T.A.E. Platts-Mills

Exposure and sensitization to dust mite allergens among asthmatic children in Sao Paulo, Brazil

A group of 20 mite allergic asthmatic children aged 6‐12 years old. living in Sao Paulo, Brazil, was studied regarding their degree of sensitization to house dust mites and exposure to mite allergens in their homes. In 18 out of 20 houses at least one dust sample was obtained which contained > 10 μg Der p I/g of dust. The highest levels of Dermatophagoides pteronyssinm allergens, Der p I and Group II, were measured in bedding samples (geometric mean 38.4 and 36.6 μg/g, respectively), followed by bedroom floor, TV room and kitchen. Mite allergen levels in Brazilian houses were as high as those reported to be associated with sensitization and acute attacks of asthma in other parts of the world. In keeping with previous reports that D. farinae is rarely found in Brazil, Der fl was undetectable or found in very low levels (<0.5 μg/g). Levels of cat allergen Pel d I of > 8 μg/g of dust were obtained only in 2 houses only. Cockroach allergen Bia g I was detected in five out of 20 houses. Levels of IgE antibodies to D. pteronyssinus were > 200 RAST U/ml in 19 out of 20 children (geometric mean 1588 RAST U/ml). IgE antibodies to cat, cockroach, A. fumigatus, ragweed and rye grass pollens were undetectable or <80 RAST U/ml. IgE antibodies to the mite Blomia tropicalix were also measured, and levels >200 RAST U/ml were observed in 13 out of 20 sera. Immunoabsorption studies demonstrated that the bulk of the IgE‐ antibody to B. tropicafis (64%) was to species‐specific allergens and that 36% were cross‐reactive with D. pteronyssinus. The implication of our results is that management of children with asthma in São Paulo should include skin testing for allergy to both Dermatophagoides and B. tropicalis as well as recommendations about environmental control of house dust mite exposure.

Is the hygiene hypothesis still a viable explanation for the increased prevalence of asthma

The hygiene hypothesis states that a reduced exposure to allergens in early life is solely implicated in the growing propensity for allergy sensitization. Important elements of the hypothesis include helminth infection, exposure to endotoxins, exposure to pets and growing up on a farm. However, the hygiene hypothesis alone does not provide an adequate explanation for the observed increase in allergic disease. For example, in North American inner cities, asthma is increasing among children who live in very poor housing, which might be assumed to be somewhat dirty. In order to explain the increase in asthma, we need to take a broader view and also consider alterations related to the adoption of a western lifestyle. It has been suggested that lifestyle changes related to obesity (e.g. a change in diet) are associated with asthma. Other changes include a progressive decrease in physical activity. This lifestyle factor seems to correlate best with the recent increase in asthma. Clearly, the link between physical activity and asthma needs to be investigated in more detail.

Exposure to house dust mite allergen of children admitted to hospital with asthma.

Eighty‐two children admitted to hospital with exacerbations of asthma were studied to determine how many were exposed to house dust mites at the time of admission and displayed immediate hypersensitivity to house dust mites. The concentration of house dust mite allergen (Der p I) was measured in dust obtained from the childs mattress, bedroom floor and living room floor. Sixty‐two (75%) children admitted had been exposed to > 10 μg Der p I/g. Sixty‐seven (82%) children were sensitive to house dust mite(RAST 1 +, or weal 3 mm): 49 (60%) children were both exposed and sensitive. In contrast in a control group of 44 children, 31 (70%)(n.s.) were exposed to > 10μg Der p I/g, 10 (23%) (P < 0.001) were sensitive to house dust mite, and 7 (16%) (P < 0.001) were both exposed and sensitive. Seventy‐three homes were revisited 6 months after the childs initial admission. During the preceding month 14 children had been readmitted, 12 were fully investigated; of these 10 were both sensitive to house dust mite and still exposed to > 10 μg Der p I/g. In contrast, of the remaining 62 children who were not readmitted, only 19 were both sensitive and still exposed to > 10μg Der p I/g (P < 0.001). In conclusion, the majority of children admitted to hospital with exacerbations of asthma were exposed to house dust mite allergen and were house dust mite sensitive. Further the results suggest that continued exposure to higher concentrations of mite allergen may be associated with the risk of readmission.

Environmental exposure to Aspergillus fumigatus allergen (Asp f I)

Asp f I is a major allergen produced by the mycelia of Aspergillus fumigatus. It is not present in spores and can be used as a specific marker for the detection of germination of this fungus. We investigated the domestic and outdoor concentration of Asp f I in Poole, U.K. and Charlottesville, VA, U.S.A. Asp f I was undetectable in 95% (281/296) of house dust extracts and present at low levels (< 0.17 μg/g of sieved dust, mean 0.038 μg/g) in the remainder. In contrast, Asp f I could be detected in 65% (15/23) of cultures of house dust, suggesting the presence of viable, but ungerminated, A. fumigatus in the majority of homes. Asp f I was detectable in 80% (28/35) of extracts of leaves and compost, but present in these outdoor samples at low levels (<0.11 μg/g, mean 0.27 μg/g). Air sampling for Asp f I was undertaken before and after vigorous disturbances at indoor (n= 5) and outdoor (n= 6) sites. Airborne Asp f I was not detected in domestic samples or in undisturbed outdoor samples. Following disturbance it could be measured in outdoor samples (range 7.6–29 ng/m3). The results suggest that while exposure to A. fumigatus is common, exposure to Asp f I and germinating A. fumigatus is uncommon. It is probable that those individuals who develop antibody responses to Asp f I have been exposed to A. fumigatus which has germinated in their respiratory tract.

