Oral administration of desloratadine prior to sensitization prevents allergen-induced airway inflammation and hyper-reactivity in mice

Background Histamine-1-receptor (H1R)-antagonists were shown to influence various immunological functions on different cell types and may thus be employed for immune-modulating strategies for the prevention of primary immune responses. Objective The aim of this study was to investigate the effects of an H1R-antagonist on allergen-induced sensitization, airway inflammation (AI) and airway hyper-reactivity (AHR) in a murine model. Methods BALB/c mice were systemically sensitized with ovalbumin (OVA) (six times, days 1-14) and challenged with aerosolized allergen (days 28-30). One day prior to the first and 2h prior to every following sensitization, mice received either I or 0.01 mug of desloratadine (DL) or placebo per os. Results Sensitization with OVA significantly increased specific and total IgE and IgG1 serum levels, as well as in vitro IL-5 and IL-4 production by spleen and peribronchial lymph node (PBLN) cells. Sensitized and challenged mice showed a marked eosinophilic infiltration in broncho-alveolar lavage fluids and lung tissues, and developed in vivo AHR to inhaled methacholine. Oral treatment with DL prior to OVA sensitization significantly decreased production of OVA-specific IgG1, as well as in vitro Th2-cytokine production by spleen and PBLN cells, compared with OVA-sensitized mice. Moreover, eosinophilic inflammation and development of in vivo AHR were significantly reduced in DL-treated mice, compared with sensitized controls. Conclusion Treatment with H1R-anatagonist prior to and during sensitization suppressed allergen-induced Th2 responses, as well as development of eosinophilic AI and AHR. This underscores an important immune modulating function of histamine, and implies a potential role of H1R-anatagonists in preventive strategies against allergic diseases.