Mite and pet allergen exposure in hotels in Uberlândia, Midwestern Brazil

Mite allergens are involved in airway sensitization and allergic diseases. We evaluated the exposure to house dust-mite (Der p 1 and Der f 1) and pet (Fel d 1 and Can f 1) allergens in hotels in Uberlândia, Midwestern Brazil. A total of 140 dust samples were collected from bedding (n = 98) and carpet (n = 42) of bedrooms in 20 hotels enrolled for this study. Geometric mean (GM) levels of Der f 1 (11.30 microg/g of dust; 95% CI: 8.34-15.30 microg/g) were significantly higher than Der p 1 (0.15 microg/g of dust; 95% CI: 0.13-0.18 microg/g) in bedding dust samples (P < 0.001), regardless of the hotel classes. Der f 1 levels were significantly higher in bedding (11.30 microg/g of dust; 95% CI: 8.34-15.30 microg/g) than carpet (6.32 microg/g of dust; 95% CI: 4.31-9.26 microg/g) dust samples (P < 0.05). High levels of Der f 1 (>10 microg/g of dust) were found in 58%, 76%, and 69% of dust samples from Simple, Economical, and Tourist/Superior hotels, respectively, while GM levels of Fel d 1 (0.11 microg/g of dust; 95% CI: 0.09-0.14 microg/g) and Can f 1 (0.30 microg/g of dust; 95% CI: 0.20-0.44 microg/g) were relatively low. These results indicate that Der f 1 is the predominant allergen in hotels in Uberlândia, especially in bedding dust samples, regardless of the hotel classes and could represent an important risk factor for exacerbation of allergic symptoms in previously mite-sensitized guests.

PRACTICAL IMPLICATIONS

Mites and pets are important sources of indoor allergens. Most people spend the greatest part of their time indoors. Hotels can constitute an important allergen reservoir of the indoor environment and could represent an important risk for exacerbation of allergic symptoms in previously sensitized guests. Thus, hotels should also be included for planning indoor allergen avoidance as part of a global management strategy, especially in patients with respiratory allergy.

Taxis but not private cars are mite allergen reservoirs in Brazil

Indoor allergens are major causative agents in allergic disease development. Besides homes, public transport vehicles have been considered important mite and pet allergen reservoirs. Our recent studies on allergen exposure in automobiles showed that different allergen levels are found in private cars versus taxis. We quantified group 1 Dermatophagoides spp. (Der 1), Felis domesticus (Fel d 1), and Canis familiaris (Can f 1) allergen levels by ELISA in dust samples from 60 taxi and 60 private car upholstered seats. Mean levels of Der 1 and Fel d 1 were significantly higher in taxis than private cars. A significantly higher percentage of taxis (42%) harboring sensitizing levels of Der 1 compared to private cars (5%) was also found. In spite of the low mean Fel d 1 levels, comparison of the percentage of vehicles with moderate Fel d 1 levels showed a significant difference between taxis and private cars (43% vs. 20%). On the other hand, mean Can f 1 levels were significantly higher in private cars compared to taxis concomitant with a significantly higher percentage of private cars containing moderate Can f 1 levels than taxis (53% vs. 28%). We conclude that upholstered seats from Brazilian taxis but not private cars constitute an important mite allergen reservoir. Thus, additional effective measures for the reduction of allergen exposure in vehicles within the global allergen avoidance strategy should also be routinely accomplished to minimize the induction of sensitization and symptoms in allergic patients.

Differential IgE reactivity to Der p 1 and Der p 2 allergens of Dermatophagoides pteronyssinus in mite-sensitized patients

Several studies have shown that the presence of IgE antibodies to house dust mites (HDM), particularly Dermatophagoides pteronyssinus (Dpt), is an important risk factor for asthma. Allergen immunotherapy is indicated for patients with IgE antibodies to clinically relevant allergens. The aims of this study were to analyze the levels of specific serum IgE to Der p 1 and Der p 2 allergens in mite-sensitized atopic patients and to compare them with both in vivo (skin prick test) and in vitro (IgE-ELISA) sensitizations to Dpt crude extract. Forty-seven atopic patients with allergic rhinitis with or without intermittent or persistent mild asthma and positive skin prick test (SPT) to Dpt total extract were studied. Thirty age-matched healthy subjects with negative SPT to HDM were included as controls. Levels of total IgE and Dpt-, Der p 1- and Der p 2-specific IgE were measured by ELISAs in SPT-positive atopic patients and SPT-negative control subjects. Among 47 symptomatic atopic patients, 27 (57.4%) were double positive IgE to Der p 1 and Der p 2 allergens, 3 (6.4%) were single positive IgE to Der p 1, 4 (8.5%) were single positive IgE to Der p 2, and 13 (27.6%) were double negative IgE to both allergens. There was a significant correlation between Der p 1- and Der p 2-specific IgE levels, but not between Der p 1- or Der p 2-IgE levels and SPT results. The double negative IgE patients had the smallest skin test reactions although they showed high mean levels of total serum IgE. Therefore, the knowledge of specific IgE levels to Der p 1 and Der p 2 major allergens might support physicians for indication or follow-up in mite-sensitized patients under allergen-specific immunotherapy. These approaches might be important for obtaining improved safety and efficacy of the current clinical practice of allergen immunotherapy.

