House dust mite components sensitization profile in China, a multi‐centre study

To the Editor: House dust mite (HDM) is one of the most important indoor allergens around the world, usually causing perennial allergic rhinitis, allergic conjunctivitis, asthma and atopic dermatitis.1 It is estimated that the prevalence of HDM sensitization was 1%– 2%, affecting 65– 130 million people worldwide.2 Our previous study revealed that HDM is the major allergen in China, and there were considerable geographical differences in the prevalence of HDM, with the highest being 40.79% in Southern China, and the lowest being 11.21% in Northeast China.3 To date, as many as 41 HDM allergen groups have been identified and categorized by molecular diagnostic techniques.4 Group 1 (Der p 1 and Der f 1) and group 2 (Der p 2 and Der f 2) allergens are considered the most clinically relevant HDM allergens worldwide, which are also the major components of current HDM immunotherapy drugs.5 A joint study from Canada, Europe, South Africa and the United States demonstrated significant geographical variability in sensitization patterns and sIgE levels of HDM allergens.6 The differences in HDM allergens may be one of the factors affecting the efficacy of immunotherapy, which is currently the only treatment that may alter the course of HDMallergic diseases.7 However, the sensitization profiles of HDM allergens in China have not yet been investigated. Due to a vast territory, and the climates, vegetation and people's living habits vary substantially in different regions, it is presumed that the sensitization profiles of HDM allergens may differ in distinct regions in China. In this study, serum from 244 subjects with suspected allergy symptoms and Der p specific IgE ≥0.35 kUA/L at seven sites from Northern (Provinces of Liao Ning, Ji Lin and Heilong Jiang), Central (Provinces of Si Chuan, Chongqin and Hubei) and Southern (Guang Dong province) China were obtained and tested for nine mitespecific allergens using a protein chip technology. The study was approved by the ethics committee of the First Affiliated Hospital of Guangzhou Medical University. All patients provided informed consent. Additional information about study methods and findings are available in the following repository (https://doi.org/10.5281/zenodo.7316876). Our study showed that the prevalence of the nine HDM allergenspecific IgE in China from high to low were Der p 1 (66.0%), Der f 2 (59.4%), Der p 2 (59.0%), Der f 1 (48.8%), Der p 23 (45.5%), Der p 21 (23.3%), Der p 7 (22.5%), Der p 5 (15.2%) and Der p 10 (9.0%) (Figure 1A). Therefore, the major HDM allergens in China were Der p 1, Der f 2, Der p 2, while Der f 1, Der p 23, Der p 21, Der p 7, Der p 5 and Der p 10 are minor allergens. The results also showed that, except for Der p 23, the prevalence of the nine mite allergens in different regions was significantly diverse (Figure 1B). In Southern China, the prevalence of all the nine mite allergens was the highest, followed by the Central regions and the Northern regions (Figure 1B). In particular, the prevalence of Der f 1 in Northern China was 13.8%, which is lower than that of Der p 23 (23.3%), suggesting that Der f 1 may not be the major mite allergen in Northern China. It also revealed that there were significant differences in the mite allergens and Der p IgE levels among the three regions (Figure 2). All the mitespecific IgE levels were significantly higher in the Southern region except Der p 10 and Der p 23 (Figure 2). Between the Central and Northern regions, the specific IgE levels of Der p 1, Der p 2, Der f 2 and Der p 23 were higher in the Central region, while no significant difference was found in other allergens. In addition, the proportion of highlevel HDM components in the Central and Southern regions was higher than that in the Northern regions. We found that higher sensitization frequencies to HDM allergens were associated with a higher risk of allergic disease. In particular, when the number of sensitization components to HDM reaches seven or more, all the sensitized subjects have allergic symptoms. Moreover, sensitized subjects with allergic symptoms had higher IgE levels of the HDM allergens than that in the sensitized subjects without allergic symptoms except for Der p 5, Der p 7 and Der p 10 of the 9 HDM allergens. This suggests that subjects with more HDM allergens sensitized and higher IgE levels have a greater probability to suffer from allergic diseases. The results were similar to the findings of Yvonne Resch et al., who confirmed that children with asthma had a higher sensitization rate and higher IgE levels of HDM allergens than those without asthma.8 It also showed that there was a positive correlation between mite componentspecific IgE and the sum of crude extracts HDM IgE. However, the correlation varied for the different HDM allergens. It demonstrated that the IgE levels to most HDM allergens in allergic rhinitis, asthma and allergic rhinitis with asthma group were significantly higher than that in skin allergic diseases (atopic dermatitis or urticaria), except for Der p 10 and Der p 23. This may be because HDM is an inhaled allergen and are more likely to induce respiratory allergic diseases, while skin allergies may not necessarily