T cell cytokine responses to outer membrane proteins of Haemophilus influenzae and the house dust mite allergens Der p 1 in allergic and non-allergic subjects

BACKGROUND: Haemophilus influenzae are ubiquitous colonizers of the nasopharynx, Little is known about the T cell cytokine responses to the antigens of these bacteria and whether or not the responses may interact with responses to aeroallergen. OBJECTIVE: To measure the T cell cytokine responses to conserved outer membrane protein antigens of Haemophilus influenzae and to house dust mite allergen of subjects allergic to the house dust mite and of subjects without allergic sensitization. METHODS: T cell responses were measured by in vitro proliferation and cytokine release from peripheral blood monocytes (PBMC). The allergen used was Der p 1 and outer membrane proteins were recombinant polypeptides representing the OMP6 and D15 antigens. RESULTS: The PBMC of most subjects had proliferative responses to OMP6 and D15, which were highly correlated. The pattern of cytokine release was Th1 biased with high levels of IFN-gamma and usually little IL-5 or IL-13 although PBMC from a few subjects did release IL-5 independent of allergic status. IL-10 release was readily detected. There was no difference in the anti-OMP cytokine response of PBMC from subjects without any known allergy and the responses of PBMC from subjects who were highly allergic to house dust mite. The responses to the Der p 1 allergen showed the expected Th2 cytokine release. CONCLUSION: The outer membrane protein antigens of the ubiquitous colonizing bacteria Haemophilus influenzae induce Th1 cytokine responses which are similar for PBMC from non-allergic individuals and subjects with a high degree of allergy to the perennial house dust mite allergen and strong Th2 responses to Der p 1.     

Personal exposure to house dust mite allergen in bed: nasal air sampling and reservoir allergen levels

BACKGROUND: Assessment of personal exposure to dust mite allergen has relied on proxy measures. Only recently has a means to directly measure inhaled allergen particle number become available (the intra-nasal air sampler). OBJECTIVE: To quantify inspired dust mite group 1 and group 2 allergen-bearing particles in bed in undisturbed conditions prior to sleep by nasal air sampling and to investigate the relationship between inhaled particles and reservoir allergen levels. METHODS: Twelve volunteers wore nasal samplers in bed for 6 evenings, nose-breathing in undisturbed conditions. Allergen-bearing particles ('halos') were detected by immunostaining for Der p 1, Der p 2, or Der p 1 and Der p 2 together, and counted by light microscopy. Count data were square root transformed for analysis of variance. Mattress dust samples were assayed for Der p 1 and Der p 2 concentrations. RESULTS: Square root detransformed mean particle counts per 30-min sample were: Der p 1, 4.22; Der p 2, 5.9; Der p 1 + Der p 2, 4.87; and for all samples, 5.01, with no difference between the groups. With replicate samples, halo number correlated significantly with mattress allergen concentrations (Der p 1 r = 0.80, P < 0.01; Der p 2 r = 0.68, P < 0.02). CONCLUSION: Nasal air sampling can be used to quantify nocturnal Der p exposure in undisturbed conditions in an area with moderate exposure to mite allergen and can provide a direct measure of inhaled mite allergen. The choice of either Der p 1 or Der p 2 is appropriate for this purpose.     

Proteolytic,lipidergic and polysaccharide molecular recognition shape innate responses to house dust mite allergens

House dust mites (HDMs) are sources of an extensive repertoire of allergens responsible for a range of allergic conditions. Technological advances have accelerated the identification of these allergens and characterized their putative roles within HDMs. Understanding their functional bioactivities is illuminating how they interact with the immune system to cause disease and how interrelations between them are essential to maximize allergic responses. Two types of allergen bioactivity, namely proteolysis and peptidolipid/lipid binding, elicit IgE and stimulate bystander responses to unrelated allergens. Much of this influence arises from Toll-like receptor (TLR) 4 or TLR2 signalling and, in the case of protease allergens, the activation of additional pleiotropic effectors with strong disease linkage. Of related interest is the interaction of HDM allergens with common components of the house dust matrix, through either their binding to allergens or their autonomous modulation of immune receptors. Herein, we provide a contemporary view of how proteolysis, lipid-binding activity and interactions with polysaccharides and polysaccharide molecular recognition systems coordinate the principal responses which underlie allergy. The power of the catalytically competent group 1 HDM protease allergen component is demonstrated by a review of disclosures surrounding the efficacy of novel inhibitors produced by structure-based design.     

