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.

Dysfunctional Gut Microbiome Networks in Childhood IgE-Mediated Food Allergy.

The development of food allergy has been reported to be related with the changes in the gut microbiome, however the specific microbe associated with the pathogenesis of food allergy remains elusive. This study aimed to comprehensively characterize the gut microbiome and identify individual or group gut microbes relating to food-allergy using 16S rRNA gene sequencing with network analysis. Faecal samples were collected from children with IgE-mediated food allergies (n = 33) and without food allergy (n = 27). Gut microbiome was profiled by 16S rRNA gene sequencing. OTUs obtained from 16S rRNA gene sequencing were then used to construct a co-abundance network using Weighted Gene Co-expression Network Analysis (WGCNA) and mapped onto Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. We identified a co-abundance network module to be positively correlated with IgE-mediated food allergy and this module was characterized by a hub taxon, namely Ruminococcaceae UCG-002 (phylum Firmicutes). Functional pathway analysis of all the gut microbiome showed enrichment of methane metabolism and glycerolipid metabolism in the gut microbiome of food-allergic children and enrichment of ubiquinone and other terpenoid-quinone biosynthesis in the gut microbiome of non-food allergic children. We concluded that Ruminococcaceae UCG-002 may play determinant roles in gut microbial community structure and function leading to the development of IgE-mediated food allergy.

Clinical significance of circulating microRNAs as markers in detecting and predicting congenital heart defects in children.

BACKGROUND: Circulating microRNAs (miRNAs) are emerging as novel biomarkers for detecting cardiovascular diseases. In this study, we aimed to investigate the usefulness of miRNAs as biomarkers in diagnosing and predicting children with congenital heart defects (CHD), particularly in the context of multiple subtypes of CHD. METHODS: We recruited 26 families, each having a child with CHD and parents who do not have any cardiovascular disorder. 27 families unaffected by cardiovascular disease were also included as controls. Firstly, we screened 84 circulating miRNAs relating to cardiovascular development in 6 children with atrial septal defects (ASD) and 5 healthy children. We validated the selected miRNAs with differential expression in a larger sample size (n = 27 for controls, n = 26 for cases), and evaluated their signal in different types of septal defects. Finally, we examined the identified miRNAs signatures in the parent population and assessed their diagnostic values for predicting CHD. RESULTS: The three miRNAs hsa-let-7a, hsa-let-7b and hsa-miR-486 were significantly upregulated in children with ASD. A further validation study showed that overexpression of hsa-let-7a and hsa-let-7b was specifically present in ASD children, but not in children with other subtypes of septal defects. A similar expression profile of hsa-let-7a and hsa-let-7b was discovered in mothers of ASD children. Receiver-operating characteristic curve analyses indicated that hsa-let-7a and hsa-let-7b had significant diagnostic values for detecting ASD and in maternal samples predicting the occurrence of ASD in offspring. CONCLUSIONS: Circulating miRNAs are important markers not only for diagnosing CHD, but also for predicting CHD risk in offspring. The distinct miRNA signatures are likely to present in various subtypes of CHD, and the phenotypic heterogeneity of CHD should be considered to develop such miRNA-based assays.

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.

Distinguishing benign from pathologic TH2 immunity in atopic children.

BACKGROUND: Although most children with asthma and rhinitis are sensitized to aeroallergens, only a minority of sensitized children are symptomatic, implying the underlying operation of efficient anti-inflammatory control mechanisms. OBJECTIVE: We sought to identify endogenous control mechanisms that attenuate expression of IgE-associated responsiveness to aeroallergens in sensitized children. METHODS: In 3 independent population samples we analyzed relationships between aeroallergen-specific IgE and corresponding allergen-specific IgG (sIgG) and associated immunophenotypes in atopic children and susceptibility to asthma and rhinitis, focusing on responses to house dust mite and grass. RESULTS: Among mite-sensitized children across all populations and at different ages, house dust mite-specific IgG/IgE ratios (but not IgG4/IgE ratios) were significantly lower in children with asthma compared with ratios in those without asthma and lowest among the most severely symptomatic. This finding was mirrored by relationships between rhinitis and antibody responses to grass. Depending on age/allergen specificity, 20% to 40% of children with allergen-specific IgE (sIgE) of 0.35 kU/L or greater had negative skin test responses, and these children also expressed the high sIgG/sIgE immunophenotype. sIgG1 from these children inhibited allergen-induced IgE-dependent basophil activation in a dose-dependent fashion. Profiling of aeroallergen-specific CD4(+) TH memory responses revealed positive associations between sIgG/sIgE ratios and IL-10-dependent gene signatures and significantly higher IL-10/TH2 cytokine (protein) ratios among nonsymptomatic children. CONCLUSION: In addition to its role in blocking TH2 effector activation in the late-phase allergic response, IL-10 is a known IgG1 switch factor. We posit that its production during allergen-induced memory responses contributes significantly to attenuation of inflammation through promoting IgG1-mediated damping of the FcεRI-dependent acute-phase reaction. sIgG1/sIgE balance might represent a readily accessible therapeutic target for asthma/rhinitis control.

