House Dust Mite-Specific Sublingual Immunotherapy Prevents the Development of Allergic Inflammation in a Mouse Model of Experimental Asthma

<b><i>Background:</i></b> Evidence regarding sublingual immunotherapy (SLIT) efficacy and its good safety profile has been demonstrated with pollen and house dust mite (HDM) allergens in the treatment of airway allergies. In addition, the use of grass pollen presents a SLIT disease-modifying treatment for respiratory allergies. <b><i>Objectives:</i></b> The aim of this study was to demonstrate the efficacy of HDM-based SLIT in mouse models of allergic airway inflammation and to gain insights into the involved local immunological mechanisms. <b><i>Methods:</i></b> Balb/c mice were sensitized/challenged with <i>Dermatophagoides farinae</i> (Der f) extract and underwent Der f-SLIT in prophylactic and therapeutic settings. The SLIT efficacy was assessed using lung function measurements, analysis of local inflammatory responses by bronchoalveolar lavage cell differentiation and lung histology. Humoral and cellular responses were monitored by ELISA, cytokine bead array and flow cytometry analyses.<b><i> Results:</i></b> In a prophylactic setting, Der f-SLIT with 12 development units per dose reduced the eosinophil-dominated inflammatory response in the lung paralleled by a marked reduction in airway hyperresponsiveness. Local Th2 responses were prevented as demonstrated by significantly lower levels of IL-5 and IL-13. Additionally, SLIT-treated mice revealed a lower proportion of CD4-CD8- &#947;δ cells and a higher frequency of CD8+CD25+IFN&#947;+ T cells in the lungs compared to sham-treated mice.<b> </b>In a therapeutic<b> </b>setting, Der f-SLIT also resulted in reduced inflammatory responses in the lung. <b><i>Conclusion:</i></b> The efficacy of Der f-SLIT was demonstrated in prophylactic and therapeutic conditions using experimental mouse models of HDM-induced airway inflammation. A potential role of a so far underestimated lymphocyte subpopulation was also indicated.