major house dust mite allergen Der p 1 and hornet allergen Dol m 5. After this, a wave of cloning with IgE immunoscreening resulted in the cloning of Der p 2, Der p 5, Bet v 1, Bet v 2, and Dac g 2 along with Fel d 1 cloned after amino acid sequencing. Recombinant allergens have now been used to define the important allergens for a wide range of allergies and to develop new types of immunotherapy, some of which have shown efficacy in human trials. The clonally pure allergens have been used to solve the tertiary structures of allergens and from this how allergens might activate innate immunity. Proprietary recombinant allergens are now being used in improved diagnostic tests.

Homology modeling and monoclonal antibody binding of the Der f 7 dust mite allergen.

The group 7 allergens are important allergenic specificities for mite-sensitive patients and may need to be incorporated into new diagnostic and therapeutic strategies. However, little is known about their biological and structural features. Position-specific iterative BLAST showed that they had strong ancestral homology to two related families of lipid-binding proteins, namely, the bactericidal permeability-increasing (BPI) proteins and the odorant-binding protein. A three-dimensional model of Der f 7 made with the Phyre and SWISS-MODEL homology-modeling servers showed a close match with the human BPI coordinates used for its construction. The binding of the monoclonal antibody HD12 known to block IgE binding could be blocked by the linear sequence (46GILDF50) with a critical role for L48 or F50. These hydrophobic residues were located on a surface loop of the model. The properties of Der f 7 that can be deduced from the model provide avenues for further characterizing these allergens, their IgE binding structures and biological properties that can enhance allergenicity.

Interactions between innate antiviral and atopic immunoinflammatory pathways precipitate and sustain asthma exacerbations in children.

Severe asthma exacerbations in children requiring hospitalization are typically associated with viral infection and occur almost exclusively among atopics, but the significance of these comorbidities is unknown. We hypothesized that underlying interactions between immunoinflammatory pathways related to responses to aeroallergen and virus are involved, and that evidence of these interactions is detectable in circulating cells during exacerbations. To address this hypothesis we used a genomics-based approach involving profiling of PBMC subpopulations collected during exacerbation vs convalescence by microarray and flow cytometry. We demonstrate that circulating T cells manifest the postactivated "exhausted" phenotype during exacerbations, whereas monocyte/dendritic cell populations display up-regulated CCR2 expression accompanied by phenotypic changes that have strong potential for enhancing local inflammation after their recruitment to the atopic lung. Notably, up-regulation of FcepsilonR1, which is known to markedly amplify capacity for allergen uptake/presentation to Th2 effector cells via IgE-mediated allergen capture, and secondarily programming of IL-4/IL-13-dependent IL-13R(+) alternatively activated macrophages that have been demonstrated in experimental settings to be a potent source of autocrine IL-13 production. We additionally show that this disease-associated activation profile can be reproduced in vitro by cytokine exposure of atopic monocytes, and furthermore that IFN-alpha can exert both positive and negative roles in the process. Our findings suggest that respiratory viral infection in atopic children may initiate an atopy-dependent cascade that amplifies and sustains airway inflammation initiated by innate antiviral immunity via harnessing underlying atopy-associated mechanisms. These interactions may account for the unique susceptibility of atopics to severe viral-induced asthma exacerbations.

Geography of house dust mite allergens.

OBJECTIVE: To consider how the different distribution of house dust mites and their species in different geographical locations affects the allergens in the environment and their use. DATA SOURCES: Data were obtained from Medline, Genbank and library and web searches. STUDY SELECTIONS: A comprehensive description of the genetic variations of allergens is given. The distribution of house dust mites is illustrated with publications that either make pertinent observations or would be useful for a broad appreciation of their geographical distribution. RESULTS: The review identifies regions where glycyphagid house dust mites have been found and the distribution of the pyroglyphid Dermatophagoides spp. The antigenic differences the allergens of D. pteronyssinus and D. farinae are outlined and how this should affect optimal allergen usage in different regions. The allelic variations within the major allergens of Dermatophagoides sp. are similarly presented. CONCLUSIONS: While there is a broad knowledge of the distribution of different species of house dust mites, regions that require further examination have been identified and there are examples of incorrect use of allergens for different regions. The extension of allergy research and practice into new regions will benefit from allergen formulations designed for regional use. Specific knowledge of the allergens in the environments will be required to optimally implement some of the new molecularly-defined medicaments currently being developed for effective allergy vaccination and immunotherapy.