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.

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.

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.

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.

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.

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.

House dust mite sublingual immunotherapy: the role for transforming growth factor-beta and functional regulatory T cells.

RATIONALE: Sublingual allergen-specific immunotherapy is gaining popularity for treatment of allergic diseases, but underlying immunological mechanisms are unresolved. OBJECTIVES: To perform detailed immunological investigation of sublingual house dust mite (HDM) immunotherapy. METHODS: A 12-month randomized double-blind placebo-controlled study of sublingual HDM immunotherapy in 30 HDM-allergic subjects was performed, with 1-year open extension in 9 patients on active treatment. HDM-stimulated blood mononuclear cells were analyzed for proliferation, cytokines, and regulatory T cells (Tregs) by flow cytometry and ELISA. Effects of blocking transforming growth factor (TGF)-beta and IL-10 on proliferation were determined. Treg suppressor function and allergen-specific antibody levels were measured. Clinical efficacy was assessed by symptom, medication, and Juniper quality-of-life scores. MEASUREMENTS AND MAIN RESULTS: Allergen-induced CD4(+) T-cell division and IL-5 production were significantly decreased after 6- and 12-months' active treatment but not placebo. sTGF-betaRII blocked immunotherapy-induced suppression of allergen-specific T-cell proliferation, maximal at 6 months. Decreased allergen-specific CD4(+) T-cell proliferation and increased IL-10 secretion and serum Der p 2-specific IgG(4) were maximal at 24 months' active treatment. Treg (CD4(+)CD25(+)CD127(lo)/Foxp3(+)) function was demonstrated by suppression of allergen-specific effector T-cell (CD4(+)CD25(-)CD127(hi)) proliferation and cytokine production. Clinical efficacy of immunotherapy was supported by significantly decreased rhinitis symptom score, total asthma score, and Juniper quality-of-life score. CONCLUSIONS: This study establishes the novel finding that TGF-beta mediates the immunological suppression seen early in clinically effective sublingual HDM immunotherapy in addition to an increase in Tregs with suppressor function. Clinical trial registered with www.clinicaltrials.gov (NCT00250263).

Linking the westernised oropharyngeal microbiome to the immune response in Chinese immigrants.

BACKGROUND: Human microbiota plays a fundamental role in modulating the immune response. Western environment and lifestyle are envisaged to alter the human microbiota with a new microbiome profile established in Chinese immigrants, which fails to prime the immune system. Here, we investigated how differences in composition of oropharyngeal microbiome may contribute to patterns of interaction between the microbiome and immune system in Chinese immigrants living in Australia. METHODS: We recruited 44 adult Chinese immigrants: newly-arrived (n = 22, living in Australia < 6 months) and long-term Chinese immigrants (n = 22, living in Australia > 5 years), with age and gender matched. Oropharyngeal swabs, serum and whole blood were collected. The 16 s ribosomal RNA gene from the swabs was sequenced on the Illumina MiSeq platform. Innate immune responses were determined by 23 Toll-like receptors (TLR) pathway cytokines, while adaptive immune responses were determined by IgG-associated response to specific microbial/viral pathogens. RESULTS: The relative abundance of the genus Leptotrichia was higher in long-term immigrants as compared to that in newly-arrived Chinese immigrants, while the genus Deinococcus was significantly lower in long-term Chinese immigrants. The genera uncultured Lachnospiraceae, Erysipelotrichaceae UCG-007, Veillonella, and Actinomycetales_ambiguous taxa were negatively correlated with cytokine IL-6 in long-term Chinese immigrants (rho range: - 0.46 ~ - 0.73). With respect to adaptive immunity, several microbial taxa were significantly associated with IgG1 responsiveness to microbial antigens in long-term immigrants, while a significant correlation with IgG1 responsiveness to viral antigens was detected in newly-arrived immigrants. CONCLUSIONS: The composition of the oropharyngeal microbiome varies between newly-arrived and long-term Chinese immigrants. Specific microbial taxa are significantly associated with immunological parameters but with different association patterns between newly-arrived and long-term Chinese immigrants.

Effects of Ser47-Point Mutation on Conformation Structure and Allergenicity of the Allergen of Der p 2, a Major House Dust Mite Allergen.