House dust mite allergen exposure in infancy

BACKGROUND: Infancy may be a critical time for exposure to house dust mite allergens, when exposure to high levels can increase the risk of allergic sensitization and the development of asthma in later life. OBJECTIVE: To measure house dust mite allergen (Der p 1) concentration in the infants' environment and examine lifestyle factors which may influence mite allergen exposure. METHODS: Infants aged between 4 and 12 months (n = 134) from the western region of Sydney, Australia. participated. Reservoir dust samples were collected from four sites within each home: infant's bed, second bed (adult or second child's bed), lounge floor and sheepskins (where available). Settling aeroallergen was collected for 10-14 d in Petri dishes in the infant's room. Der p 1 was measured by ELISA. A questionnaire on types of bedding, sleeping and playing patterns of the infant was completed by the parents at the time of dust collection. RESULTS: All infants were exposed to at least one site with Der p 1 concentrations greater than 10 microg/g fine dust. The mean settling aeroallergen level in the infants' room was 24 ng De p l/m2 day and this was weakly related to bed allergen levels (r=0.21, P<0.05). Mattress type had a weak effect on Der p 1 levels as measured in the whole bed (P = 0.07), while bed cover and bed type had no effect (P>0.6). The mean product of time spent at a site and its allergen concentration was highest for beds in 69% of infants. CONCLUSION: The high level of allergen exposure in the environment of this group of infants places them at an increased risk of early sensitization and development of asthma. Any strategy to reduce asthma prevalence should address these high and avoidable levels.     

Associations of allergic sensitization and clinical phenotypes with innate immune response genes polymorphisms are modified by house dust mite allergen exposure

Introduction

Polymorphisms within innate immunity genes are associated with allergic phenotypes but results are variable. These associations were not analyzed with respect to allergen exposure. We investigated associations of TLR and CD14 polymorphisms with allergy phenotypes in the context of house dust mite (HDM) exposure.

Material and methods

Children, aged 12-16 years (n=326), were recruited from downtown and rural locations and assessed by allergist. Skin prick tests, total and HDM-specific sIgE measurements were done. HDM allergen concentrations in dust were measured. Genetic polymorphisms were identified using restriction fragment length polymorphism (RFLP).

Results

Allergic rhinitis, asthma and atopy were more prevalent in urban area. Although HDM allergen concentrations were higher in rural households, sIgE were present more frequently in urban children. In the whole population no association was found between HDM exposure and sensitization. In children with CD14/−159CC, CD14/−159TT and TLR9/2848GA genotypes increased exposure to HDM was associated with reduced incidence of allergic rhinitis. Significant associations of increased HDM exposure with reduced incidence of atopy were found for the whole population and subjects with CD14/−159CC, CD14/−1359GT, TLR4/896AA and TLR9/2848GA genotypes. Among children with CD14/−159CC and CD14/−1359GG significant positive correlation between HDM allergen concentrations in household and sensitization to HDM was observed. In contrast, protective effect of high HDM allergen exposure against specific sensitization was seen in subjects with TLR4/896 AG.

Conclusions

Development of specific sensitization and allergy may be associated with innate immune response genes polymorphisms and is modified by allergen exposure.     

Cord blood mononuclear cell cytokine responses in relation to maternal house dust mite allergen exposure

BACKGROUND: Cord blood mononuclear cells have demonstrated specific immune responses to environmental allergens. OBJECTIVE: To establish whether the nature of this response is related to the level of maternal antenatal exposure to house dust mite (HDM) allergen and, hence, whether antenatal allergen avoidance may have a role in the prevention of allergic sensitization in children. METHODS: Children with a family history of asthma were recruited antenatally as subjects in a randomised controlled trial: the Childhood Asthma Prevention Study. HDM allergen (Der p 1) concentrations were measured in dust collected from the maternal bed at 36 weeks gestation. Cord blood mononuclear cells were stimulated in culture, separately, with phytohaemaglutinin (PHA) and HDM extract. Cytokine IL-4, IL-5, IL-10 and IFN-gamma concentrations in supernatant were measured by ELISA. mRNA signals for these cytokines were measured using RT-PCR. RESULTS: The median concentration of HDM allergen was 18.4 microg/g (interquartile range 7.3-35.3 microg/g). Median concentrations of IL-4, IL-5, IL-10 and IFN-gamma, after PHA stimulation were 4, 19, 401 and 1781 pg/mL, respectively. After HDM allergen stimulation the median concentrations were 0, 0, 20 and 14 pg/mL, respectively. The distribution of mRNA cytokine signals was similar. Neither cytokine protein concentrations nor cytokine mRNA signal levels were correlated with the concentration of HDM allergen in the mothers' beds at 36 weeks gestation. CONCLUSION: These findings do not support the view that the prevention of allergic disease in children requires the institution of HDM avoidance interventions during pregnancy.     

