Mark Craven

Manchester Asthma and Allergy Study: Low-allergen environment can be achieved and maintained during pregnancy and in early life☆☆☆★

BACKGROUND Early exposure to dust mite allergens may be critical for primary sensitization. Reducing exposure may offer a realistic chance for primary prevention of sensitization and asthma, but it is essential to implement measures that can achieve and maintain the low-allergen environment. OBJECTIVE Our purpose was to assess the effectiveness of mite allergen avoidance measures in achieving and maintaining a low-allergen environment during pregnancy and in the first year of life. METHODS The Manchester Asthma and Allergy Study is a prospective, prenatally randomized study that follows the development of asthma and atopy in a cohort of infants at high risk (both parents atopic) who are randomly allocated to full mite allergen avoidance or to a normal regimen. Avoidance measures comprise (1) mite-proof covers (mattress, pillow, and quilt) for parental bed, (2) high-filtration vacuum cleaner, (3) vinyl flooring in infants bedroom, (4) new crib and portable crib mattresses encased in mite-proof material, (5) benzyl benzoate (Acarosan) applied on carpets and soft furniture, (6) bed linens washed in hot water weekly, and (7) washable soft toys. Dust samples from the parental bed, bedroom floor, living room floor, infants mattress, and nursery floor were collected between the 10th and 14th weeks of pregnancy, immediately after birth, and then at age 6 months and 1 year, and Der p 1 levels were determined by mAb-based ELISA. RESULTS Recovered Der p 1 from maternal mattress was reduced by 97. 25% (95% confidence interval [CI] 95.25%-98.41%) during the second and third trimesters of pregnancy, with the effect persisting for 6 months (98% reduction, 95% CI 97.25%-99.1%) and 12 months (97.6% reduction, 95% CI 95.7%-98.6%) after the birth (active vs control, P <.000001). Total Der p 1 from bedroom floor in the active group was reduced by 53.7% (95% CI 25.7%-71.2%) in samples collected within 4 weeks of the childs birth, with the percentage reduction being 62. 8% (95% CI 39.3%-77.2%) at 6 months and 26.5% (95% CI -24% to 57.1%) at 1 year (active compared vs control, P <.007). Der p 1 levels in crib mattress and nursery floor in the active group were extremely low (crib mattresses geometric mean [95% CI] 2.3 ng [1.6-3.4] at birth, 6.8 ng [4.5-10] at age 6 months, and 15.6 ng [9.8-24.8] at age 1 year [active vs control, P =.001]; nursery 1 ng [0.9-1.1] at birth, 1.7 ng [1.2-2.5] at age 6 months, and 2 ng [1.3-3.5] at age 1 year [active vs control, P <.00001]). The total amount of allergen recovered at age 1 year was 29-fold (95% CI 15.1- to 56.7-fold) higher in the control group than in the active group. CONCLUSIONS The avoidance measures used in this study achieved and maintained a low mite allergen environment during pregnancy and in the first year of life in homes of infants at risk of atopy.

Relationship between mite, cat, and dog allergens in reservoir dust and ambient air.

Background: Standardized methods to measure allergen exposure are essential to assess the relationship between exposure, sensitization, and asthma. Most studies have measured allergen levels in reservoir dust, although air samples may be more representative as a measure of inhaled allergen. The aim of this study was to define the relationship between mite, cat, and dog allergen content in the reservoir dust and the levels in the ambient air.

Lymphoproliferative responses in cord blood and at one year: no evidence for the effect of in utero exposure to dust mite allergens

Background Maternal allergen exposure beyond the 22nd week of pregnancy may be important in foetal T cell priming. Allergen‐specific cord blood mononuclear cell (CBMC) immunoproliferative responses without corresponding bacterial antigen responses (tetanus toxoid), have been suggested as evidence of in utero sensitization.

Stringent environmental control in pregnancy and early life: the long‐term effects on mite, cat and dog allergen

Background As part of a primary prevention of asthma study, we measured the effect of environmental control measures on Der p 1, Fel d 1 and Can f 1 over a 3.5‐year period.

Relationship between exposure to domestic allergens and bronchial hyperresponsiveness in non-sensitised, atopic asthmatic subjects

Background: The effect of exposure to allergens not causing sensitisation in atopic asthmatic subjects has not previously been studied. A study was undertaken to assess the degree of asthma severity (measured by spirometry, airway reactivity and exhaled nitric oxide) in atopic asthmatic patients not sensitised to the domestic allergen to which they were exposed. Methods: Dust samples were collected from the living room carpet and mattress in the homes of 248 subjects and dust mite, cat and dog allergen concentrations were measured. Spirometry, non-specific bronchial reactivity (BR), and exhaled nitric oxide (eNO) were ascertained. Patients’ sensitisation status was assessed by skin prick testing. Results: Adult atopic asthmatics not sensitised to mite but exposed to high levels of mite allergen had significantly more severe BR than subjects not exposed to high levels of mite (PD20, geometric mean (GM) 0.21 mg (95% CI 0.09 to 0.47) v 0.86 mg (95% CI 0.44 to 1.67), mean ratio difference 4.1 (95% CI 1.5 to 11.4), p = 0.008). Subjects not sensitised but exposed to high levels of dog allergen also had significantly more severe BR than subjects not exposed (PD20 GM 0.16 v 0.52 mg, mean ratio difference 3.3 (95% CI 1.2 to 9.2), p = 0.01). The differences in BR between these groups were still significant after adjusting for confounding factors. This effect of greater airway reactivity was not seen in subjects exposed but not sensitised to cat allergens. Conclusion: Atopic asthmatic subjects who are exposed to high levels of dust mite or dog allergens but not sensitised to these allergens have evidence of increased airway reactivity.