PURPOSE: Hypoallergenic recombinant Der p 2 has been produced by various genetic manipulations, but mutation of a naturally polymorphic amino acid residue known to affect IgE binding has not been studied. This study aimed to determine the effect of a point mutation (S47W) of residue 47 of Der p 2 on its structure and immunoglobulin (Ig) E binding. Its ability to induce pro-inflammatory responses and to induce blocking IgG antibody was also determined. METHODS: S47 of recombinant Der p 2.0110, one of the predominant variants in Bangkok, was mutated to W (S47W). S47W secreted from Pichia pastoris was examined for secondary structure and for the formation of a hydrophobic cavity by 8-Anilino-1-naphthalenesulfonic acid (ANS) staining. Monoclonal and human IgE-antibody binding was determined by enzyme-linked immunosorbent assay. Allergen-induced degranulation by human epsilon receptor expressed-rat basophil was determined. Stimulation of the pro-inflammatory cytokine interleukin (IL)-8 release from human bronchial epithelial (BEAS2B) cells and inhibition of IgE binding to the wild type allergen by S47W-induced IgG were determined. RESULTS: S47W reduced secondary structure and failed to bind the hydrophobic ANS ligand as well as a monoclonal antibody known to be dependent on the nature of the side chain of residue 114 in an adjacent loop. It could also not stimulate IL-8 release from BEAS2B cells. IgE from house dust mite (HDM)-allergic Thais bound S47W with 100-fold weaker avidity, whereas IgE of HDM-allergic Australians did not. S47W still induced basophil degranulation, although requiring higher concentrations for some subjects. Anti-S47W antiserum-immunized mice blocked the binding of human IgE to wild type Der p 2. CONCLUSIONS: The mutant S47W had altered structure and reduced ability to stimulate pro-inflammatory responses and to bind IgE, but retained its ability to induce blocking antibodies. It thus represents a hypoallergen produced by a single mutation of a non-solvent-accessible amino acid.

T-cell responses against rhinovirus species A and C in asthmatic and healthy children.

BACKGROUND: Infections by rhinovirus (RV) species A and C are the most common causes of exacerbations of asthma and a major cause of exacerbations of other acute and chronic respiratory diseases. Infections by both species are prevalent in pre-school and school-aged children and, particularly for RV-C, can cause severe symptoms and a need for hospitalization. While associations between RV infection and asthma are well established, the adaptive immune-mechanisms by which RV infections influence asthma exacerbations are yet to be defined. OBJECTIVE: The aim of this study was to characterize and compare T-cell responses between RV-A and RV-C and to test the hypothesis that T-cell responses would differ between asthmatic children and healthy controls. METHODS: A multi-parameter flow cytometry assay was used to characterize the in vitro recall T-cell response against RV-A and RV-C in PBMCs from children with acute asthma (n = 22) and controls (n = 26). The responses were induced by pools of peptides containing species-specific VP1 epitopes of RV-A and RV-C. RESULTS: Regardless of children's clinical status, all children that responded to the in vitro stimulation (>90%) had a similar magnitude of CD4+ T-cell responses to RV-A and RV-C. However, asthmatic children had a significantly lower number of circulating regulatory T cells (Tregs), and healthy controls had significantly more Tregs induced by RV-A than RV-C. CONCLUSIONS AND CLINICAL RELEVANCE: The comparable recall memory T-cell responses in asthmatic and control children to both RV-A and RV-C show that differences in the antibody and inflammatory responses previously described are likely to be due to regulation, with a demonstrated candidate being reduced regulatory T-cells. The reduced Treg numbers demonstrated here could explain the asthmatic's inability to appropriately control immunopathological responses to RV infections.

T and B cell responses to HDM allergens and antigens.

House dust mites provide well-characterized proteins to study human responses to inhaled antigens. Even in the absence of allergy they induce a high frequency of T cell precursors. The healthy response manifests by T cell proliferation and Th1 cytokines with little antibody. Responses of allergic people include Th1 and Th2 cytokines and IgE, IgG1, and IgG4 antibodies. Regulatory cells limit effector responses in healthy people. About half the IgE and IgG antibodies bind the group 1 and 2 allergens and 30% bind the group 4, 5, and 7 allergens. Although HLA independent, the recognition of the group 1 allergen shows an immunodominant region and a T cell receptor bias. The major allergens are not produced in higher amounts than many of the poorly non-allergenic proteins. The non-allergenic mite ferritin antigen shows high T cell proliferative responses with mixed cytokine production.

Pyroglyphid house dust mite allergens.

Mites of the family Pyroglyphidae are the most important source of house dust mite allergens. A small number of allergens, namely those of groups 1, 2, 4, 5 and 7 constitute the known major and mid-potency specificities, with possible important contributions of the groups 11, 14 and 15 requiring further definition. Most of the allergens can be identified by sequence homologies and the structures of the major allergens have been solved. There are however challenges in determining the nature of the group 5 and 7 allergens and in obtaining detailed structures of the significant allergens to be used for genetic engineering.