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Background: Dermatophagoides pteronyssinus (DP) and Blomia tropicalis (BT) are the dominant house dust mites inducing allergic diseases in tropical climates. It is not known whether the efficacy of DP subcutaneous immunotherapy (SCIT) is similar in patients sensitized to DP alone or to both DP and BT. Method: Ninety-five children (5–17 years old) affected by asthma with rhinitis and sensitized to both DP and BT received 3 years of DP-SCIT. Clinical symptom and medication scores, serum-specific IgE and IgG₄ were evaluated during DP-SCIT. Patients were grouped based on DP and BT co-sensitization or cross-reactivity, according to positive or negative IgE to BT major allergen (BTMA). Results: After 3 years of DP-SCIT, all patients had significant reductions in symptoms and medication use. In all, 65% of the patients were free of asthma symptoms and medication use; in addition, 3% was free of rhinitis symptoms. FEV₁ in all patients were greater than 95% of predicted. DP-SCIT induced significant increases in DP- and BT-specific IgG₄. In 50% of patients, DP-specific IgG₄ increased more than 67-fold. BT-specific IgG₄ increased more than 2.5 fold. A moderate correlation (r = 0.48–0.61, p < 0.01) was found between specific IgE against DP and BT in the BTMA– group (n = 34) before and after DP-SCIT, whereas no correlation was found in the BTMA+ group (n = 61). The 2 BTMA groups responded similarly with regard to clinical improvement and increase in specific IgG₄ to both DP and BT. No safety finding of concern were reported in either group. Conclusion: DP-SCIT may be of clinical benefit to patients with IgE sensitizations to both DP and BT. DP-SCIT induces IgG₄ that cross-react with BT allergens.

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Pathogens are commonly presented in the human respiratory tract, but symptoms are varied among individuals. The interactions between pathogens, commensal microorganisms and host immune systems are important in shaping the...