Dust mite allergens are carried on not only large particles

The major obstacle for the successful measurement of airborne mite allergen is its very low concentration in the absence of vigorous disturbance. The aim of this study was to investigate the particle size distribution of group 2 dust mite allergen using an amplified ELISA system. Air sampling was performed using an Andersen sampler placed in the centre of the room, 1.2 m above floor level (airflow rate28.7 l/min). This is a multistage, multiorifice cascade impactor that is comprised of six stages. Any particle greater that 4.7 μm should impact on stages 1 and 2, whilst stages 3–6 measure the predominantly respiratory range. The sampling was carried out for 30 min after 15 min of vigorous disturbance (vacuum cleaning without bag and filter). Der p 2 was measured using mAb‐based ELISA with the AmpliQ amplification kit (Dako Ltd, Cambridgeshire, UK). The sensitivity was increased ˜15‐fold as compared with standard assay, bringing the level of detection to 300 pg/ml. The majority of airborne Der p 2 (79.4%) was carried on large particles (> 4.7 µm). However, a small but important proportion of airborne Der p 2 (20.6%) was associated with small particles(1.1–4.7 µm). It is worth noting that all the levels measured were below the detection limit of standard assay. In conclusion, we have shown that using an amplification system, airborne mite allergen previously undetectable owing to its low concentration can be quantified. Group 2 dust mite allergen is carried not only on large particles. A small, but potentially significant proportion of this airborne allergen is associated with small particles which, when inhaled, may penetrate deep into the human respiratory tract.

Apoptosis signals in atopy and asthma measured with cDNA arrays

A variety of studies have stressed the importance of the control of inflammatory cell longevity and the balance of pro‐survival and pro‐apoptotic signalling. Recently, asthma was found to be associated with reduced apoptosis of inflammatory cells in lung tissue. The aim of the study was to investigate the systemic activation of apoptosis pathways using cDNA array technology in atopy and asthma. Eighteen atopic asthmatics (AA), eight atopic non‐asthmatic (AN) and 14 healthy control subjects (C) were included in the study. Peripheral blood mononuclear cells were separated with gradient centrifugation, mRNA purified and the reverse‐transcribed probes hybridized to cDNA arrays. The signals were compared by standardizing to the 100 most expressed genes and group differences assessed with the Mann–Whitney U‐test. We found a concerted up‐regulation of several pro‐survival cytokines and growth factors in AN and AA. FAS and FASL were not differentially expressed, but FAST kinase was over‐expressed in AN and AA. The tumour necrosis factor pathway was activated in AN and AA with increased cytokine and receptor levels and increased TRAF2, an intracellular signalling product. There were indications of a down‐regulated p53 system. In contrast, the Bcl‐2 family of genes showed a net pro‐apoptotic profile in AN and AA. The group of caspases showed a constant gene expression pattern in all groups. In conclusion, significant differences in the expression of apoptosis‐related genes were found in peripheral blood of atopic individuals with and without asthma. cDNA array technology proved to be useful and may be complementary to DNA‐based studies in order to analyse interactive and multidimensional pathways as shown here for apoptosis.

Household characteristics and mite allergen levels in Manchester,UK

Background Mite allergen levels vary enormously between different homes in the same geographical area. No large scale studies of mite levels in Manchester homes has been conducted to identify factors associated with higher levels.

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).

Cat ownership in early life and sensitization to cat at age 5 years: A prospective study☆

Abstract Rationale We investigated the effect of cat ownership and exposure to cat allergen on sensitization to cat at age 5 years. Methods Within the context of a prospective birth cohort (Manchester Asthma and Allergy Study), 468 children had specific IgE to cat measured at age 5 years. Sensitization was defined as cat specific IgE greater than 0.2 kU/l. Pet ownership was recorded during pregnancy, at age 3 and at age 5. Fel d 1 and endotoxin levels were measured in dust collected from the living room floor at age 5. Children who had never owned a pet (cat or dog) were used as the reference (n=255). Chi square tests and logistic regression were used in the analysis. Where stated, odds ratios are adjusted for gender, parental atopy, child care arrangements, maternal age and endotoxin exposure (aOR). Results Of children who had never owned a pet, 6.7% were sensitized to cat. Cat ownership was a significant associate of cat sensitization, whether analyzed as cat ever (13.3%, p=0.027), cat always (17.1%, p=0.005), cat in early life (14.2%, p=0.018), cat at age 3 years (14.9%, p=0.015) or cat at age 5 years (16%, p=0.006). These relationships remained in the multivariate analysis (e.g. for cat age 5, aOR 2.54, 95% CI 1.1-5.6, p=0.02). Increasing levels of Fel d 1 in the living room carpet were significantly associated with sensitization to cat (aOR 1.16, 95% CI 1.02-1.32, p=0.024). Conclusions Cat ownership and exposure to cat allergen are risk factors for sensitization to cat at age 5 years.