Mite allergen levels and acarologic analysis in house dust samples in Uberaba, Brazil

Mite allergen exposure has been widely related to sensitization and development of allergic diseases. This study intended to evaluate the degree of allergen exposure in Uberaba, Brazil, through the measurements of Der f 1 and Der p 1 allergen levels associated with the acarologic analysis in house dust samples. A total of 240 dust samples were collected from 60 houses through vacuuming sofas and bedding, during the months of March and July 2000. Indoor temperature and relative humidity were also measured. Mites were counted and identified under light microscopy and allergen levels were measured by two-site monoclonal antibody ELISAs. The major mite family was Pyroglyphidae (39.4%), having D. pteronyssinus as the most frequent species (15.6%), followed by D. farinae (12.3%) and E. maynei (7.9%). The family Glycyphagidae was less commonly found (4.8%), with Blomia tropicalis (4.4%) as its majoritary member. The highest levels of Der f 1 and Der p 1 allergens were found in bedding samples in March (31.7 and 0.9 microg/g of dust, respectively), with Der f 1 levels significantly higher than Der p 1 (p < 0.0001). There was a significant positive correlation between the mite number and allergen levels. These results indicate that Dermatophagoides sp are the most frequent mites in our region followed by E. maynei. Therefore, the knowledge of the local mite fauna would improve the means of investigating the association between allergen exposure and sensitization, allowing the addition of new mite extracts in diagnostic tests.

A sensitive reverse ELISA for the measurement of specific IgE to Der p 2, a major Dermatophagoides pteronyssinus allergen

BACKGROUND

Epidemiologic studies have shown that the presence of IgE antibodies to house dust mite and other indoor allergens is an important risk factor for asthma.

OBJECTIVE

The aim of this study was to develop a reverse ELISA (rELISA) for measuring specific IgE to Der p 2, a major Dermatophagoides pteronyssinus (Dpt) allergen, as a potential tool for followup of allergen immunotherapy.

METHODS

Recombinant Der p 2 allergen or a monoclonal antibody to Der p 2 was used to coat plates in conventional ELISA (cELISA) and rELISA, respectively. Sera from 48 asthmatic patients with positive skin prick test (SPT+) to D. pteronyssinus extract were analyzed for total IgE and specific IgE to Der p 2, and the results were compared with a group of 41 SPT asthmatic and 30 SPT- control subjects.

RESULTS

The sensitivity of the two assays for Der p 2-specific IgE was 3.9 EU/mL and their specificities were confirmed by inhibition tests, in a dose-dependent manner. There was a significant positive correlation between cELISA and rELISA (r = 0.74; P < 0.0001). However, rELISA was more sensitive than was cELISA, regarding both the positive sera percentage (70.8% vs 52.1%) and the Der p 2-specific IgE levels (28.4 vs 4.5 EU/mL) in SPT+ asthmatic patients.

CONCLUSIONS

rELISA has shown to be a sensitive and alternative method for measuring Der p 2-specific IgE without using radioactive techniques. Detection of specific IgE to major allergens and relevant peptides, and identification of B cell epitopes in allergens will provide valuable information for the design of allergen analogs and peptides for immunotherapy.

Dermatophagoides farinae (Der f 1) and Dermatophagoides pteronyssinus (Der p 1) allergen exposure among subjects living in Uberlândia, Brazil

BACKGROUND

The role of mite allergen exposure in sensitization and development of asthma has been widely recognized. Previous studies have shown that Dermatophagoides pteronyssinus and Blomia tropicalis were the most prevalent house dust mites in Brazil, while D. farinae was rarely found. The aim of this study was to measure Der f 1 and Der p 1 allergen levels in Brazilian asthmatics' and controls' homes.

METHODS

Sixty-four houses (32 asthmatic, 32 control) were visited for dust sampling from five sites. Der f 1 and Der p 1 levels were measured by two-site monoclonal-antibody-based ELISAs.

RESULTS

The highest levels of Der f 1 and Der p 1 allergens were found in bedding samples from both asthmatics' and controls' homes. However, the geometric mean of Der f 1 levels (15.8 microgram/g of dust) was significantly higher than for Der p 1 (8.2 microgram/g of dust) in these samples. In addition, allergen levels >/=10 microgram/g of dust were found in 60-80% of the samples for Der f 1 and about 50% for Der p 1.

CONCLUSIONS

These results indicate that high levels of Der f 1 allergen are present in both asthmatics' and controls' homes, in contrast to previously reported data. Therefore, studies on exposure to mites should be performed in different cities, seasons and times, since the mite fauna might be subject to variations. Knowledge of the mite fauna will certainly improve the means of investigating the association between allergen exposure and sensitization, allowing to establish the inclusion of new mite extracts in inhalant skin test sets, and even to detect monosensitized patients with respiratory allergy.