Molecular cloning and immunological characterization of the house dust mite allergen Der f 7

Background The allergen Der p 7 from Dermatophagoides pteronyssinus has been defined by molecular cloning and shown to be an important specificity in 50% of miteallergic patients. Objective This study compares the cDNA sequence and serological reactivity of Der f 7 from D. farinae with Der p 7. Method cDNA encoding Der f 7 was amplified by polymerase chain reaction. sequenced and expressed as a fusion with glutathione-S-transferase for IgE and monoclonal antibody binding studies. Results Der f 7 cDNA encoded a 213 polypeptide containing a predicted 17 amino acid leader sequence, no cysteines and a single N-glycosylation site similar to Der p 7. The predicted 196 residue mature polypeptide had 86% identity lo Der p 7 and a calculated molecular weight of 22 34SDa. No homologues were found in searches of the data banks. The Der f 7 fusion protein showed a single band of 46 k Da by sodium dodccyl snlfute-polyaerylamide gel electrophoresis (SDS-PAGF) and reacted with IgE antibodies in 19/41 (46%) of sera from asthmatic children. The degree of binding was usually 30% of that to Der p 7 consistent with the exposure of the patients to D. Pteronyssinus. Monoclonal antibodies (WH9 and WH22) against Der p 7 reacted with Der f 7 but inhibition studies showed a 10-fold difference in reactivity. Conclusion Der f 7 has a predicted 213 residue polypeptide with 86% homology and serological cross reactivity to Der p 7.     

A recombinant fragment of human SP-D reduces allergic responses in mice sensitized to house dust mite allergens

C57Bl6 mice sensitized to Dermatophagoides pteronyssinus and challenged with D. pteronyssinus allergen extract given intranasally followed by treatment with intranasal applications of a 60-kDa truncated, trimeric recombinant form of human SP-D (rfhSP-D) showed a significant reduction in serum IgE, IgG1, peripheral blood eosinophilia and airway hyperresponsiveness compared to saline or bovine serum albumin-treated controls. Intracellular cytokine staining of lung and spleen homogenates showed increases in interleukin (IL)-12 production in lung tissue and normalization of IL-12 and interferon (IFN)-gamma in spleen tissue. In previous studies we demonstrated the effectiveness of native SP-D and rfhSP-D in down-regulating allergic responses to allergens of Aspergillus fumigatus. The results reported here indicate that rfhSP-D can suppress the development of allergic symptoms in sensitized mice challenged with allergens of the common house dust mite.     

Inhaled formaldehyde exposure: effect on bronchial response to mite allergen in sensitized asthma patients

BACKGROUND: Formaldehyde, an indoor air pollutant, is known to be an irritant and an etiologic factor in occupational asthma. An epidemiologic study suggests that it may also increase the risk of childhood asthma for concentrations above 60 microg/m(3). AIM: To evaluate the influence of pre-exposure to low-dose formaldehyde (100 microg/m(3) in 30 min according to the World Health Organization's recommended maximum value for indoor environments) on bronchial response to Dermatophagoides pteronyssinus. METHOD: Nineteen asthmatic subjects were included. Each subject underwent a mite allergen bronchial challenge test immediately after a standardized exposure in a chamber to formaldehyde or air (random order). Induced sputum were collected 24 h before and after mite challenge. RESULTS: After formaldehyde inhalation, patients developed an immediate bronchial response at a significantly lower dose of mite allergen than after air exposure (the geometric mean PD(20) for Der p 1 was 34.3 ng after formaldehyde and 45.4 ng after placebo, P = 0.05). The late-phase reaction, expressed as the maximum fall in forced expiratory volume in 1 s (FEV(1)) from baseline, was significantly higher after formaldehyde (15%vs 11%, P = 0.046). CONCLUSION: Our study demonstrated that exposure to low levels of formaldehyde significantly enhanced bronchial responsiveness to mite allergen in mite-sensitized subjects with asthma.     

The role of house dust mite elimination in the management of childhood asthma: an unresolved issue

Indoor allergens are likely to be direct environmental causes of asthma and mite exposure, and sensitization is the most important environmental risk factor for childhood asthma in temperate zones. Analagous to occupational asthma, allergen avoidance in asthmatic children sensitized and exposed to mite allergens is associated with a reduction in airway hyperresponsiveness and symptoms associated with improvement in lung function. The long-term effect of this strategy needs to be prospectively evaluated considering both the timing and duration of exposure, as well as the timing and duration of removal. In order to be successful, it is important to achieve and maintain a major reduction on allergen levels, for a long period of time.