Quantitative measurement of airborne allergens from dust mites, dogs, and cats using an ion-charging device.

Background Increasing evidence suggests that children raised with an animal(s) in the house have a decreased risk of becoming sensitized. However, it is not clear whether this phenomenon is related to airborne exposure.

Indoor versus outdoor allergens in allergic respiratory disease

Immediate hypersensitivity to indoor or outdoor allergens is strongly associated with asthma or hay fever, respectively. Recent progress has defined the sequences, tertiary structures and enzymatic functions of many of the proteins involved; furthermore, the immune responses to these proteins have been examined; however, the mechanisms responsible for the dichotomous response remain elusive. The resolution of such mechanisms may explain the large increase in the prevalence of eosinophil-rich inflammation of the lower respiratory tract.

Differences in both prevalence and titre of specific immunoglobulin E among children with asthma in affluent and poor communities within a large town in Ghana

Background Reports from several African countries have noted an increasing prevalence of asthma in areas of extensive urbanization.

IgE and IgG antibody responses to recombinant Alt a 1 as a marker of sensitization to Alternaria in asthma and atopic dermatitis

Background Sensitization to Alternaria alternata is a risk factor for the development of wheezing and asthma. Alt a 1 is the major Alternaria allergen causing sensitization in asthmatics. Some atopic dermatitis (AD) patients have very high immunoglobulin (Ig)E antibody (ab) to Alternaria as analysed by Pharmacia CAP, however, it is not clear whether these are specific responses or whether Alt a 1 is involved in disease symptoms.

Further confirmation of the relevance of cockroach and dust mite sensitization to inner-city asthma morbidity

Inner-city populations bare a disproportionate burden of asthma morbidity in the United States [1]. In these communities, allergens from cockroaches, mice and sometimes dust mites are common sensitizers, sensitization to these pests is strongly associated with asthma symptoms, and exposure to these allergens in the home is associated with asthma exacerbations [2–4]. In the current issue, Wang et al. have further demonstrated in a population of asthmatic children living in several inner-city communities in the United States that having specific IgE antibodies to cockroaches and dust mites was associated with an increased risk for asthma hospitalizations and corticosteroid use [5]. They found a linear association between these health outcomes and both the presence and titre of allergen specific IgE with no obvious cut-off value, further reinforcing the importance of cockroach and dust mite specific IgE antibodies to inner-city asthma. While the differences in asthma prevalence among inner-city communities and their suburban and rural US counterparts are striking, equally remarkable is the difference in asthma prevalence among the urban inner-city and higher socio-economic status communities in the same cities. For example, a report by the New York City (NYC) Department of Health and Mental Hygiene (DOHMH) found that close to one in five children living in East Harlem had a report of asthma at the age 4–5 years (1). This prevalence was higher than that of the overall United States. Even more striking, it was also three times higher than the prevalence in the neighbourhood that borders it, the Upper East Side. Clearly, differences in socio-economic determinants and access to health care can explain part of the differences in disease management and consequently, hospitalization rates. However, the explanation for the difference in prevalence of asthma, given the current theories for the cause of the increase in asthma, must be more complex than access to health care alone and more likely points to environmental exposures as causative. In addition, a substantial component of the outdoor air pollution in dense urban environments, like NYC, comes from sources outside of the city (i.e. carried by weather patterns) and therefore is also unlikely to be the sole cause for the large difference in asthma risk among children living just city blocks apart. However, the distribution of local combustion byproduct sources like major roadways, truck routes and bus depots are not evenly distributed in urban settings. Other hypothesized and observed differences include those in physical activity, race, socio-cultural and socio-economic factors and even the density of street trees [6–8]. The ‘hygiene hypothesis’ is unlikely to explain the asthma epidemic in NYC inner-city communities, but neighbourhood differences in endotoxin exposure have been observed [9] and endotoxin has been shown to be relevant to early respiratory symptoms and allergic outcomes in several urban cohorts [9–11]. Given the strong association between cockroach and dust mite sensitization and asthma exacerbations in inner-city communities [2], exposure to these allergens offers one potential explanation for the differences in asthma prevalence within urban settings. Sensitization to mouse allergen has also been shown to be common [3]. In our studies in low-income urban populations in NYC, we have demonstrated high levels of both cockroach and mouse allergens in the homes of children living in high asthma prevalence neighbourhoods [4]. However, we observed geographical variability in mouse allergen by neighbourhood suggesting that asthma triggers may vary by neighbourhood. In these same children, we have Correspondence: M. S. Perzanowski, Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, 60 Haven Avenue, Room B-116, New York, USA. E-mail: mp2217@columbia.edu Cite this as: M. S. Perzanowski and T. A. E. Platts-Mills, Clinical & Experimental Allergy, 2009 (39) 1291–1293. doi: 10.1111/j.1365-2222.2009.03327.x Clinical & Experimental Allergy, 39, 1291–1293

Human T‐cell responses to Trichophyton tonsurans: inhibition using the serum free medium Aim V

Background Proteins of the fungus Trichophyton tonsurans have been shown to give strong T cell proliferative responses in vitro using lymphocytes from individuals with immediate or delayed skin tests. Furthermore, Trichophyton‐specific T‐cell lines produce distinct patterns of cytokine production depending upon the skin‐test reactivity of the host. However, skin‐test negative individuals generally give limited responses. A recent study has demonstrated dust mite specific proliferation with lymphocytes from atopic and non‐atopic subjects using the serum free medium Aim V.